6 M&E Equipment and Hydraulic Steel Structures

Contents

6 M&E Equipment and Hydraulic Steel Structures ...... 6-1

6.1 Hydraulic Machinery ...... 6-1 6.2 Main Electric Equipment and Main Electrical Connection ...... 6-27 6.3 Control, Protection and Instrumentation ...... 6-85 6.4 Hydraulic Steel Structures ...... 6-96 6.5 Ventilation and Air Conditioning ...... 6-123 6.6 Fire Protection Design ...... 6-132

6 M&E Equipment and Hydraulic Steel Structures 6.1 Hydraulic Machinery

The Paklay Hydropower project (HPP) lies on the junction of Sayaboury Province and Vientiane Province in Laos, about 50 km away from the border of Thailand. Main function of the HPP is power generation, followed by development assignment for comprehensive utilization such as ship transport and fishery. The Paklay HPP has a normal pool level of 240.00 m a.s.l. with a corresponding storage of 890.1 million m3 and a minimum pool level of 239.00 m a.s.l. with a regulating storage of 58.4 million m3. The HPP has a design installed capacity of 770 MW, average annual energy output of 4124.8 GW·h, and annual operating hours of installed capacity of 5,357 h. A small portion of electrical power is

supplied to Laos, and the other portion is supplied to Thailand.

6.1.1 HPP Basic Parameters

a) Upstream water level Check flood level (0.01%) 240.23 m a.s.l. Design flood level (0.05%) 238.86 m a.s.l. Normal pool level 240.00 m a.s.l. Minimum pool level 239.00 m a.s.l. b) Tail water level Check flood level (0.01%) 236.49 m a.s.l. Design flood level (0.05%) 235.50 m a.s.l.

Tail water level (whole plant in full load) (Q=6101.2m3/s) 224.14 m a.s.l. c) Hydroenergy Installed capacity 770 MW Average annual energy output 4124.8 GW·h Annual operating hours 5357 h d) Turbine net head

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Maximum (gross) head 20.00 m Rated head 14.50 m Weighted average head 15.9 m Minimum (gross) head 7.5 m e) Discharge Average annual discharge 4100 m3/s f) Sediment data Average annual sediment concentration 509 g/m3

6.1.2 Selection of Rated Head

The Paklay HPP has the low head and large discharge, with a reservoir drawdown depth of only 1 m and relatively small change in reservoir water level. The power generation head of the HPP is closely related to the change of downstream water level. The Sanakham HPP is the downstream connection cascade of the Paklay HPP, with a normal pool level of 220.00 m a.s.l., connecting with the normal pool level of the Paklay HPP. In view of impact from backwater jacking of the Sanakham HPP, change of the downstream water level of the Paklay HPP dramatically reduces. The power generation head of the Paklay HPP mainly ranges from 14.00 m to 18.00 m. The head duration of this range is about 80% of the total duration. The Paklay HPP is a low-head hydropower project with a relatively poor regulating performance. Low head generally occurs in the flood period. Therefore, if the selected rated head is too high, the output of the Paklay HPP will be decreased dramatically in the flood period. According to simulation results of power generation operation of the HPP, in flood season, the reservoir water level of the Paklay HPP is basically kept at the normal pool level, with a head about of 15.50 m corresponding to power generation at full load. Therefore, in this stage, under the premise that power generation at full load will not be disabled at the normal pool level, the disabled probability and capacity in flood season shall be as less as possible. The rated head of the HPP is selected at 14.50 m based on a head dependability of about 88%.

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6.1.3 Selection of Turbine Type

The head range of the HPP is 7.5 m ~ 20.0 m, and the turbine types suitable for this head range are axial flow turbine and the tubular turbine. The tubular turbine consists of shaft-extension tubular turbine, pit turbine, bulb turbine and straight flow turbine. The shaft-extension tubular turbine is suitable for the HPP with a runner diameter less than 3 m. The pit turbine is only applicable to the HPP with low head and small capacity, with a maximum unit capacity of 3,000 kW and runner diameter of 3 m. The straight flow turbine has an extra high requirement for the sealing technology; therefore, it is only applied to the small HPPs. The HPP has a medium unit capacity and a runner diameter about of 6.90 m; therefore, the bulb turbines and axial flow turbines are selected for comparison. According to the installed capacity of the HPP, two alternatives are preliminarily proposed for comparison, i.e., fourteen 55 MW bulb turbines and eight 96.25 MW Kaplan turbines.

Main parameters of the above two alternatives are listed in the following table.

Table 6.1-1 Comparison of Turbine Types Description Bulb Turbine Axial Flow Turbine Difference Turbine model GZ-WP-690 ZZ-LH-1020 Rated output of turbine (MW) 56.4 98.7 Runner diameter (m) 6.90 10.20 Rated speed (r/min) 93.75 62.5 Rated discharge (m3/s) 435.8 788.6 Unit discharge (m3/s) 2.404 1.99 Efficiency at rated point (%) 91.0 88.0% Specific speed (m·kW) 787 694 Specific speed coefficient 2997 2643 Weight of a single turbine (t) 756 1550 Weight of a single generator (t) 460 1150 Weight of a single unit (t) 1216 2700 Total weight of all units (t) 17024 21600 -4576 Setting elevation (m) 208.5 217.0 -8.5 Elevation of draft tube base 203.0 186.4 16.6 plate (m) Clear length of powerhouse (m) 391.0 364.0 27

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Description Bulb Turbine Axial Flow Turbine Difference Clear width of powerhouse (m) 21.0 31.2 -10.2

Compared with the axial flow turbine, for this project the bulb turbine has advantages as follows: a) High efficiency. The bulb turbine has a straight and smooth water passage, with relatively well-distributed flow fields; therefore, its hydraulic efficiency is relatively high and its high efficiency area is flat and wide. Optimum efficiency of a bulb turbine model is about over 1% higher than that of an axial flow turbine model, with HPP weighted average efficiency about 2% ~ 3% higher. b) High unit parameter level of turbine. The discharge capacity of a bulb turbine is greater than that of an axial flow turbine. The unit discharge of the bulb turbine adopted by the HPP is about 20% higher than that of an axial flow turbine, with specific speed and specific speed coefficient about 13% higher. c) Less investment on M & E equipment. Because a bulb turbine has advantages of high parameter level, high speed, small size, and light weight, total weight of all units in the plant of bulb turbine alternative is 4,576 t less than that of the axial flow turbine alternative. d) Less investment on civil works. If the axial flow turbine alternative is adopted, length of the powerhouse can be reduced, which is in favor of project layout. However, the clear width of the powerhouse will be about 50% greater than that of the bulb turbine alternative and clear plane size of the powerhouse will be about 40% greater than that of the bulb turbine alternative. Although the setting elevation of a bulb turbine is lower than that of an axial flow turbine, its draft tube is arranged horizontally and no elbow draft tube is provided, thus the elevation of draft tube base plate is 16.6 m higher than that of an axial flow turbine. In this way, the bulb turbine alternative has dramatically less foundation excavation works. Generally speaking, the bulb turbine alternative can reduce foundation excavation works and control dimensions of the powerhouse, so as to reduce investment on civil works. e) Shorter construction period. Because the bulb turbine alternative has no

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construction of curved passages such as a spiral case and elbow draft tube, its civil construction period can be shortened. In addition, after the main shaft is installed, the turbine and the generator can be installed at the same time, which further reduces the construction period of the HPP. f) In favor of design of system connection and main electrical connection. According to the design requirement of grid connection, about 100 MW capacity of the HPP will supply power to Laos, and the other capacity will supply power to Thailand. In addition, national power grids of Laos and Thailand are not connected for operation. For the alternative of fourteen 55 MW bulb turbines, the scheme of output of 12 units being transmitted to Thailand and that of 2 units to Laos can be adopted. For the alternative of eight 96.25 MW Kaplan turbines, the scheme of output of 7 units being transmitted to Thailand and that of 1 unit to Laos can be adopted. In the latter case, when the unit to supply power to Laos is in maintenance, the HPP cannot supply power to the Laos power grid, which would affect the power grid greatly. According to Electrical-Mechanical Design Code of Hydropower Plants (DL/T 5186-2004), tubular turbines should be preferably for a run-of-river hydroelectric plant with a maximum head less than 20 m. In conclusion, for this project, the bulb turbine has advantages of high efficiency, high parameter level, less investment on M & E equipment and civil works, shorter construction period, being in favor of design of system connection and main electrical connection, etc. Therefore, it is recommended to select the bulb turbine.

6.1.4 Selection of Turbine Model Parameters

a) Selection of specific speed Both specific speed and specific speed coefficient of a turbine are the aggregative indexes for turbine technical parameters. High specific speed and specific speed coefficient can reduce size of the units and powerhouses and investment, which will enhance economic benefit of the HPP. However, improvement of the specific speed and specific speed coefficient is limited by turbine strength, cavitation performance, sediment abrasion, operational stability and others. To meet safe and reliable operation of a unit, both specific

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speed and specific speed coefficient should be controlled within a rational and practicable range based on practice; namely, specific speed and specific speed coefficient should not be set too high. See Table 6.1-2 for the rated specific speed and specific speed coefficient (K) of a turbine calculated by the relevant statistical formula. See Table 6.1-3 for the specific speed and specific speed coefficient of some bulb turbines put into operation, with similar head section as that of the HPP.

Table 6.1-2 Computation Sheet for Specific Speed and Specific Speed Coefficient (K)

Common Statistical Formula Specific Speed ns(m-kW)

0.5 ns=(2700~3100)/H 709~814 2700~3100

0.433 ns=2438.1/Hr 766 2917

702 2672

762 2900

Table 6.1-3 Parameters of Some Bulb Turbines Put into Operation Specific Rated Unit Maximu Rated Rated Speed Unit Number Specific Description Output m Head Head Speed Coefficie Discharge of Speed (MW) (m) (m) (r/min) nt (m3/s) Blades (m-kW) K Hongjiang 45 27.3 20 136.4 695 3107 1.892 5 HPP Qiaogong 57 24.3 13.8 83.3 757 2813 2.254 5 HPP Kangyang 40.75 22.5 18.7 125 655 2831 1.868 5 HPP Julongtan 30 18 14.2 125 798 3005 2.318 4 HPP Bailongtan 32 18 9.7 93.75 995 3099 2.959 4 HPP Nina HPP 40 18.1 14 107.1 801 2996 2.346 4 Changzhou 40 16 9.5 75 931.4 2871 2.873 4 HPP Jirau HPP 75 19.6 15.2 85.71 789 3076 2.23 4 (DEC) Jirau HPP 75 19.6 15.6 94.7 872.7 3402 2.46 4 (ALSTOM)

According to Table 6.1-3, the turbines with similar parameters as those of the HPP

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have the specific speed of about 650 m-kW~800 m-kW and specific speed coefficient of about 2800~3100. The technical schemes for the HPP prepared by major host equipment manufacturing plants at home and abroad show that the specific speed is 787 m-kW and corresponding specific speed coefficient is 2998. According to the experience formula, parameter level of the similar HPPs constructed or under construction, and parameter level stated in recommendations from host equipment manufacturing plants, the HPP shall have a specific speed coefficient of about 3000 and a corresponding specific speed of about 788 m-kW. b) Selection of unit parameter Because the bulb turbine has many advantages in the low head range and its operational stability is constantly proved by practice, in recent years, more and more research works have been focused on the bulb turbine. The applied head may be extended up and down based on 5 m to 18 m for 4-bladed runner, i.e., 16 m to 30 m for 5-bladed runner, and 3 m to 12 m for 3-bladed runner. See Table 6.1-4 for main performance parameters and applicable head range of a tubular runner.

Table 6.1-4 Main Technical Parameters of Bulb Runner 5-bladed Runner 4-bladed Runner Operating head 16~30m 5~18m n ~140r/min ~160r/min Optimum 10 3 3 operating Q10 ~1.7m /s ~1.8m /s conditions η0 ~94.2% ~94% n 160r/min~170r/min 180r/min~200r/min Rated 11 3 3 3 3 operating Q11 2.2m /s~2.3 m /s 2.9m /s~3.1 m /s conditions η ~90% ~88% Applicable to the HPP or not Applicable Applicable

The HPP has a maximum gross head of 20 m and proposed unit capacity of 55 MW. According to Table 6.1-4 as well as investigation and research made for the HPP constructed and discussion results with host equipment manufacturers, in this stage, it is recommended to adopt the 4-bladed runners temporarily. See Table 6.1-5 for the unit speed and unit discharge calculated by the relevant

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statistical formulas.

Table 6.1-5 Computation Sheet for Unit Speed and Unit Discharge Specific Speed Unit Unit Speed n Experience Formula n 11 Discharge Q s (r/min) 11 (m-kW) (m3/s)

Formula I 788 169 2.43

Formula II 788 169 2.35

Formula 788 170.8 2.41 III

According to Table 6.1-5, the unit discharge of the turbine at the rated point should be

3 3 about 2.35 m /s ~ 2.43 m /s, with a unit speed of about 170 r/min.

For a tubular turbine, its unit discharge (Q11) under the rated operation conditions shall be a value with the medium efficiency and proper cavitation factor (not too large). The reason is as follows: selection of unit discharge is directly related to the turbine-generator unit and civil quantities; when the unit discharge is large, the turbine size and plan view size of the powerhouse will be small and the turbine construction cost will be low; in addition, the large unit discharge will increase the cavitation factor, which will decrease the setting elevation of turbine and increase excavation quantities. By reference to the similar HPPs and in view of consulting results from the host equipment manufacturers, the unit discharge at the rated operating point shall be 2.4 m3/s with a unit speed of 170 r/min. c) Turbine efficiency By reference to the efficiency level of the bulb model turbine developed at home and abroad and the prototype turbine put into operation, it is preliminarily proposed to set the rated turbine efficiency of the HPP not less than 91.0%. d) Cavitation performance In comprehensive consideration of the specific speed and unit parameter of turbines of the HPP and model runner parameter currently applicable to the HPP, the critical cavitation

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factor (to the vertex position of a turbine runner) of turbines should be about 1.3. Because the HPP has a relatively large sediment concentration, the ratio (k) of cavitation factor of the HPP to critical cavitation factor of the model shall be 1.13, based on which the corresponding static suction head and setting elevation can be obtained by calculation.

6.1.5 Number of Units and Unit Capacity

The HPP is proposed to have an installed capacity of 770 MW and adopt the bulb turbine-generator unit. Because the HPP has a relatively large installed capacity, to reduce quantity of the units, it should increase the unit capacity as far as possible. The Jirau HPP (Brazil) has an installed capacity of 4,800 MW, with 64 bulb turbine-generator units of which the unit capacity is 75 MW and the runner diameters are 7.5 m (7.9 m). These units are the bulb turbine-generator units with the largest unit capacity at present. The first unit was put into operation in the end of August 2013. The Guangxi Qiaogong HPP (China) has 8 bulb turbine-generator units with the unit capacity of 57 MW and the runner diameters of 7.45 m, which are the units with the largest unit capacity in China and the second largest in the world at present. The Changzhou HPP has 15 bulb turbine-generator units with the unit capacity of 42 MW and the runner diameters of 7.50 m, which are the units in operation with the largest runner diameter in China at present. In case the HPP is equipped with 12 bulb turbine-generator units with the unit capacity of 64.17 MW, the corresponding runner diameter will be 7.5 m and the total capacity of 10 units transmitting power to Thailand will be 641.7 MW. According to the design and manufacturing level of the units at present and in consideration of the grid connection mode of the HPP (about 100 MW energy output for Laos and the rest for Thailand), in this stage, it is proposed to compare the scheme involving 13 the units with the unit capacity of 59.23 MW with the scheme involving 14 the units with the unit capacity of 55 MW. See Table 6.1-6 for main technical and economic indexes of the units in both schemes.

Table 6.1-6 Technical and Economic Indexes Corresponding to Schemes of Unit Quantity Number of Units Description Unit 13 14 Turbine Unit capacity MW 59.23 55

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parameter Rated head m 14.5 14.5

Rated discharge of single unit m3/s 469.3 435.8 Rated Speed r/min 88.24 93.8

Runner diameter m 7.2 6.9 Specific speed m·kW 768.6 786.9

Specific Speed Coefficient - 2927 2997

Average annual energy output GW·h 4143.4 4143.4 Primary energy (PE) GW·h 2886.6 2886.6 Secondary energy GW·h 1054.4 1054.4 Energy Excess energy (EE) GW·h 202.4 202.4 index Equivalent energy (PE + 0.6 x SE) GW·h 3519.2 3519.2 Utilization ratio of water resource % 85.52 85.52 Annual operating hours of installed capacity h 5381 5381 Project cost on Hydroproject million yuan 9984.38 9975.89 Project cost per kilowatt Yuan/kW 12967 12955 Economic Project cost per kilowatt hour Yuan/kW·h 2.42 2.42 indexes Project cost per KWH for equivalent energy Yuan/kW·h 2.425 2.422 Total project cost difference million yuan -8.49

In terms of the energy indexes, the Paklay HPP has the same comprehensive efficiency and basically uniform energy indexes in both schemes. In terms of the project cost, quantity of the units increases to 14 sets from 13 sets, which slightly increases the excavation works for the powerhouse but slightly decreases the total weight of the units. In terms of the total project cost, the scheme involving 14 sets can save RMB 8.49 million compared to the scheme involving 13 sets, which has better economical efficiency. In terms of the manufacturing level and operational conditions of the units, the unit capacity and runner diameter in both scheme do not exceed those used for the units of the Jirau HPP (Brazil). However, the scheme involving 13 sets uses a runner diameter of 7.2 m and unit capacity of 59.23 MW, which is more difficult in unit manufacturing; the scheme involving 14 sets uses a runner diameter of 6.90 m and unit capacity of 55 MW, which has successful manufacturing and operating experience in China at present. Therefore, in terms 6- 10

of design and manufacturing difficulty of the units, the scheme involving 14 sets will be a better choice. Based on the comprehensive comparison, in this stage, it is recommended to adopt the scheme involving 14 units with the unit capacity of 55 MW for the Paklay HPP.

6.1.6 Unit Parameter of the Recommended Scheme

a) Turbine parameter recommended by manufacturers In this stage, technical communication has been made with the unit manufacturers; there are 3 manufacturers provide their preliminary technical schemes with the recommended turbine parameters as shown in Table 6.1-7.

Table 6.1-7 Turbine Technical Parameters Recommended by Host Equipment Manufacturers Manufacturer Manufacturer A Manufacturer B Manufacturer C Turbine Parameter Model GZ-WP-690 GZ-WP-690 GZ-WP-690 Rated output of turbine (MW) 56.4 56.4 56.4 Rated head (m) 14.5 14.5 14.5 Runner diameter (m) 6.90 6.90 6.90 Quantity of runner blade 4 4 4 Rated speed (r/min) 93.75 93.75 93.75 Rated discharge (m3/s) 420 424.23 417.7 Unit speed at rated point (r/min) 170 170 170 Unit discharge at rated point (m3/s) 2.32 2.34 2.304 Specific speed (m·kW) 787 787 787 Specific speed coefficient 2998 2998 2998 Efficiency at rated point (%) 94.8 93.9 94.92 Maximum efficiency (%) 95.8 95.33 96.19 Critical cavitation factor at rated 1.3 point Static suction head (to the unit -13.5 -14.5 -13.66 centerline) (m) Weight of turbine (t) 731.4 700 860

b) Runner diameter

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According to the unit discharge at the rated operating point (2.4 m3/s) and the parameters recommended by the manufacturers, in this stage, it is proposed to adopt a runner diameter of 6.9 m. c) Rated speed According to the unit speed at the rated operating point (170 r/min), the HPP has a calculated speed of 93.81 r/min. In this stage, it is proposed to select three synchronous speeds, including 88.24 r/min, 93.75 r/min and 100 r/min for comparison. The scheme involving 88.24 r/min has a corresponding specific speed of 741 m-kW and specific speed coefficient of 2820. The scheme involving 93.75 r/min has a corresponding specific speed of 787 m-kW and specific speed coefficient of 2998. The scheme involving 100 r/min has a corresponding specific speed of 839 m-kW and specific speed coefficient of 3196. According to the comparison, the scheme involving 93.75 r/min has a relatively suitable specific speed and specific speed coefficient. In addition, the rated speed of 93.75 r/min is adopted in the technical schemes provided by 3 manufacturers. According to the selected specific speed and unit parameter level and in view of the turbine parameters recommended by the manufacturers, in this stage, it is proposed to adopt the rated speed of 93.75 r/min for the turbines. Accordingly, the specific speed (ns) at the rated operating point shall be 787m·kW, the specific speed coefficient (K) shall be 2998, the unit discharge shall be 2.404 m3/s, and the unit speed shall be 170 r/min. d) Static suction head and setting elevation According to the selected cavitation factor and safety factor, the static suction head can be calculated by the rated head. In view of consulting results from the manufacturers, the HPP shall have a cavitation factor of 1.47, an allowable static suction head (to the vertex position of a runner blade of a turbine) of -11.61 m, and an allowable static suction head (to the turbine center) of -15.34 m. The design tail water level shall be the tail water level (whole plant in full operation) of 224.14 m a.s.l.; the setting elevation of the unit shall be 209.08 m a.s.l., rounded to 208.50 m a.s.l. in this stage.

e) Turbine parameter of the recommended scheme

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See Table 6.1-8 for main turbine parameters recommended.

Table 6.1-8 Main Turbine Parameters in Recommended Scheme Description Parameter Value Turbine model GZ-WP-690 Rated output of turbine (MW) 56.4 Maximum head/rated head/minimum head (m) 20/14.5/7.5 Runner diameter (m) 6.90 Rated speed (r/min) 93.75 Rated discharge (m3/s) 435.8 Unit speed at rated point (r/min) 170 Unit discharge at rated point (m3/s) 2.404 Specific speed under rated operating condition 787 (m·kW) Specific speed coefficient 2997 Efficiency at rated point (%) 91.0 Static suction head (calculated to the unit -15.34 centerline) (m) Setting elevation (m) 208.50 Weight of turbine (t) ~756

6.1.7 Governing System

The governing system of the units has an operating oil pressure of 6.3 MPa, and the DWST-150-6.3 model dual-regulating microcomputer electro-hydraulic governor is adopted. The counter weight is provided for accident shutdown. In case of accident, the governing system can adjust oil pressure through the relief valve of the counter weight and shut down the unit by the dead load of the counter weight. Type of the oil pressure unit is HYZ-15-6.3 and the pressure level is 6.3 MPa.

6.1.8 Design of Regulation Guarantee

a) Unit information The HPP adopts the tubular turbine-generator unit, with a runner diameter of 6.9 m, rated speed of 93.75 r/min, and runaway speed of 290 r/min. The moment of inertia of a generator is about 5,500 t m2; the moment of inertia of a turbine and water body is about 6- 13

2,500 t m2; the moment of inertia of the unit and water body is about 8,000 t·m2 in total; the inertia time constant of the unit is 3.42 s. b) Calculation control value for hydraulic transition process According to the relevant codes, in the HPP, the maximum speed rising rate of the units should be less than 65%; the guarantee value of the maximum pressure rising rate in front of a guide vane should be less than 70%~100%; during load dump, the maximum vacuum guarantee value at the draft tube inlet section shall not be greater than 0.07 MPa. c) Closure rule In this stage, the 6s linear closure law shall be used for calculation. After relevant parameters such as the unit manufacturing plant and turbine model characteristic curve are determined, recalculation for the hydraulic transition process shall be carried out. d) Calculation results and analysis of transition process In this stage, calculation only applies to the transition process with large fluctuation. The operating conditions of the rated load dump at the rated head and those at the maximum head shall be used for preliminary calculation. See the table below for the calculation results.

Table 6.1-9 Calculation Results of Transition Process Design Head Maximum Head Parameter Unit Operating Condition Operating Condition Pressure rising absolute value in mH2O 16.94 22.33 front of guide vane Pressure rising rate in front of % 53.8 70.9 guide vane

Pressure at draft tube inlet section mH2O -2.41 -4.39 Rising speed (β) % 65 50

According to the calculation results, the maximum pressure rising in front of the guide vane and the minimum pressure at the draft tube inlet section both occur at the rated load dump at the maximum head, with the maximum pressure rising rate in front of the guide vane of 70.9% and minimum pressure at the draft tube of -4.39 mH2O. The maximum speed rising occurs at the rated load dump at the rated head, with the maximum speed 6- 14

rising rate of 65%. All of above conditions meet the requirement for calculation control value for hydraulic transition process. e) Determination of design value for regulation guarantee For determination of design value for regulation guarantee, the calculation error and pressure fluctuation shall be used for correction based on the calculation value of hydraulic transition process. Based on the above calculations and corrections and characteristics of the HPP, the design values for regulation guarantee in accordance with the relevant codes and temporary provisions are as follows:

1) The maximum pressure in front of a guide vane is 58 mH2O;

2) The minimum hydrodynamic pressure at the draft tube inlet is -6 mH2O; 3) The maximum speed rising of the units is 65%. In this stage, it lacks of relevant parameters such as the characteristic curve of the units and the moment of inertia of the units and water body, the transition process is calculated by linear closure law based on relevant experience formulas. After relevant parameters such as the unit manufacturing plant and turbine model characteristic curve are determined, recalculation for the hydraulic transition process shall be carried out, in order to optimize the closure law. In this way, the design value for regulation guarantee of the HPP can meet requirements for safe and reliable operation.

6.1.9 Transport of Heavy Equipment

The heavy equipment consists of a main transformer, generator rotor, turbine runner, bridge crane girder and others. The main transformer and generator rotor are the key equipment in the transport control. See Table 6.1-10 for the transport characteristic values.

Table 6.1-10 Characteristic Values for Transport of Heavy Equipment Description of Weight of A Single Unit Qty. Transport Size (m) heavy-big piece Piece (t) Turbine hub Set 14 φ3.0x5.0 (D×H) 65

Inner guide ring Nr. 14 φ5.076×2.695m (D×H) 17.5

10.479×3.9×3.92 m (L× Enclosure Nr. 56 11 W×H)

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Rotor support Set 14 5.2x5.2x2.2 (L×W×H) 40

Bridge crane girder Pcs. 4 22.0x3.0x3.0 (L×W×H) 60

Main transformer Set 6 6.5x4x6.8 (L×W×H) 100

After dredging and channelized waterway works were carried out to the upstream basin of the Mekong River, the 71 km long waterway connecting the Jinghong Port with the China - Myanmar No. 243 boundary monument is Grade V, with a single-ship navigation capacity of 300 t ~ 500 t. The 331 km long waterway connecting the China - Myanmar No. 243 boundary monument with Houayxay section, Laos has a perennial navigation capacity of 200 t ~ 300 t ships, with a navigation period of 10 ~ 11 months. The section from Houayxay to Luang Prabang is an original river course with a length of about 300 km and navigation capacity of 150 t ships. The waterway at the lower reaches of

Luang Prabang has a relatively poor navigation capacity. There are two national trunk highways passing through the vicinity of the project site. One of them is the No. 11 highway from Vientiane, capital of Laos, to Pak Lay, and the other one is the No. 4 highway connecting the Luang Prabang City with Loei, Thailand. The above two highways meet each other in the Pak Lay Town. There is a rural road of about 20 km long connecting the Pak Lay Town to the dam site, in which a section of about 7 km long has been upgraded and reconstructed so that it can meet transport of large equipment. According to the site access conditions of the Project, it is preliminarily proposed that

M & E equipment and heavy-big piece will be transported to the Luang Prabanngd Port via water transport and then transported to the site via highway. Some equipment can be transported to the site directly via water transport.

6.1.10 Auxiliary Equipment of Hydraulic Machinery

6.1.10.1 Selection of hoisting equipment for powerhouse The largest heavy piece inside the powerhouse is the weight of rotor with shaft, with a hoisting weight of about 230 t. There are 14 units in the whole plant. Given that installation

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and maintenance will be simultaneously applied to 2 units as well as in view of turnover requirement of large equipment, 2 single-trolley electric double-beam bridge cranes (250 t/30 t/10 t) will be adopted, with the span of 21.0 m. Both bridge cranes are arranged in the same unit. The main hook has a hoisting height of 30 m while the secondary hook has a hoisting height of 40 m. 6.1.10.2 Cooling water supply system Service t water supply of the whole plant consists of cooling water for a generator air cooler, cooling water for a bearing, sealing water for a main shaft, cooling water for a water-cooled main transformer, lubricating water for a deep well pump, cleaning water, domestic water and others. The generator air cooler uses a closed circulation and secondary cooling water supply method. It is designed by the unit manufacturers and will not be included to the total amount of cooling water supply. According to the preliminary estimate, the water consumption for each part of the units is as follows: Cooling water for a bearing: 55m3/h Sealing water for a main shaft: 6m3/h Other main cooling water supply in the powerhouse is as follows: Cooling water for a main transformer: 50m3/h x 5 Utilities water: 25m3/h Total cooling water of the whole plant 1129 m3/h

The HPP is a low-head and run-of-river hydropower project, with a head range of 7.5 m ~ 20.0 m. According to different requirements for water quality and reliability of water source, the whole plant is equipped with a cooling water supply system and a cleaning water supply system. The cooling water supply system will supply cooling water for unit bearings, cooling water for main transformers, water for utilities, domestic water and others; meanwhile, it will serve as the standby water source for sealing of main shafts. The cooling water supply

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system takes its water source from the reservoir and drains the wastewater to the tail water. It adopts water supply by gravity flow in groups. In one group, 7 units and 3 main transformers will share 2 routes of intake pipelines in front of dam, standby for each other; in another group, 7 units and 2 main transformers will share 2 routes of intake pipelines in front of dam, standby for each other. Each route is provided with an automatic water filter and a spiral flow filter, with the design discharge of 600 m3/h. To ensure stable hydraulic pressure of the cooling water supply, the whole plant is provided with 2 pressure stabilizing pools with an effective volume of 100m3. The cleaning water supply system will supply cooling water for sealing of main shafts, water supplement for cooling expansion tank of air cooler, etc. The water source is upstream reservoir. The wastewater is discharged into the leakage water dewatering pit and then discharged into the downstream via a leakage drainage pump. Water supply by gravity flow in groups is adopted. Every 7 units shares 2 water intake pipelines in front of the dam, standby for each other. Each route is provided with an automatic accurate water filter and a spiral flow filter, a design discharge of 100 m3/h. To ensure water quality of sealing water for a main shaft, the water inlet pipe of the main shaft shall be equipped with an accurate water filter. See "Paklay-FS-EM-Machinery-01" for details of the Cooling water Supply System Drawing. 6.1.10.3 Dewatering and drainage system The dewatering and drainage system of the HPP consists of two parts, including a dewatering system for unit maintenance and a drainage system for the powerhouse leakage. a) Dewatering system It adopts an indirect dewatering mode. When a unit is under maintenance, accumulated water in the passage will be drained to the dewatering sump through the drainage gallery, and then drained to tail water by the deep well pump. One drain valve will be set at the lowest position of upstream and downstream

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passages in each unit bay. Steel pipes are embedded behind the valves and lead to the dewatering sump at the erection bay. A sealing head cover is provided on the top of the sump and an air vent is provided as well. The water to be discharged involves accumulated water to be drained in the inlet passage and outlet passage during maintenance. According to the preliminary calculation, quantity of the accumulated water in the passages is 6000 m3. During unit maintenance, the total water leakage through upstream and downstream gates is about 90 m3/h. Dewatering duration shall be calculated based on emptying accumulated water in 4 h ~ 5 h. The pump lift shall be sum of difference between the water level at shutdown of pump and downstream head and frictional loss in the pipeline. It adopts 4 deep well pumps with a pump discharge of 370 m3/h and head of 48 m. To drain out the settled sewage in the sump, 1 submersible sewage pump shall be set, with a discharge of 90 m3/h and head of 47 m. After the passages are completely drained out, the dewatering sump will be used for storing the leakage water from upstream and downstream gates, in order to make the drainage pump to continuously operate. The effective volume of the sump shall be 90 m3 based on the discharge obtained by a drainage pump operating for 15 min. For leakage water of the gates, a level controller is used for automatically controlling startup and shutdown of a drainage pump. A level transmitter is provided in the sump, leading to the central control room. b) Drainage system

Leakage water in the powerhouse mainly comes from leakage water of hydraulic structures in the powerhouse, cooling water for bearings and main transformers, sealing leakage water for main shafts, valve leakage water of each pipeline, cleaning water etc. By reference to the similar HPPs, powerhouse leakage water shall be 60 m3/h, and the maximum discharge for sealing water of main shafts shall be 84 m3/h. In view of other discharge in the powerhouse, the total discharge shall be 200 m3/h.

A drainage gallery throughout the whole plant is set under the passage base plate. All

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leakage water is drained to the drainage gallery through floor drains and vertical drain pipes. The leakage water flows into the leakage water dewatering sump by gravity and then be drained to the downstream tail water through deep well pumps. The capacity of the leakage water dewatering sump shall be calculated based on the total leakage water amount in the powerhouse within 37.5 min, with an effective volume of 100 m3. Four vertical deep well pumps are provided, 2 for use and 2 for standby. The pump discharge shall be calculated based on the effective volume of the emptying drainage sump in 20 min. The pump lift shall be determined based on sum of difference between the maximum tail water level and the water level at shutdown of pump and the frictional loss. The pump discharge is finally determined as 370 m3/h, with a pump lift of 54 m. Startup or shutdown of a drainage pumps is automatically controlled by a level controller. A level transmitter is provided in the sump, leading to the central control room. To drain out the settled sewage in the sump, 1 submersible sewage pump shall be set, with a discharge of 90 m3/h and head of 47 m. See "Paklay-FS-EM-Machinery-02" for Drawing of Dewatering and Drainage System. 6.1.10.4 Compressed air system The compressed air system of the HPP consists of a powerhouse mediate-pressure (MP) compressed air system and a powerhouse low-pressure (LP) compressed air system. a) Powerhouse MP compressed air system

The MP compressed air system is used for air inflation into a pressure oil tank after installation or maintenance of a pressure oil supply unit in the governing system and for supplement of air consumption in the pressure oil tank during operation. Rated oil pressure of the pressure oil supply unit in the HPP is 6.3 MPa. Air supply under first-stage pressure is adopted in the design. Air supply of pressure oil tank is carried out via pipelines. The production rate of a MP air compressor shall be determined based on air inflation capacity and duration of the pressure oil tank. Three MP air compressors are selected, with

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an air displacement of 1000 L/min and a working pressure of 8.0 MPa. Among them, 2 are used as the main air compressors and 1 is used for standby. The compressed air silo volume shall be determined based on the air supplement quantity required by oil level rising of 150 mm ~ 250 mm in the pressure oil tank. According to calculations and by reference to the similar HPPs, it is determined that 2 x 3.0m3 compressed air silos with a pressure of 8.0 MPa will be adopted. b) Powerhouse LP compressed air system The LP compressed air system of the HPP is 0.7 MPa. The LP compressed air system supplies air for unit braking, maintenance, purging air, air shroud, etc. Because the HPP has many units, an air supply system for brake and main shaft sealing and a maintenance air supply system are provided in the whole plant, in order to prevent each part requiring air supply of the LP compressed air system from interacting with each other. A non-return valve is set between the above two systems; the maintenance air supply system can supply air to the air supply system for brake and main shaft sealing. According to the main electrical connection mode, the air supply system for brake and main shaft sealing is configured as follows: 3 units shall brake simultaneously; duration for restoration of operating pressure of a compressed air silo shall be 10 min; 2 LP air compressors with an air discharge of 1.4 m3/min and operating pressure of 0.85 MP and 2 x 5.0 m3 compressed air silos with a pressure of 0.8 MPa shall be provided. Configuration of the maintenance air supply system shall be that 2 air compressors simultaneously operate to meet requirement of the maximum air demand for maintenance.

By reference to the similar HPPs, the configuration details shall be as follows: 2 LP air compressors with an air discharge of 10.0 m3/min and operating pressure of 0.85 MPa and 1 x 5.0 m3 compressed air silo with a pressure of 0.8 MPa shall be provided. In addition, another 1 portable air compressor with an air discharge of 0.28 m3/ min and operating pressure of 0.7 MPa will be provided as well. Each air compressor of the MP and LP compressed air systems in the powerhouse will automatically control startup and shutdown of the air compressors based on the pressure

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settings. A safety valve and pressure signal controller will be installed on the compressed air silo. See "Paklay-FS-EM-Machinery-03" for Drawing of MP and LP Compressed Air Systems in the Powerhouse. 6.1.10.5 Oil system It consists of a turbine oil system and an insulating oil system. a) Turbine oil system The turbine oil system mainly supplies unit lubricating oil and mechanical hydraulic oil. Based on estimation, the maximum oil consumption of 1 unit is 30.4 m3. According to requirements of relevant codes and HPP operation, 2 x 20 m3 uncontaminated oil tanks and 2 x 20 m3 operating oil tanks shall be provided. Each oil pump shall have a capacity of filling up oil for 1 unit within 5 h. Two gear oil pumps (2CY-6/3.3-1) shall be adopted, with an oil delivery quantity of 6 m3/h and the maximum operating pressure of 0.33 MPa. The oil treatment equipment shall have a capacity of filtering oil for 1 unit within 8 h. One pressure oil filter (LY-100) with production rate of 100 L/min shall be adopted. In addition, 1 turbine oil filter (ZJCQ-4) with production rate of 4,000 L/h and operating vacuum (P) not greater than 3,500 Pa shall be adopted. b) Insulating oil system It mainly supplies cooling oil for main transformers. Based on estimation, the maximum oil consumption of 1 main transformer is 56 m3. According to requirements of relevant codes and HPP operation, 2 x 35 m3 uncontaminated oil tanks and 2 x 35 m3 operating oil tanks shall be provided. Each oil pump shall have a capacity of filling up oil for 1 unit within 6 h. Two gear oil pumps (2CY-12/3.3-1) shall be adopted, with an oil delivery quantity of 12 m3/h and the maximum operating pressure of 0.33 MPa. The oil treatment equipment shall have a capacity of filtering oil for 1 unit within 24 h. One pressure oil filter (LY-100) with production rate of 100 L/min shall be adopted. In

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addition, 1 vacuum oil-filter (ZJB-3KY) with production rate of 3,000 L/h and operating vacuum (P) not greater than 0.5MPa shall be adopted.

See "Paklay-FS-EM-Machinery-04" for Drawing of Oil System 6.1.10.6 Hydraulic monitoring system Configuration of the hydraulic monitoring system shall meet requirements for safe, reliable and economic operation, automatic control and test measurement of a turbine-generator unit. It consists of two parts, including plant monitoring and unit bay monitoring. The plant monitoring includes upstream/downstream water level, HPP gross head and reservoir water temperature. The unit bay monitoring includes the following items: trash rack differential pressure, pressure balancing on both sides of the intake gate and draft tube gate, passage inlet pressure, draft tube outlet pressure, operating head, unit discharge, pressure in front of guide vane, runner chamber pressure, vibration and throw of units etc. See "Paklay-FS-EM-Machinery-05" for Drawing of Hydraulic Measuring System. 6.1.10.7 Layout of main hydraulic mechanical equipment The HPP powerhouse lies at the left bank, including a powerhouse (comprising a host equipment section and an erection bay) and auxiliary plant. The powerhouse has a total length of 400.0 m, in which the host equipment section is 301.0 m long. Because the HPP has many units, 2 erection bays are provided. The main erection bay is 52.0 m long, arranged at the left side of the powerhouse; the auxiliary erection bay is 41.0 m long, arranged at the right side of the powerhouse. Area of the erection bays can meet erection progress that 2 units can be put into operation every 3 months. According to the head cover of unit passage, turbine lifting holes and equipment layout, the powerhouse has a clear width of 21.0 m. Units have a setting elevation of 208.5 m a.s.l. and the ground elevation of the host equipment floor and auxiliary erection bay is 222.5 m a.s.l.; according to flood control

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requirement of the powerhouse access road, the main erection bay has a ground elevation of 228.5 m a.s.l.; according to turnover requirement for the largest equipment and outer gate barrel, a crane has a track top elevation of 240.5 m a.s.l. The air delivery conduit of the powerhouse is arranged inside the head bay wall of the powerhouse. The oil-water-air pipeline and the air compressor room are arranged on the hydraulic mechanical equipment floor at an elevation of 222.50 m a.s.l. in the downstream auxiliary plant; the governor and oil pressure unit are arranged in the upstream first quadrant of the host equipment floor of an elevation of 222.5 m a.s.l. in the powerhouse. The drainage pump house and dewatering pump house are arranged in the auxiliary plant at an elevation of 216.5 m a.s.l. below the erection bay of the powerhouse. The turbine oil storage room and its oil treatment room as well as the insulating oil storage room and its oil treatment room are arranged in the auxiliary plant of an elevation of 216.5 m a.s.l. at the lower position of the auxiliary erection bay. The insulating oil depot and the oil treatment room are arranged in the auxiliary plant at an elevation of 228.50 at the downstream side of the powerhouse. The instruments and pressure balancing pipeline of draft tube gate are arranged in the downstream auxiliary plant of an elevation of 219.0 m a.s.l.

6.1.11 List of Main Hydraulic Mechanical Equipment

See Table 6.1-10 for main hydraulic mechanical equipment.

Table 6.1-10 Main Hydraulic Mechanical Equipment. Model, Specification and S/N Description Unit Qty. Remarks Parameter GZ-WP-690, Hr=14.5m, 1 Turbine N=56.4MW, Set 14

nr=93.75r/min, D1=6.9m 2 Governor DWST-150-6.3 Set 14 3 Oil pressure unit HYZ-15-6.3 Set 14 4 Crane 250t/30t/10t, span of 4.1 Single-trolley bridge crane Set 2 Powerhouse 21.0 m

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4.2 Single-trolley bridge crane 10t, span of 14.4 m Set 1 500kV GIS room 5 Cooling water supply system 5.1 Vertical centrifugal pump Q=600m3/h, H=20m Set 4 N=55kW DN350, Q=600m3/h, 5.2 Full-automatic water filter Set 4 PN1.0 MPa 5.3 Water treatment equipment Q=10m3/h Set 4 5.4 Pump control valve DN350, PN1.0 MPa Set 4 DN350, Q=600m3/h, 5.5 Hydrocyclone Set 4 PN1.0 MPa 6 Unit dewatering system and powerhouse drainage system Q=370 m3/h, H=48 m, 6.1 Deep well pump Set 4 Dewatering N=75 kW Q=370 m3/h, H=48 m, 6.2 Deep well pump Set 4 Drainage N=75 kW 6.3 Submersible sewage pump Q=90 m3/h, H=47 m Set 2 6.4 Piezoresistive level transmitter Set 2 6.5 Ball float type level transmitter Set 2 7 MP/LP compressed air system Q=1.0 m3/min P=8.0 7.1 MP air compressor Set 3 N=11kW MPa 7.2 MP compressed air silo V=3.0 m3 P=8.0 MPa Set 2 7.3 MP freezer dryer 8MPpa Set 3 Pressure-reducing-stabilizing DN40 P=8.0MPa/ 7.4 Set 1 valve 7.0MPa Q=10.0 m3/min P=0.85 7.5 LP air compressor Set 2 N=55kW MPa Q=1.4 m3/min P=0.85 7.6 LP air compressor Set 2 N=11kW MPa 7.7 LP compressed air silo V=5.0 m3 P=0.8 MPa Set 3 Q = 0.28 m3/ min P = 7.8 Portable air compressor Set 1 N=2.2kW 0.7 MPa 7.9 LP freezer dryer 0.8MPa Set 2 8 Oil system 8.1 Indoor oil tank 20m3 Nr. 4 Turbine oil system 2CY6/3.3-1 Q=6 m3/h 8.2 Gear oil pump Set 2 Turbine oil system H=0.32 MPa N=3kW

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LY-100 Q=100 L/min 8.3 Pressure oil filter Set 2 Turbine oil system N=2.2kW ZJCQ-4 Q=4000 L/h, 8.4 Turbine oil filter P≤0.33 MPa Set 1 Turbine oil system N=30.49kW Insulating oil 8.5 Indoor oil tank 35m3 Nr. 4 system 2CY12/3.3-1 Q=12 m3/h Insulating oil 8.6 Gear oil pump Set 2 H=0.33 MPa N=4kW system LY-100 Q=100 L/min Insulating oil 8.7 Pressure oil filter Set 2 N=2.2kW system ZJA-3KY Q=3000 L/h, Insulating oil 8.8 Two-stage high-vacuum oil filter P≤0.5 MPa Set 1 system N=52.35kW 8.9 Filter paper oven 1kW Set 2 9 Hydraulic measurement system For measuring Measuring range: 0 m ~ 9.1 Water-level gauge Pcs. 2 water level at upper 30 m and lower reaches For measuring Measuring range: 0°C ~ 9.2 Deep water thermometer Pcs. 1 reservoir water 40°C temperature Measuring range: 0 MPa 9.3 Pressure transmitter Pcs. 98 ~ 0.6 MPa Measuring range: -0.1 9.4 Vacuum pressure transmitter Pcs. 48 MPa ~ 0.6 MPa 9.5 Oscillatory pressure transmitter Pcs. 32 For measuring 9.6 Differential pressure transmitter Pcs. 81 gross head and available head 9.10 Manometer YB-150, PN0~0.6 MPa Set 104 YZ-150, 9.11 Vacuum manometer Set 48 PN-0.1~0.6MPa For measuring Measuring equipment for 9.12 Set 16 vibration and throw vibration and throw of units of units 10 "Machine maintenance equipment shall be determined via negotiation with the Employer in the

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future.

6.2 Main Electric Equipment and Main Electrical Connection

6.2.1 Design of Grid Connection

6.2.1.1 Power Supply Range The Paklay Hydropower Project (HPP) is located in Laos, which lies in the north of Indo-China Peninsula, bordered by China on the north, Cambodia on the south, Vietnam on the east, Myanmar and Thailand on the northwest and southwest respectively. The national territorial area of Laos is 236.8 x 103 km2. Mountains and plateaus account for 80% and most of them are covered by forests. Currently, the population in Laos is about 6 million. Laos' economy is dominated by its agriculture, its industrial base is weak, and its economic development level is backward. Since 1988, Laos has gradually completed its market economic system via implementation of reform and opening policies, improvement of investment environment, and adjustment of economic structure. In addition, its economic society has developed rapidly. In 2010, Laos' GNP was USD 5.97 billion with a year-on-year growth of 7.9%, and the GDP per capita was nearly USD 1,000. Although the level of national economy and social development in Laos has been improved dramatically in recent years, the power demand in Laos is still not large. Laos enjoys very rich hydropower resources. According to relevant planning results from the electric power department in Laos, even without the hydropower resources of main stream of the Mekong River, the available hydropower resources in Laos still reach 18,000 MW. In addition to 5 HPPs, including Pak Beng HPP, Luang Prabang HPP, Xayaboury HPP, Paklay HPP and Sanakham HPP, planned on the main stream of the Mekong River, the total available hydropower resources in Laos are more than 23,000 MW.

In recent years, with the increase of investments from China, Japan, Thailand and other countries in Laos' hydropower projects, the hydropower development in Laos has entered an unprecedented development stage. In the next decade, the installed capacity of hydropower to be put into operation in Laos is expected to be millions kilowatts. The power demand in Laos cannot consume such rich electrical energy. Therefore, Laos' electric power will mainly be exported to countries with more developed economy, such as China and Thailand.

Laos is located in the middle of Southeast Asian countries and bordered by China, 6- 27

Myanmar, Thailand, Cambodia and Vietnam. Geographically, it has advantages in electric power export. According to the relevant planning results, the Lao Government plans to export about 8,000 MW of electric power to its neighbors in 2020. The main object of electric power export is Thailand. The Lao Government signed a memorandum of understanding on power cooperation with the Thai Government in December, 2007. Both parties agreed that 3,000 MW ~ 5,000 MW of electric power will be supplied from Laos to Thailand before 2015, and 5,000 MW ~ 7,000 MW of electric power after 2015.

The Paklay HPP is about 50 km away from the borderline of Thailand in a straight-line distance, so it has geographical advantages in electric power export to Thailand. In view of the analysis results of electricity market space in Thailand, in 2020, the electricity market space in Thailand will be large enough to consume the electric power delivered from the Paklay HPP. Therefore, Thailand is within the power supply range of the Paklay HPP.

6.2.1.2 Scheme of Grid Connection The Paklay HPP has an installed capacity of 14 × 55 MW and a total installed capacity of 770 MW. For the HPP, it is proposed to connect 2 circuits of 500 kV transmission lines with a conductor cross-section of LGJ-4×300 to the 500 kV combined switchyard owned by Laos and located at the Laos ~ Thailand border. Electric power from Laos will be delivered to Thailand through the combined switchyard. See Fig. 6.2.1-1 for the connection diagram of Laos power grid in terms of geographical location in 2020.

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Fig. 6.2.1-1 Connection Diagram of Laos Power Grid in Terms of Geographical Location In 2020

6.2.2 Main Electrical Connection

The main electrical connection shall be safe, reliable, flexible and economical. The specific design principle is as follows: (1) Safe and reliable power supply Because the 500 kV transmission line plays an important role in the electric power system, it is required to employ a main electrical connection scheme of which the power supply has high reliability. (2) Flexible operation, convenient maintenance, and easy startup and shutdown In the design of main electrical connection, frequent operation of HPP shall be fully taken into account. When the operation mode changes, startup and shutdown operations shall be as easy as possible and such operations shall not affect the continuous operation of the station service system and other elements.

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(3) Easy connection, convenient transition, and compact and clear arrangement The main electrical connection shall be easy and reliable as far as possible. The quantity of elements in the main electrical connection shall be as less as possible, and the arrangement of these elements shall be compact and clear, in favor of operation monitoring, maintenance and accident handling. Staged transition shall not cause great changes in the arrangement of electrical equipment or secondary circuit; in addition, the staged transition shall be in favor of extension. (4) Simple and reliable relay protection and control (5) Advanced technology and rational economic efficiency In model selection of equipment, electrical equipment with mature and advanced technology shall be adopted as far as possible to minimize the investment and loss of electric energy as long as the reliability of main electrical connection can be guaranteed.

6.2.2.1 Combination Mode of Generator and Main Transformer In view of operating characteristics, quantity of units and unit capacity of the HPP, role of the HPP played in the power system, design requirement and transport conditions related to connection of the HPP to the electric system, the combination mode of generators and main transformers shall be one of the following three schemes for technical and economic comparison. Combination mode of generators and main transformers are as follows:

a) Scheme 1: Single-bus circuit breaker sectionalized connection of multi-generator-transformer unit

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Figure 6.2.2-1 Single-bus Circuit Breaker Sectionalized Connection of Multi-Generator-Transformer Unit Four generators and two main transformers are connected to form a single-bus sectionalized circuit-breaker connection. This mode of connection is simple and distinct, with flexible operation and easy protective relaying and control loop. In case any section of a bus (or any one of main transformers) fails or is under maintenance, only 2 generators will be affected, with a small shutdown range and high reliability. Disadvantages of the scheme are as follows: ① Quantity of incoming lines at the 500 kV side is large and switch quantity required by the HV side is large, which increases investment on the 500 kV switch apparatuses; ② Quantity of main transformers is large, which increases investment on the main transformers. ③ To meet requirements for economic-type generator circuit breaker (GCB with the rated short-circuit breaking current below 80kA), the section circuit breakers need to be connected with current limiting reactors in series, which increases electric energy loss and equipment failure rate. ④ Generator switchgear installation has many elements, which increases equipment investment and maintenance works.

6- 31 Paklay Hydropower Project Feasibility Study Report

b) Scheme 2: connection of multi-generator-transformer unit - united generator-transformer unit

Figure 6.2.2-2 Connection of Multi-Generator-Transformer Unit - United Generator-Transformer Unit Four generators and two main transformers are respectively connected to form connection of two multi-generator-transformer units; the two expanded unit connections are in parallel connected with each other at the HV side of the main transformers to form connection of one multi-generator-transformer unit - united generator-transformer unit. Compared with the scheme 1, advantages of the scheme are as follows: ① Quantity of incoming lines at the 500 kV side is less and switch quantity required by the HV side is less, which decreases investment on the 500 kV switch apparatuses. ② Rated short-circuit breaking current (≯80kA) can easily meets the demands, no additional current limiting reactors are required, which decreases electric energy loss and equipment failure rate. Disadvantages are as follows: in case the bus of united generator-transformer unit fails or is under maintenance, capacity of 4 generators will be impacted; therefore, the impact scope is larger; operation flexibility and manipulation convenience both are poorer than those in scheme 1.

c) Scheme 3: connection of multi-generator-transformer unit

6- 32 Paklay Hydropower Project Feasibility Study Report

Figure 6.2.2-3 Connection of Multi-Generator-Transformer Unit Three generators and one main transformers are connected to form one connection of multi-generator-transformer unit. Compared with the scheme 1, advantages of the scheme are as follows: ① Quantity of incoming lines at the 500 kV side is less and switch quantity required by the HV side is less, which decreases investment on the 500 kV switch apparatuses. ② Generator switchgear installation has less elements, which increases equipment investment and maintenance works. ③ Rated short-circuit breaking current (≯80kA) of the generator circuit breaker can easily meets the demands, no additional current limiting reactors are required, which decreases electric energy loss and equipment failure rate. ④ Quantity of main transformers is less, which decreases investment on the main transformers. Disadvantages are as follows: in case the main transformer fails or is under maintenance, capacity of 3 units will be impacted; therefore, the impact scope is larger; operation flexibility and manipulation convenience both are poorer than those in scheme 1.

Compared with the scheme 2, advantage is that this connection mode requires less main transformer, which reduces investment on the main transformer. Disadvantage is that quantity of incoming lines at the 500 kV side is large and switch quantity required by the HV side is large, which increases investment on the 500 kV switch apparatuses. d) Techno-economic comparison

See Table 6.2.2-1 for the summary of techno-economic comparison between different combination modes of generator-main transformer. Table 6.2.2-1 Summary for Technical Comparison Between Different Combination 6- 33 Paklay Hydropower Project Feasibility Study Report

Modes of Generator-Main Transformer

Sectionalize Multi-United S/ Multi-generator-transforme Item d Single-bus Generator-Transforme N r Unit Connection Connection r Unit Connection

Quantity of

1 main 7 7 5 transformer

Quantity of

2 current-limitin 3 / / g reactor

Quantity of incoming 3 7 4 5 circuit at the 500 kV side

Investment in

4 electrical Maximum Large Small equipment

In case of In case of failure or In case of failure or failure or maintenance of a bus maintenance of main maintenance in the united transformer, the capacity of

of any bus generator-transformer 3 units will be restricted section (any unit connection at the and the influence is Reliable power 5 main HV side of main relatively small. supply transformer), transformer, the the capacity capacity of 4 units of 2 units will be restricted and will be the influence is restricted relatively large.

6- 34 Paklay Hydropower Project Feasibility Study Report

and the influence is smallest.

Operation 6 Best Poor Good flexibility

e) Conclusion According to the above technical and economic analysis, the scheme 3 has advantages of high reliability, relatively flexible operation, convenient repair and maintenance. In addition, this scheme requires less incoming lines at the 500 kV side and less main transformers; therefore, it is also better in terms of cost. To sum up, the combination mode of generators and main transformers shall be the scheme 3; namely, the connection of multi-generator-transformer unit with 3 generators and 1 main transformer.

6.2.2.2 Electrical connection at 500 kV The 500 kV switchyard of the HPP has 5 incoming circuits and 2 outgoing circuits, according to the quantity of 500 kV outgoing circuit proposed for the HPP and the recommended scheme for the combination mode of generator and main transformer (multi-generator-transformer unit connection). The following 3 connection options are preliminarily proposed for techno-economic comparison:

Figure 6.2.2-4 Dual-bus Connection

6- 35 Paklay Hydropower Project Feasibility Study Report

Figure 6.2.2-5 3/2 Circuit Breaker Connection + Dual Circuit Breaker Connection

Figure 6.2.2-6 Single-bus Sectionalized Connection

a) Scheme 1: dual-bus connection The dual-bus connection mode has distinct connection; each incoming and outgoing line will be connected to one group of circuit breakers respectively, free from mutual impact. In case one group of bus and relevant equipment connected fail, switch over the circuit connected with the failed bus to another group of bus and then power can be supplies again, without any influence on the other group of bus; therefore, this mode has relatively high flexibility. According to line load conditions, switchover of two groups of bus can basically balance the load distribution on two groups of bus. Switch quantity in this mode is less than that required by 3/2 connection mode, which decreases equipment investment. 6- 36 Paklay Hydropower Project Feasibility Study Report

Disadvantages are as follows: transfer switching operation of the isolators is very complicated; in this scheme, in case any one of elements on the bus fails, all elements on the bus have to be removed; when a bus tie circuit breaker fails, power failure will be applied to the whole plant in short time.

b) Scheme 2: 3/2 circuit breaker connection + dual circuit breaker connection The mode of 3/2 circuit breaker connection + dual circuit breaker connection has high reliability in power supply. Each incoming and outgoing line will be connected to two groups of circuit breakers respectively. In case a line or a main transformer fails, the failed element will be deactivated by transfer switching operation and then power supply in other circuits can be guaranteed. In case any groups of bus or a circuit breaker is under maintenance, the relevant circuit needs no switchover and operation of isolator is not frequent, which decreases possibility of misoperation, convenient for operation and maintenance.

Disadvantages are as follows: protective relaying and control loop are relatively complicated; switch quantity required is more than that in the scheme of dual-bus connection, which increases equipment investment.

c) Scheme 3: single-bus sectionalized connection This mode has simple and distinct connection, with 7 groups of circuit breakers, simple protective relaying configuration and secondary connection, and distinct equipment layout. Each incoming and outgoing line will be connected to 1 group of circuit breakers. In case a main transformer fails, other circuits can properly operate. This mode has flexible operation and convenient manipulation, which can meet all operating conditions of the HPP. It is convenient for putting in operation in stages for transition and further expansion. It has the minimum investment in equipment.

Disadvantages are as follows: in case any one circuit of circuit breakers is under maintenance or fails, power failure has to be applied to the relevant connected circuit; in case a bus tie circuit breaker fails or is under maintenance, a short-time shutdown has to be applied to the whole plant. d) Techno-economic comparison

See Table 6.2.2-2 for the techno-economic comparison between each connection

6- 37 Paklay Hydropower Project Feasibility Study Report option at the 500 kV side. Table 6.2.2-2 Techno-Economic Comparison Between Each Connection Option at the 500 kV Side

Option 3: Option 1: Option 2: 3/2 Sectionalized Item Name Double-bus Connection Single-bus Connection Connection

Connection diagram

Quantity of circuit breaker/disconnectin 8/23 11/29 8/16 g switch

Investment in Large Maximum Small electrical equipment

Each circuit is Each circuit is Each circuit is respectively respectively respectively connected with 1 connected with 2 connected with 1 group of circuits. groups of circuit group of circuit

Normal operation is breakers. Normal breakers. Normal

Operation carried out by a operation is carried operation is circuit breaker; in out by a circuit carried out by a

addition to breaker, and a circuit breaker, maintenance and disconnecting switch and a isolation, a is only used for disconnecting disconnecting switch maintenance and switch is only

6- 38 Paklay Hydropower Project Feasibility Study Report

is also used for isolation. Therefore, used for transfer switching; operation in this maintenance and therefore, operation option is relatively isolation. in this option is simple. Therefore, complex. operation in this option is simple.

This option needs This option needs This option needs many circuit many circuit breakers a few of circuit breakers and and disconnecting breakers and

Arrangement disconnecting switches, so the disconnecting switches, so the arrangement is switches, so the arrangement is complex. arrangement is relatively complex. simple.

Reliable power supply:

In case of failure or In case of failure or In case of failure maintenance of one maintenance of any or maintenance of group of bus and bus and equipment one bus section equipment connected connected with the and equipment with the bus, power bus, and in case of connected with supply of another maintenance of any the bus section, Safe power supply bus will not be circuit breaker, power supply of

influenced. After the normal power supply another bus circuit connected of any circuit will not section will not be with the failed bus is be influenced. influenced but 1/2 switched over to of the plant another group of bus, capacity will be power restoration is restricted. achieved.

6- 39 Paklay Hydropower Project Feasibility Study Report

Affected range of power cut:

In case of In case of failure of In case of maintenance of a circuit breaker at each maintenance of a circuit breaker at any circuit connected with circuit breaker at incoming or a bus, only short-time any incoming or outgoing circuit, power supply of the outgoing circuit, power cut will only circuit subjected to power cut will be carried out for the the failure will be only be carried out circuit under influenced. In case of for the circuit maintenance and failure of under other power supply interconnection maintenance and circuit will work circuit breaker other power properly. In case of between two circuits, supply circuit will failure of bus tie only short-time power work properly. In circuit breaker, supply of these two case of failure of power cut is required circuits will be sectionalized to be carried out for influenced. circuit breaker, the whole plant, and power cut is power restoration required to be will be conducted carried out for the after the failure is whole plant, and eliminated. power restoration will be conducted

after the failure is eliminated.

Probability for power cut of whole plant:

In case of this Power cut of whole When a bus tie option, the plant will not occur in circuit breaker

6- 40 Paklay Hydropower Project Feasibility Study Report

probability for power the following fails, power cut cut of whole plant is conditions: a circuit will be carried out small. fails when one bus is for the whole under maintenance (in plant. the single-bus operation mode) and the circuit breaker fails to operate; a bus fails in the single-bus operation mode; two buses fail at the same time in the double-bus operation mode.

Relay protection and Relay protection and Relay protection control circuit are control circuit are and control circuit Relay protection both complex, not in relatively complex. are both simple. favor of automation or telemechanization.

e) Conclusion According to the above technical and economic comparison, the scheme 1 has relatively lower investment and flexible operation but its operation and manipulation are relatively complicated; the scheme 2 has high reliability but its investment is relatively higher. The scheme 3 has the lowest investment but its reliability is the poorest. In view of the installed capacity of the HPP and the role and function of the HPP in Thailand power grid, it is recommended to adopt the scheme 1 for connection at the 500 kV HV side; namely, the dual-bus connection mode at the 500 kV side.

6.2.3 Station Service System and Power Supply System at Dam Area

6- 41 Paklay Hydropower Project Feasibility Study Report

6.2.3.1 Features of Station Service System and Power Supply System at Dam Area ⑴ The range of power supply is wide, load points are decentralized, and the farthest power supply point is about 1.0 km ~ 2 km away. ⑵ Power supply loads are large and the maximum station service load is about 8,000 kVA. 6.2.3.2 Design Principle Because the HPP plays an important role in the electric power system, the station service system of the HPP is required to have high reliability of power supply. According to Code for Designing Auxiliary Power System of Hydro-power Station (NB/T35044-2014) and Electrical-mechanical Design Code of Hydropower Plant (DL/T5186-2004), the design principle for the service power of plant of the HPP is as follows: a) Arrangement principle for station service power supply When all units are under operation, at least 3 station service power supplies shall be provided. When only some units are under operation, at least 2 station service power supplies shall be provided. When all units are shut down, at least 2 reliable power supplies shall be provided but one of them is allowed to stand by. b) Selection principle for voltage class of service power of plant Loss of electric energy and equipment investment shall be reduced as far as possible, while considerations shall be given to the voltage class of station service motor with a large capacity. c) Design principle for station service connection:

⑴ The connection shall meet the requirements for sectionalized power supply of each load center. ⑵ The connection shall be as simple as possible, in favor of relay protection system used for service power of plant and spare power source automatic switch. ⑶ The connection shall meet the power supply requirements in staged construction or continuous construction and shall be convenient for transition.

⑷ The common power system of the whole plant and the auxiliary power supply

6- 42 Paklay Hydropower Project Feasibility Study Report system of units shall be fed separately. The auxiliary power supplies of units shall be independent, so that frequent startup or shutdown of units will not influence the continuous power supply of the common power system of the whole plant, in favor of rapid power restoration. ⑸ The connection shall meet the power supply requirements for startup and shutdown of units. Switching operation for service power of plant shall be reduced as far as possible. ⑹ The lighting power supply system shall be equipped with a lighting transformer independently. ⑺ In view of flood control by the dam, a diesel generator unit shall be arranged on the dam crest as the safety emergency power supply when the dam is used for flood releasing. ⑻ The powerhouse shall be equipped with a diesel generator unit as the safety emergency power supply of the HPP powerhouse, to prevent the powerhouse from inundation. 6.2.3.3 Leading of Station Service Power Supply According to Article 3.1.1 of Code for Designing Auxiliary Power System of Hydro-power Station (NB/T35044-2014), the leading mode and arrangement of the working power supply used for the service power of plant shall meet the requirement of "When the voltage circuit of generator is equipped with a generator circuit breaker, the working power supply used for service power of plant shall be arranged between the generator circuit breaker and the LV side of main transformer" in Paragraph 4. Because all units of the HPP are equipped with a generator circuit breaker, the station service power supply shall be arranged at the LV side of main transformer. Normally, the units will feed the service power of plant. In case of shutdown, the electric power system can reversely feed the service power of plant. This scheme is characterized by highly reliable power supply, simple connection, convenient arrangement, and good economic efficiency.

Therefore, it can be applied to the main power supply used for service power of plant of

6- 43 Paklay Hydropower Project Feasibility Study Report the HPP. Because the HPP is a Grade I large (1) scale HPP, an external power supply shall be arranged and used as the spare station service power supply, so as to improve the reliability and continuity of the service power of plant. For the HPP, the external power supply can be provided as follows: Mode 1: The service power of plant can be supplied reversely from the electric power system through the main transformer. Mode 2: A diesel generator unit shall be arranged. Therefore, the leading scheme for station service power supply is as follows: The whole plant is equipped with 4 HV station service transformers, and the main power supplies used for service power of plant are respectively led from the LV sides of main transformers TM1~TM4. For the spare station service power supply, in addition to reverse power transmission from the electric power system through main transformers, 1 diesel generator unit is respectively arranged on the dam crest and in the powerhouse, serving as the safety emergency power supply for flood releasing by dam and the safety emergency power supply of powerhouse.

6.2.3.4 Voltage Selection for Service Power of Plant The HPP is of a water-retaining type powerhouse on the ground. Because the plant area is relatively large, the power transmission distance is relatively long, and the load capacity is relatively large, the station service system shall be of the two-stage voltage power supply. According to the design principle specified in Article 3.2.2 of Code for Designing Auxiliary Power System of Hydro-power Station (NB/T35044-2014) that "The HV service power voltage should be 10 kV and the LV service power voltage should be 0.4 kV" and Article 3.3 that "According to Code for Design of AC Electrical Installations Earthing (GB/T 50065), the grounding mode of LV station service system should be of the TN-S or TN-C-S system", the station service system of the HPP shall be of the two-stage voltage power supply (10 kV and 0.4 kV), the LV distribution system shall be of the three-phase four-wire system, and the neutral point shall be directly grounded.

6.2.3.5 Connection mode for station service power The Paklay HPP respectively supplies power to the unit service power, common power demand of plant and lighting power. Connection mode for station service power 6- 44 Paklay Hydropower Project Feasibility Study Report adopts single-bus sectionalized connection. a) Power supply mode at 10.5 kV voltage level The bus at 10.5 kV voltage level of the station service power consists of 4 sections, in 2 groups. Bus sections ① and ② constitute 1 group while sections ③ and ④ constitute another 1 group. The THA1 HV station service transformer connected to the LV side of the TM1 main transformer supplies power to the bus section ① . The THA2 HV station service transformer connected to the LV side of the TM2 main transformer supplies power to the bus section ② . A bus tie switch is set for the bus sections ① and ② . The THA3 HV station service transformer connected to the LV side of the TM3 main transformer supplies power to the bus section ③ . The THA4 HV station service transformer connected to the LV side of the TM4 main transformer supplies power to the bus section ④ . A bus tie switch is set for the bus sections ③ and ④ .

During normal operation, 4 HV station service transformers will respectively supply power to operate the station service loads in the whole plant. In case any one section of bus in the bus sections ① and ② loses its voltage, automatic bus transfer equipment will automatically operate via the bus tie switch and then 1 HV station service transformer will drive the bus sections ① and ② for operation. In case any one section of bus in the bus sections ③ and ④ loses its voltage, automatic bus transfer equipment will automatically operate via the bus tie switch and then 1 HV station service transformer will drive the bus sections ③ and ④ for operation.

See Fig. 6.2.3-1 for the schematic diagram of HV station service connection.

Fig. 6.2.3-1 Schematic Diagram of HV Station Service Connection 6- 45 Paklay Hydropower Project Feasibility Study Report

b) Power supply mode at 0.4 kV voltage level 1) Common power system of whole plant The bus at 0.4 kV voltage level of the common power demand of plant consists of 4 sections, in 2 groups. Bus sections I and III constitute 1 group while sections II and IV constitute another 1 group. The bus section I is connected to the bus section ① at 10.5 kV voltage level via the TLA1 common transformer. The bus section III is connected to the bus section ③ at 10.5 kV voltage level via the TLA3 common transformer. A bus tie switch is set for the bus sections I and III. The bus section II is connected to the bus section ② at 10.5 kV voltage level via the TLA2 common transformer. The bus section IV is connected to the bus section ④ at 10.5 kV voltage level via the TLA4 common transformer. A bus tie switch is set for the bus sections II and IV.

2) Lighting power system

The bus at 0.4 kV voltage level for lighting power consists of 2 sections. Bus section I is connected to the bus section ② at 10.5 kV voltage level via the TL1 lighting transformer. Bus section II is connected to the bus section ③ at 10.5 kV voltage level via the TL2 lighting transformer. A bus tie switch is set for the bus sections I and II.

3) Auxiliary power supply system of units

The 0.4 kV bus connected with the main panel of auxiliary power supply of unit consists of 6 sections, namely, section I, section II, section III, section IV, section V, and section VI. The 0.4 kV bus is connected with the 10.5 kV bus as follows:

The bus section I of the main panel is connected to the bus section ① at 10.5 kV voltage level via the TLP1 unit service power transformer; the bus section II of the main panel is connected to the bus section ③ at 10.5 kV voltage level via the TLP2 unit service

power transformer; the bus section III of the main panel is connected to the bus section ① at 10.5 kV voltage level via the TLP3 unit service power transformer; the bus section IV of the main panel is connected to the bus section ③ at 10.5 kV voltage level via the TLP4 unit service power transformer; the bus section V of the main panel is connected to the bus section ② at 10.5 kV voltage level via the TLP5 unit service power transformer; the bus section VI of the main panel is connected to the bus section ④ at 10.5 kV voltage level via the TLP6 unit service power transformer

The connection mode of No. 1 ~ No. 5 multi-generator-transformer units is as 6- 46 Paklay Hydropower Project Feasibility Study Report

follows:

⑴ No. 1 multi-generator-transformer unit connection

The bus section I of main panel is connected with the load point of auxiliary power supply of G1 unit. The bus section II of main panel is connected with the load point of auxiliary power supply of G2 unit. The bus sections I and II of main panel are equipped with a bus tie switch to ensure that both G1 and G2 units have 2 main power supply points.

⑵ No. 2 multi-generator-transformer unit connection

The 0.4 kV bus connected with the sub-panel of auxiliary power supply of No. 2 multi-generator-transformer unit consists of 3 sections that are respectively connected with the load points of auxiliary power supply of G3, G4 and G5 units. The 0.4 kV bus of sub-panel is equipped with two power supplies that are respectively connected with bus sections III and IV of main panel, so as to ensure that G3, G4 and G5 units have 2 main power supply points.

⑶ No. 3 multi-generator-transformer unit connection

The 0.4 kV bus connected with the sub-panel of auxiliary power supply of No. 3 multi-generator-transformer unit consists of 3 sections that are respectively connected with the load points of auxiliary power supply of G6, G7 and G8 units. The 0.4 kV bus of sub-panel is equipped with two power supplies that are respectively connected with bus sections III and IV of main panel, so as to ensure that G6, G7 and G8 units have 2 main power supply points.

⑷ No. 4 multi-generator-transformer unit connection

The 0.4 kV bus connected with the sub-panel of auxiliary power supply of No. 4 multi-generator-transformer unit consists of 3 sections that are respectively connected with the load points of auxiliary power supply of G9, G10 and G11 units. The 0.4 kV bus of sub-panel is equipped with two power supplies that are respectively connected with bus sections V and VI of main panel, so as to ensure that G9, G10 and G11 units have 2 main power supply points.

⑸ No. 5 multi-generator-transformer unit connection

The 0.4 kV bus connected with the sub-panel of auxiliary power supply of No. 5 multi-generator-transformer unit consists of 3 sections that are respectively connected with

6- 47 Paklay Hydropower Project Feasibility Study Report the load points of auxiliary power supply of G12, G13 and G14 units. The 0.4 kV bus of sub-panel is equipped with two power supplies that are respectively connected with bus sections V and VI of main panel, so as to ensure that G12, G13 and G14 units have 2 main power supply points.

4) Protective load power system

The bus at 0.4 kV voltage level for protective load consists of 1 section. Dual power supply is adopted for the bus section for power supply and the bus section is respectively connected to the bus sections ② and ③ at 10.5 kV voltage level via TLA5 and TLA6 common transformers. In addition, a 0.4 kV 800 kW diesel generator unit shall be provided for the HPP as the emergency power supply. 5) Power supply system at dam area According to the dam crest load information upon preliminary estimates, the utilization voltages of electrical equipment on the dam crest shall all be 380/220 V. Therefore, the dam crest power supply system shall supply 0.4 kV primary voltage. The dam crest connection is of single-bus sectionalized connection mode. Bus section I is connected to the bus section ② at 10.5 kV voltage level via the TLA7 dam crest transformer. Bus section II is connected to the bus section ④ at 10.5 kV voltage level via the TLA8 dam crest transformer. A bus tie switch is set for the bus sections I and II, to ensure 2 main power supply points for the crest power consumption. In addition, a 0.4 kV 800kW diesel generator unit shall be provided as the emergency power supply for flood releasing on the dam.

6.2.4 Type Selection for 500 kV HV Switchgear Installation

6.2.4.1 Construction Scale for 500 kV Switchyard The 500 kV switchyard of the Paklay HPP has 5 incoming lines and 2 outgoing lines. See Table 6.2.4-1 for the construction scale.

Table 6.2.4-1 Construction Scale for 500 kV Switchyard

Construction Scale (Equipment S/N Item Name Quantity)

1 500 kV incoming line

6- 48 Paklay Hydropower Project Feasibility Study Report

Incoming circuit breaker bay of No. 1 main 1.1 1 transformer

Incoming circuit breaker bay of No. 2 main 1.2 1 transformer

Incoming circuit breaker bay of No. 3 main 1.3 1 transformer

Incoming circuit breaker bay of No. 4 main 1.4 1 transformer

Incoming circuit breaker bay of No. 5 main 1.5 1 transformer

2 500 kV outgoing line

2.1 Circuit breaker bay of 500 kV outgoing line I 1

2.2 No. 1 line trap 3

2.3 Capacitor voltage transformer at No. 1 line 3

2.4 Arrester at No. 1 line 3

2.5 Circuit breaker bay of 500 kV outgoing line II 1

2.6 No. 2 line trap 3

2.7 Capacitor voltage transformer at No. 2 line 3

2.8 Arrester at No. 2 line 3

3 Bus tie circuit breaker bay 1

4 Bus PT&LA bay

4.1 1M PT&LA bay 1

4.2 2M PT&LA bay 1

6.2.4.2 Selection Principle for 500 kV Equipment According to relevant electric power export plan made by the Lao Government, upon the completion of the Paklay HPP, the electric power will be completely exported to Thailand and play a very important role in the Thailand power grid. The operation management of 6- 49 Paklay Hydropower Project Feasibility Study Report

the HPP is "unmanned-on-duty" (few-on-duty). Selection of 500 kV switchgear installation shall comply with the following basic principles:

⑴ In the service environment, the equipment shall meet the requirements for proper operation, maintenance, short circuit and over-voltage; in addition, long-term development shall also be taken into account.

⑵ The equipment shall have mature operation experience and advanced technology.

⑶ The equipment shall have safe and reliable operation and convenient maintenance, being adaptive to the management mode of the HPP, which is "unmanned-on-duty" (few-on-duty).

⑷ In the design level year, the rated short-time withstand current for electrical equipment at a 500 kV switchyard shall be temporarily considered as 50kA/2s.

6.2.4.3 Preliminary Determination of Switchyard Site a) Considerations for site selection

With respect to a 500 kV switchyard, the following factors shall be taken into account for its site selection:

⑴ Topographic conditions: Civil excavation and backfilling shall be carried out as less as possible to avoid occurrence of a high slope.

⑵ Geological conditions: shall meet the foundation requirements for switchyard equipment and framework.

⑶ Incoming and outgoing lines: The outgoing line corridor of transmission line shall be as open as possible, in favor of arrangement of outgoing line.

⑷ 500 kV HV outlet: The length of outlet at the HV side of main transformer shall be as short as possible.

⑸ The switchyard site shall be convenient for operation management and close to the powerhouse as much as possible.

⑹ The site shall be away from the vibration area of tailrace platform as far as possible.

b) Preliminarily determined site scheme

According to the combination mode of generator and transformer as well as the quantity of outgoing circuit of transmission line, the 500 kV switchyard has 5 incoming lines and 2 6- 50 Paklay Hydropower Project Feasibility Study Report

outgoing lines in total and its connection at the 500 kV side is of the double-bus connection mode. The HPP is of a water-retaining type hydroelectric station and the powerhouse is arranged in a compact manner.

⑴ Option 1: GIS switchyard site for auxiliary plant

According to the arrangement of electromechanical equipment in auxiliary plant, if an SF6 gas insulated switchgear (GIS) is adopted, the GIS switchyard can be arranged at the downstream auxiliary plant (E.L. 245.50 m) at the No. 3 ~ No. 5 unit bay. Meanwhile, the GIS is directly connected with main transformers through an SF6 tubular bus.

⑵ Option 2: Right-bank AIS switchyard site

According to topographical conditions of the site area, if the air insulated switchgear (AIS) is adopted, the AIS switchyard can be arranged on the bottomland on the right bank of the river. However, main transformers are far away from the switchyard, with limited outgoing line gallery; the HV side of the main transformers shall be connected to the switchyard via a 500 kV HV cable. Therefore, it requires an additional 500 kV HV cable of about 7.5 km in length and 30 cable heads.

6.2.4.4 Equipment model selection and arrangement in GIS option

In the GIS option, the 500 kV GIS circuit breaker is of a horizontal double-break type; the GIS is connected with main transformers and outgoing bushing through an SF6 tubular bus. The GIS switchyard is arranged as follows:

The GIS switchyard is arranged in 2 layers. The first layer is the SF6 tubular bus layer and the second layer contains a GIS room and a 500 kV open-type outgoing line platform.

The plane arrangement dimension of the GIS room and the 500 kV open-type outgoing line platform is 138.90 m × 21.40 m. The plane dimension of the GIS room at the left side is 68.50 m × 17.40 m. The GIS room is mainly equipped with 5 circuit breaker incoming bays, 2 circuit breaker outgoing bays, 1 circuit breaker bus tie bay, and 2 PT&LA bays. The plane dimension of the 500 kV open-type outgoing line platform at the right side is 70.50 m × 21.40 m. The platform is mainly equipped with 6 traps, 6 capacitor voltage transformers, and 6 arresters.

6.2.4.5 Equipment model selection and arrangement in AIS option

The 500 kV AIS mainly consists of HV distribution equipment and outgoing line

6- 51 Paklay Hydropower Project Feasibility Study Report equipment. The HV distribution equipment includes circuit breaker, disconnecting switch (including grounding switch), current transformer, voltage transformer, arrester and bus. The outgoing line equipment includes line arrester, voltage transformer and so on. The circuit breaker is of the SF6 insulation porcelain stanchion type and the disconnecting switch is of the single-arm folded structure. The AIS switchyard has a plane arrangement dimension of 250 m × 100 m and an occupied area of about 25,000 mm2. The 500 kV AIS is arranged as follows:

A suspended tubular bus is employed, porcelain stanchion circuit breakers are arranged in a single row, and both the incoming and outgoing lines are arranged at a single side. Facing the outgoing line side, bays are arranged from left to right as follows: No. 1 incoming bay (to the TM1 main transformer), No. 2 incoming bay (to the TM2 main transformer), No. 3 outgoing bay, No. 4 incoming bay (to the TM3 main transformer), No. 5 bus tie bay, No. 6 incoming bay (to the TM4 main transformer), No. 7 outgoing bay, and No. 8 incoming bay (to the TM5 main transformer).

6.2.4.6 Technical Comparison for AIS Option and GIS Option

In conclusion, both AIS switchyard and GIS switchyard can meet the technical requirements of the Project. Technical analysis and comparison of the GIS switchyard and AIS switchyard are as follows:

a) Reliability and safety Generally, a GIS is more reliable and safer than an AIS in terms of operation because the GIS has a lower failure rate. The GIS has advantages in reliability and safety as follows:

(1) Electrical equipment in the GIS is more reliable than that in the AIS in terms of insulating property. (2) Contact resistance at the connection part of the GIS conductors is less than that of the AIS conductors. (3) Personal injury accidents: according to the statistical data, personal injury accidents caused by the AIS occur every 1,000 station years, while those caused by the GIS occur every 4,000 station years. b) Maintenance management and repair (1) The GIS is nearly free from maintenance, with a small quantity of maintenance

6- 52 Paklay Hydropower Project Feasibility Study Report works. (2) Most elements of the AIS are susceptible to environmental conditions, with a large quantity of maintenance works. (3) The GIS has a heavy maintenance cycle of 15~20 years, with a relatively longer maintenance time; the AIS has a shorter heavy maintenance cycle, with more frequent maintenance works. According to the statistical data, the ratio of the AIS maintenance cycle to the GIS maintenance cycle is 1:5. c) Installation Generally, the GIS has complete components and its parts and components are model-building blocks; therefore, the GIS has convenient site installation and commissioning. However, the AIS has relatively conditions, with longer installation and commissioning time.

d) Seismic resistance The GIS elements are enclosed inside a shell and the whole switchgear installation is connected to be an integrated structure; in addition, its height is lower than that of the AIS; therefore, it has better integral rigidity and seismic resistance than the AIS.

e) Electrostatic Induction and radio interference level Most GIS elements are installed inside an enclosed shell that is grounded. Based on shielding effect of the shell, it is much better than the AIS in terms of electrostatic induction and radio interference level.

f) Internal fault test The structure of GIS equipment is highly intensive; therefore, fault of one element inside may impact other elements. Compared with the AIS, the GIS has a larger fault impact scope and it is more difficult to find out the failed element in the GIS.

g) Civil construction period and difficulty of the switchyard In case of the AIS option, it will be arranged on a bottomland on the right bank of the river, with an occupied area of about 150.0 m x 70.0 m. In case of the GIS option, the GIS will be arranged in the auxiliary plant downstream at an elevation of 245.50m in the section of No. 3~5 units and the GIS room will have an area of 68.50m×17.40. Therefore, the AIS switchyard has a larger occupied area than the GIS switchyard, with more civil works. Compared with the GIS switchyard, the AIS has disadvantages as follows:

6- 53 Paklay Hydropower Project Feasibility Study Report

(1) The AIS switchyard has a longer civil construction period.

(2) The AIS switchyard has a larger civil works.

(3) The AIS switchyard requires an additional investment on the electrical equipment such as 500 kV HV cables.

(4) The AIS switchyard is of decentralized layout of equipment, with inconvenient operation and maintenance.

In conclusion, the GIS scheme is better than the AIS scheme technically.

6.2.4.7 Economic Comparison for AIS Option and GIS Option According to the quantities of civil works and relevant investment amounts provided by the powerhouse discipline, the investment comparison for civil works of 500 kV switchyard is listed in Table 6.2.4-2, the investment comparison for main electrical equipment is listed in Table 6.2.4-3, and the comparison for comprehensive investment is listed in Table 6.2.4-4. Table 6.2.4-2 Investment Comparison for Civil Works of 500 kV Switchyard Total Total Differenc Unit Price Price of Price of e Value S/N Item Name Unit GIS AIS GIS AIS (USD) (USD) (USD) (USD) GIS-AIS

Open earth 1 m3 / 221902 3.31 / 734939 -734939 excavation

Open rock 125744 -1141758 2 m3 / 9.08 / 11417582 excavation 3 2

3 Shotcrete m3 / 3008 201.17 / 605119 -605119

Anchor rod 4 (Ф25, L=6 Nr. / 2228 89.978 / 200471 -200471 or 8m)

C20 5 structure m3 / 15000 121.03 / 1815450 -1815450 concrete

6- 54 Paklay Hydropower Project Feasibility Study Report

C25 6 structure m3 5400 / 138.49 747846 / 747846 concrete

Reinforcem 7 t 648 750 1585.36 1027313 1189020 -161707 ent

Drainage 8 hole (D56, m / 3759 41.07 / 154382 -154382 L=3m)

Total (USD 9 1775 16117 -14342 103)

Remarks: Investments in the above table are all based on the approximate price in September

2013.

6- 55 Paklay Hydropower Project Feasibility Study Report

Table 6.2.4-3 Investment Comparison for Electrical Equipment of 500 kV Switchyard S/N Description Main Electrical Equipment Unit Qty. Price (USD)

I Option 1: GIS switchyard for auxiliary plant

GIS circuit breaker bay Nr. 8 1.1 million/bay

1 500kV GIS GIS PT&LA bay Nr. 2 400,000/bay

Capacitor voltage Set 6 12,500/set transformer 500kV 2 Zinc oxide arrester Set 6 6,000/set open-type equipment Trap Set 3 46,000/set

Investment in 3 9.849 million electrical equipment

II Option 2: Right-bank AIS switchyard

AIS circuit breaker bay Nr. 8 460,000/bay

1 500kV AIS AIS PT&LA bay Nr. 2 80,000/bay

Capacitor voltage Set 6 12,500/set transformer 500kV 2 Zinc oxide arrester Set 6 6,000/set open-type equipment Trap Set 3 46,000/set

500kV XLPE m 7500 385/m

3 500 kV HV cable GIS cable terminal Nr. 15 61,500/Nr.

AIS cable terminal Nr. 15 61,500/Nr.

4 500kV GIB 500kV Set 5 230,000/set

Investment in 5 9.9715 million electrical equipment

6- 56 Paklay Hydropower Project Feasibility Study Report

6- 57 Paklay Hydropower Project Feasibility Study Report

Table 6.2.4-4 Comparison for Comprehensive Investment of 500 kV Switchyard 103 (USD) Option 1: GIS Switchyard for Option 2: Right-bank AIS S/N Item Name Auxiliary plant Switchyard

1 Investment in civil works 1775.0 16117.0

Investment difference in civil 2 0.00 +14342 works

Investment in electrical 3 9849.0 9971.5 equipment

Investment difference in 4 0.00 +122.5 electrical equipment

5 Total project investment 11624.0 26088.5

6 Total investment difference 0.00 +14464.5

6.2.4.8 Conclusion According to the above techno-economic analysis and comparison, it is recommended that the 500 kV HV distribution equipment of the HPP should be of the GIS option and the GIS switchyard shall be arranged at the downstream auxiliary plant (E.L. 245.50 m). Reasons are as follows: ① The investment in the GIS option is USD 14.4645 million less than that in the AIS option, because a GIS switchyard occupies less land and has a lower cost of civil works. ② It is easy to implement "unmanned-on-duty" (few-on-duty) management mode for a GIS, due to its high power supply reliability, small workload of maintenance work, convenient management and easy centralized monitoring.

6.2.5 Position Selection for 500 kV GIS Switchyard 6.2.5.1 Determination of GIS Arrangement Scheme

The review meeting for the feasibility study report on Paklay HPP at the Mekong River in Laos was held on April 21~22, 2014. In the meeting, the technical parts of the Project were reviewed. Review comments on the 500 kV HV distribution equipment are as follows: It is rational to adopt the GIS scheme for the 500 kV HV distribution equipment. However, it is suggested that the GIS arrangement position should be further studied to make proper

6- 58 Paklay Hydropower Project Feasibility Study Report adjustment because the tailrace platform will suffer from vibrations when a GIS room is arranged at the unit bay. According to the review comments from experts, 3 GIS arrangement options are proposed for technical comparison as follows:

Option 1: The 500 kV GIS room is arranged at the downstream auxiliary plant (E.L. 245.50 m) at the No. 3 ~ No. 5 unit bay, while the 500 kV open-type outgoing line platform is arranged side by side at the No. 1 ~ No. 2 unit bay and at the ① erection bay of downstream auxiliary plant (E.L. 245.50 m).

Option 2: The 500 kV GIS room is arranged at the ② erection bay of downstream auxiliary plant (E.L. 245.50 m), while the 500 kV open-type outgoing line platform is arranged side by side at the downstream auxiliary plant (E.L. 245.50 m) at the No. 11 ~ No. 14 unit bay.

Option 3: The 500 kV GIS room is arranged at the ① erection bay of downstream auxiliary plant (E.L. 245.50 m), while the 500 kV open-type outgoing line platform is arranged on the roof of GIS room (E.L. 260.50 m).

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6.2.5.2 Technical Comparison

See Table 6.2.5-1 for the summary of technical comparison between each GIS arrangement option.

Table 6.2.5-1 Technical Comparison for GIS Arrangement Options

Item Option 1 Option 2 Option 3 Name

The 500 kV open-type The 500 kV open-type The 500 kV open-type outgoing line platform is outgoing line platform is outgoing line platform is arranged against the left arranged in the middle of the arranged against the left bank of the Mekong River. riverbed, far away from both bank of the Mekong River. The span and deflection banks. Therefore, a terminal The span and deflection angle between the outgoing tower is needed to be angle between the line framework and the arranged on the retaining outgoing line framework 500 kV terminal tower are both wall at the dredging area. and the terminal tower are outgoing small. The outgoing line However, the elevation of the both small. The outgoing line corridor is relatively wide. retaining wall at the dredging line corridor is relatively corridor To sum up, this option is in area is relatively low, and it wide. To sum up, this favor of the design of is difficult to deal with the option is in favor of the transmission line. tower foundation, and the design of transmission quantities of tower are line. relatively large. To sum up, this option is not in favor of the design of transmission line.

Vibration of tailrace platform:

The 500 kV GIS is arranged The 500 kV GIS is arranged The 500 kV GIS is at the downstream auxiliary at the ② erection bay of arranged at the ① erection plant at the No. 3 ~ No. 5 downstream auxiliary plant. bay of downstream unit bay. When water flow In flood season, the whole auxiliary plant. The Vibration passes through the units, the plant will be shut down when substructure is free of GIS structure will suffer the bottom discharge orifice discharging facilities. To from vibrations which will is used for flushing. To sum sum up, equipment vibrate the electrical up, equipment vibration does vibration does not exist in equipment. To sum up, not exist in this option. this option.

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equipment will suffer from vibrations in this option.

Solutions:

1. The 500 kV GIS circuit Equipment vibration does not Equipment vibration does breaker should be of the exist in this option. not exist in this option. horizontal type. In addition, expansion joints in a proper number shall be provided for connections of 500 kV GIS SF6 tubular bus, 13.8 kV isolated-phase bus and relevant equipment, so as to improve the anti-vibration performance of equipment.

2. In the design, a flexible circuit conductor shall be used for fixture wire and equipment connections as far as possible, and the flexible circuit conductor shall be long enough, so as to improve the anti-vibration performance of equipment.

3. A connection terminal with spring fasteners should be used as the secondary connection terminal, to avoid disconnection of the secondary connection and to improve the anti-vibration performance of equipment.

Refer to the Taoyuan HPP, Examples for arrangement of A tubular HPP complex the Feilaixia Hydropower switchyard on the tailrace generally has a wide Examples Project, and the Shihutang platform in the middle of landform. In most cases, a Navigation and Hydropower riverbed are seldom. switchyard is arranged at

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Complex Project for the erection bay of arrangement of switchyard downstream auxiliary on the tailrace platform at plant at the side of river the side of river bank. bank, and the switchyard and the outgoing line platform are arranged at one elevation.

The space of downstream The space of downstream For the Project, if the auxiliary plant is fully used auxiliary plant is fully used switchyard is arranged at to arrange the switchyard to arrange the switchyard and the ① erection bay of and open-type outgoing line open-type outgoing line downstream auxiliary equipment. To sum up, the equipment. To sum up, the plant, the switchyard and Structure structure pattern is relatively structure pattern is relatively the outgoing line platform pattern rational. rational. shall be arranged in a stagger manner because the end of the ① erection bay is a high slope. To sum up, the structure pattern is irrational.

6.2.5.3 Conclusion

According to the above technical comparison, option 1 is in favor of the arrangement of 500 kV outgoing line of switchyard and its structure pattern is rational. Therefore, option 1 is the recommended GIS arrangement scheme of the HPP.

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6.2.6 Selection of Main Electrical Equipment 6.2.6.1 Estimate of short circuit current Because of lack of relevant data to connect to the power system, it is temporarily consider the short circuit current of the HV bus at 500 kV side to be 50 kA and the power supply to be infinite. Upon estimate, the short circuit current at the generator outlet of the multi-generator-transformer unit is less than 80 kA.

6.2.6.2 Main electrical equipment a) Turbo- generator Model: SFWG55-64/8000

Quantity: 14

Type: Three-phase, horizontal type, bulb, closed forced circulation, air-cooling and synchronous generator

Rated capacity: 55 MW

Rated voltage: 13.8 kV

Rated current: 2422.1 A

Rated power factor: 0.95

Rated frequency: 50 Hz

Rated speed: 93.8 r/min

Direct-axis subtransient reactance X"d ≮0.21 (tentative) Insulation grade: F

Brake mode: mechanical

Excitation mode: self-shunt thyristor static excitation mode

Fire control method: fixed water spray

b) Generator voltage switchgear installation (1) Generator voltage bus

From the generator main outlet to the 13.8 kV switchgear, the generator voltage bus is of the common enclosure bus or the insulating tubular bus with a rated current of 3,150 A and a thermal stability current/time of 80kA/2s. From the 13.8 kV switchgear to the LV side of

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main transformer, the generator voltage bus is of the isolated-phase bus with a rated current of 8,000 A and a thermal stability current/time of 80kA/2s. Main technical parameters are as follows:

Type: common enclosure bus or the insulating tubular bus/isolated-phase bus

Cooling mode: natural cooling

Conductor type: Copper conductor/tubular aluminum conductor

Rated voltage: 13.8kV

Maximum voltage: 15.8kV

Rated current: 3150A/8000A

Rated frequency: 50Hz

Thermal stability current (2s):

Main circuit (effective value) 80kA

Branch circuit (effective value) 125kA

Dynamic stability current:

Main circuit (peak value) 200kA

Branch circuit (peak value) 315kA

⑵ Generator outlet circuit breaker

The HPP is of the multi-generator-transformer unit connection. The generator has a rated capacity of 55 MW, a rated voltage of 13.8 kV and a rated current of 2422.1 A. The corresponding generator outlet circuit breaker shall have a rated current of 3,150 A and a rated short-circuit breaking current of 80 kA, and its main technical parameters shall be as follows:

Type: SF6 generator circuit breaker

Insulating medium: SF6

Rated voltage: 13.8kV

Rated current: 3150A

Rated frequency: 50Hz 6- 64 Paklay Hydropower Project Feasibility Study Report

Rated short-circuit making current (peak value): 220kA

Rated peak withstand current: 220kA

Rated short-time withstand current (effective value)/time: 80kA/3s

Rated short-circuit breaking current 80kA

(3) 13.8 kV switchgear installation

The HV station service circuit is proposed to be equipped with an HV current limiting fuse cabinet. Normal operation (breaking of rated current) is implemented by a load switch. In case of short circuit, the HV current limiting fuse will provide corresponding protection for the circuit. A potential transformer, current transformer, surge arrester and others are all installed inside a fully-closed metal-armored cabinet. All electrical cabinets are of three phases. Grounding of the generator neutral point is realized by the grounding transformer.

c) Main transformer The multi-generator-transformer unit connection is adopted for the combination mode of generator and main transformer. If the multi-generator-transformer unit connection consists of 3 generators and 1 transformer, in 4 groups, the rated capacity (180 MVA) of main transformer shall match with the rated capacity of 3 generators. If the multi-generator-transformer unit connection consists of 2 generators and 1 transformer, in 1 group, the rated capacity (120 MVA) of main transformer shall match with the rated capacity of 2 generators. Selection for type and parameters of main transformer:

1) Type of main transformer

⑴ Transport of heavy-big piece

Transport scheme of heavy-big piece for the HPP: The transport of heavy-big piece is carried out by water, rail and road together. Restricted by the load standard of rail tunnel and road bridge, the transport dimension of the biggest piece shall be within the level-2 over-limit range of railway and the maximum weight shall not exceed 100t.

According to the data on main transformers provided by manufacturers, the transport weight of common three-phase transformer with nitrogen is beyond the transport conditions for heavy-big piece of the HPP. Therefore, the following 2 options (i.e. single-phase transformer bank and combined three-phase transformer) shall be taken into account for the type of main transformer. 6- 65 Paklay Hydropower Project Feasibility Study Report

Option 1: single-phase transformer bank

In this option, three common single-phase transformers are combined into one three-phase transformer, featuring mature design and fabrication experience, small transport weight and dimension, short installation period, and rich operation experience. However, the arrangement area in this option is relatively large.

Option 2: combined three-phase transformer

Upon study and analysis, the combined three-phase transformer composed of three special single-phase transformers is characterized by mature design and fabrication experience and wide application. The special single-phase transformer has a structure basically the same as that of the common one. In combination, independent oil tanks are adopted and only a lead conduit is used to connect three transformers as a whole. Namely, oil lines of three independent single-phase transformers are connected as a whole. In this option, the transport weight, transport dimension and occupied area of arrangement are small, and the installation period is relatively short.

⑵ Technical analysis

◇ Single-phase transformer bank:

① Reliability

The single-phase transformer bank is composed of three single-phase transformers. In general, three transformers are respectively arranged in an independent room so their oil lines are totally separated. Therefore, three-phase short circuit will not occur and reliability of HPP operation will be improved.

② Arrangement

The single-phase transformer bank is composed of three single-phase transformers. In general, three phases are arranged separately. According to the typical fire law for electrical equipment in China, a transformer of which the oil amount is 2,500 kg or above must be arranged separately; a fire partition shall be used for separation if the interval is less than 10 m (500 kV). The oil amount of single-phase transformer at an ultra-large type HPP far exceeds the value specified in the fire law, so the transformers must be arranged and installed separately and the occupied area is large accordingly.

③ Spare phase 6- 66 Paklay Hydropower Project Feasibility Study Report

Application of single-phase transformer bank to a large HPP is to ensure the reliability of HPP operation. When the quantity of transformer is relatively large, a spare phase shall be used to improve the reliability of HPP operation and reduce the outage cost. The replacement of spare phase of single-phase transformer bank shall be convenient. Specifically, a faulted phase can be taken out from the connecting part between HV side and LV side and then the spare phase is installed at the connecting part and then the HV and LV sides are connected again and finally corresponding tests are made.

◇ Combined three-phase transformer:

① Reliability

With the continuous development of design, fabrication and installation technologies of transformer, the combined three-phase transformer is of independent oil tanks and only a lead conduit is used to connect three phases as a whole. Namely, oil lines of three independent single-phase transformers are connected as a whole. In addition, the workload of site installation is reduced as much as possible. Meanwhile, with the continuous improvement of construction means and installation process, the reliability of HPP operation can be guaranteed as long as the field construction management and supervision are strengthened.

Moreover, after the combined three-phase transformer is assembled on the site, it can work as a three-phase transformer, sharing one set of oil protection and cooling system. Therefore, the total quantity of coolers, medium-pressure and low-pressure bushings, and oil conservators will be reduced, in favor of equipment arrangement and cost reduction. At present, many HPPs in China have been equipped with the combined three-phase transformer (such as Lingtan HPP and Xiluodu HPP), and rich experience in both fabrication and operation has been accumulated.

To sum up, the combined three-phase transformer is inferior to the single-phase transformer in terms of reliability, but it still can meet the requirements for safe operation of HPP.

② Arrangement

The combined three-phase transformer has a simplified arrangement mode and less occupied area. A lead conduit is used to connect three single-phase transformers as a whole. The single-phase transformers have nearly the same arrangement mode as the three-phase 6- 67 Paklay Hydropower Project Feasibility Study Report

transformer. Compared with the single-phase transformer bank, the combined three-phase transformer has the following advantages: ① small occupied area; ② simple connection with isolated-phase bus at generator outlet; ③ reduction in dimension of auxiliary plant for arrangement of auxiliary equipment of main transformer, reducing the quantities of civil works. Therefore, technically and economically, the combined three-phase transformer is more rational than the single-phase transformer bank in terms of transformer arrangement.

⑶ Conclusion

According to the above factors, in view of reliability and operation and maintenance of main transformers, the single-phase transformer bank has slightly higher reliability, easier installation, shorter replacement period of spare phase and easier replacement process than the combined three-phase transformer. However, the single-phase transformer bank has a relatively large occupied area and project cost. Therefore, it is recommended that the type of main transformer of the HPP should be of the combined three-phase transformer to follow the principle of less project investment.

2) Cooling mode of main transformer

The ODWF and OFAF are both feasible technically for the main transformer. However, the design of ventilation system will be difficult if the air cooling mode is adopted because the HPP is of a water-retaining type hydroelectric station and the main transformers are arranged inside the main transformer room of auxiliary plant. Based on advantages of convenient water taking at the HPP, mature technology of water cooler and good water quality of river, it is recommended that the cooling mode of transformers at the HPP should be of the water cooling mode, so as to simplify the design of ventilation and heat dissipation and to reduce noise.

3) Technical parameters of main transformer:

The combined three-phase, dual-winding, ODWF, copper winding, non-excitation voltage-regulation boosting power transformer is selected as the main transformer. Its main parameters are as follows:

Type: SSP-H-180000(120000)/500

Rated capacity: 180,000 kVA/4 sets

Rated capacity: 120,000 kVA/ 1 set

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Rated transformation ratio: 525±2×2.5%/13.8kV

Rated frequency: 50Hz

Connection symbol: YNd11

Short-circuit impedance: Uz=14%

Connection mode of incoming line at the LV side: connected with IPB

Connection mode of outgoing line at the HV side: connected with GIB

Transport weight of biggest piece: ~100t

d) 500 kV HV distribution equipment

1) 500 kV GIS

The indoor SF6 GIS is proposed to be used as the 500 kV switchgear. The GIS switchyard is arranged at the downstream auxiliary plant (E.L. 245.50 m). Main parameters are as follows:

Rated voltage: 550kV

Rated current: 3150A

Rated frequency: 50Hz

Rated short-circuit breaking current: 50 kA (effective value)

Rated making current: 125kA

Rated short-time withstand current/time 50kA/3s

2) 500 kV open-type outgoing line equipment

The outdoor open-type outgoing line equipment of the HPP mainly includes a capacitor voltage transformer, an arrester, a trap and so on. The open-type outgoing line equipment is arranged at the downstream auxiliary plant and its platform has an elevation of 245.50 m a.s.l.

⑴ Voltage transformer at the 500 kV outgoing line side

It is recommended that the voltage transformer at the 500 kV outgoing line side should be of the capacitor voltage transformer. Compared with the electromagnetic voltage transformer, the capacitor voltage transformer is of the capacitor divider and

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characterized by less internal insulating oil, high operation reliability, small workload of maintenance. In addition, the capacitor voltage transformer can also be used as carrier coupling capacitor of power line. Main technical parameters of capacitor voltage transformer are as follows:

Type Capacitive

Transformation ratio 550/ 3 /0.1/ 3 /0.1/ 3 /0.1kV

Accurate degree 0.1/0.5/0.5/3P

Capacity 5VA/50VA/50VA/100VA

⑵ 500 kV line arrester

The line arrester is of the zinc oxide arrester for over-voltage protection against lightning invasion wave and over-voltage protection against operation. Main technical parameters are as follows:

Type zinc oxide arrester (MOA)

Rated voltage 444kV

System voltage 500kV

Continuous operating voltage 324kV

Nominal discharge current grade 20kA

DC lmA, reference voltage ≤597kV

Switching impulse-current residual voltage (peak value) ≤907kV

Residual voltage under lightning impulse current (peak value) ≤l106kV

Residual voltage under steep current impulse (peak value) ≤1238kV

2 ms rectangular wave current (peak value) 2,000 A, 20 times

⑶ Line trap

The line trap is of the outdoor seat-type trap, with main technical parameters as follows:

Model XZF-2000-1.0/50

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Rated voltage 550/ 3 kV

Rated frequency 50Hz

Rated working current 2000A

2s rated thermal stability current (effective value) 50kA

Peak value of short-circuit current 125kA

Rated inductance (it will be adjusted after specific frequency range is determined) 1mH

Allowable deviation ±5%

Bandwidth (it will be adjusted after specific frequency range is determined) 64~464kHz

Wave form: Approximate to sine wave

Quality factor of main coil (at 100 kHz) ≥30

e) Electrical equipment of station service system

The electrical equipment of station service system shall be selected based on the station service connection and estimated loads of service power of plant.

⑴ HV station service transformer

The HV station service transformer is of 4 dry-type transformers, in 2 groups. The capacity is under the consideration that 2 transformers back up each other. Namely, the capacity of each group of transformer is half of the whole plant load (8,000 kVA). Main technical parameters are as follows:

Type SCB11-4000/13.8

Rated capacity 4000kVA

Transformation ratio 13.8±2×2.5%/10.5kV

Impedance voltage 7%

Type of voltage regulation no-load voltage regulation

⑵ Station service transformer

Type SCB11-2000/10.5 6- 71 Paklay Hydropower Project Feasibility Study Report

Rated capacity 2000kVA

Transformation ratio 10.5±2×2.5%/0.4kV

Impedance voltage 6%

Type of voltage regulation no-load voltage regulation

⑶ Unit service transformer

Type SCB11-1600(500)/10.5

Rated capacity 1,600 kVA (4 in total)/500 kVA (2 in total)

Transformation ratio 10.5±2×2.5%/0.4kV

Impedance voltage 6%

Type of voltage regulation no-load voltage regulation

⑷ Lighting transformer

It is recommended that a lighting transformer should be arranged independently and the on-load voltage regulation should be adopted, so as to prevent lighting quality from being affected by fluctuation of station service supply voltage cause by drastic changes in station service loads. Main technical parameters are as follows:

Type SCB11-400/10.5

Rated capacity 400kVA

Transformation ratio 10.5±4×2.5%/0.4kV

Impedance voltage 4%

Type of voltage regulation on-load voltage regulation

⑸ Dam crest transformer

Type SCB11-1000/10.5

Rated capacity 1000kVA

Transformation ratio 10.5±2×2.5%/0.4kV

Impedance voltage 6%

Type of voltage regulation no-load voltage regulation

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⑹ In-plant emergency transformer

Type SCB11-630/10.5

Rated capacity 630kVA

Transformation ratio 10.5±2×2.5%/0.4kV

Impedance voltage 6%

Type of voltage regulation no-load voltage regulation

⑺ Diesel generator unit

A diesel generator unit is arranged on the dam crest to serve as the emergency power supply for flood control by dam. The capacity of diesel generator unit shall comply with the maximum quantity of flood gates opened at the same time. A diesel generator unit is arranged in the powerhouse to serve as the emergency power supply for powerhouse and to meet the requirements for earthquake resistance and prevention of powerhouse and leakage water dewatering pump. Main technical parameters are as follows:

Capacity 800 kW (powerhouse)/800 kW (dam)

Voltage 380V/220V

Frequency 50Hz

⑻ HV station service switchgear

The 10.5 kV station service system will be of the indoor metal armored movable switchgear inside which a vacuum circuit breaker will be provided.

⑼ LV station service switchgear

The 0.4 kV station service system will be of the MNS drawer type switchgear. 6.2.7 Over Voltage Protection (OVP) and Grounding 6.2.7.1 Principle of Insulation Coordination

The design of over-voltage protection and insulation coordination shall be carried out according to Insulation Co-ordination — Part 2: Application Guide (GB311.2-2013), Code for Design of Overvoltage Protection and Insulation Coordination for AC Electrical Installations (GB/T 50064-2014) [clause explanations are attached], and Overvoltage

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Protection and Insulation Coordination Design Guide for Hydro-power Station (NB/T 35067-2015). The Principle of insulation coordination is as follows:

⑴ Under each over-voltage, the insulation strength of electrical equipment shall be higher than the voltage level and have proper margins.

⑵ The resonance over-voltage shall be avoided and eliminated during design and operation.

6.2.7.2 Neutral Point Grounding Mode

⑴ Generator neutral point

The grounding of generator neural point will be achieved by a grounding transformer.

⑵ Main transformer neutral point

Because no special requirements are proposed in the design of grid connection, the 500 kV main transformer neutral point of the HPP is temporarily of the direct grounding mode. 6.2.7.3 Direct lightning protection The roof lightning strips of powerhouse and auxiliary plant of the HPP are used to prevent them from direct lightning. The 500 kV open-type outgoing line platform is equipped with a framework lightning rod and a lightning conductor, which will work together to prevent the platform from direct lightning. The whole 500 kV transmission line is equipped with double lightning conductor to prevent the whole line from direct lightning.

6.2.7.4 Lightning invasion wave OVP1) Arrangement scheme of arrester

According to Overvoltage Protection and Insulation Coordination Design Guide for Hydro-power Station (NB/T 35067-2015), the arrangement scheme of 500 kV arrester of the HPP is as follows: (1) Each circuit of 500 kV outgoing lines shall be equipped with 1 group of zinc oxide arresters aside; (2) Each group of 500 kV GIS bus shall be equipped with 1 group of zinc oxide arresters; ⑶ The 13.8 kV bus at the LV side of each main transformer is equipped with 1 group of zinc oxide arresters, to prevent the LV winding insulation of main transformer from being damaged by the electrostatic component of lightning coupling over-voltage

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generated at the HV winding of main transformer. 2) Lightning over-voltage simulation

The calculation for the over-voltage protection against lightning invasion wave is carried out based on the EMTP software, to check if the arrangement scheme of arrester is rational or not. According to the diagram of main electrical connection of the HPP, the operation mode suffering from the severest over-voltage is "single transformer ~ single line". Therefore, the shortest route is as shown in Fig. 6.2.6-1 (LA1→CVT1→ABS1→CB1→MVT1→LA2→CB2→TR1).

Fig. 6.2.7-1 Simulation Calculation Equivalent Circuit Diagram

The ground capacitance model is applied to a capacitor voltage transformer, a GIS circuit breaker assembly unit, an electromagnetic voltage transformer, and a main transformer.

The wave impedance model is applied to an overhead transmission line and a GIS SF6 tubular bus.

◇ Parameters of line arrester

Rated voltage 444kV

Maximum continuous operating voltage 324kV

8/20μs residual voltage under lightning impulse (20 kA) 1106kV

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30/60μs residual voltage under switching impulse (2 kA) 907kV

◇ Parameters of GIS bus arrester

Rated voltage 420kV

Maximum continuous operating voltage 318kV

8/20μs residual voltage under lightning impulse (20 kA) 1046kV

30/60μs residual voltage under switching impulse (2 kA) 858kV

See Table 6.2.7-1 for volt-ampere characteristics of arrester.

Table 6.2.7-1 Volt-Ampere Characteristics of 500 kV Zinc Oxide Arrester

I(kA) 0 1 5 10 20 40 1mA(DC)

Line side 0 950 1009 1050 1106 1212 597 U(kV) Bus 0 891 946 984 1046 1136 565

◇ Parameters of lightning invasion wave

In the calculation of traveling wave protection, the lightning invasion wave form is of the oblique-angled and flat-topped wave, and only lightning stroke within 0.2 km (the first base tower) is taken into account. The lightning invasion wave has an amplitude of U0=2450kV and a wave head of τ=2.6μs.

◇ Analysis of calculated results

Under the "single line ~ single transformer" operation mode (the worst case), the maximum voltage value and equipment insulation level in case of nearby lightning stroke are listed in Table 6.2.7-2 and the simulation waveform is as shown in Fig. 6.2.7-2.

Table 6.2.7-2 Comparison for Maximum Over-voltage Value and Insulation Level of Equipment

Equipment Node Equipment Maximum Voltage In Case of Equipment Name Insulation Level No. Code Nearby Lightning Stroke (kV)

Zinc oxide arrester at the 1 LA1 835 1675 line side

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Equipment Node Equipment Maximum Voltage In Case of Equipment Name Insulation Level No. Code Nearby Lightning Stroke (kV)

Capacitor voltage 2 CVT1 840 1675 transformer

SF6/air bushing + SF6 3 ABS1 842 1550 conduit

GIS circuit breaker 4 CB1 846 1550 assembly unit

Electromagnetic voltage 5 MVT1 1036 1550 transformer

Zinc oxide arrester at the 6 LA2 1048 1675 GIS bus

GIS circuit breaker 7 CB2 1112 1550 assembly unit

8 Main transformer TR1 1132 1550

Fig. 6.2.7-2 Simulation Waveform for Lightning Over-voltage

3) Conclusion

Under the "single line ~ single transformer" operation mode suffering from the severest

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lightning over-voltage, the arrangement scheme of arrester meets the requirements as follows: the lightning over-voltage level on the 500 kV distribution equipment and main transformer does not exceed the equipment insulation level; both the insulation coordination and the insulation protection margin comply with relevant design codes and specifications.

6.2.7.5 Grounding Design of HPP

a) Principle of grounding design

The working grounding, protective grounding and lightning protection grounding of the HPP share one integral grounding device. The grounding design complies with Ground Design Guide for Hydro-power Station (NB/T 35050-2015) and Code for Design of AC Electrical Installations Earthing (GB 50065-2011).

Lacking of relevant data on grid connection, the allowable value of grounding resistance is temporarily designed as 0.5 Ω. The design principle of grounding system of the HPP is as follows:

⑴ Make full use of the underwater structural reinforcement for ground connection with a natural grounding body, and erect a reservoir grounding grid as the main grounding grid.

⑵ Arrange a voltage balancing net to ensure that neither the contact potential difference nor the step potential difference of the grounding grid will exceed the specified value in relevant codes and specifications.

⑶ Arrange a centralized grounding device near the grounding point with a large earth current, such as main transformer neutral point, grounding point of outgoing line portal framework, grounding point of lightning conductor or grounding point of downlead of open lightning strip, and grounding point of arrester.

⑷ Take the aperiodic component of short-circuit current into account, to prevent 6 kV ~ 10 kV arrester from operation or explosion under the effect of power-frequency transient reverse over-voltage.

⑸ Carry out corresponding grounding grid treatment if the measured grounding resistance of the whole plant cannot meet the design requirements for allowable value of grounding resistance.

b) Constituent parts of grounding grid 6- 78 Paklay Hydropower Project Feasibility Study Report

According to the layout of hydroproject of the HPP, the grounding system of the whole plant is mainly composed of three parts, including reservoir area grounding grid in front of dam, underwater grounding grid behind dam, and grounding grid used for powerhouse, auxiliary plant and ship lock. The grounding grids at each position are interconnected with each other in a multiple manner. According to relevant calculation, the grounding resistance of the HPP is about 0.48 Ω. The constituent parts of the grounding grid at each position are as follows:

⑴ The reservoir area grounding grid in front of dam is composed of reservoir grounding grid in front of dam, grounding grid of dam upstream face and so on.

⑵ The underwater grounding grid behind dam is mainly composed of tailrace grounding grid, grounding grid at dredging area, stilling basin grounding grid after dam, tailrace system grounding grid and so on.

⑶ The grounding grid used for powerhouse, auxiliary plant and ship lock is mainly composed of such natural grounding bodies as grounding steel flat, structural reinforcement mesh of hydraulic structure, and gate slot.

c) Voltage balancing measures

Because grounding grids at each position have different current divergence effects, current shunt will be a major means for the grounding system of the HPP. Because grounding grids are connected via long grounding wires, in case of grounding fault, a large fault current will pass through grounding wires between grounding grids, generating a relatively large voltage drop. In this case, reduction in grounding resistance only cannot achieve the purpose of reduction of grounding grid potential, contact potential and step potential. Therefore, the calculation of contact potential and step potential must be conducted based on the arrangement conditions of grounding grids at each position. In addition, various measures shall be taken to ensure personnel safety of operators at the HPP.

In view of actual conditions of the HPP, the following measures will be taken comprehensively:

⑴ Design of voltage balancing net

The grounding grid used for powerhouse and auxiliary plant of the HPP is composed of special grounding sheet flat and structural reinforcement mesh of structures. The structural

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reinforcement meshes are welded with each other to form small mesh openings. The grounding grid made of special grounding sheet flats is reliably welded and connected with the structural reinforcement mesh, to connect the grounding grids at each structure as a whole. In this way, a voltage balancing net with good effects can be obtained without increase of steel consumption. In addition, the voltage balancing net can reduce the distribution gradient of potential for each grounding grid.

⑵ Control of transfer potential

The control of transfer potential at the HPP is mainly of the high potential isolation, focusing on the communication line and neutral line of LV distribution system.

An isolation transformer and equipment with good insulation performance are used for the communication line, to avoid personal injury or damage of weak current equipment caused by high voltage of communication equipment and line.

If a metal pipe coming out from a grounding grid is an exposed pipe, insulated isolation measures shall be taken for the flange connections.

⑶ Fast fault clearing

Fast fault-clearing measures shall be taken to shorten the duration of grounding fault, to meet the requirements for step potential and contact potential in the guide, to ensure personnel safety. In addition, such measures can reduce difficulties in grounding design and material consumption.

⑷ Multipoint grounding protection and equipotential connection

The LV distribution system of the HPP is of the multipoint grounding mode. Namely, equipotential connection shall be applied to the PE line and neutral line of distribution equipment, grounding main line of electrical equipment, metal case of equipment, metal pipe and metal members of structures. The above items shall be connected with the grounding system. In this way, the personnel safety of operators can be guaranteed.

⑸ Model selection for 10 kV arrester

In model selection of 10 kV arrester, the aperiodic component of short-circuit current shall be taken into account to prevent 6 kV ~ 10 kV arrester from operation or explosion under the effect of power-frequency transient reverse over-voltage.

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6.2.8 Layout of Electrical Equipment The HPP is of a water retaining ground powerhouse, with a powerhouse being 402.0 m in total length and 22.5 m in width, with a main erection bay being 52.0 m in length and 22.5 m in width, with an auxiliary erection bay being 42 m in length and 22.5 m in width, and with downstream auxiliary plant being 376.0 m in length and 23.4 m in width.

The generator operation floor is at the elevation of 222.50 m a.s.l. in the powerhouse, with a unit spacing of 21.5 m. It mainly consists of a governor, oil pressure unit and so on. The main erection bay has an elevation of 228.5 m a.s.l. and the auxiliary erection bay has an elevation of 222.5 m a.s.l. Both main and auxiliary erection bays are provided with 3 positions for stator field assembly, 2 positions for rotor field assembly, 2 positions for field assembly of gate operating mechanism, 2 positions for runner field assembly, 2 positions of field assembly of bulb head, 2 positions for field assembly of cooling jacket, and 2 positions for field assembly of main shaft. The pipeline - bus floor is at the elevation of 219.0 m a.s.l., mainly equipped with such equipment as non-segregated phase enclosed bus (or insulated tubular bus).

Auxiliary plant is arranged closely to the downstream side of the powerhouse. The generator voltage switchgear installation floor is at the elevation of 222.5 m a.s.l., mainly equipped with a VT & LA arrester cabinet, enclosed bus, excitation transformer and others. The main transformer floor is at the elevation of 228.5 m a.s.l., mainly equipped with a main transformer room, HV control room of service power, LV control room of service power, 13.8 kV switch gear and others. The main transformer transport passage is at the downstream side of the main transformer room. The SF6 pipeline floor is at the elevation of 240.5 m a.s.l., mainly equipped with an SF6 pipeline. The GIS switchyard and opened outgoing line platform are set at a floor of an elevation of 245.5 m a.s.l. The outgoing line platform is mainly equipped with an SF6/air bushing, arrester, high frequency wave trap, capacitor voltage transformer, outgoing line framework and others.

6.2.9 List of Main Primary Electrical Equipment See Table 6.2.9-1 for List of Main Primary Electrical Equipment

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Table 6.2.9-1 Main Primary Electrical Equipment

Main S/N Description Parameter Unit Qty. Remarks Equipment

Generator SFWG55-64/8000 55MW Set 14

Excitation 13.8kV Set 14 transformer

VT cabinet 13.8kV Nos. 14

VT & LA 13.8kV Nos. 5 cabinet

SF6 gas circuit breaker of 13.8kV 3150A 80kA Set 14 generator

Grounding 3 Set 14 transformer 13.8/ kV

Isolated-phase QZFM-13.8/8000 1 m 300 enclosed bus 13.8kV 8000A 80kA

HV current limiting fuse 13.8kV Nos. 4 cabinet

Non-segregated phase enclosed

bus (or 13.8kV 3150A 63kA m 1250 insulated tubular bus)

Isolation switch 13.8kV Nos. 5 cabinet

Generator and generator voltage switchgear installation switchgear voltage generator and Generator SSP-H-180000/500 Main Combined 2 180000kVA Set 4 transformer 3-phase 525±2×2.5%/13.8kV Power Power transform er

6- 82 Paklay Hydropower Project Feasibility Study Report

Ud=14% YNd11 transformer

SSP-H-120000/500 Combined Main 120000kVA Set 1 3-phase transformer 525±2×2.5%/13.8kV transformer Ud=14% YNd11

Circuit breaker 500kV 3150A 50kA Set 8

Including Isolator 500kV 3150A 50kA Group 23 earthing switch

3 Electromagnetic voltage 500kV Set 6 transformer

GIS SF6 arrester YH10W-444/1050 Set 6

500kV 500kV GIS

SF6/air bushing 500kV 3150A 50kA Nr. 6

High frequency 500kV Set 6 wave trap

Capacitor

potential 500kV Set 6 transformer 4 Zinc oxide YH10W-444/1065 Set 6 arrester

500 kV opened outgoing line equipment line outgoing opened 500 kV

HV station SCB10-4000/13.8 5 service Set 4 transformer 13.8±2x2.5%/10.5kV Station Station service power equipment

6- 83 Paklay Hydropower Project Feasibility Study Report

Dam crest SCB10-1000/13.8 Set 2 transformer 13.8±2x2.5%/0.4kV

Unit service SCB10-500/10.5 power Set 2 transformer 10.5±2x2.5%/0.4kV

Unit service SCB10-1600/10.5 power Set 4 transformer 10.5±2x2.5%/0.4kV

Diesel generator 0.4kV 800kW Set 1 unit at dam

Transformer for SCB10-2000/10.5 common power Set 4 10.5±2x2.5%/0.4kV demand of plant

Protective load SCB10-630/10.5 Set 2 transformer 10.5±2x2.5%/0.4kV

Transformer SCB10-400/10.5 special for Set 2 10.5±2x2.5%/0.4kV lighting

HV switchgear 10.5kV 630A 31.5kA Nos. 35

Isolation 10.5kV Nos. 2 cabinet

VT & LA 10.5kV Nos. 4 cabinet

LV switchgear 0.4kV MNS3.0 Nos. 180

Diesel generator unit for 0.4kV 800kVA Set 1 powerhouse

13.8 kV cable 13.8kV YJV22-3x35 m 4000 6 Cable LV cable Item 1

7 Grounding Item 1

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8 Lighting Item 1

9 Bridge Item 1

Fire 10 Item 1 Protection

6.3 Control, Protection and Instrumentation 6.3.1 Control The Paklay HPP is the first cascade HPP proposed to be developed on the main stream of the Mekong River in Laos, with a planned total installed capacity of 770 MW and 14 sets of 55 MW bulb turbine-generator units. The HPP plays an important role in the electric power system. Due to lack of relevant data about the electric power system at present, in the follow-up design, relevant codes and design information of the system connection shall be used for defining the dispatching management relationship, telecontrol and other information exchange. At present, it is temporarily determined that the 500 kV system shall be dispatched by Laos Power Dispatching Center.

6.3.1.1 Plant centralized computer monitoring system

The plant is proposed to operate with no fulltime personnel on duty (a few people on watch) and be monitored in centralized manner by computer monitoring. The computer monitoring system shall be of an open network architecture distributed in layers. The system shall consist of a main control level and a local control level. Ethernet with 100M redundancy shall be used for communication between the upper and lower levels. The network topology of the main control level shall be of a twin-stelliform network while that of the local control level shall be of a double loop network. Main control level equipment shall use twisted pair cables as its communication media while local control level equipment shall use optical fibers as its communication media. See attached drawing - PAKLAY-EM-ES-01 for structural configuration of the computer monitoring system.

The main control level equipment of the computer monitoring system shall consist of 2 historical database servers, 1 set of disk arrays, 2 application program servers, 2 operator workstations, 1 engineer workstation, 1 training workstation, 1 plant intercommunication server, 2 remote communication servers, 1 voice alarm and report forms workstation, 1 set of mimic board and drive device, 2 sets of network equipment, 2 network printer, 1 set of 6- 85 Paklay Hydropower Project Feasibility Study Report clock synchronization system, 2 sets of UPS power supplies and so on. The main control level equipment shall be used for monitoring the whole plant. Operating crew can monitor main M & E equipment in the whole plant via the mimic board in the central control room, liquid crystal display (LCD), keyboard, mouse and others in the operator workstations. The 2 remote communication servers shall be used for communication with Laos Power Dispatching Department, in order to achieve remote dispatch. The plant intercommunication server shall be used for communication with fire alarm system, MIS system of the HPP etc., in order to achieve information exchange. A unit emergency shutdown button and an emergency incident shutdown button shall be provided for the mimic board, independent of the monitoring system, in order to achieve manual operation in case of emergency.

In view of each unit, 500 kV switchyard, station service power, plant utilities and dam gates, the local control level shall consist of 18 local control units (LCU), including 14 LCUs for the units, 1 LCU for the 500 kV switchyard, 1 LCU for the station service power, 1 LCU for the utilities and 1 LCU for the dam gates. The micro-computer governor, micro-computer excitation device, micro-computer relay protection device and micro-computer monitoring instrument of units shall communicate with their corresponding LCUs.

Unit auxiliary equipment, plant utilities and others shall respectively adopt an independent programmable logic controller (PLC) so as to independently achieve automatic control based on their own control programs; in addition, the above items shall be able to communicate with their corresponding LCUs. The LCU shall be used for implementing process control for the controlled objects, collecting and processing data, and carrying out accident detecting and alarming.

Each dam crest flood gate shall be provided with 1 local control cabinet, composed of a PLC and a motor starter. Ethernet shall be used for communication between the dam gates and LCU.

The main control level equipment of the whole plant shall be respectively arranged in the computer room and central control room; the unit control level equipment shall be respectively arranged beside each unit and in the corresponding relay protection room.

The HPP shall be provided with 1 monitoring system for flooding of powerhouse.

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Both ends of the gallery floor of the powerhouse shall be equipped with one water level annunciator, which will transmit alerting signals in case of water and shall be connected to the computer monitoring system.

6.3.1.2 Automation of unit

The self-shunt thyristor rectifier static excitation system is adopted for the excitation system, which is composed of an excitation transformer, three-phase full-control power rectifier unit, micro-computer excitation regulator, magnetic field circuit breaker, AC/DC overvoltage and incomplete phase protection, excitation build-up device current transformer and potential transformer for measurement, etc. The excitation system is of a micro-computer excitation regulator with two channels. Each channel is provided with an automatic voltage regulator (AVR) unit and an automatic current regulator (ACR) unit. Interface for communication with LCU of the computer monitoring system unit is adopted for the micro-computer excitation regulator to achieve monitoring and regulation of the generator excitation via the monitoring system. Normal shutdown is achieved by inverse de-excitation, while emergency shutdown is achieved by a DC de-excitation switch plus oxidizing nonlinear resistor de-excitation.

To ensure units, relevant auxiliary equipment and plant utility system can safely operate, the selected automation elements shall be able to correctly and reliably monitor the operating parameters and conditions of oil, gas, water and important parts such as bearing and generator stators, in order to provide reliable and accurate information for the computer monitoring system and form a reliable hydraulic mechanical protection system. Non-electric quantity items mainly consist of temperature, discharge, pressure, liquid level, etc. A resistance temperature detector (RTD) of the computer monitoring system is used for directly sampling so as to measure the unit temperature. Other non-electric quantity items are collected by a transmitter and transformed to be 4 ~ 20 mA of analog signals and finally transmitted to the computer monitoring system.

6.3.2 Protective Relaying 6.3.2.1 Protective relaying of main equipment

Protective relaying of all equipment in the HPP adopts digital protection equipment, with each level of protection function in accordance with relevant standards and provisions. In view of specific characteristics of main electrical connection of the Paklay HPP, single

6- 87 Paklay Hydropower Project Feasibility Study Report protection configuration is applied to the generators; electric quantity protection of main transformers, protection of 500 kV lines, and protection of 500 kV bus all adopt duplex configuration. See attached drawing - PAKLAY-EM-ES-02 for details.

It is preliminarily to provide the generators with the following protections: completely longitudinal differential protection, zero-sequence current transverse differential protection, LV over-current protection with current memory, over-load protection of stator, protection for loss of excitation, negative-sequence over-current protection, stator grounding protection, one-point grounding protection of rotor, stator OVP protection, shaft-current protection, over excitation protection, excitation winding overload protection, reverse power protection, CT break-wire protection, PT break-wire protection, etc.

It is preliminarily to provide the 500 kV main transformer with the following protections: longitudinal differential protection, zero-sequence current protection, over-current protection of compound voltage, CT break-wire protection, PT break-wire protection and over excitation protection. Non-electric protection of the transformers includes gas protection, gusty pressure relief protection, temperature protection, abnormal oil level protection, cooler failure protection, etc. Bus protection: each 500 kV bus is provided with two sets of bus differential protection.

Line protection, protection of a 500 kV line shall be configured according to the relevant provisions and requirements of the electric power system.

Excitation transformer protections consist of cut-off protection, over-current protection and temperature protection.

Station service transformer protections consist of cut-off protection, over-current protection and temperature protection.

Protection of station service power: digital protection equipment is provided in corresponding switchgear and communicates with the LCU of the station service power.

6.3.2.2 Fault recorder and automatic safety device

For the convenience of fault analysis, the 500 kV switchyard is provided with 2 sets of micro-computer fault recorders, while the 220 kV switchyard is provided with 1 set of micro-computer fault recorders. Configuration of the automatic safety device shall meet

6- 88 Paklay Hydropower Project Feasibility Study Report requirements of the electric power system.

6.3.3 Secondary Connection To meet measuring, metering and synchronizing requirements of the HPP, 0.5-level current transformers for measurement are respectively configured at the HV side of the excitation transformer and at the HV side of the station service transformer; 0.2-level current transformers for measurement are configured for the 500 kV circuit breaker etc.; a 0.2-level current transformer for metering and measurement is configured at the generator terminal; 0.2S-level current transformers for metering are configured at the HV side of main transformers and 500 kV outgoing lines; corresponding potential transformers are configured for the generator terminal, generator voltage bus, 500 kV bus and line etc.

6.3.3.1 Measurement

Electric quantity of the station service power, DC system, and switchgear installation of the HPP is measured by a transmitter and collected by an AC sampling device. The electric quantity then will be transformed to be 4 mA ~ 20 mA of analog quantity or transmitted to the computer monitoring system via data communication mode. Water level, pressure, discharge, temperature etc. of the HPP are measured by a transmitter or directly collected by a RTD, and then transformed to be 4 mA ~ 20 mA of analog quantity or directly transmitted to the computer monitoring system via the RTD temperature measurement module.

6.3.3.2 Synchronization system

Microcomputer-based automatic precise synchronizing device is selected as the main synchronization method of the HPP. Manual precise synchronization with asynchronous blocking is provided as a back-up synchronization method. Each generator circuit breaker and 500 kV circuit breaker will serve as synchronizing points. Each unit is equipped with 1 set of single-object synchronizing device and the 500 kV switchyard is equipped with 1 set of multiple-object synchronizing device.

6.3.3.3 Signal

No routine central alarm signal is set in the central control room of the HPP. An alarm is given by voice alarm device of the computer monitoring system and displayed by the operator workstation. To meet requirements of local control and monitoring, each LCU is

6- 89 Paklay Hydropower Project Feasibility Study Report equipped with a LCD. The local control cabinet of all equipment is equipped with signal lights for equipment status and monitoring of power supply.

6.3.3.4 Operation and locking

The computer monitoring system in the central control room can be used for centralized monitoring of all HV circuit breakers, 500 kV isolators and earthing switches, circuit breakers at the LV side of station service transformers, station service bus sectionalizing circuit breakers and others of the HPP. Local control is set for other isolators, earthing switches, outgoing breakers of 400 V station service power, etc.

Status signal indication is set for all circuit breakers on the local control cabinet, which can be controlled manually. Necessary locking function is set at tripping and closing circuits of the isolators and earthing switches to prevent from misoperation.

The mimic board in the central control room is equipped with simply measuring meters, equipment status signal device and emergency operation button, etc.

6.3.4 Control Power Supply System The HPP has a large powerhouse area and decentralized layout of M & E equipment. To reduce distance and scope of power supply, the control power supply system shall be arranged in a properly decentralized manner, so as to reduce the impact scope related to power failure or maintenance, and improve reliability of the control power supply system.

The HPP is proposed to employ 4 sets of 220 V AC/DC control power supply systems. Fourteen units, accident lighting, utilities and station service power system will share 2 sets of the control power supply systems. Unit control, protection and operation, station service power, utilities control and accident lighting in the No. 1 ~ No. 7 unit bays will share 1 set of control power supply system. Unit control, protection and operation, station service power, utilities control and accident lighting in the No. 8 ~ No. 14 unit bays will share 1 set of control power supply system. Switchyard and central control room will share 1 set of control power supply system. In addition, dam site will be provided with 1 set of control power supply system. Each set of DC power supply system shall employ two groups of batteries, in order to ensure safe operation of the HPP and be convenient for maintenance. All DC systems shall adopt single-bus sectionalized connection. Each section of bus shall be connected with one group of battery and one set of float charging device. Normally, a battery operates in float charging mode and two groups of batteries stand up for each other. 6- 90 Paklay Hydropower Project Feasibility Study Report

The battery shall be valve-controlled sealed lead-acid battery, with a rated voltage of 2 V. Each group of batteries of the 4 sets of control power supply systems respectively has a capacity of 600 Ah, 600 Ah, 600 Ah and 200 Ah. See attached drawing - PAKLAY-EM-ES-03 for the control power supply system.

6.3.5 Communication The HPP communication consists of dispatching communication of the electric power system, HPP internal dispatching and administrative management communication, communication with local telephone department, etc.

The dispatching communication of the electric power system shall be set according to requirements of the electric power system. Due to lack of relevant data about the electric power system at present, it is temporarily considered to use two types of communication channels, with a main communication channel using the OPGW optical fiber and a standby communication channel using the power line carrier.

The HPP internal dispatching and administrative management communication shall use 1 set of dispatching communication equipment and 1 set of administrative communication equipment, equipped with corresponding intelligent dispatching console, attendant desk, digital recording system, maintenance and charging terminal, wiring devices, etc. It shall also be equipped with 1 set of in-plant addressable broadcast system and 1 set of in-plant wireless intercom system.

Communication with the local telephone department shall be set according to the existing local conditions. At present, it is temporarily proposed to use digital relay lines for connecting the digital program-controlled exchangers with program-controlled switching equipment of the local telephone department.

The HPP is equipped with 2 sets of power supply units for communication. Each set consists of 2 groups of high-frequency switch rectifiers, 2 groups of valve-controlled sealed lead-acid battery of 48 V/200 Ah, etc. AC power of the high-frequency switch rectifiers comes from the station service power.

Emergency communication of the HPP is temporarily proposed to use 2 satellite phones.

6.3.6 Industrial Television Monitoring System

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One set of all-digital industrial television monitoring system shall be provided, which includes two areas - the HPP area and navigation lock area. Each area shall be equipped with an independent server, hard disk video, monitoring terminal, camera, switching control device, exchanger, etc., which will form two area systems operating independently. Network shall be used for communication between the two systems; important video images can be uploaded to the central control room of the HPP. The industrial television monitoring scope involves the powerhouse, switchyard, control building, dam crest, navigation lock, important safety exits, etc. The system transmits the camera video signal and control signal via Ethernet. It is able to carry out digital coding, compressing, picture recording, monitoring, multi-picture separating and controlling for video signals. In addition, it is also able to interlock with the fire alarm system and monitoring system for flooding of powerhouse.

At present, the HPP is proposed to employ 80 cameras, a hard disk video with 128-channel capacity, 2 serves, 1 monitoring terminal and 1000M backbone network. The ship lift is proposed to employ 20 cameras, a hard disk video with 32-channel capacity, 1 serve, 1 monitoring terminal and 100 M backbone network. A 100M Ethernet is used for connecting the HPP with the ship lift area.

The monitoring terminals are installed in the central control room and navigation lock control room. The servers, hard disk videos and main network equipment panels are installed in the relay protection room. The cameras and front-end accessory equipment etc. are installed on site. Power supply of all cameras and front-end accessory equipment is taken nearby where they are installed.

6.3.7 Electrical testing laboratory Electrical testing consists of HV test, relay protection test, automation test, electrotechnical instrument verification, etc. Selected instrument and testing apparatuses shall meet requirements of operation and maintenance, acceptance and preventive test, general test, supervising verification and adjustment test, repair, element test, etc. Equipment for electrical testing laboratory shall be provided as per Grade-I electrical testing laboratory.

6.3.8 Navigation Control System of Navigation Lock Navigation control of the navigation lock is achieved by a navigation lock control

6- 92 Paklay Hydropower Project Feasibility Study Report system focused on a computer. The system consists of 1 set of upstream gate control unit, 1 set of downstream gate control unit, and 1 set of centralized control unit. Ethernet with 100M redundancy is used for communication between each unit. The network topology is of a twin-stelliform network and equipment communication media is optical fiber. The control system and gate hoisting device are equipped with 1 set of independent AC/DC control power supply system.

The fire alarm and joint control devices as well as communication devices in the navigation lock area are all included in the fire fighting system and communication system of the HPP.

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6.3.9 List of Main Secondary Electrical Equipment See Table 6.3.9-1 for List of Main Secondary Electrical Equipment

Table 6.3.9-1 Main Secondary Electrical Equipment

S/N Description of Equipment Qty. Remarks I Automatic system of unit 1 Control cabinet for unit governor and oil pressure unit 14 x 1 Included in the unit governor 2 Unit excitation system 14 x 1 3 Control system of auxiliary equipment 14 x 1 Included in the unit II Computer monitoring system 1 Historical database server 2 2 Disk array 1 3 Application server 2 4 Operator workstation 2 5 Engineer workstation 1 6 Simulation training workstation 1 7 Voice alarm and report forms workstation 1 8 Mimic board and drive device 1 9 Remote communication server 2 10 In-plant communication server 1 11 Network printer 2 12 Double-seat console 1 13 Ethernet network device 2 14 Clock synchronization system 1 15 LCU for unit (including synchronizing devices, etc.) 14 x 1 LCU for switchyard (including synchronizing devices, 16 1 etc.) 17 LCU for dam gate 1 18 LCU for utilities 1 19 LCU for station service power 1 Utilities control system (including drainage and 20 1 compressed air system, etc.) 21 Monitoring system for vibration and throw of unit 14 x 1 Included in the unit Included in the complete 22 Local control cabinet of dam flood gate hoist equipment 23 Ventilation control system 1 III Relay protection and automatic safety device 6- 94 Paklay Hydropower Project Feasibility Study Report

S/N Description of Equipment Qty. Remarks 1 Generator protective equipment 14 x 1 2 Transformer protective equipment 5 x 2 3 500 kV line protective equipment 2 x 2 4 500 kV bus protective equipment 2 5 500 kV fault recorder 1 Configured as per 6 Automatic safety device for 500 kV system 1 requirements of the electrical power system 10 kV protective equipment and automatic bus transfer 7 Included in the switchgear equipment 400 V protective equipment and automatic bus transfer 8 Included in the switchgear equipment IV Control power supply system With 2 groups of batteries 1 AC/DC control power supply in No. 1 ~ No. 7 unit bays 1 being 600 Ah and 2 groups of float charging devices With 2 groups of batteries AC/DC control power supply in No. 8 ~ No. 14 unit 2 1 being 600 Ah and 2 groups bays of float charging devices With 2 groups of batteries 220 V control power supply for GIS switchyard and 3 1 being 600 Ah and 2 groups central control room of float charging devices With 2 groups of batteries 4 220 V control power supply of dam gate 1 being 200 Ah and 2 groups of float charging devices UPS for Main control level of computer monitoring 5 2 30 kVA, free of battery system V Communication system 1 Carrier communication equipment 2 2 Optical fiber communication equipment 1 Including navigation lock 3 In-plant administrative communication equipment 1 part 4 Dispatching communication equipment 1 5 In-plant addressable broadcast equipment 1 6 In-plant wireless intercom equipment 1 7 Communication power supply equipment 2 8 Communication cable 50km 9 Emergency communication equipment 1 2 hand-held satellite phones Equipped with 100 cameras VI Industrial TV system 1 (including navigation lock part) Including navigation lock VII Automatic fire control and alarm system 1 part Including 4 gateway energy VIII Electric energy metering system 1 meters IX Navigation lock control system 1 AC/DC control power supply system for navigation X 1 lock XI Control cable Armored, fire-proof and Estimated as per 8 x 1.5 cables 500km overall shield XII Others Electrical testing equipment 1 6- 95 Paklay Hydropower Project Feasibility Study Report

6.4 Hydraulic Steel Structures

Hydraulic steel structure equipment of the Paklay HPP is mainly distributed in the flood discharging system, headrace and power generation system, navigation lock system and fish pass structure. Work amount of the hydraulic steel structures is 23,170 t in total. See Table 6.4-1 - Summary Sheet of Main Metal Structure Equipment of the Paklay HPP for details.

6.4.1 Metal Structure Equipment of Flood Release System

According to project layout, the flood releasing and flushing system structures are provided with 2 flushing bottom outlets, 3 low-level surface bays (the low-level surface bays are set for the purpose of flood releasing and sediment discharge) and 11 high-level surface bays in sequence from left to right.

The hydraulic steel structure equipment of the flood releasing and flushing system is composed of the upstream bulkhead gate and service gate of the release sluice, downstream bulkhead gate of the release sluice, the emergency bulkhead gate, service gate and outlet bulkhead gate of the flushing bottom outlets, as well as the corresponding hoists. For the details of arrangement, please refer to the Layout Plan for Gates and Hoists of the Flood Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (1/5)), the Layout for Gates and Hoists of Low-level Surface Bays of the Flood Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (2/5)), the Layout for Gates and Hoists of High-level

Surface Bays (with stilling basin) of the Flood Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (3/5)), the Layout for Gates and Hoists of High-level Surface Bays (without stilling basin) of the Flood Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (4/5)) and the Layout for Gates and Hoists of Flushing Bottom Outlets of the Flood Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (5/5)).

6.4.1.1 Upstream Bulkhead Gate for Low-Level Surface Bay of Flood Discharge Gate

The upstream bulkhead gate for the low-level surface bay of the flood discharge gate 6- 96 Paklay Hydropower Project Feasibility Study Report is set at the upstream side of the service gate for the low-level surface bay. There are 3 outlets in total. For the bulkhead gate, the orifice width is 16.0m, the normal pool level is 240.000m, the design flood level is 239.020m, the check flood level is 240.530m. For the low-level surface bay, the crest elevation is 212.000m, the elevation of sill is 212.000m, the design water head is 28.0m and the gate height is about 29.0m. The gate shall be the emerged plane stoplog sliding gate supported by a high-strength and low-friction composite slide block. The gate is closed in static water and lifted by filling water between segments. The gate is operated by the gantry crane main hook on the dam crest of release sluice dam monolith through the automatic hydraulic pick-up beam. The gate is normally locked at the top of gate slot with flashboard locking device. One segment is locked in each orifice. The gate leaves exceeding the number of gate slot orifices shall be locked on the dam crest between oil cylinder trunnion of high-level surface bays and downstream pedestrian bridge.

6.4.1.2 Upstream Bulkhead Gate for High-Level Surface Bay of Release Sluice

The upstream bulkhead gate for the high-level surface bay of release sluice is set at the upstream side of the service gate for the high-level surface bay. There are 11 outlets in total. For the bulkhead gate, the orifice width is 16.0m, the normal pool level is 240.000m, the design flood level is 239.020m, the check flood level is 240.530m. For the high-level surface bay, the crest elevation is 220.000m, the elevation of sill is 220.000m, the design water head is 20.0m and the gate height is about 20.3m. The gate shall be the emerged plane stoplog sliding gate supported by a high-strength and low-friction composite slide block. The gate is closed in static water and lifted by filling water between sections. The gate is operated with the gantry crane main hook on the dam crest of the release sluice dam monolith through the automatic hydraulic pick-up beam. One upstream bulkhead gate is set for the high-level surface bay and the gate is normally locked at the top of gate slot with flashboard locking device. Each gate segment leaf is exchangeable with each segment leaf of the upstream bulkhead gate for the low-level surface bays. The 14 crest overflowing

6- 97 Paklay Hydropower Project Feasibility Study Report outlets share 2 bulkhead gates. The gate is normally locked at the top of gate slot with flashboard locking device.

6.4.1.3 Dam Crest Gantry Crane of Release Sluice

One two-way gantry crane with a downstream cantilever is provided on the top of flood releasing dam monolith. It is mainly used to hoist the upstream and downstream bulkhead gates of the release sluice and for the erection, examination and repairing of the service gate of the release sluice and its hoists. The main hook capacity of the dam crest two-way gantry crane is 2×800kN. An auxiliary trolley, with hoisting capacity of 2×400kN, is provided on the downstream cantilever of the gantry crane. The track gauge of the gantry crane is 32.5m, the main hook lift is 50.0m and the secondary hook lift is 58.0m.

6.4.1.4 Service Gate for Low-level Surface Bay of Release Sluice The low-level surface bay of the release sluice is provided with 3 service gates, each outlet is provided with 1 service gate. There are 3 service gates in total. Given the radial gate of the release sluice has no gate slot, with good flowing condition and small vibration upon partial lifting of the gate, the radial gate is adopted as the service gate. The width of gate orifice is 16.0m, the normal pool level is 240.000m, the design flood level is 239.020m and the check flood level is 240.530m. For the low-level surface bay, the crest elevation is 212.000m. And for the service gate, the elevation of sill is 212.000m, the design water head is 28.0m, the gate height is about 28.5m and the panel curvature radius is 31.0m. The elevation of the radial gate trunnion is decided as 235.000m as per the principle that the trunnion shall not be impacted while discharging a 100-year flood. Three main beam and oblique supporting arms structure is employed for the radial gate structure. And the spherical sliding bearing is adopted for trunnion bearing. It is designed to be lifted and closed in dynamic water and to allow partially lifting for flow regulation. When the radial gate is fully opened, the bottom edge of the gate is preliminarily considered to be at an elevation of 241.000m; this ensures that the radial gate will not be subject to the strike of the water flow or the floating debris during flood release at check flood level.

6- 98 Paklay Hydropower Project Feasibility Study Report

6.4.1.5 Service Gate Hoist for the Low-level Surface Bay of the Release Sluice Each service gate with the low-level surface bay is provided with 1 set of hoist. Since the hydraulic hoist is characterized by simple structure, small volume, stable transmission, such advantages as no adoption of high bent frame, convenience of remote control and good-looking arrangement of dam surface, it is used for the service gate. The hoist for the radial gate with the low-level surface bay has a capacity of 2×6500kN with an operating stroke of about 13.0 m. The hoist for the radial service gate with the low-level surface bay is suspended, with the upper bearings of the two oil cylinders being respectively fixed onto the side walls of the left and right gate piers and the lower ends being connected to the gate lifting eye on the rear flange of the lower main beam. Each set of hydraulic hoist shall be provided with a pump station and the hoist shall be controlled both locally and remotely. 6.4.1.6 Service Gate for the High-level Surface Bay of the Release Sluice

At the right side of the low-level surface bay of the release sluice, 11 high-level surface bays are provided, each outlet is provided with 1 service gate. There are 11 service gates in total. The crest elevation is 220.000m. And for the gate, the elevation of sill is 220.000m, the design head is 20.0m, the gate height is about 20.5m and the panel curvature radius is 25.0m. The elevation of the radial gate trunnion is decided as 235.000m as per the principle that the trunnion shall not be impacted while discharging a 100-year flood. Double main beam and oblique supporting arms structure is employed for the radial gate structure. And the spherical sliding bearing is adopted for trunnion bearing. It is designed to be lifted and closed in dynamic water and to allow partially lifting for flow regulation. When the radial gate is fully opened, the bottom edge of the gate is preliminarily considered to be at an elevation of 241.000m; this ensures that the radial gate will not be subject to the strike of the water flow or the floating debris during flood release at check flood level.

6.4.1.7 Service Gate Hoist for the High-level Surface Bay of the Release Sluice

One set of hydraulic hoist with hoisting capacity of 2×3800kN and working stroke of

6- 99 Paklay Hydropower Project Feasibility Study Report about 10.0m is provided for each service gate. The radial service gate hoist for the high-level surface bay shall be hanging mounted. The upper bearings of the two oil cylinders shall be fixed on the side walls of the left and right gate piers of the gate, respectively, while the lower ends shall be connected with the gate hoist eye of the lower main beam rear wing plate of the gate. Every set of hydraulic hoist shall be equipped with 1 pump station. The hoist shall be controlled by the combination of local control and remote control.

6.4.1.8 Downstream Bulkhead Gate of the Release Sluice

At the downstream of each service gate for release sluice, a 1-orifice bulkhead gate slot shall be provided. There are 14 orifices in total. The orifice width of the bulkhead gate is 16.0m. The elevation of sill for the downstream bulkhead gate of the low-level surface bay is 204.201m, while that for the 5 high-level surface bays at left is 212.206m and that for the 6 high-level surface bays at the right is 220.000m. One downstream bulkhead gate is provided by taking the tailwater level of 224.140m when the unit is at full load as the downstream service level. The bulkhead gate, with a height of about 20.9m and design water head of about 19.939m, is provided for service gate and gate slot repairing and maintenance. For low-level surface bays, 11 segments shall be used; for high-level surface bays with stilling basin, 7 segments shall be used; for high-level surface bays without stilling basin, 3 segments shall be used. The gate shall be the emerged plane stoplog sliding gate. It is supported by a high-strength and low-friction composite slide block. Each leaf of gate segments are exchangeable and 1 bulkhead gate is shared by 14 outlets. The gate is closed in static water and lifted by filling water between sections. The gate is normally locked by segment on the platform with an elevation of 245.000m above the downstream side orifice of the downstream track of the dam crest gantry crane at the high-level surface bay dam monolith.

6.4.1.9 Downstream Bulkhead Gate Hoist of the Release Sluice

The downstream bulkhead gate of the release sluice is operated with the secondary 6-100 Paklay Hydropower Project Feasibility Study Report hook of downstream cantilever on the dam crest two-way gantry crane at the release sluice dam monolith through the hydraulic automatic pick-up beam.

6.4.1.9 Emergency Bulkhead Gate of the Flushing Bottom Outlet

Two flushing bottom outlets share 1 emergency bulkhead gate. The emergency bulkhead gate is of plane fixed wheel gate for closing in dynamic water in case of service gate accident, and for orifice closing during service gate and gate slot maintenance; for the gate, the orifice size is 10.0m×12.1m, the elevation of sill is 205.000m and the design water head is 35.0m. The emergency bulkhead gate adopts the form of upstream board and upstream water stop. And the gate is closed by dead weight of itself. A filling valve is equipped at the top of the gate for gate lifting in static water after the pressure is balanced by water filling of the filling valve. The gate is normally locked at the top of the gate slot.

6.4.1.10 Emergency Bulkhead Gate Hoist of the Flushing Bottom Outlet

The emergency bulkhead gate of the flushing bottom outlet is operated with the platform hoist set on the dam crest bent. For the platform hoist, the hoisting capacity is 2500kN and the lift is about 42.0m.

6.4.1.11 Service Gate of the Flushing Bottom Outlet

The service gate is arranged at the downstream outlet of the flushing bottom outlet with 1 service gate for each flushing bottom outlet. There are 2 service gates in total. The gate is of plane fixed wheel gate with an orifice dimension of 10.0m×10.0m, the elevation of sill of 205.000m and the design water head of 35.0m; to prevent sediment deposition in the tunnel and beam grillage of the gate, the service gate adopts the form of upstream board and upstream water stop. The gate is lifted and closed in dynamic water and the maximum head difference during operation in dynamic water is about 20m.

6.4.1.12 Service Gate Hoist of the Flushing Bottom Outlet

The service gate of the flushing bottom outlet is operated with the stationary winch hoist set on the dam crest bent. For the hoist, the hoisting capacity is 3200kN and the lift is 6-101 Paklay Hydropower Project Feasibility Study Report about 34.0m. A bridge crane with capacity of 30kN shall be set on the top of the hoist room for maintenance of the hoisting equipment for the service gate of the flushing bottom outlet.

6.4.1.13 Outlet Bulkhead Gate of the Flushing Bottom Outlet

As the sill is submerged in the downstream water level of the flushing bottom outlet for a long time, for the maintenance of the waterway, tunnel and embedded parts of the slot, 1 bulkhead gate slot shall be provided at the downstream side of the service gate slot at the outlet of each flushing bottom outlet. There are 2 outlets in total which share 1 bulkhead gate. For the gate, the orifice dimension is 10.0m×10.0m, the elevation of sill is 205.000m, the design water level is 235.600m which is also the downstream design flood level and the design water head is 30.6m. The gate is of plane sliding gate supported by a high-strength and low-friction composite slide block. And the simple supporting side wheels are used to serve as the lateral support. The gate closed in static water is lifted when the pressure is balanced by water filling of the filling valve set on the top of the gate. The gate is normally locked on the top of the gate slot in two segments.

6.4.1.14 Outlet Bulkhead Gate Hoist of the Flushing Bottom Outlet

Lifting and closing of the outlet bulkhead gate of the flushing bottom outlet are realized by tailrace 2×1600kN gantry crane through the hydraulic automatic pick-up beam. 6.4.2 Hydraulic steel Structure Equipment of Headrace and Power Generation System The headrace and power generation system is equipped with 14 units in total and each unit is equipped with a single headrace tunnel and a single draft tube. Hydraulic steel structure equipment of headrace and power generation system mainly consists of an intake trashrack, intake trash rack, intake bulkhead gate, tailrace emergency gate and corresponding hoists. For the details of arrangement, please refer to the Layout Plan for the Trashrack of the Headrace and Power Generation System (Drawing No.: Paklay-FS-MS-02(1/2)) and Layout for Gates and Hoists of the Headrace and Power Generation System (Drawing No.: Paklay-FS-MS-02(2/2)).

6.4.2.1 Intake trashrack and embedded parts 6-102 Paklay Hydropower Project Feasibility Study Report

One trashrack guide slot column is provided on the guide wall between the flushing outlet dam monolith and the power station dam monolith and one provided at the place about 610m upstream of the power station on the left bank. Between the aforementioned two trashrack guide slot columns, another two trashrack guide slot columns are arranged to divide the whole trashrack into 3 sections. 3 sets of trashracks are furnished. Each set of trashrack is composed of the pedestals with floating camel at both ends and several floating caissons which are interconnected with tie bars. Pedestals with floating camel at both ends shall be restrained in the guide slot arranged in vertical and lifted up and down along the guide slot track through rollers. Grids are welded at the upstream face of the floating caisson, allowing the whole trashrack to go up and down along with the water. The trash before the trashrack shall be cleaned manually with wastes cleaning boats. The reason why trash cleaning boat is used to remove the trashes in front of the trash boom rather than setting a flap gate in the radial service gate of flood discharging for surface trash discharging is mainly based on the following consideration: during the non-flood season, the surface trashes are comparatively of small quantity and frequent discharge of the trashes is not good for concentrative cleaning and will affect the downstream environment. Besides, the discharge of the trashes from the trash boom does not ensure the thorough cleaning and trash cleaning boat may still be needed. During the flood season, in case of the occurrence of a 2-year flood or flood with longer return period, there will be a lot of surface trashes. For this case, as the flood discharge is realized by fully opening the gate, the trashes could be discharged to the downstream as well with the fully-opened radial gate. 6.4.2.2 Intake trash rack

An intermediate pier is set at the water intake of each unit, which evenly divides the water intake to be 2 orifices and 2 trash racks are provided. The 14 units are corresponding to 28 orifices; therefore, 28 trash racks are required in total. The trash rack has an orifice width of 6.65 m and orifice height of 28.0 m, all of which are arranged vertically. All trash racks are designed as per a head difference of 4.0 m. The composite sliding block is employed for both reverse guide and support of the trash rack, connected to the dam crest by a tie bar for locking. A cleaning guide slot is set in front of a trash rack slot. The cleaning grab bucket is operated by the dam crest gantry crane at the intake monolith to

6-103 Paklay Hydropower Project Feasibility Study Report remove trash of the trash rack. When a trash rack needs to be maintained, a dam crest gantry crane at the intake monolith is used for hoisting the trash rack onto the dam crest. 6.4.2.3 Intake bulkhead gate

Behind each intake trash rack slot, 1 intake bulkhead gate slot is set. The 14 units are corresponding to 14 orifices in total; after power generation by the first generator unit, intakes shall be closed for installation of other units; therefore, 14 bulkhead gates are needed in total, including 4 permanent bulkhead gates and 10 gates for temporary water retaining during construction. The bulkhead gates have an orifice width of 15.1 m, height of 16.3 m, sill elevation of about 201.020 m a.s.l., normal pool level of 240.000 m a.s.l., design flood level of 239.020 m a.s.l., and design head of 38.98m. The gate type is of the down-hole plane sliding stoplog gate, supported by high-strength low-friction composite steel slide blocks. Gates are opened and closed in still water. Pressure balancing method of gates is that a filling valve on the top of gate is used for filling water so as to balance pressure. Pressure balancing is carried out by the automatically hydraulic pick-up beam operated by the dam crest gantry crane at the intake monolith. At ordinary times, gates are placed inside a gate chamber.

6.4.2.4 Temporary Water Retaining Gate at the Intake

Given that water inlets shall be sealed for installation of other units after power generation of the first unit, 10 temporary water retaining gates are provided for water retaining during project construction. For the temporary water retaining bulkhead gate, the orifice width is 15.1m, the height is 16.3m, the elevation of sill is 201.020m, the normal pool level is 240.000m, the design flood level is 239.020m and the design water head is 38.98m. The gate shall be the down-hole sliding plane stoplog gate supported by a high-strength and low-friction composite slide block. The gate is lifted and closed in static water. The pressure is balanced by water filling of the filling valve provided on the top of the gate. The operation is carried out with the dam crest gantry crane at the intake dam monolith through the hydraulic automatic pick-up beam. Gates are normally stored in the

6-104 Paklay Hydropower Project Feasibility Study Report gate chamber. After the gate is used, it is properly stored in some place at the station or will be recycled. 6.4.2.5 Dam crest gantry crane at intake monolith

One two-way gantry crane is installed on the dam crest at the intake monolith, mainly used for hoisting the intake trash rack and intake bulkhead gate as well as cleaning the intake trash rack. The two-way gantry crane has a main hook capacity of 2 x 1000 kN, auxiliary hook capacity of 2 x 400kN, gantry crane track gauge of 15.0 m, and head of main and auxiliary hooks is about 55 m.

6.4.2.6 Tailrace emergency gate Draft tube outlet of each unit is equipped with 1 tailrace emergency gate slot. The 14 units are corresponding to 14 orifices in total; after power generation by the first generator unit, draft tubes shall be closed for installation of other units; therefore, 14 tailrace emergency gates are needed in total, including 5 permanent emergency gates and 9 gates for temporary water retaining during construction. The gates have an orifice width of 13.6 m, orifice height of 10.88 m, sill elevation of 203.060 m a.s.l., downstream design flood level of 235.600 m a.s.l. and design head of 32.54 m. The above permanent gates are down-hole plane gates, with two-way water seal. The gates are supported by high-strength low-friction composite steel slide block on the upstream side and fixed roller on the downstream side, closed in flowing water (maximum head difference at lowering of gate is 20 m) and opened in still water. The gates used for temporary water retaining are down-hole plain sliding gates, supported by high-strength low-friction composite steel slide blocks, opened and closed in still water. Pressure balancing method of gates is that a filling valve on the top of gate is used for filling water so as to balance pressure. Pressure balancing is carried out by the automatically hydraulic pick-up beam operated by the tailrace gantry crane. At ordinary times, gates are locked at the top of gate slots.

6.4.2.7 Temporary Water Retaining Gate of the Tail Water For the temporary water retaining gate, the orifice width is 13.6m, orifice height is 10.88m and the elevation of sill is 203.060m. And the design level is 232.980m as per the downstream flood level specified in the construction and flood control standard of 100-year flood, while the design water head is 29.92m. The temporary water retaining gate

6-105 Paklay Hydropower Project Feasibility Study Report shall be the down-hole plane sliding gate supported by a high-strength and low-friction composite slide block. The gate is lifted and closed in static water. The pressure of the gate is balanced by water filling of the filling valve provided on the top of the gate. The operation is carried out through the hydraulic automatic pick-up beam of the tailrace gantry crane. The gate is normally locked on the top of the gate slot. After the gate is used, it is properly stored in some place at the station or will be recycled. 6.4.2.8 Tailrace gantry crane One single-way gantry crane is installed on the tailrace platform, with a capacity of 2 x 1600 kN, track gauge of 6.5 m, and head of about 36.0 m. It is mainly used for hoisting the permanent tailrace emergency gates, gates used for temporary water retaining and bulkhead gate at the sediment releasing bottom outlet. 6.4.3 Hydraulic steel Structure Equipment of Navigation Lock System The navigation lock is the one-stage type, arranged on the right side of riverbed, with a lock chamber width of 12.00 m, upstream check flood level of 240.530m m a.s.l., upstream maximum stage of waterway of 240.000 m a.s.l., upstream minimum stage of waterway of 239.000 m a.s.l., downstream maximum stage of waterway of 229.600 m a.s.l., and downstream minimum stage of waterway of 219.000 m a.s.l. The navigation lock is composed of an upstream approach channel, upper lock head, lock chamber, lower lock head, downstream approach channel, etc. The main hydraulic steel structure equipment of navigation lock system mainly includes emergency bulkhead gate and service gate of the upstream lock head, service gate and bulkhead gate of the downstream lock head, bulkhead gate and service gate for water conveyance gallery at upstream and downstream lock heads, corresponding hoists and floating makefast in the gate chamber. For the details of arrangement, please refer to the Layout for the Gates and Hoists of the navigation lock system (Drawing No.: Paklay－FS－MS－03).

6.4.3.1 Gates and Hoists of the Upstream Lock Head a) Emergency bulkhead gate of the upstream lock head One emergency bulkhead gate of upper lock head is set at the upstream side of the upper lock head, with an orifice width of 12.0 m, height of about 5.73 m, sill elevation of 235.000 m a.s.l., and design head of 5.53 m. The gate type is of the emersed plane sliding gate, supported by steel-based high-strength low-friction composite sliding blocks. The gates are opened and closed in still water. In case of emergency, the gates can be closed in 6-106 Paklay Hydropower Project Feasibility Study Report flowing water as well. At ordinary times, the gates are placed inside the gate chamber for the bulkhead gate of upper lock head.

b) Emergency bulkhead gate hoist of the upstream lock head The emergency bulkhead gate for the upstream lock head is operated with the platform hoist with capacity of 2×400kN at the dam crest of the upstream lock head dam monolith through the hydraulic automatic pick-up beam. c) Service gates of the upstream lock head

Miter gates or submergence gates are adopted as service gates of the lock head. At present, the service gates for domestic medium-high water head navigation lock are generally miter gates, while the service gates for the low water head navigation lock are generally miter gates, lateral drawing gates and submergence gates. However, most of the service gates are miter gates. When the miter gate is adopted, small capacity of the hoist is required with easy control and convenient maintenance, while the hoist for submergence gate requires large capacity, high degree of synchronization and complicated control. The miter gate basically adopts rigid water seal as it show excellent water stop effect, long service life and short navigation interference time. The water seal of the submergence gate has short service life and overall poor sealing and water stop effect. It also shows high maintenance frequency, long maintenance duration and long navigation interference time. The miter gates are generally arranged horizontally with relatively complicated civil structure and relatively large gate structure weight. The hoist of the submergence gate is set on the top of the gate with simple civil structure, gate structure and low construction cost. For the convenience of future maintenance and minimize the influence of equipment maintenance on navigation, the service gates of the upstream lock head of navigation lock shall adopt miter gate. For the miter gate, the orifice width shall be 12.0m and the height shall be about 6.0m. Pedestrian steel bridge and guardrail shall be provided on the top of gate. The elevation of threshold is 235.000m and the design water head is 5.0m. The miter gate adopts the beam structure with the fixed bottom pintle hinged with the frame-type top pintle. The continuous support pillow spacers serve as support and water stop. And

6-107 Paklay Hydropower Project Feasibility Study Report prestress diagonal tie bars are adopted for torsion resistance.

d) Service gate hoist of the upstream lock head The miter gate of the upstream lock head shall be lifted and closed in static water with the 2×320kN horizontal hydraulic hoist (a water head difference of 0.2m is allowed during operation). 6.4.3.2 Hydraulic steel structure equipment of lower lock head a) Service gates of the downstream lock head The service gate of lower lock head is a mitre gate, with an orifice width of 12.0 m, height of about 26.0 m, sill elevation of 215,000 m a.s.l., and design head difference of 21.0 m. The mitre gate is of a cross beam structure, with the pedestrian steel bridge and guardrail on the top, as well as a fixed bottom pintle, and a top pintle in hinged frame manner. Bolsters and cushion blocks are continuously used for support and water seal. A pre-stressed diagonal draw bar is used for torsion resistance.

b) Service gate hoist of the downstream lock head The miter gate of the downstream lock head shall be lifted and closed in static water with the 2×1250kN horizontal hydraulic hoist (a water head difference of 0.2m is allowed during operation).

c) Bulkhead gate of the downstream lock head At the downstream side of the downstream lock head, 1 bulkhead gate of the downstream lock head shall be provided. For the bulkhead gate, the orifice width is 12.0m, the height is about 9.64m, the elevation of the sill is 215.000m, the downstream maintenance water level is 224.140m and the design water head is 9.14m. The gate shall be the emerged plane sliding gate supported by a high-strength and low-friction composite slide block. The gate shall be lifted and closed in static water. The gate is normally locked on the dam crest of the downstream lock head with flashboard locking device. The bottom elevation of the gate leaf shall not affect ship navigation. The control elevation is 238.000m.

d) Bulkhead gate hoist of the downstream lock head The bulkhead gate of downstream lock head shall be operated through the stationary

6-108 Paklay Hydropower Project Feasibility Study Report winch hoist with capacity of 2×630kN on the dam crest bent of the downstream lock head.

6.4.3.3 Gates and Hoists of the Water Conveyance Gallery

a) Trash racks of the water conveyance gallery of the upstream lock head

Trash racks are provided at the left and right inlets of the water conveyance gallery of the upstream lock head. Every water conveyance gallery inlet is divided into 5 sections with separating piers. There are 10 sections in the left and right water conveyance galleries. And 10 stationary trash racks are provided. For the trash racks, the orifice width is 2.3m, the orifice height is 3.3m and the design water head difference is 5.0m.

b) Bulkhead gates of the water conveyance gallery of the upstream lock head

One set of bulkhead gate for water conveyance gallery is arranged at the downstream side of trash rack at the left and right water conveyance gallery of the upstream lock head, respectively. There are 2 sets in total. For the gate, the orifice width is 2.2m, the height is 3.3m, the elevation of sill is 226.200m and the design water head is 14.33m. The gate shall be the down-hole plane sliding gate which is closed in static water and lifted in static water after small lifting of the gate for water filling and pressure balancing. The gate is normally locked on the top of the gate slot.

c) Bulkhead gates hoist of the water conveyance gallery of the upstream lock head The bulkhead gate for the left and right water conveyance galleries of the upstream lock head is operated with the platform hoist with capacity of 2×400kN at the dam crest of the upstream lock head dam monolith through tie bars.

d) Service gates of the water conveyance gallery of the upstream lock head One set of service gate is arranged for the left and right water conveyance galleries of the upper lock head, respectively. There are 2 sets in total. Service gates commonly used for the water conveyance gallery are of two types, i.e. reverse radial gates and plane gates. For water head larger than 15m, the adoption of plane gates may cause gate vibration and slot cavitation. The reverse radial gates are normally provided as the service gates for the water conveyance gallery of navigation lock with higher water head. Without the 6-109 Paklay Hydropower Project Feasibility Study Report interference of gate slot, it provides relatively good hydraulic conditions. With small hoisting force, light water fluctuation and vibration, the water entering the gate chamber is in good state of flow. Therefore, reverse radial gates are adopted as the service gates of the water conveyance gallery. The orifice width of the gate is 2.2m, the height is 2.6m, the elevation of sill is 209.700m, the design retaining water head is 30.83m and the dynamic operation water head is 30.3m. The gate is lifted in dynamic water and closed in static water (closing in dynamic water is allowable in emergency conditions).

e) Service gate hoists of the water conveyance gallery of the upstream lock head The water conveyance gallery of the upstream lock head shall be operated with the 630kN hydraulic hoist through tie bars.

f) Bulkhead gates beside the service gate chamber for the water conveyance gallery

One bulkhead gate slot is provided beside the upstream and downstream service gate chambers of the left and right water conveyance galleries, respectively. There are 4 bulkhead gate slots in total. For the convenience of repair and maintenance of the service gates for the water conveyance gallery, 2 bulkhead gates are provided beside the service gate chamber of the water conveyance galleries. For the gate, the orifice width is 2.2m, the height is 3.3m and the elevation of sill is 211.90m. The design water level of the gate is 240.000m, which is also the maximum upstream stage of waterway. The design water head for the gate is 28.1m. The gates shall be the down-hole plane sliding gates supported by a high-strength and low-friction composite slide block. The gates are closed in static water and lifted in static water after small lifting of the gate for water filling and pressure balancing. The gate is normally locked on the top of the gate slot.

g) Bulkhead gate hoists beside the service gate chamber for the water conveyance gallery

The bulkhead gate beside the service gate chamber of the water conveyance gallery shall be operated with a temporary floating crane with a hoisting capacity equal to or larger than 400kN. 6-110 Paklay Hydropower Project Feasibility Study Report h) Service gates of the water conveyance gallery of the downstream lock head Left and right water conveyance galleries of lower lock head are respectively equipped with 1 service gate of water conveyance gallery, 2 in total. The gate has an orifice width of 2.2 m, height of 2.6 m, sill elevation of 209.700 m a.s.l., and design head difference of 21.0 m. The gate type is of reversed radial gate and is opened in flowing water and closed in still water. In case of emergency, it can also be closed in flowing water. i) Service gate hoists of the water conveyance gallery of the downstream lock head The service gate of the water conveyance gallery for the downstream lock head shall be operated with the 630kN hydraulic hoist through tie bars. j) Bulkhead gates of the water conveyance gallery of the downstream lock head Downstream sides of the service gates of the left and right water conveyance galleries of lower lock head are respectively equipped with 1 bulkhead gate of water conveyance gallery, 2 in total. The gate has an orifice width of 2.2 m, height of 3.3 m, sill elevation of 209.700 m a.s.l., downstream water level during maintenance of 224.140 m a.s.l., and design head of 14.44 m. The gate type is of down-hole plain sliding gate. The operating condition of the gate is as follows: the gate is closed in still water; the gate is then slightly opened for water filling and pressure balancing, after which the gate is completely opened in still water. At ordinary times, gates are locked at the top of the gate slot. k) Bulkhead gate hoists of the water conveyance gallery of the downstream lock head The bulkhead gates of the left and right water conveyance galleries for the downstream lock head shall be operated with a stationary winch hoist with capacity of 250kN on the bent at the top of gate chamber. 6.4.3.4 Floating makefast of lock chamber There are 12 floating makefasts in total at both sides of the lock chamber. The floating makefast is of floating camel structure. Upper part of the floating camel is equipped with a double-deck floating makefast. There are 6 sets of rollers provided respectively at three positions including upper, intermediate and lower parts. The floating camel can go up and down along the guide slot based on change of water level.

6.4.3.5 Anticollision device and hoisting equipment of gate chamber To avoid the clash on the service gate of lower lock head by the ships due to their failure in speed control, a set of anticollision device is provided in front of the service gate. This anticollision device uses steel wire rope as the ship holding rope, which goes across

6-111 Paklay Hydropower Project Feasibility Study Report the gate chamber, with both ends of the rope tied to the buffering device of the butterfly spring at the lifting platform in both sides of the gate wall slot. The anticollision device could withstand a max. striking energy of 250kNm from the ships, having a max. buffering distance of around 2.32m. The anticollision device is operated by the 2×200kN (lifting force)/2×300kN (holding force) stationary winch-type hoist set on the bent frame at the top of the gate wall. 6.4.4 Hydraulic steel Structure Equipment of Fish Pass Structure The fish pass structures shall be arranged at the left side of the powerhouse dam monolith. The hydraulic steel structure equipment for the fish pass structures include upstream flood control service gates, downstream flood control gates and corresponding hoists.

6.4.4.1 Service Gates of Upstream Flood Control

One service gate slot for flood control and one service gate for flood control shall be provided at the fishway entrance in front of the dam. For the service gate, the orifice width is 6.0m, the height is 3.3m, the elevation of sill is 237.240m and the design water head is about 3.29m. The gate shall be emerged plane sliding gate supported by a high-strength and low-friction composite slide block. The gate shall be lifted and closed in dynamic water. For maintenance of service gate slot for flood control, water retaining shall be carried out by sandbag cofferdams.

6.4.4.2 Service Gate Hoists of Upstream Flood Control

The service gate for upstream flood control shall be operated through the stationary winch hoist with capacity of 2×100kN set on the dam crest bent.

6.4.4.3 Service Gates and the Hoists for Downstream Flood Control

According to the requirements of the fish pass structure arrangement, 1 flood control gate is arranged at the middle section of the fishway close to the access road on the left bank of the power station. For the gate, the orifice width is 6.0m, the height is 3.0m, the elevation of sill is 232.140m, the downstream design flood level is 235.500m and the design water head is about 3.46m. The gate shall be the down-hole plane sliding gate 6-112 Paklay Hydropower Project Feasibility Study Report supported by a high-strength and low-friction composite slide block. The gate shall be lifted and closed in dynamic water.

6.4.4.4 Service Gate Hoists of the Downstream Flood Control

The service gate for downstream flood control shall be operated through the stationary winch hoist with capacity of 2×100kN set on the bent of the platform with an elevation of 237.500m on the top of gate slot.

6.4.5 Correction Protection Scheme for Hydraulic steel Structure Equipment The correction protection scheme for hydraulic steel structure equipment of the Project mainly consists of four classifications as follows: a) Except structural components for the temporary gates, all other structural components for trash racks, gates, exposed surface (unfinished surface) of embedded parts, and hoists shall be sprayed with zinc for corrosion prevention. The minimum partial thickness of zinc spraying shall be 120 μm. After zinc spraying, seal coat, intermediate coat and finishing coat shall also be painted. The seal coat is 30 μm thick epoxy primer, the intermediate coat is 50 μm thick epoxy micaceous iron antirust paint and the finishing coat is 60 μm ~ 100 μm thick chlorinated rubber pain. b) Structural components for the temporary gates shall be applied with coatings for corrosion prevention. The coatings consist of epoxy asphalt antirust primer with a thickness of 125 μm and epoxy asphalt antirust finishing coat with a thickness of 125 μm. c) Surface of non-fit mechanical components of hoists shall be applied with coatings for correction prevention. The coatings consist of epoxy zinc-rich primer with a thickness of 70 μm at the bottom course, epoxy micaceous iron antirust paint with a thickness of 80 μm at the intermediate course, and chlorinated rubber paint with a thickness of 70 μm at the surface course. d) Embedded parts of all gate slots, rack slots and guide slots in concrete shall be painted with cement mortar for corrosion prevention. 6.4.6 Summary Sheet of Main Hydraulic steel Structure Equipment of Paklay HPP

6-113 Paklay Hydropower Project Feasibility Study Report

Table 6.4-1 Summary Sheet of Main Hydraulic steel Structure Equipment of Paklay HPP

Unit S/N Description Type Specification Qty. Unit Subtotal Remarks Qty.

(t) (t)

1. Flood Releasing 10458 System Upstream Plane Bulkhead Gate 1.01 stoplog 16.0m×29.0m-28.000m 1 Set 500 500 of the Release sliding gate Sluice (I)

Embedded Parts of Upstream 1.02 3 Orifice 30 90 Bulkhead Gate of the Release Sluice (I)

Upstream Plane Bulkhead Gate 1.03 stoplog 16.0m×20.3m-20.00m 1 Set 350 350 of the Release sliding gate Sluice (II)

Embedded Parts of Upstream 1.04 11 Orifice 23 253 Bulkhead Gate of the Release Sluice (II)

Upstream Bulkhead Gate Two-way 1.05 2×800kN/2×400kN 1 Set 650 650 Hoist of the gantry crane Release Sluice

D a m C r e s t Single track has a Gantry Crane 1.06 QU120 1 Set 105 105 length about 285m, Track of the two tracks Release Sluice

Service Gate for the 1.07 Radial gate 16.0m×28.50m-28.000m 3 Set 550 1650 Low-level Surface Bay of

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the Release Sluice

Embedded Parts of the Service Gate for the 1.08 3 Orifice 40 120 Low-level Surface Bay of the Release Sluice

Service Gate Hoist for the Low-level Hydraulic 1.09 2×6500kN 3 Set 110 330 Surface Bay of hoist the Release Sluice

Service Gate for the Surface 1.10 Radial gate 16.0m×20.5m-20.000m 11 Set 330 3630 Outlet of the Release Sluice

Embedded Parts of the Service Gate 1.11 11 Orifice 29 319 for the Surface Outlet of the Release Sluice

Service Gate Hoist for the Hydraulic 1.12 Surface Outlet 2×3800kN 11 Set 70 770 hoist of the Release Sluice

Downstream Plane Bulkhead Gate 1.13 stoplog 16.0m×20.9m-19.939m 1 Set 330 330 of the Release sliding gate Sluice

Embedded Parts of 1.14 Downstream 3 Orifice 29 87 Bulkhead Gate of the Release

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Sluice (I)

Embedded Parts of Downstream 1.15 5 Orifice 23 115 Bulkhead Gate of the Release Sluice (II)

Embedded Parts of Downstream 1.16 6 Orifice 15 90 Bulkhead Gate of the Release Sluice (III)

D o w n s t r e a m Bulkhead Gate Two-way Shared dam crest 1.17 Hoist of the gantry crane gantry crane Release Sluice

Emergency Plane Bulkhead Gate 1.18 fixed-roller 10.0m×12.1m-35.0m 1 Set 165 165 of the Flushing gate Bottom Outlet

Embedded Parts of Emergency 1.19 2 Orifice 50 100 Bulkhead Gate of the Flushing Bottom Outlet

Emergency Bulkhead Gate Platform 1.20 Hoist of the 2500kN 1 Set 110 110 Including track hoist Flushing Bottom Outlet

Service Gate of Plane 1.21 the Flushing fixed-roller 10.0m×10.0m-35.0m 2 Set 140 280 Bottom Outlet gate

Embedded Parts of Service 1.22 2 Orifice 42 84 Gate of the Flushing

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Bottom Outlet

Service Gate Hoist of the Stationary 1.23 3200kN 2 Set 75 150 Flushing winch hoist Bottom Outlet

Maintenance Crane of the Service Gate Electric 1.24 30kN 1 Set 10 10 Hoist Room of block the Flushing Bottom Outlet

Bulkhead Gate Plane 1.25 of the Flushing 10.0m×10.0m-30.6m 1 Set 110 110 sliding gate Bottom Outlet

Embedded Parts of 1.26 Bulkhead Gate 2 Orifice 30 60 of the Flushing Bottom Outlet

Bulkhead Gate Hoist of the One-way Shared tailrace gantry 1.27 Flushing gantry crane crane Bottom Outlet

2. Headrace and 11354 power generation system Intake 2.01 3 Set 300 900 Trashrack

Guide Slot of 2.02 the Intake 3 Set 20 60 Trashrack

Plane Intake trash 2.03 vertical 6.65m×28.0m-4.0m 28 Set 55 1540 rack trash rack

Embedded Parts of the Intake Trash 2.04 28 Orifice 25 700 Rack and Embedded Parts of the

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Cleaning Guide Slot

Plane Intake 2.05 stoplog 15.1m×16.3m-38.98m 4 Set 260 1040 Bulkhead Gate sliding gate

Temporary Plane Water 2.06 stoplog 15.1m×16.3m-38.98m 10 Set 260 2600 Retaining Gate sliding gate at the Intake

Embedded Parts of the 2.07 14 Orifice 33 462 Intake Bulkhead Gate

Embedded Parts of Intake 2.08 14 Orifice 5 70 Bulkhead Gate Chamber

Dam Crest Two-way Including cleaning 2.09 Gantry Crane at 2×1000kN/2×400kN 1 Set 360 360 gantry crane equipment Intake

Single track has a Intake Gantry 2.10 QU100 1 Set 100 100 length about 345m, Crane Track two tracks

Tail Water Plane Maximum gate closing 2.11 Emergency fixed-roller 13.6m×10.88m-32.54m 5 Set 190 950 water head 20m Gate gate

Temporary Water Plane 2.12 Retaining Gate 13.6m×10.88m-29.92m 9 Set 172 1548 sliding gate of the Tail Water

Embedded Parts of the Tail 2.13 Water 14 Orifice 41 574 Emergency Gate

Tailrace Gantry One-way 2.14 2×1600kN 1 Set 320 320 Crane gantry crane

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Tail Water Single track has a 2.15 Gantry Crane QU120 1 Set 130 130 length about 345m, Track two tracks

3. Navigation Lock 1328 System Emergency Bulkhead Gate Plane 3.01 12.0m×5.73m-5.53m 1 Set 42 42 of the Upstream sliding gate Lock Head

Embedded Parts and Chamber of the 3.02 Emergency 1 Orifice 15 15 Bulkhead Gate of the Upstream Lock Head

Emergency Bulkhead Gate Platform 3.03 Hoist of the 2×400kN 1 Set 70 70 hoist Upstream Lock Head

Platform Hoist Single track has a Track of the 3.04 QU80 1 Set 12 12 length about 44m, two Upstream Lock tracks Head

Service Gates 3.05 of the Upstream Mitre gate 12.0m×6.0m-5.0m 1 Set 70 70 Lock Head

Embedded Parts of the 3.06 Service Gate of 1 Orifice 8 8 the Upstream Lock Head

Service Gate Hoist of the Hydraulic 3.07 2×320kN 1 Set 8 8 Upstream Lock hoist Head

Service Gates 3.08 of the Mitre gate 12.0m×26.0m-21.0m 1 Set 290 290 Downstream

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Lock Head

Embedded Parts of the Service Gate of 3.09 1 Orifice 25 25 the Downstream Lock Head

Service Gate Hoist of the Hydraulic 3.10 2×1250kN 1 Set 25 25 Downstream hoist Lock Head

Bulkhead Gate of the Plane 3.11 12.0m×9.64m-9.14m 1 Set 58 58 Downstream sliding gate Lock Head

Embedded Parts of the Bulkhead Gate 3.12 1 Orifice 20 20 of the Downstream Lock Head

Bulkhead Gate Hoist of the Stationary 3.13 2×630kN 1 Set 25 25 Downstream winch hoist Lock Head

Trash Racks and Embedded Parts of the Water Stationary 3.14 2.3m×3.3m-5.0m 10 Set 2.5 25 Conveyance type Gallery Inlet of the Upstream Lock Head

Bulkhead Gates of the Water Conveyance Plane 3.15 2.2m×3.3m-14.33m 2 Set 8 16 Gallery of the sliding gate Upstream Lock Head

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Embedded Parts of the Bulkhead Gates of the Water 3.16 2 Orifice 6 12 Conveyance Gallery of the Upstream Lock Head

Bulkhead Gates beside the Gate Chamber for Plane 3.17 2.2m×3.3m-28.1m 2 Set 9 18 the Water sliding gate Conveyance Gallery

Embedded Parts of the Bulkhead Gates beside the Gate 3.18 4 Orifice 9 36 Chamber for the Water Conveyance Gallery

Bulkhead Gates of the Water Conveyance Plane 3.19 2.2m×3.3m-14.44m 2 Set 8.5 17 Gallery of the sliding gate Downstream Lock Head

Embedded Parts of the Bulkhead Gates for the Water 3.20 2 Orifice 9 18 Conveyance Gallery of the Downstream Lock Head

Bulkhead Gate Hoists of the Stationary 3.21 Water 250kN 2 Set 5 10 winch hoist Conveyance Gallery of the

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Downstream Lock Head

Service Gates of the Water Conveyance Reverse 3.22 Gallery of the 2.2m×2.6m-30.83m 4 Set 32 128 radial gate Upstream and Downstream Lock Head

Embedded Parts of the Service Gates for the Water 3.23 Conveyance 4 Orifice 50 200 Gallery of the Upstream and Downstream Lock Head

Service Gate Hoist of the Water Conveyance Hydraulic 3.24 630kN 4 Set 8 32 Gallery of the hoist Upstream and Downstream Lock Head

Floating 3.25 12 Set 2.5 30 Makefast

Embedded Parts of the 3.26 12 Orifice 6.5 78 Floating Makefast

Butterfly spring Anticollision buffering 3.27 device of gate 1 Set 25 25 type ship chamber holding rope Embedded parts of

3.28 anticollision 1 Set 6 6 device of gate chamber

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Hoist of Stationary 2×200kN (lifting anticollisio 3.29 winch type force)/2×300kN 1 Set 9 9 n device of hoist (holding force) gate chamber 30 4. Fish Pass System Service Gates Plane 4.01 of Upstream 6.0m×3.3m-3.29m 1 Set 6 6 sliding gate Flood Control

Embedded Parts of the 4.02 Service Gates 1 Set 4 4 for Upstream Flood Control

Service Gate Hoists of Stationary 4.03 2×100kN 1 Orifice 5 5 Upstream Flood winch hoist Control

Service Gates Plane 4.04 of Downstream 6.0m×3.0m-3.46m 1 Set 6 6 sliding gate Flood Control

Embedded Parts of the Service Gates 4.05 1 Orifice 4 4 for Downstream Flood Control

Service Gate Hoists of the Stationary 4.06 2×100kN 1 Set 5 5 Downstream winch hoist Flood Control

23170 5. Total

6.5 Ventilation and Air Conditioning

6.5.1 Overview

The Paklay HPP is in Laos, where the climate is hot, and annual average temperature is 25.3 °C, extreme maximum temperature is 40.5 °C, and extreme minimum temperature is 1.3 °C. 6-123 Paklay Hydropower Project Feasibility Study Report

The HPP is of a water retaining powerhouse. Main auxiliary plant is composed of powerhouse and downstream auxiliary plant. Generator floor, busbar floor, and operation gallery floor are set for the powerhouse only. Floors of the downstream auxiliary plant from bottom to top are busbar cable floor, power distribution device floor, SF6 pipeline floor, GIS floor, outgoing line platform floor. Two erection bays, which are 1# erection bay (at left side of the powerhouse) and 2# erection bay (between the 11# 12# units), are set for the HPP. The central control building is at left side of the downstream auxiliary plant and downstream side of the 1# erection bay.

6.5.2 Design Parameters of Indoor Air

a) Summer Generator floor ≤33 °C 75% Main transformer room <40 °C Station service transformer room ≤35 °C Turbine oil depot and insulating oil depot ≤33 °C 80% Air compressor room ≤35 °C 75% Cable room (passage) ≤35 °C Central control room and computer room ≤28 °C 60%±5% Local panel room, relay protection room, storage room, etc. ≤28 °C 60%±5% Office, meeting room, etc. ≤28 °C 60%±5% b) Winter

Generator floor ≥10 °C Main transformer room ≥10 °C Central control room and computer room ≥20 °C Oil disposal room ≥10 °C Air compressor room ≥12 °C Office, meeting room, etc. ≥18 °C

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6.5.3 Preparation of System Scheme

Location of the HPP is of a hot climate. According to meteorological and local conditions, etc., method of mechanical ventilation (the major part) supported by multi-split air condition is adopted for design scheme of ventilation and air conditioning of the whole plant. Mechanical ventilation is adopted for the powerhouse, electrical equipment room for the main transformer, station service transformer, etc. Multi-split central air conditioning system is adopted for rooms of the central control building and equipment rooms (such as local panel room) which are within the unit bay scope and have high requirement for temperature and moisture while holding a heavy thermal load. Ventilation method of natural air intake and mechanical air exhaust is adopted for GIS room and pipeline floor. Independent air exhaust system of natural air intake and mechanical air exhaust is adopted for the battery room, which is of maintenance-free type.

6.5.4 Organization and Systematic Design of Ventilation Air

According to layout of the electromechanical equipment, method of air blown from upstream and exhausted from downstream is adopted for the whole plant. Blower room ① is set at upstream side at left of the powerhouse, and blower rooms ② and ③ are set at upstream side of the erection bay ② . Unit bay ⑫~⑭ is air supply area of blower room ① and unit bays ① ~⑪ is air supply area of blower rooms ② and ③ . One air blow gallery of powerhouse is set in wall at upstream of the powerhouse as channel to blow outdoor fresh air to operation floor and busbar floor by centrifugal fan. An air exhaust interlayer is set at downstream side of the downstream auxiliary plant as channel to exhaust the air to outside by 5 exhaust fans set at downstream side of the main transformer floor. As the GIS and pipeline floor is above ground outside, wall axial flow fan is adopted to exhaust the air to outside of downstream. Unit battery room is at downstream side with an elevation of 228.50 m a.s.l. of the downstream auxiliary plant. Natural air flows into the lower auxiliary access gallery and is exhausted outside by explosionproof axial flow fan set in the battery room via

6-125 Paklay Hydropower Project Feasibility Study Report umbrella-shaped vent cap at roof. Multi-split central air conditioning system is adopted for rooms of the central control building and equipment rooms (such as local panel room) which are within the unit bay scope while holding a heavy thermal load. The outside unit is set at an elevation of 236.50 m a.s.l. of the tailrace platform. a) Air blow system of powerhouse Outside air is induced and sent to operation floor and busbar floor of powerhouse via upstream air blow gallery by blower. Total air capacity of the system is 320000 m3/h; air capacity of the operation floor and busbar floor are 160000 m3/h respectively. The 1# blower room is provided with 1 dual-inlet centrifugal fan of 4-79No.2-12E model with air capacity of 80000 m3/h; 2# and 3# blower rooms are provided respectively with 1 dual-inlet centrifugal fan of 4-79No.2-14E model with air capacity of 120000 m3/h. b) Air exhaust system of downstream auxiliary plant Air of busbar floors of powerhouse and downstream auxiliary plant, as well as downstream equipment rooms (water supply room and circuit breaker room) of operation floor of the downstream powerhouse are all exhausted to the air exhaust interlayer of downstream auxiliary plant, which has a total air capacity of 215000 m3/h and exhausts air to outside via its downstream exhaust fan of the operation floor (elevation of 228.50 m a.s.l.). There are 5 blower rooms in total and 1 dual-inlet centrifugal fan of 4-79No.2-10E model is set for each blower room. c) Air exhaust system of oil depot and oil disposal room

Blower rooms are set at downstream side of the insulation oil room and oil disposal room, and turbine oil depot and oil disposal room. Air ducts are embedded in upstream wall of the oil depot as channel to exhaust air of the oil depot and oil disposal room outside via blower room. Air capacities of air exhaust systems of the insulating oil and turbine oil are both 10000 m3/h, with blower model of B4-79 No.8D, and each system has 1 blower. d) Air exhaust system of GIS room

Ventilation method of natural air intake and mechanical air exhaust is adopted for the 6-126 Paklay Hydropower Project Feasibility Study Report

GIS room. Lower part of the upstream wall is set with air intake window and axial flow fans are set for upper and lower parts of the downstream wall. The upper axial flow fan is used for ventilation and the lower one is used for emergency ventilation. Total air capacity of the system is 100000 m3/h and 20 axial flow fans of BFT35-11No.5 model are adopted. e) Air exhaust system of pipeline floor Ventilation method of natural air intake and mechanical air exhaust is adopted for the pipeline floor. Air is taken from upper large space of the generator floor. Lower part of the upstream wall of pipeline floor is set with air intake window and upper part of the downstream wall is set with axial flow fan. Total air capacity of the system is 35000 m3/h and 12 axial flow fans of T35-11 No.4 model are adopted. f) Air exhaust system of main transformer and station service transformer room Ventilation method of natural air intake and mechanical air exhaust is adopted. Air flows from operation floor of the powerhouse and exhausted to outside of the downstream side via axial flow fan. Total air capacity of the system is 150000 m3/h and 20 axial flow fans of T35-11 No.5.6 model are adopted. g) Air exhaust of switchgear room, DC panel room, etc. of downstream auxiliary plant Ventilation method of natural air intake and mechanical air exhaust is adopted. Air flows from transportation channel of the main transformer and exhausted to outside of the downstream side via axial flow fan. Total air capacity of the system is 50000 m3/h and 5 axial flow fans of T35-11 No.6.3 model are adopted.

h) Air exhaust from battery room No. 1, No. 2, and No. 3 batteries of the unit are all at downstream side with an elevation of 228.50 m a.s.l. of the downstream auxiliary plant. Natural air flows into the lower auxiliary access gallery and is exhausted outside by explosionproof axial flow fan set in the battery room via umbrella-shaped vent cap at roof. Air capacity of each battery room is 2000 m3/h and each room is provided with 1 axial flow fan of BT35-11 No.3.55 model. 6-127 Paklay Hydropower Project Feasibility Study Report

6.5.5 Dehumidification in Plant

Inside of the plant is set with 10 mobile dehumidifiers for dehumidification of wet districts (such as operation gallery) in the plant. Dehumidifying capacity of the dehumidifier is 5 kg/h. The dehumidifiers can be set in flexible way as required and can be moved.

6.5.6 Smoke Exhaust of Main and Auxiliary plants

According to requirements of the specification, smoke exhaust system should be set for generator floors of the main and auxiliary plants and transportation channel of main transformer. Smoke exhaust system of generator floor: smoke exhaust pipes are set in central part of the upper part of generator floor; smoke exhaust holes are set on the pipes, which are closed under common condition and opened automatically upon fire. Axial flow fan for smoke exhaust connects with the smoke exhaust pipe directly and are mounted under the arc crown. Smoke is directly exhausted to upstream outside of 2# erection bay when there is a fire. Smoke exhaust capacity of the system is 60000 m3/h. There are only 1 smoke exhaust fan with model of HTF-11.2-I. Smoke exhaust system of transportation channel of main transformer: smoke exhaust pipes are set at upper part of transportation channel of the main transformer; smoke exhaust holes are set on the pipes, which are closed under common condition and opened automatically upon fire. Axial flow fan for smoke exhaust connects with the smoke exhaust pipe directly. Smoke is directly exhausted to downstream outside when there is a fire. Smoke exhaust capacity of the system is 15000 m3/h. There are only 1 smoke exhaust fan with model of HTF-8-I.

6.5.7 Main Equipment of HVAC System

Refer to Table 6.5-1 for main equipment of the HVAC system.

Table 6.5-1 Main Equipment of HVAC System S/N Description Model Specifications Unit Qty. Remarks

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S/N Description Model Specifications Unit Qty. Remarks

L=123000m3/h H=431Pa Air blown to 1 Centrifugal fan 4-79No.2-14E Set 2 n=460rpm powerhouse N=22kW L=82600m3/h H=451Pa Air blown to 2 Centrifugal fan 4-79No.2-12E Set 1 n=520rpm powerhouse N=15 kW L=45000m3/h Air exhausted H=657Pa from 3 Centrifugal fan 4-79No.2-10E Set 10 n=660rpm N=15 downstream kW auxiliary plant L=11000m3/h Air exhausted 4 Centrifugal fan B4-72-8D H=480Pa Set 2 from oil depot n=730rpm N=3 kW L=11534m3/h Air exhausted H=114Pa 5 Axial flow fan T35-11No.6.3 Set 5 from switchgear n=960rpm N=0.75 room kW Air exhausted L=8100m3/h H=90Pa from 6 Axial flow fan T35-11No.5.6 n=960rpm N=0.37 Set 20 transformer kW room L=3505m3/h Air exhausted H=76.2Pa 7 Axial flow fan T35-11No.4 Set 12 from pipeline n=1450rpm floor N=0.18 kW L=5235m3/h H=63.5Pa Air exhausted 8 Axial flow fan T35-11No.5 Set 20 n=960rpm N=0.37 from GIS room kW L=2692m3/h H=69.7Pa Air blown to 9 Axial flow fan T35-11No.3.55 Set 30 n=1450rpm busbar floor N=0.09 kW

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S/N Description Model Specifications Unit Qty. Remarks

Air blown to L=2692m3/h water supply H=69.7Pa 10 Axial flow fan T35-11No.3.55 Set 30 room and n=1450rpm circuit breaker N=0.09 kW room L=2078m3/h Air blown to H=61.7Pa 11 Axial flow fan T35-11No.3.15 Set 14 operation n=1450rpm gallery N=0.09 kW L=59007m3/h Smoke High-temperature H=593Pa exhausted from 12 smoke exhaust fan HTF-11.2-Ⅰ Set 1 n=1450rpm N=22 generator floor box kW of powerhouse Smoke L=14336m3/h High-temperature exhausted from H=508Pa 13 smoke exhaust fan HTF-8-Ⅰ Set 1 transportation n=1450rpm N=4 box channel of main kW transformer L=2683m3/h H=75Pa Air exhausted Explosionproof 14 BT35-11No.3.55 n=1450rpm Set 3 from battery axial flow fan N=0.12kW room L=2692m3/h H=69.7Pa 15 Axial flow fan T35-11No.3.55 Set 30 Auxiliary fan n=1450rpm N=0.09 kW Mobile 16 5 kg/h Set 10 dehumidifier Outdoor machine Air condition of Refrigerating 17 of multi-split air Set 4 central control capacity QL: 75 kW conditioning unit room Air conditions Outdoor machine of equipment Refrigerating 18 of multi-split air Set 7 rooms such as capacity QL: 80 kW conditioning unit local panel room

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S/N Description Model Specifications Unit Qty. Remarks

Air conditions Outdoor machine of equipment Refrigerating 19 of multi-split air Set 1 rooms such as capacity QL: 40 kW conditioning unit local panel room Air conditions of areas of 20 Indoor unit Set central control room, local panel room, etc.

21 Fire damper Pcs.

Smoke exhaust 22 Pcs. damper Opposed 23 multi-blade Pcs. damper Aluminium air 24 hole of window Pcs. blind Manufacturing Galvanized iron air 25 m2 including the duct air duct Air conditions Outdoor machine of equipment Refrigerating 18 of multi-split air Set 1 rooms such as capacity QL: 40 kW conditioning unit local panel room Air conditions of areas of 19 Indoor unit Set central control room, local panel room, etc. 20 Fire damper Pcs. Smoke exhaust 21 Pcs. damper

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S/N Description Model Specifications Unit Qty. Remarks

Opposed 22 multi-blade Pcs. damper Aluminium air 23 hole of window Pcs. blind Manufacturing Galvanized iron air 24 m2 including the duct air duct

6.6 Fire Protection Design

6.6.1 Project Overview

6.6.1.1 Overview The Paklay HPP has storage of 0.89×109 m3 corresponding to normal pool level of 240.00 m a.s.l. and of 904.4×106 m3 corresponding to check flood level of 240.23 m a.s.l., with total installed capacity of 770 MW (14×55 MW). The hydraulic structures mainly consist of the flood releasing and energy dissipation (sediment releasing) structure, water retaining structure, powerhouse, navigation lock and fish way. The non-overflow dam section on the left bank, water retaining powerhouse dam section, sediment releasing bottom outlet dam section, low-level surface bay, overflow surface bay dam section (11 in total, with underflow for the energy dissipation downstream for the 5 bays on the left), navigation lock dam section and the non-overflow dam section on the right bank are arranged in sequence from left to right. 6.6.1.2 General Layout of Powerhouse a) Layout of powerhouse area Main structures in the powerhouse area include the powerhouse, auxiliary plant, GIS room of main transformer switchyard, outgoing line platform, central control building, entrance channel, tailwater canal, access road, etc.

Main unit bay of the powerhouse is located on the main riverbed of the left bank with 6-132 Paklay Hydropower Project Feasibility Study Report a total length of 301.00 m. For the main unit bay, its left end is connected with the non-overflow dam section and its right end is connected with the bottom outlet dam section. The total width of the powerhouse dam section along the water flow direction is 83.05m. Water retaining type intake is arranged on the upstream side of the generator hall, while the downstream side of the generator hall is provided with downstream auxiliary plant. The GIS switchyard and outgoing line platform are provided on the top of unit ① ~ unit ⑤ in downstream auxiliary plant. One erection bay is provided on the left and the right ends of the generator hall respectively. Auxiliary erection bay is located on the sediment releasing bottom outlet at the right end of generator hall, while the main erection bay is located on the left end of generator hall. Auxiliary plant of central control building is located 26 m downstream of the main erection bay on the right side, and turnaround is located 26 m on the left side. Powerhouse access road leads to the site horizontally from the downstream and connects with the turnaround. Direct access to the floor of main erection bay can be realized through the turnaround.

Sand-guide sill and trashrack are arranged in front of the powerhouse dam section. Upstream guide wall is arranged on the right side slope of the entrance channel. After extending upstream 60.00 m, the upstream guide wall will extend upstream 50.00 m along the sand-guide sill.

b) Layout of intake Each unit is set with 1 intake. Elevation of foundation surface of the intake is 194.02 m a.s.l.; dam crest elevation of the intake is 245.20 m a.s.l.; height of the intake is 50.98 m. Width of each intake front is 21.50 m and thickness of abutment pier is 3.20 m. To reduce span of trash rack, an intermediate pier which is 1.80 m thick is set at the intake. Abutment pier at intake and water retaining wall at upstream of the generator hall integrate as a whole. Thickness of the water retaining wall is 6.00 m. Air delivery conduit and air vents for emergency gate are set in the wall. Platform at top of the intake is 30.05 m long along the flow direction, which is set with an 8-meter-wide road, upstream track of gantry, trash rack, emergency gate chamber and slot, and downstream track of gantry. A breast wall 6-133 Paklay Hydropower Project Feasibility Study Report connecting the abutment piers and intermediate pier is set between trash rack slot and emergency gate slot. Base plate elevation of the intake is 201.02 m a.s.l. Grouting and drainage gallery is set in the base plate of the intake. One gantry is set at top of the intake to lift the trash rack and emergency gate. A highway bridge of dam crest connecting the overflow monolith and non-overflow monolith is set at front of the dam crest.

c) Layout of powerhouse The powerhouse consists of generator hall and erection bay, with a dimension of 400.00m×22.50m×52.44m (length×width×height). The distance between generator units is 21.50m. Two single-trolley bridge cranes are set in the powerhouse, with the rated lifting capacity per crane of 2500 kN; the span is 21.00 m, and elevation of rail top is 240.50 m. The crane can operate between erection bay and generator hall. In the powerhouse, bottom elevation of the roof is 246.50 m a.s.l, and elevation of the foundation surface is 194.06 m a.s.l. The generator hall has a length of 301.00 m and a net width of 21.00 m. The generator hall consists of operation floor, pipeline floor, and flow passage floor from top to bottom. Ground elevation of operation floor is 222.50 m a.s.l. and this floor is set with oil pressure apparatus, governor, generator and turbine lifting holes at the upstream and downstream sides. The pipeline floor has a ground elevation of 219.00 m. Pipe gallery and cable gallery are set respectively at both sides of the pipeline floor to connect with the generator lifting hole and turbine lifting hole. Setting elevation of the unit is 208.50 m a.s.l. An access gallery running through the whole powerhouse is set below the runner room. Bottom elevation of the gallery is 198.06 m a.s.l., and the gallery connects with tubular shaft of the unit. The auxiliary erection bay has a length of 47.00 m, a net width of 21.00 m and a ground elevation of 222.50 m, same as that of the operation floor. It is the place for unit installation and maintenance. Two sand releasing bottom outlets are arranged at the lower part of the auxiliary erection bay. 6-134 Paklay Hydropower Project Feasibility Study Report

The main erection bay has a length of 52.00 m, a net width of 21.00 m and a ground elevation of 228.50 m, 6.00m higher than that of the operation floor. At 26.00m on the left end of main erection bay, the lower part is solid concrete. The place of 26.00m on the right end is a 3-layer reinforced concrete structure. The top floor is the place for unit installation and maintenance. Middle floor with a ground elevation of 222.50 m is equipped with an air compressor room. The ground floor with an elevation of 216.50 m is equipped with a turbine oil depot and a pump house for leakage water drainage sump and maintenance drainage sump. Such two drainage sumps are arranged below the pump house. The elevation of drainage sump bottom is 192.00 m.

d) Layout of auxiliary plant The auxiliary plant consists of downstream auxiliary plant and auxiliary plant of the central control building. The downstream auxiliary plant, which is 21.40 m wide, is set at downstream side of generator hall and is a 5-storey reinforced concrete structure. The bottom is pipeline floor with an elevation of 219.50 m a.s.l. Local panel room and power distribution room are set at the elevation of 222.50 m a.s.l. The generator floor consisting of main transformer room, switchgear room, station service transformer room, exhaust fan room, and main transformer transportation rail, etc. is set at the elevation of 228.50 m a.s.l. SF6 pipeline floor is set at the elevation of 240.50 m a.s.l. with the roof elevation of 245.50 m. 500 kV GIS room with a plan size of 64.50m×17.40m (L×W) is arranged at the section of units ③~⑤, and 1 bridge crane of 150 kN is set indoor. The GIS room has a roof elevation of 260.50 m and outgoing line platform with a plan size of 69.00 m×23.40 m

(L×W) is formed jointly by section of units ① ~ ② and roof of auxiliary plant of central control building. Auxiliary plant of central control building is arranged at downstream of the main erection bay, with the plan size of 26.00 m×21.40 m (L×W); it is of a 5-storey reinforced concrete structure. Elevation of the ground floor is 216.50 m a.s.l. with turbine oil treatment room, powerhouse drainage sump and sewage pool arranged. Drainage pump room, sewage pump room, air conditioning equipment room and HV laboratory, etc. are 6-135 Paklay Hydropower Project Feasibility Study Report arranged at an elevation of 222.50 m a.s.l. Relay protection room and diesel engine room are arranged at an elevation of 228.50 m a.s.l. Central control room and computer room are arranged at an elevation of 234.50 m a.s.l. Battery room, tool room, communication equipment room and communication power supply room of the central control building are set at an elevation of 240.50 m a.s.l.; and the outgoing line platform is arranged at the roof elevation of 245.50 m. Exhaust fan room is arranged in the space between main erection bay and upstream non-overflow dam, with a plan dimension of 11.00 m×7.00 m (length×width) and a ground elevation of 228.50m. Fire pump house and public auxiliary panel cabinet are arranged in the space at the downstream part of auxiliary erection bay. e) Internal and external access of the powerhouse Internal access of the powerhouse: 1 staircase is set at upstream of main erection bay of the powerhouse to connect with each floor and the deep well pump house. Manholes for dewatering sump and leakage drainage sump are set in the deep well pump house at the lower part. At the downstream auxiliary plant, 1 staircase is arranged respectively at ③, ⑥, ⑨, ⑪, ⑭ unit bays and bottom outlet dam section end, to connect to each floor. Staircase and elevator are set at the downstream side of the central control room to connect to each floor. Meanwhile, door opening is set for foundation wall at downstream between the powerhouse and auxiliary plant for horizontal transportation of each floor and ensure easy operation management. External access of the powerhouse: horizontal access to the powerhouse is adopted.

Access road of the powerhouse is set along hillside toe at left bank of downstream of the powerhouse. One end of the access road connects with downstream of the turnaround loop and the other end connects with outside highway at downstream of the powerhouse. The access road is 8 m wide and about 150 m long, with average longitudinal slope of 6.07%. Drainage ditches are set at both sides of the road; the left side is excavated side slope, and the right side is gravity retaining wall.

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6.6.2 Design Basis and Principle for Fire Protection

6.6.2.1 Overview a) Scope and key point of design Fire protection design of the Paklay HPP includes the powerhouse area (including powerhouse, auxiliary plants, 500 kV switchyard, insulating oil disposal room, and tailrace platform) and head structure (including dam crest at intake and dam crest of spillway). Design of the powerhouse area is key point of fire protection of the Project. b) Fire extinguishment method Fire hydrant, water spray, and dry powder fire extinguisher are adopted for fire protection of the station. As water yield of the HPP is sufficient, fire extinguishment with water is the main fire protection way. Fire hydrant is adopted for fire extinguishment with water and ammonium phosphate dry powder extinguisher (MFA type) is adopted. c) Design of fire protection of powerhouse area Design of fire protection of powerhouse area includes buildings such as powerhouse, auxiliary plants, 500 kV switchyard, insulating oil disposal room, and tailrace platform, as well as their electromechanical equipment inside. Fire hydrant is adopted for fire protection of buildings of the plant area; fixed system for fire extinguishment of water spray is adopted for fire protection of the generator; ammonium phosphate dry powder extinguisher is adopted for fire protection of the central control room, relay protection panel room, computer room, tailrace hoist room, etc.

d) Head works Fire protection of head works includes buildings and electromechanical equipment. Dry powder extinguisher is adopted for fire protection of electromechanical equipment of power distribution room at dam crest of the head, diesel engine room, hydraulic hoist room, etc. e) Design basis

Design for fire protection of the Paklay HPP is based on following latest rules and 6-137 Paklay Hydropower Project Feasibility Study Report codes issued by the People’s Republic of China and the industry. 1) Fire Control Law of the People's Republic of China 2) Code of Design on Building Fire Protection and Prevention 3) Code for Design of Fire Protection of Hydraulic Engineering 4) Typical Rules of Fire Protection for Electric Power Installations 5) Code of Design for Water Spray Extinguishing Systems 6) Code of Design for Carbon Dioxide Fire Extinguishing Systems 7) Code for Design of Extinguisher Distribution in Buildings 8) Code for Design of Automatic Fire Alarm Systems 9) Code for Design of Heating, Ventilation, and Air Conditioning 10) Design Code for Heating, Ventilation and Air Conditioning of Power House of Power station 11) Electrical-mechanical Design Code of Hydropower Plant 6.6.2.2 Design Principle Fire control design of the Project should be implemented on the basis of "prevention first, combination of prevention and elimination", ensuring key points, giving consideration to general points, easy management, and economical and practical. Provisions of current regulations and specifications should be strictly followed during the design. Comprehensive fire control technical measures should be adopted for the fire control. Functions of the fire control system requires complete consideration of fire control, monitoring, alarm, control, fire extinguishment, fume exhaust, life saving, etc. to achieve

“prevention before a fire starts”. And fire can be extinguished in short time once it happens to minimize fire damage. Allocation of fire control facilities is based on fire self-rescue. In general layout of the project, fire lane, fire separation distance, emergency exits and signs should all be arranged to meet the requirements of specifications. Fire protection devices and apparatuses should be allocated according to production significance and risk level of the fire. Special fire control measures should be adopted for special parts according to fire control specification. 6-138 Paklay Hydropower Project Feasibility Study Report

Monitoring apparatus of automatic fire alarm system should be set in the central control room. Fire control products to be used should all be safe and reliable, easy for use, economical, with advanced technology, and meet special requirements of the Project. All the products should be qualified by related national quality supervision and inspection departments. Water spray, fire hydrant, dry powder fire extinguisher, and CO2 fire extinguishment are adopted. Fire protection water is taken from the upstream reservoir with sufficient and reliable water. Double-circuit independent power supply is used as the fire protection power supply. Ventilation and smoke exhaust system after fire protection should be set. Electrical equipment using nonflammable or flame-retardant materials as insulating medium should be used if possible. Apparatus rooms with fire risk should be insulated by fire-proof materials; holes and cable channels should be blocked by fire-proof materials. Fire separation zones should be set to prevent fire spreading.

6.6.3 Design for Fire Protection of the Project Buildings

6.6.3.1 Fire Risk Classification and Fire Resistance Rating of Workshop a) Fire risk of workshops is classified as Class C, Class D, or Class E according to principles of Code of Design on Building Fire Protection and Prevention (GB 50016—2006).

b) According to the hydro-project layout and production characteristics, fire protection zones of buildings and structures of the workshops are naturally divided to the powerhouse and erection bay, auxiliary plant, busbar floor, main transformer floor, 500 kV switchyard, inlet and water intake of flood release and desilting buildings, dam area, etc.

c) According to stipulations of Code for Design of Fire Protection of Hydraulic Engineering (GB50872-2014), fire risk classification, fire resistance rating, and fire protection measures of buildings and structures are classified as what are shown in Table 6.6-l.

Table 6.6-1 Fire Risk Classification, Fire Resistance Rating, and Fire Protection

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Measures of Buildings and Structures

Buildings, Structures, Fire Risk Fire S/N and Electromechanical Fire Protection Measures Classification Rating Equipment 1 Powerhouse and erection bay Generator floor and Wheeled and portable fire 1.1 Class D II erection bay extinguisher and fire hydrant System for fire extinguishment of 1.2 Hydraulic generator Class D II water spray Portable fire extinguisher and fire 1.3 Busbar floor Class D II hydrant Layered arrangement of cables; fireproof bulkhead, coating, gas 1.4 Cable floor Class C II mask, cable-type thermal detector, portable fire hydrant, system for fire extinguishment of water spray Portable fire extinguisher and fire 1.5 HV cable adit and shaft Class D II hydrant Portable fire extinguisher and fire 1.6 Turbine floor Class D II hydrant 1.7 Operation gallery Class D II Portable fire extinguisher 1.8 Air compressor room Class D II Portable fire extinguisher Deep-well pump house of 1.9 Class D III Portable fire extinguisher powerhouse Bridge crane of 1.10 Class D II Portable fire extinguisher powerhouse 2 Auxiliary plant Central control room, Automatic alarm, fire extinguishing 2.1 relay protection room, Class C II system of IG541 mixed gas, and computer room, etc. portable fire extinguisher 10 kV station service HV 2.2 Class D II Portable fire extinguisher switchgear room 0.4 kV station service LV 2.3 Class D II Portable fire extinguisher switchgear room Generator voltage 2.4 distribution equipment Class D II Portable fire extinguisher room

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Buildings, Structures, Fire Risk Fire S/N and Electromechanical Fire Protection Measures Classification Rating Equipment Layered arrangement of cables; fireproof bulkhead, coating, gas 2.5 Power cable floor Class C II mask, cable-type thermal detector, portable fire hydrant, system for fire extinguishment of water spray Layered arrangement of cables; fireproof bulkhead, coating, gas 2.6 Control cable floor Class C II mask, cable-type thermal detector, portable fire hydrant, system for fire extinguishment of water spray Automatic alarm, portable fire Turbine oil depot and oil extinguisher, sand box, and system 2.7 Class C II treatment room for fire extinguishment of water spray Isolated-phase enclosed Portable fire extinguisher and fire 3 Class D II bus hydrant 4 Main transformer

4.1 Main transformer room Class C I Water spray extinguishing system

Portable fire extinguisher, system for Insulating oil tank room, 5 Class C II fire extinguishment of water spray, oil disposal room fire hydrant, and sand box Portable fire extinguisher and sand 6 Oil testing room Class C II box 500 kV cable adit and Portable fire extinguisher and fire 7 Class D II cable shaft hydrant 8 500KV switchyard Ammonium phosphate fire Indoor switchgear of 8.1 Class D II extinguisher of trolley type, gas 500kV SF GIS 6 mask, and fire hydrant Automatic alarm, portable fire 8.2 500 kV cable floor Class D II extinguisher, and water spray extinguishing system Ammonium phosphate fire 8.3 Outgoing line platform Class D II extinguisher of trolley type, and fire hydrant

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Buildings, Structures, Fire Risk Fire S/N and Electromechanical Fire Protection Measures Classification Rating Equipment

9 Dam area and parts outside the plant Power distribution room 9.1 Class D II Portable fire extinguisher at dam crest Portable fire extinguisher and fire 9.2 Diesel generator room Class C I hydrant 9.3 Hoist room Class D II Portable fire extinguisher Equipment repairing Portable fire extinguisher and fire 10 Class D III workshop hydrant

6.6.3.2 Fire Protection Zones and Emergency Exit According to stipulation of Article 3.2.1 of Code of Design on Building Fire Protection and Prevention, there is on limit for maximum allowable floor area of fire protection zones with production category of Class D, fire resistance rating of Grade II, and multilayer. Thus, powerhouse of the Paklay HPP can be divided to 2 fire protection zones. The powerhouse and auxiliary plant are set as two independent fire protection zones; firewalls, fireproof doors, and wall-type fire dampers are adopted to segregate the big space in the powerhouse.

According to stipulations of clauses of Article 4.2 of Code for Design of Fire Protection of Hydraulic Engineering, two emergency exits are set for operation floor of the powerhouse, and at least two evacuation exits are set for each floor such as generator floor, cable floor, and operation gallery. Only 1 evacuation exit is set for the central control building as the floor area of each floor is less than 800 m2 and number of staff on duty is not more than 15.

For each floor, distance between the farthest work place and nearest evacuation exit should be not more than 60.0 m. Net width of evacuation door, which opens towards evacuation direction, is not less than 0.9 m. Net width of corridor is not less than 1.2 m.

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Net width of staircase is not less than 1.1 m and slope gradient of the staircase is not more than 45°. Fireproof doors and firewalls are set between the underground buildings and ground buildings for segregation.

Number of staircase and safe evacuation distance should both meet requirements of the Codes.

6.6.3.3 Fire Lane a) Fire lane outside the plant

Permanent access road can lead to the generator floor and head structures. Both the permanent access road and dam crest road can be used as fire lane.

b) Fire lane inside the powerhouse

The station is of a ground-type powerhouse; the fire truck can reach to powerhouse via access road and do fire protection operation. Turnaround loop, which can also be used as turnaround loop for fire truck, is set before the plant gate.

6.6.3.4 Fire Water Supply and Design of Water Supply System Water source of the HPP is abundant. Upstream reservoir is the source of fire water supply and direct water supply system of pressurization of water pump is adopted. Capacity of fire pump is not less than sum of maximum water yield of water spray and fire water yield of hydrant; the sum is 360 m3/h by calculation. Elevation of the water pump should ensure that pressure at outlet of water sprayer at highest place should be not less than 0.35 MPa (35.7 mH2O) stipulated in the Code, and that value is 50 mH2O by calculation. Two water supply pumps are provided (one for use and one for standby). Circular pipe for water supply of fire protection should be set crossing the whole plant. Water is led by branch pipes of the circular pipe to each water consumption system. According to requirement of the Code, sectionalized valves should be set on the circular pipe. When a section is damaged, fire hydrants out of work should be not more than 5 in same floor.

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6.6.3.5 Design for Fire Control of Main Electromechanical Equipment a) Turbine generator Water spray should be adopted for fire extinguishment of generators according to the capacity, scale, and fire protection technology at present. Detectors for temperature sensing and smoke sensing should be set in foundation pit of generators. When the fire alarm of generator gives alarm signal to fire control centers of whole plant, staff on duty should confirm the alarm and then connect the separated hoses of fire hydrant of the generator manually to open the water supply valve to put out fire. b) Main transformer Independent water spray extinguishing system should be adopted for each main transformer. When the transformer is on fire, the sprayer seals both its body and oil sump in the water spray, and extinguishes fire by cooling down and asphyxiating effects. Oil discharging pipe is set at bottom of the oil storage pit to discharge fire protection water and transformer oil which may overflow to the emergency oil pool. Capacity of emergency oil pool is sum of transformer oil capacity and water yield of fire protection for 24 min. The sum is 195.4 m3. Capacity of emergency oil pool of main transformer is 200 m3. c) Turbine oil depot and oil disposal room, insulating oil depot and oil disposal room The turbine oil depot and oil disposal room, and insulating oil depot and oil disposal room are all set at the floor with an elevation of 216.500 m a.s.l. below the central erection bay. Two fireproof doors opening outward are set at that floor. Firewalls with fire endurance of 4 h are set for the oil depots and oil disposal rooms. Explosionproof electric appliances are provided for the oil disposal room. Fixed fire extinguishment appliance for water spray is adopted for fire protection of the oil depot and oil disposal room. Complete set of deluge valves, which are set outside the turbine oil depot, is adopted as operation valves for inflow of fire protection water. Detectors for temperature sensing and smoke sensing are set in the oil depots to send alarm to the fire control center automatically when there is a fire. At that time, the fire damper will close automatically, the exhaust fan stops exhausting immediately, deluge valves start

6-144 Paklay Hydropower Project Feasibility Study Report spraying water to put out fire, and the exhaust fan starts exhausting after the fire is put out. d) Central control room, computer room, and relay protection room

Fixed fire extinguishment system of CO2 is adopted for this part. Combined and distributed pipeline system is adopted and one set of storage vessel is adopted. Design capacity of the system is determined as per demand capacity of the biggest central control room and a standby capacity of 8% should be considered. By calculation, 22 storage cylinders are adopted. The cylinders are controlled by fire alarm control panel. Point-type temperature and smoke sensing detectors as well as audible and visual alarms should be set in fire extinguishing districts. Gas indicators should be set at upper parts outside the doors, which should be provided with emergency interrupting boxes. When the temperature and smoke sensing detectors give alarms simultaneously, the controller will stop air conditioners and fans of the district immediately, and the audible and visual alarms give alarms to alert people to evacuate immediately. After a time delay of 30 s (adjustable), the fire protection door will be closed and fire extinguishing apparatus will be used. Cylinders will be started by solenoid valve to start the CO2 storage cylinders. When the gas indicators are on, it means that the fire extinguishing system is working. Supporting sprayers of the fire extinguishment system are adopted as sprayers of the protection zone. Number of both kinds sprayers are 8 respectively. When the staff on duty finds a fire, he must press the emergency interrupting box, and then the fire extinguishment appliance will start to work immediately. Or if the staff finds that the alarm is a false one during time delay before the gas is emitted, he can press the emergency interrupting box to stop the fire extinguishment appliance. e) Cable Flame retardant cables should be adopted to prevent and reduce occurrence and spreading of fire disasters. Temperature sensing cables are laid for each floor of enclosed cable bridge. Fire resistant plates should be set for spaces between the power cable floors and control cable floors in the enclosed cable bridge. Fire retardant sections should be set at 6-145 Paklay Hydropower Project Feasibility Study Report appropriate position. Fire proof materials should be adopted to seal holes on walls, floors, etc. those are crossed by cables, and ends of cables. Fire extinguishment appliances of water spray are set for main cable channels such as those of the central control room, cables of the powerhouse, etc. Combining layout of equipment and cables, cable zones without fixed fire extinguishment systems of water spray should be set with portable fire extinguishers at certain interval distances. Fire protection sealing measure, as well as sand boxes and portable fire extinguishers, etc. is set at entrances and outlets where cables are centralized. 6.6.3.6 Electrical Works for Fire Control a) Power Distribution for Fire Fighting

Electrical fire fighting equipment includes smoke exhaust fans, fire dampers, fire and smoke exhaust dampers, automatic fire alarm control system, safety evacuation identifications and emergency lightening, etc.

Power supply for the electrical fire fighting equipment is provided with second class load through independent power supply circuit. The arrangement ensures the availability of fire fighting power supply in case of a fire. And the power distribution equipment is provided with the sign of “Dedicated Equipment for Fire Fighting”.

The power station is equipped with dedicated fire fighting power panel. The power supplies come from the II-section and III-section bus of the public power supply for the whole powerhouse, respectively to ensure 2 reliable power supplies for the electrical fire fighting equipment.

The emergency system is powered by the AC and DC switching system. In normal conditions, AC power supply shall be used for supplying power. If the AC power supply is out of service, switch to the DC power supply system to convert DC power supply into AC power supply. Under normal conditions, AC power supply shall be used for supplying power for evacuation indicator lights. If the AC power supply is out of service, batteries of the lights shall be used for supplying power.

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Evacuation indication lighting and emergency lighting are also the emergency lighting in case of fire. Continuously supplying power of the fire emergency lighting and evacuation signs shall not be less than 30 min.

Cables for power supply of the fire fighting power supply system, emergency lighting system and evacuation indication lighting shall adopt fire resisting cables and be laid in conduit.

b) Fire emergency lighting, evacuation sign indication and lamps

Main evacuation exits, staircases, emergency exits are provided with fire emergency lighting and emergency sign indication lighting with minimum illumination no less than 0.5Lux.

The emergency lighting lamps are mounted on wall or ceiling. Evacuation lighting of the emergency exits shall be mounted on the top. Evacuation indication signs of the evacuation corridor shall be mounted on the wall with a distance of 0.5m to the ground

(floor). The distance between the signs shall not be larger than 20m.

The emergency lighting and evacuation indicator lights shall be equipped with protection covers made of glass or other refractory materials. 6.6.3.7 Smoke Prevention and Exhaust System a) Fire protection plan for ventilation system According to requirements of fire protection code, fire protection design of ventilation system of the whole plant conforms to the following principles. Open fire heating is prohibited at parts such as oil depots, oil disposal room, places neat to the oil pipes and their accessories, battery room, etc. Fire dampers are set for spaces of different fire protection zones, for spaces between important equipment rooms and the outside, and for areas among different fire ratings for segregation. Independent exhaust systems are set for equipment rooms with superior fire ratings, such as oil depots, battery rooms, etc. 6-147 Paklay Hydropower Project Feasibility Study Report

Based on the above principles, fire dampers are adopted for exhaust outlets set at exhaust interlayer of the downstream auxiliary plant to complete fire protection function of the ventilation system, for exhaust inlets for fire protection, alarm, and air volume regulation, for air inlets and exhaust outlets of main transformer room of the exhaust system for main transformers to separate the main transformers with other zones, separate the transformers with each other to prevent spreading of fire, for air inlets and exhaust outlets of oil depots and battery room to prevent and cut off fire. The exhaust fan is of direct-connection explosionproof type and axial exhaust fan of SF6 switchyard is of explosionproof type. Galvanized iron-sheet air hose with good fireproof performance is adopted for all air ducts of the plant to eradicate fire risk. Joint control is carried out for the fire dampers and their corresponding exhaust fans. When there is a fire, the fire damper will start to work and send electric signal to stop its corresponding exhaust fan. After the fire is put out, fire damper will open again to start the exhaust fan to exhaust smoke after the fire. b) Design of smoke prevention and exhaust of whole plant According to requirements of the Code, mechanical smoke exhaust system is set for generator floor of the powerhouse and transportation channel of main transformer, as the HPP is of a ground-type powerhouse. Smoke exhaust system of generator floor: smoke exhaust pipes are set in central part of the upper part of generator floor; smoke exhaust holes are set on the pipes, which are closed under common condition and opened automatically upon fire. Axial flow fan for smoke exhaust connects with the smoke exhaust pipe directly and are mounted under the arc crown. Smoke is directly exhausted to upstream outside of 2# erection bay when there is a fire. Smoke exhaust capacity of the system is 60000 m3/h. There are only 1 smoke exhaust fan with model of HTF-11.2-I. Smoke exhaust system of transportation channel of main transformer: smoke exhaust pipes are set at upper part of transportation channel of the main transformer; smoke 6-148 Paklay Hydropower Project Feasibility Study Report exhaust holes are set on the pipes, which are closed under common condition and opened automatically upon fire. Axial flow fan for smoke exhaust connects with the smoke exhaust pipe directly. Smoke is directly exhausted to downstream outside when there is a fire. Smoke exhaust capacity of the system is 15000 m3/h. There are only 1 smoke exhaust fan with model of HTF-8-I. Air exhaust system of downstream auxiliary plant exhausts smoke as well. When there is a fire, fans of related parts should be stopped; after the fire disaster, fans should be started to exhaust smoke. Twenty axial flow fans with model of T35-11No.5 are set at upper and lower parts (10 for the upper part and 10 for the lower part) of downstream wall of GIS room. The upper fans can exhaust smoke and the lower fans can exhaust SF6 gas leaked when putting out the fire. For areas such as generator floor of powerhouse and transportation channel of main transformer that are set with immediate smoke exhaust facilities, their smoke exhaust dampers are interlocked with corresponding exhaust fans so that when the smoke exhaust damper is started (via the fire control center), the exhaust fan will operate automatically. For areas set with emergency exhaust facilities, fire alarm controller will automatically close the corresponding fire dampers and stop corresponding exhaust fans via joint module when there is a fire. Fire dampers will be open to start smoke exhaust fan after the fire is put out. 6.6.3.8 Fire Alarm Control System A set of automatic fire alarm and fire joint control cabinet and fire monitoring computer (including professional fire monitoring software) is set in the control room to achieve fire detection, audible and visual alarm, joint control of fans and air conditioners, join control of smoke prevention and exhaust, joint control of fire extinguishment, etc. of the HPP and monitoring scope within the navigation lock. The fire monitoring computer can monitor, deal with, store, and print all alarm information to display the system status via plane graph, as well as control all controllable fire extinguishment apparatuses. Each one regional fire alarm and fire joint control cabinet is set for the dam area and navigation

6-149 Paklay Hydropower Project Feasibility Study Report lock. Coaxial cables or optic fiber communication is adopted for all control cabinets. The alarm and joint control apparatus connects with the fire monitoring computer via communication interface, connects with the computer monitoring system via I/O interface to send general alarm information to the computer monitoring system, and connects with industrial television monitoring system via I/O interface and communication interface to link with facility of the industrial television monitoring system to achieve automatic tracking and video recording of the alarm site. Operators in the control room can operate the facility of the industrial television monitoring system to carry out remote monitoring to area with the scope of fire protection monitoring of the HPP and facilities. Detectors are installed at areas where important facilities are set and places where fire may occur easily. Detectors, manual fire alarm buttons, etc. are set according to Code for Design of Automatic Fire Alarm Systems (GB50116-98) and actual layout of the HPP. Joint control modules are provided according to requirement of automatic control of fire extinguishment apparatus. Point-type smoke sensing detectors are provided for areas (such as hydraulic generator room, central control room, relay protection panel room, computer room, communication facility room, and main transformer room) where important and common facilities are set. Explosionproof infrared-beam smoke sensing detectors are provided for turbine oil depot and oil disposal room. Point-type and cable-type temperature sensing detectors are provided for areas where fixed fire extinguishment apparatus of water spray are set. Manual alarm buttons, audible and visual alarms are provided for important transportation channels, evacuation channels, galleries, stairs, and main facilities.

Complete administration and dispatching communication facilities are set in the HPP to cover the area of fire monitoring system, thus, there is no need to set fire protection communication facilities. Fireproof treatment is carried out to communication line according to laying requirement of fire protection line. Meanwhile, a number of wireless intercoms are provided for the HPP as standby communication for the wire communication.

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6.6.4 Fire Protection Design for Finishing Works of Buildings

6.6.4.1 Overview Design for finishing works of the HPP should not only meet the requirement of operation function, pay attention to appearance, but also meet the requirement of durability, anti-corrosion ability, and good fireproof performance. Therefore, materials which are non-inflammable and fire-retardant should be used as finish to meet the architectural effect and prevent flame. In addition, fire protection zones should be set reasonably at the same time.

Suspended ceiling is an important part of the finishing. As many lighting lines are set, the suspended ceiling is a part where fire may occur easily. Therefore, suspended ceilings of important places and provided with light-steel keel and aluminium alloy perforated plate (with requirement of sound absorption) should be paved with mineral cotton with thickness of 50 mm. Thus, requirement of sound absorption and flame prevention can be met. In addition, constant temperature sensing detectors should be laid at the suspended ceiling.

Interior wall is plastered by cement mortar, whitened after leveling, and finished by environmental wall paint.

Except the computer room, communication room, etc. which are paved by aluminium alloy antistatic floor, other grounds are paved by granite, floor tile, cement floor, cement mortar, and terrazzo.

Class A or Class B fireproof doors are adopted for windows and doors of partition walls according to fire ratings of rooms. Fireproof materials are adopted to seal facility holes which cross the walls.

6.6.4.2 Powerhouse Generator hall and erection bay are key places of interior safety design of the powerhouse. White wall paints are adopted as finish of the wall. Magenta marble boards which are 2000 mm high are adopted for wainscot. The 1000×1000 copper bar frames of cast-in-situ terrazzo are adopted for the generator hall and erection bay. Color plate arc-shaped roof is adopted as the roof. Stainless-steel metal guard rods which are 1050 mm high are adopted for interior surrounding of the generator hall. Cover plates are adopted to seal the lifting holes. 6-151 Paklay Hydropower Project Feasibility Study Report

6.6.4.3 Downstream Auxiliary plant and Central Control Building Class A fireproof doors are adopted for power distribution room, 10 kv switchgear room, central control room, communication power supply room, communication facility room, relay protection room, and battery room of the downstream auxiliary plant and central control building as safety design measure of fire protection. Double-layer fireproof glass windows are adopted for windows of the central control room. Architectural finishing: white wall paints are adopted for walls of the power distribution facility room, station-service power distribution panel room, 10 kv switchgear room, local small room, duty room, office, galleries, relay protection room, and shift room as finish. In addition, tiles with skirting which is 150 mm high, 600×600 anti-skidding floor tiles of the ground, and white aluminium alloy light-steel keel for the suspended ceiling is adopted for the above rooms. The 600×600 antistatic floors are adopted for the central control room, communication power supply room, and communication facility room. White wall paint is adopted as finish and white aluminium alloy light-steel keel is adopted for the suspended ceiling. White wall paint is adopted for the exhaust fan room, cable floor, and pump room as finish. Cement mortar with skirting which is 150 mm high is adopted and cement mortar is adopted for the ground. Acid-proof floor tiles are adopted for the battery room. Acid-proof tile with wainscot which is 1.5 m high is adopted and other wall surfaces should be of cement mortar top with white paint. Enamel paint is adopted for the ceiling as finish after it is whitened. 6.6.4.4 Other Rooms White wall paint is adopted for other rooms. Cement mortar with skirting which is 150 mm high is adopted and cement mortar is adopted for the ground.

6.6.5 Summary Sheet of Fire protection Apparatus

Refer to Table 6.6-2 for main fire protection apparatuses of the HPP.

Table 6.6-2 Summary Sheet of Fire protection Apparatus

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S/N Description Specification Unit Qty.

1 Fire pump Q=360m3/h H=50m Set 2

2 Pump control valve DN250, PN1.6MPa Nr. 2

3 Fire fighting device of generator Set 14

4 Y-type filter DN200 PN1.6MPa Nr. 39

5 Automatic water filter Q=360m3/h P=1.0MPa Nr. 2

6 Ball valve DN250 PN1.6MPa Nr. 4

7 Ball valve DN65 PN1.6MPa Nr. 33

8 Butterfly valve DN150 PN1.6MPa Nr. 11

9 Butterfly valve DN100 PN1.6MPa Nr. 6

10 Water spray nozzle ZSTWB-40-90 Nr. 2140

11 Water spray nozzle ZSTWB-160-120 Nr. 240

12 Deluge valve DN200 Nr. 39

13 Indoor fire hydrant SN65 Nr. 58

14 Signal butterfly valve DN200 PN1.6MPa Nr. 78

15 Check valve DN200 PN1.6MPa Nr. 4

16 Check valve DN150 PN1.6MPa Nr. 4

17 Pump adapter DN200 PN1.6MPa Nr. 4

18 Pump adapter DN150 PN1.6MPa Nr. 4

22 Start cylinder V=70L PN=15MPa Nr. 2 Portable dry powder fire 23 MFA6 Nos. 92 extinguisher Wheeled dry powder fire 24 MFAT35 Nos. 4 extinguisher 25 Gas mask Set 20 Anti-fire plug (fast 26 SFD-II type t 4.5 solidification) Anti-fire plug (fast 27 XFD type t 1.5 solidification) 28 Anti-fire plug (soft) DFD-III(A) type t 12

29 Fireproof coating G60-3D type t 4.5

30 Fireproof bag of expansible PFB-720 type m3 30 6-153 Paklay Hydropower Project Feasibility Study Report

S/N Description Specification Unit Qty.

cable

31 Fireproof bulkhead EFW-A type m2 150

32 Fireproof bulkhead EFF-C type m2 200

33 Fireproof tray ESW-Z type m2 450 Power distribution panel for fire 34 400 V Nos. 2 protection 35 Emergency lighting 25 W Pcs. 180

36 Exit indicator light 13 W Pcs. 110

37 Emergency light 2×32 W Pcs. 100

38 Fire alarm and control system Monitoring computer and 39 Set 1 software for fire protection 40 Fire alarm and joint controller Set 1 Point-type smoke and 41 Nr. 300 temperature sensing detectors Infrared beam smoke sensing 42 Pair 20 detector Cable type temperature sensing 43 km 5 detector 44 Manual alarm button Nr. 40

45 Isolator and connector modules Nr. 100

46 Audible and visual alarm Nr. 40 Alarm and control signal line 47 km 10 and power line Protection casing of 48 flame-retardant flexible metal km 8 cable 49 Sand box 2m3 Pcs. 6

50 Explosionproof axial flow fan Set 3

51 Fire damper Nr. 20

6-154