THE WEST BENGAL POWER DEVELOPMENT CORPORATION LIMITED
DETAILED PROJECT REPORT FOR 1 x 660 MW PHASE-III EXTENSION UNIT # 5
SAGARIGHI THERMAL POWER STATION AT SAGARDIGHI, DIST.: MURSHIDABAD, WEST BENGAL
MAY, 2016
CONSULTANT
DEVELOPMENT CONSULTANTS PRIVATE LIMITED BLOCK DG-4, SECTOR-II, SALT LAKE CITY, KOLKATA – 700 091, INDIA
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
DETAILED PROJECT REPORT FOR SAGARDIGHI THERMAL POWER STATION
1 x 660 MW PHASE-III EXTENSION UNIT # 5 SAGARDIGHI, WEST BENGAL
I N D E X
SECTION – 1 : PROJECT BACK GROUND AND EXECUTIVE SUMMARY
1.1 Foreword 1.2 Executive Summary 1.3 Project At a Glance
SECTION – 2 : JUSTIFICATION OF THE PROJECT
2.1 Introduction 2.2 All-India Power Scenario 2.3 Power Scenario of Eastern Region 2.4 Power Scenario in West Bengal 2.5 Justification of the Project
2.6 Unit Size Selection
Index - 1 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION – 3 : BASIC REQUIREMENTS
3.1 Introduction 3.2 Land – Requirement & Availability for Phase-III Unit
3.3 Water – Requirement & Availability 3.4 Fuel Requirement 3.5 Ash Disposal 3.6 Power Evacuation 3.7 Infrastructural Facilities
SECTION – 4 : SITE FEATURES
4.1 Introduction 4.2 Features of the Identified Site 4.3 Meteorological Details
SECTION – 5 : POWER GENERATING EQUIPMENT
5.1 Introduction 5.2 Selection of Technology 5.3 Thermodynamic Cycle 5.4 Steam Generating Unit 5.5 Turbine Generator Unit
Index - 2 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
5.6 Condensing Equipment & Accessories 5.7 Boiler Feed Water Pumps 5.8 Deaerating Heaters & Closed Heaters
SECTION – 6 : AUXILIARY SYSTEMS
6.1 Introduction 6.2 Plant Water System 6.3 Coal Handling System 6.4 Ash Handling System 6.5 Fuel Oil Handling System 6.6 Ventilation & Air-conditioning System 6.7 Compressed Air System 6.8 Fire Protection System 6.9 Piping, Valves, Fittings & Specialties 6.10 Miscellaneous Auxiliaries 6.11 Associated Facilities
SECTION – 7 : ELECTRICAL SYSTEM & EQUIPMENT
7.1 Introduction 7.2 Design Parameters 7.3 Electrical System 7.4 Control of Electrical System 7.5 Metering
Index - 3 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
7.6 Protection System 7.7 Plant Illumination 7.8 Grounding & Lightning Protection 7.9 In-Plant Cabling
SECTION – 8 : CONTROL AND INSTRUMENTATION
8.1 Design Objective
8.2 Plant Control Philosophy
8.3 Design Basis Requirements
8.4 Major Instrumentation & Control Systems
8.5 Control Room / Equipment Room Desk & Panel
8.6 Power Supply System
8.7 Instrument Air Supply
8.8 Instrumentation & Control Cables & Accessories
8.9 Erection Hardware
8.10 Tools & Tackle and I&C Laboratory Instruments
8.11 Spares & Consumable
8.12 Fire Detection & Alarm System
8.13 Plant Communication System
8.14 Closed Circuit Television System
Index - 4 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION – 9 : STATION LAYOUT AND CIVIL ENGINEERING ASPECTS
9.1 Introduction 9.2 Plant Layout 9.3 Civil Engineering Aspects 9.4 Description of Building & Superstructure
SECTION – 10 : ENVIRONMENTAL ASPECTS
10.1 Introduction 10.2 Environmental Pollution from a Thermal Power Plant 10.3 Basic Information for Environmental Clearance 10.4 Commercial Utilisation of Fly Ash 10.5 Environmental Laboratory
SECTION – 11 : CONSTRUCTION FACILITIES
11.1 Introduction 11.2 Construction Features 11.3 Organisational Set-up for Plant Construction 11.4 Safety & Health Hazard Monitoring 11.5 Security 11.6 Labour Welfare & Statutory Regulations
Index - 5 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION – 12 : ORGANISATION STRUCTURE
12.1 Philosophy of Plant Design & Operation 12.2 Organisation Set-up for Plant Operation 12.3 Training of Personnel
SECTION – 13 : EMPLOYEE FACILITIES AND RESIDENTIAL TOWNSHIP
13.1 Employee Facilities 13.2 Residential Township
SECTION – 14 : PROJECT IMPLEMENTATION AND MONITORING
14.1 Introduction 14.2 Project Organisation of the Owner 14.3 Project Execution 14.4 Project Monitoring, Co-ordination & Control 14.5 Role of Consultant 14.6 Project Implementation Schedule
Index - 6 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION – 15 : PROJECT COST ESTIMATE AND TARIFF
15.1 Major Assumptions
15.2 Project Cost, Cost of Production and Financial Analysis
15.3 Profitability
15.4 Energy Generation and Revenue
15.5 Interest, Depreciation and Tax
15.6 Financial Evaluation
Index - 7 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
LIST OF ANNEXURES & DRAWINGS
SECTION - 2
Annexure - 2.1 Category & Year-wise Forecast of All India Power Scenario
Annexure - 2.2 Demand / Load Growth Trend in West Bengal (Energy)
Annexure - 2.3 Demand/ Load Growth Trend in West Bengal (Peak Demand)
SECTION - 3
Annexure - 3.1 Raw Water Analysis
Annexure - 3.2 Estimation of Consumptive Water Requirement
Annexure - 3.3 Analysis of Coal & Ash
Annexure - 3.4 Analysis of Heavy Fuel Oil (HFO)
Annexure - 3.5 Analysis of Light Diesel Oil (LDO)
SECTION - 4
Annexure – 4.1 Climatological Table of Berhampur
Drawing No. 16A03-DWG-M-003B Vicinity Map
Drawing No. 16A03-DWG-M-003C Site Location Map
Index - 8 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION - 5
Annexure - 5.1 Brief Technical Features of Main Plant & Equipment
Drawing No. 16A03-DWG-M-0100 Heat balance Diagram (Typical)
Drawing No. 16A03-DWG-M-0101 Single line diagram of steam and water system.
SECTION - 6
Annexure - 6.1 Salient Features of Auxiliary Plant & Equipment
Drawing No. 16A03-DWG-M-0001 Flow Diagram of Plant Water System
Drawing No. 16A03-DWG-M-0002 Water Balance Diagram
Drawing No. 16A03-DWG-M-0002A Water Balance Diagram (Based on MoEFCC notification dated 7.12.15)
Drawing No. 16A03-DWG-M-0003 Flow Diagram for Coal Handling System
Drawing No. 16A03-DWG-M-0004 Single Line Diagram for Ash Handling System
Drawing No. 16A03-DWG-M-0005 Single Line Diagram for Fuel Oil System
Drawing No. 16A03-DWG-M-0006 Single Line Diagram of Compressed Air System
Drawing No. 16A03-DWG-M-0007 Typical Flow Scheme of Anhydrous Ammonia Based SCR
Drawing No. 16A03-DWG-M-0008 Typical Flow Scheme of LSFO FGD
Index - 9 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION - 7
Annexure - 7.1 Technical Particulars of Major Electrical Equipment
Drawing No. 16A03-DWG-E-0001 Single Line Diagram for Auxiliary Power Distribution
Drawing No. 16A03-DWG-E-0002 Single Line Diagram for 400 KV Substation
SECTION - 8
Drawing No. 16A03-DWG-I-0010 Control System Architecture
SECTION - 9
Annexure - 9.1 Salient Features of Major Civil Works
Drawing No. 16A03-DWG-M-003A Plot Plan
SECTION - 10
Drawing No. 16A03-DWG-EV-0001 Single Line Diagram for Waste Water Management Scheme
SECTION - 11
Drawing No. 16A03-DWG-M-0102 Organisation Chart (Project Management Team)
Index - 10 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC)
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION – 12
Drawing No. 16A03-DWG-M-0103 Organisation Chart (O&M)
SECTION - 14
Drawing No. 16A03-DWG-PL-0001 Project Schedule
SECTION – 15
Annexure – 15.1 Estimated Project Cost Annexure – 15.2 - 15.18 Financial Tables
Index - 11 - Development Consultants Pvt. Ltd. (PCA.CD-006.16A03-DPR2_INDEX.DOC) Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION-1
PROJECT BACKGROUND AND EXECUTIVE SUMMARY
1.1 Foreword
West Bengal is one of the states with highest population density (1030 per sq. km) covering an area of 88,752 sq. km with total population of 9.13 Core as per 2011 census. The state is generally divided in two regions namely, Himalayan north and Alluvial plain. The state has widely diversified farming base with a rich variety of food and crop having 62% of cultivable land under irrigation and 15.3% under forest cover. Agriculture sector accounts for 65% of state’s income and provides livelihood for more than 70% of the population. The state had major investment in engineering industries and other industrial sector till seventies. Lately, again under open economy regime, the investment in industrial sector has picked up accelerated growth. The interest in investment is mainly attributable to suitable industrial infrastructure available.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In order to accelerate growth in the state, particularly in the industrial sector under the open economic policy the state government have taken a number of initiatives including investment subsidies, tax benefit etc. In the energy sector, major steps have been taken to support the accelerated industrial growth and enhanced production in the agricultural sector. The industrial development in the state till date has been concentrated mostly along Gangetic plain viz. Kolkata, Howrah, Haldia and industrial towns in Durgapur-Asansol axis. But in the past few years efforts are being made to promote new industries in other parts of the state as well particularly in central and northern parts of the state.
Lack of availability of sufficient electric power is a major deterrent to the growth of industry and agriculture. The responsibility of generation, transmission and distribution of power to the consumers in the state, at present, lies with The West Bengal Power Development Corporation Limited (WBPDCL), West Bengal State Electricity Transmission Company Limited (WBSETCL) and West Bengal State Electricity Distribution Company Limited (WBSEDCL) besides other licensees like CESC Limited, Durgapur Projects Limited and Disergarh Power Supply Co. Limited. The Government of West Bengal is therefore, taking-up a number of strategic steps for development of infrastructural facilities including augmentation of power supply to nurture this trend.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The West Bengal Power Development Corporation Limited (WBPDCL) proposes to extend their on-going Phase-II extension project of 2x500 MW at Sagardighi by adding one super critical unit of 660 MW as Phase-III extension unit. Sagardighi TPS is located in the village Manigram in Murshidabad district of West Bengal, India. The West Bengal Power Development Corporation Limited, a Company fully owned by the Government of West Bengal formed in the year 1985, have commissioned 2x300 MW Thermal Power Plant together with all other infrastructure at Sagardighi Thermal Power Project. Presently WBPDCL is also working on their under-construction Phase- II extension project of 2x500 MW at Sagardighi.
The site is about 20 km from National Highway (NH-34) and an access road is laid to connect the station with road network of the country. The nearest broad gauge (B.G.) railway station is Manigram on Bandel- Barhawara branch of Eastern Railway. This line grazes past the western boundary of the plot.
All construction material, heavy equipment, over dimensioned consignments (ODC) for the station during construction may be transported through road/rail access. During operation stage, coal would be transported through rail access. Presently, WBPDCL have 365 Ha of land under possession for Phases I, II & III of the plant proper and another 184 Ha for ash disposal.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Phase-III Extension :
The new unit (1 x 660 MW) would be located on the north of under- construction Phase-II 2 x 500 MW Units.
It is considered that coal would be received from the same source as the plant under Phase-I and Phase-II station with similar characteristics and a new mine at Pachwara (north) in Jharkhand being developed by WBPDCL. These sources being connected by B.G. rail track, coal would be transported by rail only. For coal unloading, crushing and storage facility it is proposed to utilise coal handling plant of Phase-II station with suitable extension from the end of Transfer Point (TP-19).
Available allocation of raw water for Phase-II station is 60 Cusec. However, it is estimated that 50.7 Cusec of water would be consumed for Phase-II & III together.
The adequacy of landmass in the identified plot for Phase-III extension was reviewed considering unit size and space for auxiliary equipment required viz. the cooling tower, switchyard etc. This space is also adequate to accommodate FGD and SCR packages required as per latest MoEFCC notification.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
With the above in view, WBPDCL have entrusted M/s. Development Consultants Private Limited (DCPL) to study and prepare the Detailed Project Report (DPR) for installation of the 5th unit (Phase-III) of Sagardighi Thermal Power Station of 660 MW unit with Super Critical technology in the identified plot and address other relevant features for implementation.
1.2 Executive Summary
It has been observed from the WBSEB’s statistics and the 18th Electric Power Survey (EPS), published by the Ministry of Power, Government of India, that the energy demand/supply position for West Bengal at the end of the 12th Plan and the 13th Plan requires substantial capacity addition particularly in thermal sector. Hydel generation, in the state has nominal contribution to the state grid and has possibility of nominal capacity addition. Thus the above scenario highlights the need for measures to bridge the gap between the demand and supply. In order to induct more base load thermal power stations for stability of the state grid, the extension station with 660 MW nominal capacity unit has been proposed for implementation. . In Section-2 of this report, the justification of the project along with the energy and peak demand is discussed.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In Section-3 of the report, the basic requirements for a thermal power station vis-à-vis availability at the designated site has been elaborated.
The proposed 660 MW unit would be accommodated within the northern side of the acquired boundary of the under-construction Phase-II units. For the proposed 1x660 MW unit 3.42 Million ton per annum of coal at a planned plant load factor of 90% is estimated. The existing allocation of 60 cusec of water from Bhagirathi River for Phase-II stations would be adequate for the 660 MW Phase-III unit as well.
The site is about 20 km from National Highway (NH-34) and an access road had been drawn to connect the station with road network of the country. The nearest broad gauge (BG) railway station is Manigram on Bandel-Barhawara branch of Eastern Railway. This line grazes past the eastern boundary of the plot. Considering the direction of coal source, a 6.5 km long spur had been drawn from Gosaingram R. S. on Sainthiya-Azimganj line to Poradanga halt on Azimganj-Farakka line. Necessary augmentation, if required, would be done to handle additional rake loads of daily coal required for Phase-III unit.
In Section-4 of the report, the features of the selected site are discussed.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In Section-5 of the report, the technical features of the 660 MW set size outlining the design parameters of main plant and equipment are discussed. A reheat steam cycle with regenerative feed heating arrangement operating at super-critical range has been proposed.
Raw water supply to the plant is planned from the proposed pump house for Phase-II on the Bhagirathi River. Recirculating cooling water system with natural draft cooling tower is envisaged for this 660 MW unit.
Coal with 3300 kcal/kg of heat value is planned for use for the station. The 2000 TPH twin-stream coal conveyor system proposed for the Phase-II units would be extended from the end transfer point TP-19 to the bunker level of the Phase-III unit #5.
Fly ash generated is proposed to be extracted in dry form. Both bottom ash and fly ash (only under emergency) would be disposed in lean slurry form with provision of ash water recirculation. Fly ash dry disposal has been envisaged after identification and linkage of suitable utilisation of dry fly ash. The focus is on use of ash for cement production, bricks manufacture, as mine-fill, low lying area filling, for road construction and other usages, as per guidelines of MoEFCC.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Other auxiliaries and accessories would deploy the state-of-the-art technology to ensure safe and continuous operation of the unit with minimum unscheduled outage. In Section-6 of the report, the auxiliary systems of the power generating unit are discussed.
In Section-7 of this report, the electrical equipment and systems are discussed.
The electric generators will be 3-phase, 50 Hz, hydrogen-cooled, 3000 rpm machines with static/brushless excitation system and will generate power at 21 kV at 0.85 power factor (lagging). The unit will be connected to existing 400 kV outdoor switchyard of Phase-II for evacuation of generated power.
In Section-8 of this report, instrumentation and control philosophy of the proposed station is dealt in adequate detail.
A safe, efficient and reliable operation of the Plant Instrumentation & Control System is envisaged for Control and Monitoring of all equipment of the Main Plant & Auxiliaries from the Central Control Room (CCR) . The I&C system for the BTG unit will be based on a state-of-the-art Microprocessor based Distributed Digital Control, Monitoring & Information System (DDCMIS) with functional & geographical distribution of various function groups.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Plant operation and control will be through the Operator Interface Units located on the Unit Control Desk (UCD) in the Central Control Room which will consist of colour graphic LCD (TFT) monitor, keyboard / Mouse and also through Large Video Screen (LVS).
The plant layout for the proposed station has been developed keeping in view optimum use of land available within the identified land limit, land contour, wind rose pattern of the area, direction of supplies of input, direction of road access, merry-go-round and railway entry, operational ease and initial investment requirement.
Details of basic plant features and the relevant layout within the identified plot are furnished in Section-9 of this report.
A thermal power station utilizing coal as its source of energy may pollute the environment in a number of ways. A detailed scheme for alleviating these pollutants has been provided in Section-10 of this report along with general discussion on the entire environmental aspects.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Broadly the various pollution control measures have been envisaged:-
1. Emissions from Stack - Particulate matter will be arrested in an efficient electrostatic precipitator to limit emission within 30 mg/Nm3. A properly designed boiler furnace with SCR/SNCR unit will keep the emission of NOx to within 100 mg/Nm3.
Similarly, FGD plant will keep the emission of SO2to within 100 mg/Nm3. A stack of 275 m height has been envisaged to limit ground level concentration of SOx, NOx, etc. within acceptable limits by proper dispersion. Generation of CO will be minimised with a properly designed furnace and burner system. Hg emission, if any, will get removed in SCR/SNCR unit and in the FGD plant. For the proposed project, supercritical technology has been planned which will improve the cycle efficiency and as a consequence reduce emissions.
2. Heat loss - Nominal heat loss through the stack which will be dispersed with the plume from the high stack. Further, majority of the heat in cooling tower is rejected in the form of evaporation which does not cause any appreciable thermal pollution to the surrounding area.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
3. Liquid Effluents - The waste water treatment and management plan will be developed with the prime approach of maximum recycling & reuse and minimum discharge.
4. Noise Emission - Will be controlled at source with suitable silencers to attenuate the noise to acceptable level.
Liquid effluents will be collected in retention pits and would be suitably treated in the Effluent Treatment Plant being constructed under Phase-II. The treated water will be stored in the treated water retention tank and will be used for CHP dust suppression system and in horticulture.
Adequate green belt, as per norm, will be developed in and around the project area and the ash disposal area to arrest fugitive dust, acting as noise-barrier and will help in improvement of ecology and aesthetics of the area.
The station location is at a reasonable distance from localities, and necessary facilities would have to be developed for execution of the project. As per the prevailing trend, the project will be implemented on multi-package EPC basis with battery limits well identified. All equipment/systems inside/outside the plant will be procured through different EPC Contractors i.e. BTG (Boiler, turbine, generator,
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
etc.) and remaining systems through respective Contractors. The EPC contractors will arrange most of the construction equipment. Project authority will provide clear site, road access, and construction power and construction water to the Contractors. In Section-11 of the report, the construction facilities have been discussed.
In Section-12 of the report, O&M staff requirement for operating and maintaining the plant is narrated. It is assumed that some of the functions during annual maintenance would be contracted out. A total manpower requirement of 200 persons has been envisaged for the proposed Phase-III unit. This may undergo revision as per project authority’s own model of manpower deployment. The training requirements of O&M personnel are also discussed under this section.
Being located near major habitation at Jangipur, Raghunathganj and Manigram etc. and from the viewpoint of operation of a continuous plant, it would be necessary to augment the existing residential township where adequate vacant land is available. In Section-13 of the report, employee facilities and residential township requirement are outlined.
The project is proposed to be implemented by reputed, experienced and financially sound Turnkey Contractors to ensure timely completion. The entire project is envisaged to be implemented in different packages so that specialised Turnkey Contractors can be
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
engaged for the various jobs. The interfaces of the packages shall be well defined. Project authority would also engage the services of an Owners’ engineer for preparation of specification, review of design and drawings prepared by Turnkey Contractor, project co-ordination and monitoring and overview construction quality. Some of the enabling works viz. land grading, construction of road to the site, boundary wall, etc. would also be undertaken by the Contractors. The entire project is planned to be implemented and handed over for commercial operation within a timeframe of 42 months from the date of ‘Letter of Award’ to the Main Plant (BTG) Contractor. The project execution, monitoring and control, project schedule have been discussed under Section-14 of the report.
Based on available quotes and in-house data, the project cost estimate has been worked out. A total capital outlay of Rs.36954.36 Million, including interest during construction and other financial charges, would be involved. The details are furnished in Section-15 of the report.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
1.3 Project at a Glance
General :
Project Authority : The West Bengal Power Development Corporation Limited (WBPDCL).
Project : Phase-III extension of Sagardighi Thermal Power Station (SGTPS) by adding 1x660 MW to the northern side of under-construction 2x500 MW Phase-II station.
Selected Location : Sagardighi in Murshidabad District, West Bengal.
Latitude – 24 22’ 13.7” N Longitude – 88 6’ 15.8” E
Nearest Major Towns : Ajimganj, Jangipur, Raghunathganj.
Seismic Zone : Zone-III as per IS 1893-1984.
Access by Road : From National Highway (NH-34).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Access by Rail : Manigram R.S. on Bandel-Barhawara branch line.
Access by Sea : Nearest port is Kolkata.
Access by Air : Netaji Subhas Chandra Bose International Airport at Dum Dum in Kolkata.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Preliminary Project Particulars :
Main Fuel : Coal from allocated block to WBPDCL at Pachwara north in Jharkhand.
Fuel Transportation : By rail in rake loads of BOBR/’N’-BOX wagons.
Water : From river Bhagirathi (5 km) through the proposed intake pump house under implementation for Phase-II station.
Land : Vacant land adjacent to the units in Phase-II identified for setting up the extension unit.
Layout Features : One 660 MW unit under Phase-III to be accommodated within the available space alongside the battery of two 500 MW units under Phase-II power house.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Land Development : The main power plant would be built at an elevation of 34.5 m above mean sea level (MSL). The plot is well above highest flood level (HFL) of the area.
Technical Features :
Power Generating Units : One unit of standard 660 MW turbine generator sets fed by steam from independent coal fired P.F. boilers operating at super-critical range.
Cooling System : Semi-open recirculating condenser cooling system with wet-type natural draft cooling tower.
Coal Handling System : It will be shared with the CHP of ongoing Phase-II station. Suitable extension from the end of Transfer Point (TP-19) to be done.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Ash Disposal System : Bottom Ash (BA) shall be extraction in wet form and conveyed to the disposal area in lean slurry form. Whereas Fly Ash (FA) shall be extracted in dry form and stored in dry form for onward usage. However, arrangement shall be also made to dispose fly ash in lean slurry form to ash dump yard under exigency.
Power Evacuation : At 400 kV level through the existing double circuit out-going feeder lines to Parulia/Durgapur (PGCIL) and the LILO at Sagardighi of Farakka-Jeerat- Subhashgram 400 kV line and proposed 400 kV D/C line to Gokarna of WBSETCL.
Environmental Aspects : A 275 m high single-flue stack as per MoEFCC guidelines and an adequately designed electrostatic precipitator with more than 99.96% efficiency are envisaged. Waste water quality to be maintained as per MoEFCC
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
notification. Flue Gas Desulphurization (FGD) & Selective Catalytic Reducer (SCR) have to be installed to meet revised MoEFCC norms dated 07.12.15.
Rehabilitation Requirement : Nil
Other Facilities :
Township : 162 dwelling units along with civic amenities would be developed in the vacant spaces available in the township. A satisfaction level of 80% is considered.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Project Cost & Cost of Generation :
Mode of Implementation : Multi-package EPC basis.
Project Time Frame : Forty two (42) months from zero date i.e. the date of ‘Letter of Award’ to the Main Plant Contractor for commercial operation of the unit.
Project Cost :
For Coal based station : Present-day cost excluding interest during construction, financing charges etc. Rs.32280.24 Million.
Capitalised Project Cost : Rs.35627.24 Million
Cost of Generation :
1st Year of Full Generation : Rs.3.13 per kWh.
Cost of Energy at bus bar : Rs.3.96 per kWh. @ 90% PLF (10 Yrs. average)
25 Years’ Levelised Tariff : Rs.6.15 per kWh. (Discount Factor @ 9.52%)
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION-2
JUSTIFICATION OF THE PROJECT
2.1 Introduction
Electricity is the prime mover of growth and is vital to the sustenance of a modern economy. The projected growth of the Indian Economy depends heavily on the performance and growth of the power sector. The contribution of power sector in country’s growth has grown significantly since independence. Total installed generation capacity of the country, which was 1362 MW at the time of independence, has increased to about 280328.5 MW as on October 31, 2015. It is the endeavour of the government to ensure uninterrupted supply of electricity at affordable rates to the following categories of consumption to sustain steady economic growth:-
a. Domestic b. Commercial c. Public Lighting d. Public Water Works e. Irrigation f. Industrial (LT, HT less than 1 MW, HT 1 MW and above) g. Railway Traction h. Bulk Non-Industrial HT supply
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
However, the power industry in India is historically being characterized by energy shortages i.e. demand for electricity far exceeding the supply. The following graph shows the differences between demand and supply of energy in India from the year 2009-10 to the year 2015-16 upto October 2015.
Gap Between Demand & Supply 1100 1068.9 1050 995.6 1002.3 1000 937.2 1030. 8 950 959. 8 Energy Requirement 900 861.6 830.6 Energy Supply 850 908.7 857.9 800
750 Units) Billion (In 788.4 700 746.6 662.2 650 600 646.2
10 11 15 9- 0- 1-12 2-13 3-14 4- '0 '1 '1 '1 '1 '1
'15-16 (upto Oct)FINANCIAL YEAR
( Source : Ministry of Power,GOI) Due to inadequate generation, supply and distribution infrastructure, the per capita consumption of energy in India is extremely low in comparison to most of the developing and developed nations. The following chart shows per capita electricity consumption of energy as per the World Bank record for the year 2013 in various developed and developing countries.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Electricity Consumption Per Capita (kWh) for 2013
18,000 15,519 15,000 12,985 12,000 10,134
9,000 7,836
5,407 6,000 3,762
3,000 2,529 2,057 765 0
zil ico U.S. U. K. a x tralia Japan China Br e India Canada M Aus
(Source : World Bank) However, as per CEA record, the per capita consumption of electricity in India in the year 2013-14 stands as 957 kWh.
Electricity is an essential requirement for all facets of our life. It is the critical infrastructure on which the socio-economic development of the country depends. Availability of reliable and quality power at competitive rates to industry would make it globally competitive and enable it to exploit the tremendous potential of employment generation.
Electricity being one of the key drivers for rapid economic growth and poverty alleviation, power sector attracts special attention of the Govt. of India (GOI).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The National Electricity Policy has set the goal of adding new generation capacity and enhancing per capita availability of electricity per year and to not only eliminate energy and peaking shortage but to also have a spinning reserve as specified by the Central Electricity Authority. Development of power sector has also to meet the challenge of providing access for affordable electricity to all household in next five years.
The Policy stipulates that in addition to enhancing the overall availability of installed capacity to 85%, a spinning reserve of at least 5% at national level would need to be created to ensure grid security and quality and reliability of power supply. A committee on National Electricity Policy has made recommendation that SERCs should incentivize the intra-state trading in line with Act & policy and should impose reasonable trading margin for the intra-state sale.
In accordance with the provisions of National Electricity Policy (NEP), eminent experts of Electric Power Survey Committee (EPSC) formulated 18th Electric Power Survey report to work out All-India electricity demand forecast for 12th Plan period (2012-13 to 2016-17) and upto terminal year of 13th Plan 2021-22. 18th EPS Committee Notes highlights the following observations:
National GDP is likely to grow at an average rate of 8 to 10% p.a. upto the year 2016-17.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Higher growth rates of electricity consumption have been assumed for poor performing states/UTs having low per capita electricity consumption, economic potential and scope of development of various sectors.
All rural households shall get electrified within the year 2016- 2017 under accelerated rural electrification programme and Rajiv Gandhi Grameen Vidyutikaran Yojna.
2.2 All-India Power Scenario
The energy deficit in India is mainly caused by slow progress in the capacity addition which in turn is attributable to difficulty in land acquisition, shortage of coal, lack of fund allocation and the clearances involved. The Indian economy is directed by the successive five year plans that set out targets for economic development in various sectors, including power sector. In the implementation of the last three (3) Five Year Plans (the 8th, 9th and 10th Plans covering fiscal years 1992 to 2007), less than 50% of the targeted additional energy capacity could be attained. Capacity addition to the tune of approximately 20,000 MW and 27,000 MW was achieved in 9th and 10th Plan periods (Source : CEA and CII).
The following graph shows the targeted capacity addition in terms of energy for Five Year Plans vis-à-vis the values achieved at the end of those Five Year Plans including current Five Year Plan (upto Oct., 2015).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
100 88 90 78
80 * 69 70 55 60
50 40 41
G W 40 31 27 30 22 20 21 16 19 20 13 14 7 9 10 10 1 1 4 2 5 5 0 I II III IV V VI VII VIII IX X XI XII
FIVE YEAR PLAN
Targeted Installed *Upto October 2015 (Source : CEA)
The total capacity addition during the past 20 years between the 7th and the 10th Five Year Plans was approximately 90,000 MW. A total capacity addition of 78700 MW was planned for the 11th Five Year Plan (2007-12). As per the Mid Term Appraisal (MTA) of Planning Commission it was reduced to 62,374 MW. The total capacity addition ultimately achieved under the 11th plan period (2007-12) is noted to be 54,963 MW.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In the 12th Five Year Plan, a capacity addition of 88,537 MW in the next five years has been targeted. As per latest data available (upto October 2015), capacity addition achieved under the 12th plan period (2012-17) is noted to be 69,210 MW.
As per the prevailing situation, of the total installed generation capacity of 280,328.5 MW (as on 31.10.15) under utility sector, hydel generation accounts for 42,473.42 MW, Nuclear power 5,780 MW, thermal power 195,604.44 MW and the balance 36,470.64 under Renewable Energy Sources (RES). Of the thermal generation:
Coal accounts for 170,137.88 MW
Diesel accounts for 993.53 MW
Gas accounts for 244,73.03 MW
A long term projection on Indian Power Scenario as featured in 18th EPS is furnished in Table-A.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Table-A
Y e a r Y e a r 2016-17 2021-22 2016-17 2021-22 Northern 415220 576010 60676 82784 Western 389807 535851 60259 83268 Southern 364443 506589 56388 78857 Eastern 163294 231646 24020 33747 N-Eastern 15751 22421 2834 3905 Andaman & 366 505 67 89 Nicobar Lakshadeep 47 60 10 16 All-India 1348515 1872517 196398 271795 (Source : 18th EPS).
The working group on Power for 12th plan has recommended the following capacity addition requirement in the 13th plan-
Type of Plant Capacity addition (in MW) Thermal 63,400 Hydro 12,000 Nuclear 18,000 Total 93,400 ( Source : 18th EPS) Category-wise and year-wise forecast on energy consumption and peak load for 12th Plan and 13th Plan periods are given in Annexure-2.1.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
As per the 18th EPS, the restricted Compound Annual Growth Rate (CAGR) in peak load from 2009-10 to 2016-17 works out to 9.58%. This is expected to fall to 7.27% during the period 2016-17 to 2021-22. Likewise, the CAGR in energy requirement, from 2009-10 to 2016-17 works out to 8.55%. This is expected to fall to 7.05% during the period 2016-17 to 2021-22
There is little doubt that power sector in the country needs to grow at much higher pace. Moreover to achieve GDP growth rate target of 8- 9% p.a., growth in the power sector needs to be assured.
Govt. of India has laid special emphasis on accelerated rate of capacity addition and also on containing the cost of energy within reasonable limits. Availability of power will improve the overall life style vis-à-vis economic growth at an accelerated rate. This has prompted the entrepreneurs to venture investment opportunity in power sector. Railway network is being beefed up to facilitate transportation of coal from mine site to Power Plant site at competitive rate.
2.3 Power Scenario of Eastern Region
For the purpose of power planning and operation of regional grid the Eastern Region consists of the following states/UT/Command area : West Bengal Bihar Jharkhand
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Odisha Sikkim Andaman-Nicobar (UT) DVC CESC DPSC
All three sectors namely Central, State & Private contribute to the power generation capability in the region. Power Grid Corporation of India Limited (PGCIL), the central sector constructs, operates and maintains transmission facilities for inter-state and inter-region transfer of power. The power generating capability in the region is predominantly thermal.
The total installed capacity in eastern region as on 31.10.2015 is 33416 MW. Energy deficit to the tune of (-) 624 MU and peak demand deficit of (-) 277 MW had been recorded during the period of April 2015 to October 2015 in the Eastern Region (Ref. CEA Data).
As per 18th EPS, electrical energy requirement for eastern region would be 163790 MU by the end of 12th Plan and 236952 MU by the end of 13th Plan period. Average peak electrical load for eastern region is forecast to be 24303 MW and 35928 MW by the end of 12th and 13th Plan respectively. Thus, total capacity addition of 11625 MW is needed in the Eastern Region by the end of 13th Plan period. The projected value may be higher considering the cascading effect due to the slippage of required capacity addition during the 11th Plan period (2007-2012).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
2.4 Power Scenario of West Bengal
The State of West Bengal falls within Eastern region as per central Electricity Authority (CEA). The total Installed capacities of Power Utilities as on 31.10.2015 with break-up in Eastern region are as follows:
Eastern region Thermal Coal : 28582 MW Gas : 190 MW Diesel : 0 MW Total Thermal : 28772 MW Nuclear : 0 MW Hydro : 4209 MW RES (Renewable Energy Sources) : 434 MW Grand Total : 33416 MW ( Source : CEA)
The following table shows section wise break-up of Installed capacity of Power utilities in the state of West Bengal ;
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The State of West Bengal Installed Sl. Name Capacity Command Area No. of Utility (MW) UNDER PUBLIC SECTOR 1. WBSEDCL 1069.53 Entire state except command areas under other utilities i.e. DPL, CESC, DPSC, DVC. 2. WBPDCL 3865 WBSEDCL distributes entire power generation by WBPDCL. 3. DPL 641 Part of Durgapur, surplus fed to WBSEDCL Grid. 4. WBREDA - No command area of its own. Helps to promote use of alternate sources of energy. Total : 5575.53 UNDER CENTRAL PUBLIC SECTOR : 1. DVC 1400 Helps in unified development of the Damodar Valley area. DVC supplies power at 33 kV in the districts of Bankura, Bardhaman, Howrah, Hooghly, Purulia. Caters to core sector like railway, collieries and steel industries. 2. NTPC & 2100 WBSEDCL has the following shares :- NHPC From W.B. Share ● NTPC Farakka 661 MW ● NTPC Talcher 91 MW ● Kurichhu Hydro 30 MW ● Tala Hydro 390 MW ● Rangit Hydro 17 MW ● Teesta V 122 MW ● Chukha Hydro 107 MW Total Share from NTPC & 1418 MW NHPC Total 3500 UNDER PRIVATE SECTOR : 1. CESC Ltd. 1225 Kolkata and suburb 2. DPSC Ltd. 42.5 Asansol, Raniganj Area 3. Total 1267.80 TOTAL (Installed 10,343.33 Nuclear = Nil Capacity in W.B.) ( Source : WBPDCL-2016)
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
As per ‘Executive Summary of Power Sector’ published by CEA, Oct.- 2015, the following Demand, Supply and Deficit scenario has been captured in the state of West Bengal during the period of six months (April’15 to Oct.’15) which is the latest published data.
◙ Peak Demand : 7905 MW
◙ Peak Met : 7885 MW
◙ Deficit : -20 MW (-0.3%)
◙ Energy Requirement : 29747 MU
◙ Energy Availability : 29630 MU
◙ Energy Deficit : 117 MU (0.4%)
As per 18th Electric Power Survey of CEA the electric energy requirement in the State of West Bengal during the end year of 12th & 13th Plan periods have been projected as follows:
Plan Period Energy Peak Requirement(MU) Demand(MW) 12th Plan: Year ‘16-‘17 70352 11793 13th Plan: Year ‘21-‘22 103283 17703
Some Thermal Power Projects having total installed capacity of 1450 MW, presently under construction, will contribute power to the state in 13th plan period.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
However, from the above statistics, it is noted that although there is not much of shortfall in peak power demand in the state at present, substantial requirement of capacity addition is needed to bridge the gap of electricity demand and supply in future and also to meet the objective of National Electricity Policy of Government of India. Moreover, with National grid being set up in the country, it makes sense to generate power economically near pit head locations and transmit the same to power starving states.
Thus, considering the Power Scenario of All-India, the Eastern Region and West Bengal by the end of 13th Plan, as explained above, the proposed project of 1 x 660 MW coal based extension power station by The West Bengal Power Development Corporation Limited (WBPDCL) at Sagardighi TPS, West Bengal fits well under 13th Plan period.
In Annexure-2.1, Category & Year-wise Forecast on All India Power Scenarios for 12th & 13th Plan Period is shown.
In Annexure-2.2, the Demand/Load growth trend of Energy in the state is shown. .
In Annexure-2.3, the Demand/Load growth trend of Peak Demand in the state is shown.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
2.5 Justification of the Project
With the present and anticipated mismatch between demand and supply for Indian power scenario, any capacity addition will be a welcome relief to attain the growth figures projected in Electricity Power Survey (EPS) as well as to maintain a steady growth in Gross Domestic Product (GDP). Moreover, open access provision of transmission system provided in the Electricity Act, 2003 enables a Power generating station to wheel the generated power to any parts of India.
The major reasons for setting up proposed 1 x 660 MW Sagardighi Extension Unit #5 are :
It is an extension unit of existing 2 x 300 MW and 2 x 500 MW station. Land availability within the acquisition limit of project authority. Availability of water. Allotment of 60 cusecs of water from river Bhagirathi by WRD, Govt. of W. B. would be sufficient for ongoing Units #3 & #4 and Extension unit #5.
Availability of coal from captive mines. Extensive infrastructure developed during execution of Phase-I & Phase-II.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Auxiliary facilities viz. raw water reservoir, intake pump house, LDO & HFO System, railway siding, CHP area etc. can be shared among Phase-III through Phase-I.
400 kV sub-station would require marginal extension for Unit #5. An attractive timeframe for commissioning the unit can be attained.
With the above in view, it is expected that the energy cost would be reasonable. Considering the above, the proposed project of new capacity addition of 1x660 MW coal based unit at Sagardighi will be a welcome move and it fits well in the overall power scenario of the state .
2.6 Unit Size Selection
For selecting the unit size of the proposed extension unit#5, the criteria given importance are :
Cost of energy generated from the station at reduced price. Steady load requirement and variations in maximum demand Thermodynamic cycle efficiency and reduced emission Operating flexibility for better load cycle Station availability PLF attainable Specific investment requirement Project timeframe and manpower requirement Economic performance and reduced environmental aspect.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
For the proposed extension project, one unit of 660 MW set deploying supercritical steam parameters emerges as favourite as this set size is endowed with the following merits :
Present-day technology
High thermodynamic efficiency Favourable operating experience Load variation capability, if required. Availability of skilled and unskilled personnel Environment-friendly in terms of emission Easier availability of vendor’s engineers.
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Annexure – 2.1 Sheet 1 of 1
Category & Year-wise Forecast on All India Power Scenarios For 12th & 13th Plan Period (Figures in MUs)
Domestic 262202 289924 315335 339762 366224 394939 426148 Commercial & Misc. 105472 116535 128099 140506 154153 169173 185722 Public Lighting 9315 10021 10675 11315 11995 12718 13488 Public Water Works 23829 25742 27651 29592 31677 33918 36329 Irrigation 194559 210611 225044 239194 254338 270524 287926 Industrial LT 70010 76898 84096 91626 99714 108480 117984 Industrial HT 286699 316408 339228 367341 397991 431358 467835 Railway Traction 18635 19832 21055 22353 23714 25232 26810 Bulk Supply 30523 33024 35759 38754 42027 45622 49566 Total (Energy 1001244 1098995 1202097 1280444 1381833 1491963 1611809 Consumption) T&D Losses-MU 246836 255879 264040 271564 278950 286145 293052 T&D Losses-in % 19.78 18.89 18.20 17.50 16.80 16.09 15.38 Energy Requirement – MU 1248081 1354874 1450982 1552008 1660783 1778109 1904861 Annual Load Factor - % 78.29 77.51 77.37 77.21 77.05 76.57 76.71 Peak Load – MW 181988 199540 214093 229465 246068 264041 283470 (Source : 18th EPS).
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Detailed Project Report
1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure – 2.2 Sheet 1 of 1
Demand/Load growth trend in West Bengal (Energy)
120000
100000
80000
60000
40000
20000 Energy Requirement (MU) Requirement Energy
0 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16 2016-17 2021-22 Requirement 43449 47083 51021 55288 59912 64923 70352 103283 YEAR
Note: 2010-11 means April 2010- March 2011 (Source : 18th EPS).
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Detailed Project Report
1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure – 2.3 Sheet 1 of 1
Demand/Load growth trend in West Bengal (Peak Demand)
20000 18000 16000 14000 12000 10000 8000 6000 Peak Demand (MW) Peak Demand 4000 2000 0 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16 2016-17 2021-22 Actual Avl. 6949 7589 8289 9052 9887 10798 11793 17703 YEAR
Note: 2010-11 means April 2010- March 2011 (Source : 18th EPS).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION-3
BASIC REQUIREMENTS
3.1 Introduction
The basic requirements for setting up and operating the proposed 1X660 MW supercritical Phase-III extension unit#5 within the available space at Sagardighi TPS along with all necessary auxiliaries including FGD and SCR for meeting latest MoEF notification and all related BOP packages using coal as main fuel are :-
Availability of adequate land for setting up the Unit#5 utilising the infrastructure developed during Phase-I and Phase-II units installation.
Availability of sufficient water of appropriate quality on year- round basis.
Ensured supply of adequate fuel with appropriate transportation system to ensure the least delivered cost of fuel at the plant end.
Power evacuation possibility to the grid at desired voltage level(s).
Possibility of extensive utilisation of the existing infrastructure viz. utilisation of existing road network during construction and operation, accessibility of power and water during construction, optimum utilisation of manpower deployed.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
This section discusses the requirements vis-à-vis the availability of above features at the proposed site for coal based 1 x 660 MW Unit#5 for implementation within stipulated time frame.
Sagardighi Thermal Power Project is located at 24 22’ 13.7” N latitude and 88 6’ 15.8” E longitude in Murshidabad district of West Bengal. The location of the station enjoys the advantage of basic features viz. proximity to coal and water sources, road and railheads, nearness to major habitation viz. Jangipur, Manigram etc. and evacuation facility both at 400 kV and 220 kV levels.
Sagardighi project site is located at Manigram village, 13 km north of Sagardighi block by the side of the SMGR (Sagardighi-Manigram- Gankar-Raghunathganj) Road, 20 km from National Highway (NH–34) and 240 km from Kolkata. Nearest broad gauge railway station Manigram on Bandel-Barhawra branch line is about 1 km from the site. Sagardighi Railway Station (R.S.) on Sainthia-Ajimganj branch line is about 6.5 km from the site.
The project site is encompassed by villages Manigram, Chhamugram, Karaia, Thakurpara on the south; Bhumhar, Khasittor, Ekrakhi on the west; Dhalo, Bagpara, Santoshpur on the north and Harirampur, Chandparam, Dogachhi on the east. Bandel-Barharwa broad gauge line of Eastern Railway grazes past the western fringe of the plot. River Bhagirathi is within 5 km east of the project site. Vicinity map of the site is shown in Drawing No.16A03-DWG-M-003B enclosed.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
3.2 Land Requirement & Availability for Phase-III Unit
The Phase-I station implemented along with the space for Phase-II & Phase-III Unit#5 is located within a common boundary covering an overall area of about 365 Ha excluding the ash dump area, township etc. The layout in Phase-I (2x300 MW) and Phase-II (2x500 MW) was developed on the basis of ground survey and soil investigation conducted earlier keeping adequate space provision for extension of one more unit of 500 MW set ( as conceived earlier) and giving due consideration of the natural slope, drainage canal, nearness to existing railhead, ease of evacuation of power etc.. The layout of the station under implementation is shown in Drawing No.16A03-DWG-M-003A enclosed.
With the available land contour, the proposed Phase-III 1x660 MW Unit#5 would be laid at the same ground level (GL). This plot would be able to accommodate the main plant with cooling towers, transformer yard, switchyard and all other auxiliaries. Coal Handling System proposed for Phase-II units would be gainfully utilised for Phase-III unit as well. Raw water reservoir planned to be constructed for Phase-II would cater the water requirement for Phase-III extension unit also.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The proposed 1 x 660 MW extension unit would generate about 1.84 million tonnes of fly ash annually. There is a high demand for fly ash from the cement plants nearby. It is thus considered that ash from the station would be partially lifted by various consumers. It is therefore proposed that the balance ash would be disposed to the ash pond earmarked for Phase-I & II station with suitable extension towards north of the plot.
The township proposed under Phase-I & II would be augmented to accommodate additional housing required for the staff of the 1 x 660 MW Unit #5. It is planned to develop residential quarters with necessary civic amenities considering 80% satisfaction level. The civic amenities provided in the township can be shared by the employees of the proposed extension unit#5 under Phase-III with necessary augmentation. Thus no land acquisition for Phase-III extension unit would be involved.
3.3 Water Requirement & Availability
The station has an allocation of 60 Cusec of raw water for Phase-II. The raw water analysis as received to meet the cooling and consumptive water requirement is given in Annexure-3.1. The estimated raw water requirement for Phase-II & Phase-III station together works out around 5068 m3/hr (50.7 cusec). As stated above, raw water availability from the Bhagirathi River is assured and it may be summarized thus the water for the Phase-II & III units would be available from the present allocation.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
. The break-up of the estimates is shown in Annexure-3.2 of the report. The above estimate considers semi-open recirculating cooling water system with cycle of concentration (COC) as 5 and lean slurry disposal of ash with provision of recovery and recirculation of ash water for both Phase-II & Phase-III. The consumptive water requirement for the units installed in Phase- II & Phase-III is shown in water balance diagram attached herewith.
No separate pump house is envisaged for the extension unit #5. It is planned to feed raw water requirement for the Phase-III station through 3 x 50% (2 W + 1 S) raw water intake pumps designed under Phase-II stage. Water would come to the in-plant reservoir through 1 no. 1200 NB pipe.
3.4 Fuel Requirement
Sagardighi Thermal Power Station is linked to the mines of ECL. Coal is planned to be transported in rake loads through the existing Pakur- Tildanga-Dhulian-Monigram broad gauge line or through Pakur- Nalhati (proposed)–Takipara-Gosaingram-Poradanga-Monigram broad gauge line. The coal would be carried in rake loads of BOBR/BOX-N wagons.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Pachwara (North) Block is one of the linked mines allotted for Sagardighi Thermal Power Project. Geological reserve of the block is about 609.35 MMT whereas mineable reserve of the block is estimated as 392.84 MMT.
It is envisaged that coal from the Pachwara (N) block would be transported by mechanised conveying system to the dedicated Pakur siding which is presently under construction (about 50 km distance). Till completion of the mechanised system, coal will be transported by road dumpers to Pakur siding. From there coal would be transported to the plant site through rakes covering a route length of around 87 km and would take approximately 4 hours.
Depending on source, the range of different parameters of proximate and ultimate analysis of coal and ash to be received by the station is given in Annexure-3.4 enclosed. Coal would be received in sizes of (-) 300 mm and would have volatile matter in the range of 18-22%.
Coal consumption for 2X500 MW (Phase-II) and 1X660 MW (Phase-III) is estimated to be around 1140 TPH in TMCR condition and 1250 TPH in BMCR running condition.
Hence, it can be concluded that with the present selected guaranteed capacity of 2000 TPH for coal conveyor stream, coal requirement of Phase- II & III units can be met. Presently installed coal stock-pile of capacity 3,00,000 m3, is sufficient for 10 days’ consumption of units of Phase-II & III at 90% PLF firing design Coal.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Coal Requirement for Phase-III station is tabulated below :
Particulars Unit Value Station Heat Rate Kcal/ kWh 2151 GCV of Coal kCal/ kg 3300 PLF % 90 Hourly Coal TPH 430 Consumption Daily Coal TPD 10326 Consumption Annual Coal MTPA 3.4 Consumption
One (1) track hopper was constructed for Phase-I station. For Phase-II station one additional track hopper of 225 m length and one (1) wagon tippler are under installation. These are considered adequate for Phase- III extension station also. Further two (2) nos. stacker-cum-reclaimers have been proposed for Phase-II & III units. Two conveyor streams having guaranteed/rated capacity of 2000 TPH with facility for crushing and stock piling/reclaiming have been proposed for supplying coal required for the station.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Auxiliary Fuel
Requirement of auxiliary fuel is guided by CEA guideline which permits 1 ml/kWh auxiliary fuel consumption. The actual consumption will, however, depend on average daily plant load factor, grid stability, quality of coal etc. Fuel oil (HFO/LDO) would be normally transported by railway oil tankers from the nearest oil depot. The existing two (2) nos. of LDO tanks of 2000 m3 each and two (2) nos. of HFO tanks of 2000 m3 each for the Phase-I and additional two (2) nos. of HFO tanks of 2000 m3 each being constructed under Phase-II project, will cater for storage of LDO and HFO required for start-up and coal firing support purpose of the Phase-II & III units also. One additional HFO pressuring pump along with HFO Heater would be installed to cater the requirement of Phase-III unit#5. Installed LDO forwarding pumps of Phase-II can also cater requirement of Phase-III unit#5. Tentative compositions of HFO & LDO are given in Annexure-3.4 & Annexure-3.5 respectively.
3.5 Ash Disposal
Ash handling plant was earlier conceived as lean slurry disposal both for bottom ash (BA) and Fly ash (FA) for 3X500 MW i.e. for Phase-II & Phase-III combined. Accordingly ash handling plant has been designed for Phase-II station, which can also cater the requirement of newly proposed 1X660 MW unit instead of 1 x 500 MW unit under Phase-III with suitable augmentation as described in Section-6. However, with
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
the latest MoEF notification for water consumption limitation, it has been decided to consider ash water recovery system under operation from the beginning for Phase-II & III units.
. Fly ash in dry form has high demand in the local cement plants and also as backfill of low lying areas. This aspect is to be investigated at a later stage to ensure gainful utilisation of fly ash.
3.6 Power Evacuation
Power generated from 660 MW extension U#5 would be evacuated at 400 kV level through existing lines/ new double circuit line of WBSETCL at Sagardighi TPS.
For this existing 400 kV switchyard of Phase-II will be extended to accommodate following bays: a. 1 No. Generator Transformer b. 1 No. Station Transformer c. 2 Nos. future Lines/bays
3.7 Infrastructural Facilities
The existing facilities planned in the area for Phase-I & II and with the available local infrastructure, the proposed 1 x 660 MW unit#5 would enjoy the much needed initial support during project implementation stage. Moreover, the major habitation centres in the area namely, Jangipur, Manigram, Sagardighi etc. are in a position to provide the necessary infrastructural assistances in the form of housing, education, market, healthcare, skilled and unskilled manpower, SSI units etc.
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1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure – 3.1 Sheet 1 of 1 RAW WATER ANALYSIS
SL.NO. Different Characteristic Results
++ 1. Calcium (Ca ) as CaCO3 86 ++ 2. Magnesium (Mg ) as CaCO3 52 + + 3. Sodium & Potassium (Na & K ) as CaCO3 138 Total Cations 276
4. Bicarbonates (HCO3) as CaCO3 200
5. Carbonates (CO3) as CaCO3 -
6. Hydroxyde (OH) as CaCO3 -
7. Sulphate (SO4) as CaCO3 35
8. Chloride (Cl) as CaCO3 41
9. Nitrate (NO3) as CaCO3 -
10. Phosphate (PO4) as CaCO3 - Total Anions 276
11. Total Hardness (as CaCO3) 138
12. Permanent Hardness (as CaCO3) -
13. Temporary Hardness (as CaCO3) 138
14. Methyl Orange Alkalinity (as CaCO3) 200
15. Phenolphthalein Alkalinity (as CaCO3) - 16. Iron (Original) (as Fe) - 17. Iron (in solution) (as Fe) 1.0 18. Manganese (as Mn) -
19. Ammonia, free (as NH3) -
20. Carbon Dioxide free (as CO2) -
21. Silica (in solution (as SiO2) 20.0
22. Dissolved Oxygen (O2) - 23. Suspended Solids - 24. Dissolved Solids 438 25. pH at 25 C 7.5 – 8.0 26. Organic Matter (in terms of Oxygen absorbed 2.0 from acid permanganate solution in 4 hours) 27. Appearance Turbid 28. Odour Nil 29. Turbidity 500 NTU
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure – 3.2 Sheet 1 of 1
ESTIMATION OF CONSUMPTIVE WATER REQUIREMENT For 2 x 500 MW + 1X660 MW Coal Based Extension Units 3, 4 & 5 at Sagardighi, Dist. Murshidabad in West Bengal
(m3/hr) (m3/hr) (m3/hr) (m3/hr) 1. a. Heat Cycle Make-up 110 b. Chemical Feed System 6 c. Make-up Reqmt. for Closed Circuit Cooling System 6 d. CPU Regeneration 15 e. H2 Generation Plant 2 f. Reject Water from DMRO System 25 g. Regeneration Waste from MB Exchanger 2 Sub-Total : 166 166 2. a. Potable Water for plant 17 b. AC Plant Make-up 10 c. Chemical Cleaning Waste (Intermittent) - d. (UF+ Filtration) Backwash 75 Return to clariflocculation plant
Sub-Total (1 + 2) : 268 268 3. a. Cooling Tower Make-up Requirement 4043 CTBD - 798, COC- 5 b. Ventilation System 80 c. Service Water 140 d. Ash Handling System- Sealing 50 Add: 662 m3/hr from CTBD-Ash Water Make-up e. Coal Handling - Sealing 30 Add: 126 m3/hr from CTBD (Unit#5)- DE/DS f. DG Set 10 Add: 10 m3/hr from CTBD- Plantation g. Fire fighting - h. FGD + SCR (For Unit #3, #4 & # 5) 400 Sub-Total (1 + 2 + 3) : 5061 4. 141 m3/hr return to clariflocculation plant from sludge a. Desludging 150 thickener Sub-Total (1 + 2 + 3 + 4) : 5211 5211 5. a. Evaporation loss in reservoir 173 b. Reuse of water from sludge thickener & filtration plant (-) 216 GRAND TOTAL : 5168 50.7 Cusec
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5,
Sagardighi, West Bengal
Annexure – 3.3 Sheet 1 of 1 Analysis of Coal & Ash
PROXIMATE ANALYSIS OF COAL (As received Basis) Sl. Range of Design Worst Best No Description Symbol Adequacy Coal Coal Coal . Coal 1. Total Moisture TM% 15.00 18.00 12.00 12 - 18 2. Ash A% 40.00 46.00 36.00 33 - 46 3. Volatile Matter VM% 19.00 18.00 22.00 23 – 18 4. Fixed Carbon FC% 26.00 18.00 30.00 31 - 18 ULTIMATE ANALYSIS (As Received Basis) 1. Carbon C% 29.73 23.08 37.32 40.60-23.08 2. Hydrogen H2% 3.70 3.54 3.92 4.02-3.54 3. Nitrogen N2% 1.80 1.45 1.60 1.40-1.45 4. Oxygen (by O2% 8.66 6.70 8.32 8.12-6.70 difference) 5. Sulphur S% 0.50 0.60 0.40 0.40-0.60 6. Carbonates CO3% 0.58 0.60 0.40 0.03-0.04 7. Phosphorous P2% 0.03 0.03 0.04 0.03-0.04 8. Total Moisture TM% 15 18 12 12-18 9. Ash A% 40 46 36 33-46 10. Total % 100 100 100 11. Gross Calorific Value GCV 3300 2800 4000 4300-2800 (as received basis) kCal/kg 12. Hard Grove Index HGI 55 50 60 50-65 13. YGP Index mg/kg 95 110 80 ASH ANALYAIS 1. Silica (SiO2)% 59.79 61.30 56.70 62.00 – 56.00 2. Alumina (Al2O2)% 25.36 26.00 23.00 28.00 – 23.00 3. Iron Oxide (Fe2O2)% 7.20 6.00 1000 6.00 – 10.00 4. Titanium (TiO2)% 1.20 1.00 1.50 1.00 – 1.70 5. Phosphoric (P2O5)% 2.60 1.50 3.00 1.00 – 3.00 Anhydride 6. Lime (CaO)% 0.88 0.50 1.50 0.50 – 1.70 7. Magnesium (MgO)% 0.55 0.40 1.00 0.40 – 1.10 8. Sulphuric Anhydride (SO2)% 1.20 0.50 1.40 0.50 – 1.70 9. Alkalis (by difference) (Na2O+K2O 1.22 0.80 1.40 0.60 – 1.80 )% ASH FUSION RANGE (Under reducing atmosphere) 1. Initial Deformation IDT C 1100 1100 1100 1100-1150 Temp. 2. Hemispherical Temp. HT C 1300 1250 1350 1250-1400 3. Flow Temperature FT C 1400 1400 1400 1400-1450
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1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure – 3.4 Sheet 1 of 1
ANALYSIS OF HEAVY FUEL OIL [HFO]
Sl. Heavy Fuel Oil (HFO) Properties No. (As per IS-1593 1971 Heavy Grade) 1.0 Viscosity CS 370 maximum at 50 C 2.0 Flash point, minimum C (pensky – 68 Martens closed) 3.0 Pour Points C 4.0 GCV, kCal/kg 10,000 5.0 Ash content (by weight) % max. 0.1 6.0 Total sulphur (by weight) % max. 4.5 7.0 Sediment (by weight) % max. 0.25 8.0 Water content (by volume) % max. 1.0 9.0 Acidity (inorganic) Nil 10.0 Carbon residue (Ramsbottom) (by - weight) % max. Note : For calculation, in case of HFO, 30% wax content with latent heat of fusion 54 kCal/kg has been assumed.
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1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure – 3.5 Sheet 1 of 1
ANALYSIS OF LIGHT DIESEL OIL [LDO]
SL. PARAMETERS VALUE NO.
1. Ash Content (% by wt.) 0.02%
2. Kinematic Viscosity (CSt) at 37 C 2.0 to 7.0
3. Sediment (% by wt.) 1.00
4. Water (% by wt.) 0.05
5. Sulphur (% by wt.) 1.0
6. Lower Calorific Value (Kcal/kg) 10,900 Kcal/kg.
7. Density at 37 C 800
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION-4
SITE FEATURES
4.1 Introduction
Sagardighi Thermal Power Project located in village Manigram in Murshidabad district of West Bengal, India is one of the projects of The West Bengal Power Development Corporation Limited (WBPDCL). Government of West Bengal had set up WBPDCL in the year 1985 with a goal to carry on inter alia the business of electric power generation and supply in the state. It has five operating units at Kolaghat, Bandel, Bakreswar, Santaldih and Sagardighi with generating capacity of 3865 MW at present.
At Sagardighi 2x300 MW units are under operation in Phase-I with another 2x500 MW units under implementation stage in Phase-II.
Now, it is proposed to add one super critical unit of 660 MW under Phase-III extension in the space available towards the north of Phase-II units.
4.2 Features of the Identified Site
Relevant site data of the project at Sagardighi are given below :
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Location : Manigram village, Sagardighi, Raghunathganj sub-division, Murshidabad District, West Bengal.
Latitude and Longitude : 24 22’ 13.7” N, 88 6’ 15.8” E (Toposheet No.78/D/3)
Nearest Towns : Ajimganj, Jangipur, Raghunath-ganj.
District Head Quarters : Berhampore - 40 km.
Approach Road : 20 km from National Highway (NH-34)
Nearest Railhead : Manigram railway station on Bandel- Barhawara branch line 1 km from site.
Source of Water : Bhagirathi River - 5 km
Source of Coal : Pachwara (North) mine block in Jharkhand.
Fuel Transportation : By rail in rake loads of BOBR/BOX-N wagons.
Surrounding Habitations : Villages - Manigram, Chhamugram, Karaia, Thakurpara on the south; Bhumhar, Khasittor, Ekrakhi on the west; Dhalo, Bagpara, Santoshpur on the north and Harirampur, Chandparam, Dogachhi on the east.
Nature of Land :- Level : Within 34.5 m contour. Land is above HFL (highest flood level) of the area.
Soil : Less fertile alluvial soil. Land Use : Within existing plant boundary of WBPDCL.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
A site location map showing the villages within and around the plot identified for putting up the station along with the land features is shown in Drawing No.16A03-DWG-M-003C enclosed.
Site for the proposed extension unit #5 is located within the acquired limits of the Sagardighi TPP and is situated above the highest flood level (HFL) of the area. The vicinity map of the area identified for putting up the station is shown in Drawing No.16A03-DWG-M-003B enclosed.
The site is connected to coal fields of West Bengal and Jharkhand. The site being only 14 km from the sub-divisional headquarters at Raghunathganj, the project can utilise the infrastructural facilities and amenities available in the vicinity during construction and operation of the extension station. Finally the facility for inter-state and intra-state transmission of generated power has already been achieved by connecting Phase-I of the station to the 400 kV grid.
The proposed Phase-III extension would be laid at the same ground level as the ongoing Phase-II station. The available vacant land on the north of the Phase-II station would be able to accommodate the main plant with cooling towers, transformer yard, switchyard and all other auxiliaries.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Coal handling plant of Phase-I (in operation) & Phase-II station (under implementation) would be utilized for Phase-III unit#5 also and the conveyors would be extended suitably from the end transfer point i.e. TP-19.
For the plant water system, no separate augmentation is required other than the interconnection between Phase-II and Phase-III. The water treatment plant of Phase-II units will have adequate margin and that would be utilized for the proposed Phase-III 1 x 660 MW Unit#5.
The unit would generate about 1.84 MTPA of fly ash . There is a high demand for fly ash from the cement plants nearby. It is thus considered that ash from the station would be partially lifted by various consumers. It is proposed that the balance ash would be disposed to the existing ash pond of the Phase-I & Phase-II units.
The area available in the existing township of the Phase-I station and the ongoing township for the Phase-II units will be used for the staff of Phase-III unit as well. The civic amenities provided for the Phase-I & Phase-II township of the station can be shared by the employees of the Phase-III extension unit with appropriate augmentation. Thus, no additional land acquisition is required for the new 1 x 660 MW unit#5.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
4.3 Meteorological Details
The nearest Indian Meteorological Department (IMD) station is at Berhampore. The climatological table is given in Annexure-4.1 enclosed.
The annual rainfall of the area is about 140 cm, with 80% of precipitation being in the months of June to October. Major meteorological features which will form the design basis for the unit are given hereunder :-
Maximum temperature : 46.1 C Minimum temperature : 3.9 C Average annual rainfall : 1388.9 mm Maximum rainfall in 24 hours : 286.3 mm Seismic Zone : Zone-III as per IS1893 Maximum wind velocity : 47 m/sec.
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Detailed Project Report 1 x 660 MW Sagardighi Phase-III Extn. Unit-5 in Murshidabad District, West Bengal Annexure – 4.1 STATION:Berhampore 42603 LAT:24 08 N LONG:88 16 E HT. ABOVE M.S.L.19 METERS DATA 1951 TO 1980 Sheet 1 of 2
CLIMATOLOGICAL TABLE OF BERHAMPORE
Mean Temperature Extremes Cloud Rainfall ------MN SLP DB WB MAX MIN HIGH LOW MAX DT MIN DT RH VP TOT LOW TOT RAINY WET DRY HEAVY DAY WS ------1 1015.2 16.1 13.6 25.4 11.9 28.9 8.4 34.9 07 3.9 16 75 13.7 1.5 0.8 13.4 1.0 92.1 0.0 69.6 10 0.8 1011.4 21.6 16.6 1973 1933 58 14.9 1.0 0.6 1957 1957
2 1012.7 19.5 15.4 28.9 14.0 33.7 9.9 36.7 28 5.0 12 64 14.4 1.3 0.8 13.2 1.2 154.2 0.0 60.7 13 1.3 1008.8 25.5 18.1 1926 1950 47 14.8 1.2 0.6 1937 1937
3 1009.7 24.9 19.4 34.2 18.8 39.0 13.6 44.5 27 8.9 05 58 18.1 1.8 0.9 18.3 1.8 129.3 0.0 62.2 30 2.3 1005.1 30.7 21.1 1980 1898 41 17.3 1.6 0.7 1887 1887
4 1006.0 28.8 23.7 37.9 23.4 42.8 18.8 46.4 20 15.6 11 64 25.2 2.7 1.5 40.6 2.5 261.3 0.0 84.9 24 3.7 1001.2 34.3 23.5 1970 1936 40 20.3 2.7 1.4 1971 1967
5 1002.2 29.5 25.9 37.4 25.1 42.4 20.4 46.1 25 15.3 17 74 30.4 3.9 2.2 101.6 5.9 370.8 0.0 155.7 11 5.4 997.7 33.5 25.6 1916 1968 55 26.5 4.1 2.3 1915 1915
6 998.7 29.3 26.8 34.8 25.8 40.4 22.6 46.9 10 16.6 20 82 33.2 6.2 3.8 212.5 11.0 596.7 35.4 202.4 19 4.7 995.4 30.8 27.0 1966 1974 75 32.7 6.3 4.0 1922 1975 1898
7 998.7 28.5 26.8 32.8 25.6 35.9 23.4 43.9 01 21.1 27 87 34.0 7.3 5.1 339.8 16.5 784.5 109.7 228.2 10 3.9 995.6 29.6 27.2 1980 1962 82 34.1 6.9 4.6 1970 1934 1970
8 999.7 28.6 26.9 32.6 25.9 35.8 23.3 42.4 03 19.6 21 87 34.0 7.0 4.7 257.7 14.6 779.8 89.9 183.4 01 3.3 996.5 29.6 27.3 1978 1969 83 34.4 6.7 4.4 1918 1931 1939
9 1003.3 28.6 26.6 33.0 25.5 35.9 23.1 40.3 24 21.1 23 85 33.3 6.0 3.6 227.7 12.2 557.8 70.1 182.9 20 2.6 999.9 29.2 26.8 1979 1977 83 33.6 6.1 3.9 1900 1883 1900
10 1009.1 27.3 24.6 32.4 23.4 35.3 19.5 38.3 09 15.6 27 79 28.8 3.2 2.1 119.4 6.0 684.8 0.0 286.3 31 1.3 1005.4 28.2 25.0 1979 1980 76 29.2 3.5 2.1 1917 1917
11 1012.8 22.5 19.5 29.8 18.0 32.8 13.9 37.8 01 8.3 30 75 20.5 1.3 0.7 13.3 0.9 126.7 0.0 75.2 20 0.7 1009.2 25.1 21.0 1969 1934 68 21.7 1.2 0.8 1930 1930
12 1015.2 17.5 15.0 26.5 13.2 29.6 9.8 32.2 07 * 5.7 24 75 15.1 0.9 0.5 3.0 0.3 61.7 0.0 33.5 13 0.6 1011.6 22.0 17.7 1951 1961 64 16.8 0.7 0.4 1934 1913 ------YR 1006.9 25.1 22.0 32.1 20.9 43.9 8.3 46.9 3.9 75 25.1 3.6 2.2 1395.1 73.9 2329.3 774.9 286.3 2.6 LY 1003.2 28.3 23.1 64 24.7 3.5 2.2 1971 1934
YRS 30 30 30 30 30 30 30 100 100 30 30 30 23 30 30 100 100 100 29 30 30 30 30 30 30 24
Detailed Project Report 1 x 660 MW Sagardighi Phase-III Extn. Unit-5 in Murshidabad District, West Bengal Annexure – 4.1 STATION:Berhampore 42603 LAT:24 08 N LONG:88 16 E HT. ABOVE M.S.L.19 METERS DATA 1951 TO 1980 Sheet 2 of 2
* Occurred More Than Once Weather Wind Speed % Wind Direction Total Cloud Low Cloud Visibility ------MN PPT HAIL THUN FOG D.STM SQUA 62 61 19 0 N NE E SE S SW W NW 0 0 T-2 3-5 6-7 8 0 T-2 3-5 6-7 8 F8 <1 1-4 4-10 10-20 >20 ------
1 1.8 0.0 0.1 15.8 0.0 0.0 0 0 7 24 6 1 3 0 6 2 4 1 77 24 1 2 1 3 26 1 1 1 1 1 13.1 8.5 4.8 4.5 0.1 0 0 3 28 2 0 2 0 3 0 1 0 92 25 1 2 1 2 27 0 2 1 1 0 0.1 0.8 3.0 27.0 0.1
2 1.8 0.0 0.4 9.3 0.0 0.0 0 0 10 18 4 0 4 1 9 4 9 2 67 22 1 1 1 3 24 0 2 1 1 0 8.2 6.7 5.4 7.7 0.0 0 0 6 22 1 1 3 0 4 1 5 3 82 22 1 2 1 2 24 1 1 1 1 0 0.1 0.2 0.7 27.0 0.0
3 2.7 0.0 0.7 2.9 0.2 0.0 0 0 14 17 3 1 7 2 19 6 11 2 49 22 1 2 2 4 24 1 2 3 1 0 2.3 5.8 5.3 17.4 0.2 0 0 10 21 2 1 5 1 12 4 9 3 63 23 1 3 1 3 26 1 2 1 1 0 0.1 0.2 0.3 30.3 0.1
4 3.6 0.2 1.8 0.3 0.0 0.0 0 0 21 9 3 2 12 3 36 8 8 0 28 17 1 3 3 6 20 1 4 4 1 0 0.1 0.6 2.4 26.9 0.0 0 0 15 15 2 2 12 2 18 5 8 2 49 15 2 4 3 6 20 2 5 2 1 0 0.1 0.3 0.5 29.1 0.0
5 7.6 0.0 3.8 0.0 0.2 0.0 0 0 25 6 2 1 24 6 42 7 3 1 14 12 1 4 4 10 17 1 6 5 2 0 0.0 0.2 0.9 29.7 0.2 0 0 22 9 3 3 25 5 29 5 3 1 26 10 2 6 4 9 15 2 7 4 3 0 0.3 0.4 0.5 29.6 0.2
6 13.3 0.0 3.0 0.0 0.0 0.0 0 0 22 8 3 1 24 7 36 3 3 0 23 4 1 3 5 17 9 1 8 7 5 0 0.0 0.9 1.3 27.3 0.5 0 0 19 11 1 2 28 9 25 2 4 1 28 2 1 5 5 17 8 2 8 6 6 0 0.1 1.1 1.4 27.1 0.3
7 20.1 0.0 2.4 0.0 0.0 0.0 0 0 21 10 2 1 26 5 32 4 4 0 26 1 0 2 6 22 2 1 12 9 7 0 0.1 1.8 2.3 26.5 0.3 0 0 18 13 1 1 24 6 29 2 2 0 35 1 1 4 6 19 2 3 11 8 7 0 0.2 0.9 2.4 27.2 0.3
8 19.1 0.0 1.8 0.0 0.0 0.0 0 0 21 10 2 1 27 4 26 4 6 0 30 1 1 2 6 21 5 1 9 10 6 0 0.1 1.7 2.6 26.5 0.1 0 0 16 15 1 1 24 5 24 2 2 0 41 1 1 4 7 18 4 3 10 8 6 0 0.1 1.0 1.6 28.0 0.3
9 15.9 0.0 2.4 0.0 0.1 0.0 0 0 17 13 4 1 25 3 19 4 3 1 40 4 1 5 4 16 8 2 8 8 4 0 0.3 1.6 2.0 26.0 0.1 0 0 11 19 1 1 18 4 15 2 1 1 57 3 1 5 5 16 7 3 8 6 6 0 0.1 1.6 1.7 26.4 0.2
10 7.7 0.0 1.4 0.1 0.0 0.0 0 0 12 19 5 2 14 2 12 2 3 0 60 15 2 3 3 8 19 1 5 3 3 0 0.1 1.3 1.8 27.4 0.4 0 0 6 25 1 1 9 2 8 1 0 0 78 14 2 3 3 9 18 2 5 3 3 0 0.3 1.5 1.9 27.0 0.3
11 1.4 0.0 0.1 4.6 0.0 0.0 0 0 6 24 6 1 6 0 4 1 2 1 79 24 1 1 1 3 26 0 1 2 1 0 1.1 5.8 3.9 18.8 0.4 0 0 3 27 1 0 4 0 3 0 0 0 92 23 1 2 1 3 25 1 2 1 1 0 0.0 0.8 2.2 26.6 0.4
12 0.4 0.0 0.0 12.8 0.1 0.0 0 0 5 26 6 1 2 0 4 1 2 1 83 27 1 1 1 1 29 0 1 1 0 0 11.4 10.9 4.0 4.7 0.0 0 0 2 29 1 0 1 0 3 0 0 0 95 27 1 1 1 1 29 0 1 1 0 0 0.0 1.1 2.1 27.6 0.2 ------YR 95.4 0.2 17.9 45.8 0.6 0.0 0 0 181 184 4 1 15 3 20 4 5 1 47 173 12 29 37 114 209 10 59 54 32 1 36.8 45.8 36.7 243.4 2.3 LY 0 0 131 234 1 1 13 3 14 2 3 1 62 166 15 41 38 105 205 20 62 42 36 0 1.5 9.9 18.3 332.9 2.4
YRS 27 24 29 28 28 28 24 30 28 28 28
Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION-5
POWER GENERATING EQUIPMENT
5.1 INTRODUCTION
The West Bengal Power Development Corporation Limited intends to set up 1×660 MW Unit#5 Super Critical technology based coal fired thermal power plant at Sagardighi District Murshidabad West Bengal. The proposal is mooted to deploy state-of-the-art technology for the extension project. Coal will be made available in adequate quantity from allocated block to WBPDCL at Pachwara north in Jharkhand. Water will be made available from river Bhagirathi (5 km) through the proposed intake pump house under implementation for Phase-II station.
The basic plant design will consider unitised concept. Judicious provisions will be considered for reasonable spare capacities in various systems and system components and inter-changeability of equipment/ system.
Basic design parameters for equipment and systems are as follows: -
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Ambient temperature, Extreme High : 46.1 C Low 3.9 C
Design wet bulb temperature : 27.1 C
Seismic Zone as per IS :1893 : III
Design wind speed : 47 km/h
Condenser cooling water inlet : 33 C temp.
Auxiliary Equipment inlet : 33 C cooling water temp
Instrument air/plant air : Oil-free. In addition, Instrument & Plant air will be moisture-free.
Power supply to drives (3 Ph, : Rating below and equal to 200 50 Hz) kW – 415V. Rating above 200 kW and up to 2000 kW – 3.3 kV Rating above 2000 kW - 11 kV.
5.2 SELECTION OF TECHNOLOGY
From the viewpoint of available state-of-the-art technologies, two alternate proposals attract attention for planning the thermal power station under consideration. For electric power generation deploying Rankine Cycle, applications of both sub-critical and supercritical steam
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
parameters are in vogue. Sub-critical steam cycle which represents the current dominant technology for converting heat from fuel into electricity, operate well below the steam/water critical pressure of 22.1 MPa. However, higher plant thermal efficiency as well as improved environmental performance can be attained by increasing the operating pressure and temperature of steam. The technology deploying supercritical steam parameters in once-through mode was initiated in early 1950's, but was not pursued in USA due to poor plant availability. However, the technology was pursued in Europe and Japan to avail the intrinsic benefit available in terms of lower specific fuel consumption. With improvement in metallurgy of heat exchanger surfaces by newer alloying elements, the technology has attained desired level of success with high availability of plant in the 1990's. With extensive research in the field, the technology has now achieved acceptance both in developed and developing countries.
In supercritical boiler (boiler operating above the critical point, the critical pressure and temperature being 22.1 MPa & 374.2°C respectively for water), as heat is applied to water, temperature rises but water does not boil. With addition of further heat, water molecules gradually get agitated, inter molecular space increases uniformly and fluid becomes less dense. Transition from dense phase water with compact molecular arrangement to wide spaced random arrangement of vapour is uniform. No internal bubbles are formed. Enthalpy
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
changes uniformly and all other physical properties change uniformly from liquid to vapour stage with gradual rise in temperature.
Unlike sub-critical boiler, each tube in a supercritical boiler receives same quantity of heat input since all tubes pass through all heat zones minimizing variation in enthalpy.
Steam generator consists of a number of parallel circuits connected by inlet and outlet headers. Pressurised water enters the circuit at one end and leaves as superheated steam at other end. Hence, Supercritical boilers are essentially "once-through type".
Once-through boilers have been designed in both two-pass and tower type design. Since flow is once-through, furnace wall tube temperature tends to increase at low load. Assisted circulation mode is superimposed to overcome this problem.
The volume of the evaporator system of once-through boiler is much smaller compared to a natural circulation boiler. This leads to smaller amount of water in the evaporator. Due to smaller inventory of stored water and steam, theoretical rate of response of supercritical unit is much faster than drum unit. In comparison to the sub-critical unit, the supercritical unit has low thermal inertia resulting in a shorter start-up time, faster rates of load change and shorter time of forced cooling
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
operation during emergency shut down. Pressure changes can be achieved more easily and a true sliding pressure operation mode with reasonable load change capabilities becomes possible. In supercritical unit, main steam temperature is controlled by water-fuel ratio control with back up spray attemperation. As a result, rated steam outlet temperature can be achieved at all loads with wide range of fuel quality. With supercritical parameters, there is an improvement of cycle efficiency attributable to elevated pressure and temperatures. However, for smaller units the improvement in heat rate is marginal. Using supercritical parameters is more advantageous for larger units where heat rate improvement is more.
Increase in overall plant thermal efficiency results in reduction of fuel consumption per unit of electricity generated, which in turn also
reduces CO2 emissions in coal fired power plant. Supercritical units
also emit less SOX and NOX. Improvement in thermal efficiency also causes substantial reduction in emission of suspended particulate matter to the environment. Last but not the least better efficiency is associated with lower fuel costs.
As per the prevailing trend, single reheat has been selected and the final steam temperature at reheater outlet may be selected adequately high (about 595 °C) to avoid wet vapour in the later stage of the turbine and to attain a high cycle efficiency.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In general, water is considered as a good solvent and steam as poor one. This generalisation becomes increasingly less valid as operating pressure increases. As densities of two phases in equilibrium approach each other so do their solvent characteristic. Common impurities, like silica, sodium chloride, sodium sulphate, calcium sulphate, etc., remain soluble in water and their solubility in sub-critical steam is less. But above critical pressure solubility of these substances becomes higher in steam phase and since there is no phase separation, impurities get carried to steam phase. Hence, supercritical unit needs extremely pure feed water, resulting in the best possible feed water treatment. The make-up water and condensate must also be purified since marginal blow down is available to remove impurities. Thus, condensate polishing unit is a must in the condensate circuit for supercritical units.
For identical size, although once-through boilers avoid thick walled components like drum and replace it with small diameter separator vessel, the installation costs of supercritical plants are marginally higher than sub-critical plants. Due to high pressure and high temperature, superheater and reheater need to adopt costly alloy steel metallurgy. Similarly, HP/ IP turbine section require higher Chromium, Molybdenum, Vanadium and Nickel content to retain high tensile strength at elevated temperature. All these added together raises the installation cost. The wall-thickness of HP turbine section
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
also needs special consideration. While the wall-thickness should be high enough to withstand elevated pressure and temperature, the thickness has to be as low as possible to avoid massive material in order to increase the thermal flexibility and fast load changes. The wall thickness of the tubes and headers of once-through boiler needs to be designed for the selected pressure level.
Globally, hundreds of supercritical plants are in operation. As per available information, their availability and maintenance costs are comparable to sub-critical plants. The benefits of supercritical technology, in a nutshell, may be surmised as:
• Improved thermal efficiency attainable • Reduced fuel cost • Reduction of carbon-di-oxide emission. • Better part load efficiency.
• Reduction in emissions of NOX, SOX and SPM due to higher thermal efficiency. • Shorter start up times.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Based on pressure and temperature of Main steam, boilers are usually classified as follows-
Classification of Boilers
Steam Main / Reheat Typical Pulverized coal Pressure Steam Efficiency (% option (M Pa) Temperature (0C) HHV) Sub critical <22.1 538 / 538 35.0-38.0 Supercritical (SC) 24.7 538‐568 / 565-596 38.0‐40.0 ‐ Ultra supercritical 27.0 565‐625 40.0 ‐42.5 (USC)
As per guidelines of Central Electricity Authority of India (CEA), units 660 MW and above should adopt Supercritical technology and hence sub-critical boilers have not been considered.
For the proposed project, one unit of 660 MW with supercritical technology has been planned by the project proponent. The choice of supercritical steam parameters in once-through boiler is prima facie guided by the improvement in cycle efficiency as mentioned above. The salient technical features of the power generating equipment have been furnished in Annexure 5.1.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
5.3 THERMODYNAMIC CYCLE
To achieve higher efficiency without sacrificing availability, it is decided to consider steam parameters in the super critical range, which is also in line with the established practice of most of the manufacturers of 660 MW units.
The fuel considered for the station is coal, which will be made available from nearby coal mines of ECL. Coal will be transported to the plant site by railway wagons. The thermodynamic cycle will consist of Boiler, Steam Turbine, condenser, condensate extraction system, boiler feed system and condensate and feed water heaters along with all other necessary equipment for single reheat and regenerative feed heating.
Drawing No. 16A03-DWG-M-0101 shows the typical flow diagram for steam and water envisaged for the proposed 1 x 660 MW project. A reheat steam cycle with regenerative feed heating system is proposed. A typical heat balance with three (3) HP Heaters, four (4) LP Heaters and one (1) direct contact heater – deaerator, is presented in Drawing No. 16A03-DWG-M-0100. Project specific HBD will be developed by BTG Contractor during detail engineering stage. The heat balance is
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
based on ‘zero’ make up, 33C condenser cooling water inlet temperature and condenser pressure of 74.7 mm Hg Abs.
As shown in the scheme and heat balance diagrams, the main steam from the boiler, after expansion through the HP turbine, will be sent back to the boiler for re-heating. The reheated steam, after expansion through the single casing double flow IP and LP turbines will be exhausted into surface type, two-pass condenser having divided water box, any other proven configuration may also be considered. Vacuum will be maintained by two (2) (1 working + 1 standby) 100% capacity vacuum pumps. The LP feed heating system will consist of three(3) - four (4) stages of low pressure heaters, one (1) gland steam condenser, one (1) external drain cooler for the low pressure heater and one (1) deaerator. HP feed heating system will consist of three (3) stages of High Pressure Heaters. The condensate from the hot well will be extracted by 3 × 50% capacity condensate extraction pumps (2 working + 1 standby) and pumped to the deaerator through polishing unit, gland steam condenser, drain cooler and the LP heaters. The feed water after being deaerated in the deaerator will be pumped to the boiler through the high-pressure heaters. Oxygen content and pH of the feed water will be closely monitored to prevent corrosion damage to power cycle equipment. Continuous injection of dilute solution of hydrazine is envisaged at outlet of Deaerator (suction of Boiler Feed Pumps) for oxygen scavenging purpose. In order to control the pH of the feed
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
water, continuous injection of dilute solution of Ammonia is envisaged at outlet of Condensate Polisher. Provision will also be kept for injecting hydrazine at outlet of Condensate Polisher and ammonia at outlet of Deaerator. For 1 x 660 MW unit, two (2) nos. 50% capacity turbine driven boiler feed pumps and one 50% capacity motor driven boiler feed pump have been envisaged. Normally the steam turbine driven pumps will be in operation. The motor driven pump will be operated during start-up and during the failure of any of the two turbine driven pumps. The boiler feed pumps will be provided with lube oil system, automatic leak off and minimum flow re-circulation valves. The capacities of the pumps are regulated by varying the pump speed. In case of Turbine-driven Boiler Feed pumps, the speed regulation is carried out by varying the turbine speed. In case of Motor- driven Boiler Feed pump, the pump speed is regulated by means of modulating variable speed hydraulic coupling. Condensate drain from the HP heaters will be cascaded to the deaerator feed storage tank and the condensate drains from the LP heaters will be cascaded to the condenser through the drain cooler.
To meet the continuous and startup auxiliary steam requirements, two numbers auxiliary pressure reducing and desuperheating stations (PRDS), one taking tap off from main steam line (high capacity PRDS) and other taking tap off from cold reheat line (low capacity PRDS) shall be provided for each unit. The high capacity PDRS shall come into
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
operation particularly during unit start-up and other exigencies while the low capacity PRDS shall cater to the normal operation requirements of the unit. Two nos. auxiliary steam headers shall be provided downstream of the PRDS, a high temperature header and a low temperature header, from where the auxiliary steam requirements of various systems shall be tapped off. High temperature auxiliary steam header shall have an interconnection with auxiliary stream header of existing units. During unit start-up, auxiliary steam comes from existing units.
The unit will also be provided with 60% HP and corresponding LP Turbine bypass system for quick start and large load rejections. The turbine generator unit will be so designed that it will be capable of cyclic duty and frequent start-ups and shutdowns during its lifetime. The salient features of major equipment of the 660 MW set which describes the general requirements are furnished hereinafter. The details of the units may however vary to some extent as per vendors’ standard product.
5.4 STEAM GENERATING UNIT
The steam generator unit proposed for the station will be super-critical, once through, outdoor, pulverized coal fired, balanced draft, single reheat, dry bottom type with two pass or tower type arrangement as
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
per manufacturer’s standard. For improved efficiency at part loads and flexible operability, boiler, capable of sliding pressure operation, is favoured. An added advantage is that these type of boilers feature Boiler circulation pumps which shorten the start-up time and heat loss during start-up period.
The capacity of steam generating unit will have adequate margin over the requirement of turbine at VWO condition in order to cater to:
(a) Auxiliary steam requirement for soot blowing operation (b) Fuel oil heating and atomisation. (c) Deaerating of the steam generating unit during start-up and low load operation. (d) Gland steam supply to turbine during start-up and low load operation.
The steam generator will be designed to operate with “the HP heaters out of service” condition (resulting in lower feed water temperature at economiser inlet) and deliver steam to meet the turbo-generator requirement at base load. Economiser section of the boiler will be non- steaming type with provision for recirculation during start-up, chemical cleaning etc. Superheater section will be divided in convection and radiant zones and designed so as to maintain rated steam temperature of around 568C (± 5C) at the outlet over a control
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
range of 60% TMCR to 100% BMCR load. The reheater section will be designed to maintain rated steam temperature of around 596C (± 5C) at the outlet over a control range of 60% TMCR to 100% BMCR load. Main steam de-superheating station will be provided with arrangement for spraying water tapped off from feed water piping. The steam generator will be conservatively designed for satisfactory, continuous and reliable operation at high efficiency with the range of coal expected for this station with minimum requirement of auxiliary fuel oil for flame stabilization etc. within its control range. Furnace will be conservatively designed to allow adequate residence time for the fuel to burn completely. The design air and flue gas velocities will be carefully selected to minimise erosion of pressure parts and other vital components. The pressure parts will be designed as per ISO/ASME Sec.1 and will conform to the current Indian Boiler Regulation. Each boiler will be provided with a set of automatic sequential electrically operated type steam soot blowers with provision of manual retraction in emergency for on-load cleaning of the heat transfer surfaces. Air pre- heaters of rotary bisector/trisector regenerative type of 2 x 60% capacity will be provided for the boiler. The regenerative type air heaters will be designed for minimum leakage and be practically maintenance-free with provision of air bypass. Cold start-up operation using steam coil air pre-heater (SCAPH) will be provided. The boiler furnace and flue gas passages will be designed for low gas velocities in
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
order to minimise erosion or slagging. The basic parameters of steam generator are furnished in Annexure-5.1.
The Steam Generator Control will include Burner Management System (BMS), Master Fuel Trip, Secondary Air Damper Control, Soot Blower System etc. Flame monitoring systems and field instruments including process switches & transmitters will be provided for the above controls. Final control elements for modulating and on-off duty control valves and dampers will also be provided to achieve remote control of the steam generating unit from central control room.
Draft system is envisaged to have two (2) sets each of Forced Draft (FD) fans, Induced Draft (ID) fans and Primary air (PA) fans, each set rated for 60% of BMCR capacity. The FD fans and PA fans will be of variable blade pitch control axial flow type with silencer at air inlet. The ID fans will also be axial type with variable blade pitch control. The equipment will be complete with lube oil, hydraulic regulations and all other accessories required for continuous operation. All equipment will be suitable for outdoor installation.
The Steam Generator unit will be equipped with suitable pulverized coal firing arrangement comprising coal bunkers, gravimetric raw coal feeders, pulverizing mills, primary air fans and seal air fans, fuel and air pipes, burners etc. as necessary. Pulverizing plant consisting of
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
suitable nos. of vertical spindle type mills is envisaged to be located on front side/two sides of the furnace as per BTG vendor standard practice. With worst coal firing at BMCR condition, all mills will be working. When the unit is operating at TMCR with worst coal, one mill will remain as standby. When the unit is operating at TMCR with design coal, two mills will remain as standby. Coal feed size is assumed to be (-) 25 mm. The feed control for coal will be done through selector switch either on manual mode or automatic mode and controlled as per the plant load and composition of the fuel. The firing
system will employ latest low NOX burners and permit load variation from 30-100% BMCR without auxiliary stabilizing fuel.
LDO oil is envisaged to be used for cold start-up, coal flame stabilization at low loads and HFO will be used for Load support up to 40 % BMCR of the Steam Generator. The fuel oil system of 2 x 500 MW Phase-II units comprising the oil storage tank, pressurizing pumps, strainers, heating units, piping, controls etc. will be utilised for the proposed 1 x 660 MW unit#5 for feeding the burners. One additional HFO pressuring pump along with HFO Heater would be installed to cater the requirement of Phase-III unit#5. Oil from the Storage tank will go to the inlet of fuel oil pressurizing pumps passing through suction strainer and there from be pumped to the burners. Excess oil from burners will be re-circulated back to the storage tanks. Oil burners will be complete with tips, extension pipes, atomizers, burner
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
shut-off valve, flexible hoses and accessories. A good turn down ratio for the fuel oil system will be possible through burner turn down and selective use of a number of guns in steps. New HFO lines for the proposed unit#5 would be provided with suitable heating arrangements.
The complete boiler will be top supported type and will be provided with all supporting steel structures, platforms, galleries, elevator and stairways for easy approach and maintenance of the unit. Adequate weather protection will be provided for instruments and operating personnel. Necessary lining and insulation along with fixing materials to limit outside surface temperature to a safe level will be provided. Monorails and hoists required for handling heavy equipment, motors, fans etc. will be supplied along with the steam-generating unit for ease of maintenance.
Each steam-generating unit will be provided with two sets of Electrostatic Precipitators (ESP). Each ESP will have two parallel passes, any of which can be isolated for maintenance as and when required, keeping the other path in operation. Each path will have multiple fields in series for collection of fly ash. The design of ESP will be such that the outlet dust-burden does not exceed 30 mg/Nm3 at 100% BMCR with worst coal firing and one field remaining as operational standby. The ESP will have adequate number of ash
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
hoppers provided with electric heaters. The control of ESP will be based on microprocessor using semi-pulse device. Each ESP Outlet Pass shall be equipped with Opacity Monitors.
To reduce the NOX emission from the Steam Generator, SCR/SNCR unit will be provided to reduce NOX emission from the unit below 100 mg per Nm3 (as per MoEF stipulation) including thermal NOX produced during the entire operating range of Steam Generators. Similarly, FGD plant will also be provided to reduce SO2 emission from the unit below 100 mg per Nm3 (as per MoEF stipulation). Hg emission, if any, will be removed/arrested in SCR/SNCR unit and in the FGD plant.
In addition to the foregoing, the 275 Meter high stack proposed is expected to bring down the ground level concentration of SO2 based on 24-hourly average to a minimum. One (1) no. Single Flue RCC chimney has been proposed for this 1 x 660 MW unit#5 of the project. The location of chimney at 24º 22’ 13.7" N latitude and 88º 6’ 15.8” E longitude does not fall in the flight path of any airlines. The nearest domestic airport is in Kolkata.
The Steam Generator and auxiliaries will perform continuously within noise limits as per relevant standard specification but not more than 85 dB (A) at 1 meter from any equipment or sub-equipment. For TG set the noise level will not exceed 90 dB (A).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
5.5 TURBINE GENERATOR UNIT
The steam turbine will be super-critical, multi-stage, tandem compound, single reheat, condensing type machine operating at 3000 rpm with eight (8) uncontrolled extractions for regenerative feed heating. The turbine will be designed for main steam inlet parameters of around 24.2 MPa (a) pressure and 565C temperature before the emergency stop valves of the HP turbine, reheat steam temperature of 593 C at IP turbine inlet with design exhausting condenser pressure of 74.3 mm Hg and design condenser cooling water temperature of 33 C. The turbo-generator set will be designed for a maximum throttle steam flow at turbine valve wide open (VWO) condition of 105% of turbine maximum continuous rating (TMCR) flow. A quick acting HP and LP turbine bypass station will be provided as a part of the turbine package. The bypass station will act not only to stabilize boiler condition with sudden load dump/turbine trip out but also as a protection to the turbine during pressure rise resulting from sudden load throw off. In addition, it will enable quick start-up of the unit following a hot trip out by proper matching of boiler steam and turbine metal temperature. The bypass station will be sized for a flow corresponding to about 60% of Boiler MCR.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The steam turbine will be equipped with hydraulic turning gear for uniform heating/cooling of the rotor during start-up/shut-down. Redundant electro-hydraulic governing (EHG) system with the standby governor in follow up mode with the main governor, will be provided to ensure fast speed of operation and safety under any grid fluctuation and load throw off condition. The turbo-generator unit will be provided with self-contained lubricating oil system for supplying oil to the turbine and generator bearings and also to the generator seal oil system. The lubricating oil will be cooled by closed circuit cooling water system utilising passivated demineralised water as cooling medium.
The unit will be capable of generating at Maximum Continuous Rating (MCR) and also with valves wide open (VWO) conditions continuously with maximum cooling water temperature of 33°C and specified make- up to heat cycle. It will also be capable of operating continuously under HP heaters out of service condition generating rated output. The design of the turbine will be based on the maximum pressure and temperature it is subjected to. The rotors will be dynamically balanced and heat stabilized with thermal deflection within prescribed limits of relevant codes.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The Steam Turbine and Generator will include suitable emergency stop valve, reheat stop valve, interceptor valve, turbine control valves, HP- LP steam turbine bypass system, piping, all special insulation, paints etc. Other protective devices i.e., emergency governor, emergency trip, unloading gears, vacuum breaker etc. as required for a modern utility plant will be provided. The sets will be complete with self-contained governing fluid, lube oil, seal oil, hydrogen filling, purging and pressure/purity monitoring/control system etc. as required for continuous safe and trouble-free operation. Besides these, a fully automatic gland steam sealing system will be provided.
The electric generator will be three-phase, directly coupled, two-pole machine capable of generating 660 MW at generator terminals after meeting power requirement for excitation at a power factor 0.85 (lag). The generator will deliver power at 21 kV, 3 Ph, 50 Hz with short circuit ratio not less than 0.48.
The rotor and the stator windings will be hydrogen and DM water cooled respectively. The generator will be suitable for connection by means of isolated phase bus duct to the low voltage winding of the step-up transformer. The generator will have Class-F insulation but rated for Class-B temperature rise.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The Turbine-Generator set will be capable of delivering continuously the rated power of 660 MW at 0.85 (lag) rated power factor when the voltage variation is within (-) 5% to (+) 5% of rated value and also when frequency variation is within (-) 5% to (+) 3% that is 47.5 Hz and 51.5 Hz. Generator will have static/brushless excitation system and be capable of maintaining steady generator terminal voltage under variable load conditions and also ensure generator stability under transient conditions.
5.6 CONDENSING EQUIPMENT & ACCESSORIES
For increasing the turbine cycle efficiency, one (1) no. single pass condensers have been proposed per turbine. Cooling water flows from one Condenser to another Condenser in series manner.
The condensers will be of divided flow, single pass, horizontal, surface type. The condenser unit(s) will be transverse mounted and will condense exhaust steam by circulation of clarified water (design inlet temperature 33C) in a re-circulating cooling water system using wet type cooling tower. Condenser outlet water temperature will be maintained within 42 C. Clarified water will be the cooling medium in the condenser and in other auxiliary coolers. Condenser with Stainless Steel heat exchanger tubes, with steel tube sheet, baffle plates, etc. are envisaged for clarified water application. The condenser will be
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
designed as per HEI code or equivalent. The design heat load of the condenser will consider the turbine operating condition at VWO having 105% MCR steam flow, maximum expected make-up, 90% tube cleanliness factor and a condenser cooling water inlet temperature of 33C to maintain rated condenser pressure(s). The condenser will also be capable of accepting full HP-LP bypass steam flow (60% BMCR) safely without undue pressure rise, vibration, noise or other detrimental effects. Oxygen content of condensate leaving condenser hot well will be less than 0.015 mg per litre over the entire load range.
Two vacuum pumps (2x100%) are provided for the condenser to remove non-condensable gases and maintain vacuum in the condenser at the desired level during normal operation. For start-up both the pumps will be operated simultaneously. The condenser will be spring mounted with rigid connection to the turbine exhaust.
Condensate Extraction Pumps
The condensate cycle will comprise three nos. (2W + 1S) 50% capacity motor-driven, vertical condensate extraction pumps of CAN-type construction. Connection between condenser and each pump suction will be through a block valve and removable strainer. The pumps will discharge through check valve and motor operated stop valves into a common discharge header. Connection for condensate supply to the
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
following major services will be tapped off from this condensate discharge header.
a. LP bypass de-superheating spray.
b. Turbine exhaust hood spray.
c. Gland sealing system de-superheating.
Condensate will then pass in series through the condensate polishing system, gland steam condenser and drain cooler before being passed through the low pressure feed water heaters. Condensate polishing system will have 3 x 50% mixed bed polishers for the 660 MW unit along with an external regeneration system. Condensate will be finally pumped to the deaerator.
Condensate Extraction Pump will be suitable to operate at 60% HP/LP bypass condition and also all heaters out condition without reaching run-out flow.
5.7 BOILER FEED WATER PUMPS
The feed water system will comprise three (3) nos. (2 nos. turbine driven having capacity 50% each + 1 no. electric motor driven having capacity 50%) boiler feed pumps of centrifugal, multi-stage, horizontal, barrel type construction. Two nos. steam turbine driven feed pumps
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
will be normally in operation while the electric motor-driven pump will remain as standby. The electric motor driven feed pump will also be used during start-up of the unit. The head, capacity and net positive suction head (NPSH) will be so selected as to permit parallel operation at all loads and be compatible with the heat cycle considered to meet the boiler MCR condition without encroaching on normal margins. Booster pumps will be considered to ensure appropriate head at main pump inlet. The pumps will be provided with mechanical seal and flushing arrangement as per API 610. The feed pumps will be complete with variable speed hydraulic coupling, lube oil system, automatic leak-off, minimum flow recirculation valves, bypass valves, base plates, foundation bolts, couplings and 11 kV, 3 pH, 50 Hz electric motor drive/steam turbine drive.
5.8 DEAERATING HEATERS & CLOSED HEATERS
The regenerative feed heating system will comprise horizontal shell and tube-type feed water heaters with suitable bypass arrangement and a direct contact type heater (Deaerator), which will serve the additional purpose of deaerating the feed water. The low pressure feed water heaters will be horizontal U-tube type and equipped with condensing and drain cooling zones. Besides these, separate drain cooler, gland steam condenser etc. as per manufacturer's standard are envisaged. A horizontal spray-cum-tray type deaerator with integral
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
vent condenser will limit the oxygen content in the feed water to a maximum value of 0.005 cc/litre at all operating conditions with minimum loss of steam. The deaerator storage tank will be adequately sized to accommodate at least 6 minutes’ water requirement of the boiler at BMCR condition. The high pressure heaters will be of horizontal U-tube type having desuperheating, condensing and drain- cooling zones. All steel construction of condensate/feed water wetted surfaces is desired to facilitate uniform chemical conditioning of steam- condensate-feed water system.
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Annexure-5.1 Sheet 1 of 6
Brief Technical Features of Main Plant & Equipment
1. Steam Generator & Auxiliaries
Type : Super Critical, direct pulverized fuel tangentially fired, once through, single reheat, balanced draft, two-pass/tower type, dry bottom, outdoor type unit with associated auxiliaries suitable for both constant pressure and sliding pressure mode operation.
Nominal Outlet Steam Parameters at TMCR:
Main Steam Hot Reheat Pressure MPa(a) : 24.5 5.2 Temperature, C : 568 596 Flow (TPH) : 1899 1565
Feed water temperature at : 291 economiser inlet, C
- Steam temp. control range : 60-100% BMCR or better (to be decided in design stage).
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Annexure-5.1 Sheet 2 of 6 - Superheater/Reheater : Attemperation and tilting burner Temperature control control
Nominal Air Heaters Capacity : 2 x 60% of BMCR – bisector/trisector type
Solid Particulate matter(SPM) at : 30 Electrostatic Precipitator outlet, mg/Nm3
Draft Fans : 2 x 60% BMCR capacity axial flow forced draft (FD) fans with variable blade pitch control with silencer at air inlet..
2 x 60% BMCR capacity induced draft (ID) fans, axial type with variable blade pitch control .
2 x 60% BMCR capacity axial flow primary air (PA) fans with variable blade pitch control with silencer at air inlet.
Pulverizing Mills : Slow speed large bowl or ball and race type in N+2 configuration [N- denotes the number of mills required to reach TMCR with design coal and 85% mill loading]
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Annexure-5.1 Sheet 3 of 6
Coal Firing System : Direct suspended firing with state-
of-the-art low NOX burners giving stable fire above 40% TMCR load.
Start-up/auxiliary fuel : LDO oil for cold start-up, for coal flame stabilisation at low loads (upto 10% BMCR) and HFO for load support (capacity up to 40% BMCR).
Ash removal
Bottom Ash : Wet Extraction and disposal through Lean Slurry System to ash pond.
Fly Ash : Evacuation in dry form through vacuum & pressurised air conveying to fly ash storage silos for ultimate disposal by truck/rail wagons for cement and brick manufacturing, filling mines etc. Provision for wet disposal through Lean Slurry to Ash Pond during exigency.
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Annexure-5.1 Sheet 4 of 6
2, Turbine Generator & Auxiliaries
Type : Super Critical, single reheat, multi cylinder, tandem compound, with HP, IP and LP sections, regenerative, condensing steam turbine directly driving a 3000-rpm, 2-pole, 50 Hz, electric power generator.
Nominal Capacity : 660 MW at 33°C condenser cooling water temperature.
Normal Operating Frequency Range : 47.5 to 51.5 Hz.
Inlet Steam Parameters : Main Steam Hot Reheat Pressure, MPa(a) : 24.2 5 Temperature, C : 565 °C 593 °C
Steam Extractions : CRH + other stages from HP, IP and LP turbines for condensate / feed water heating.
Type of governing : Redundant Electro-hydraulic governing with fire resistant fluid.
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Annexure-5.1 Sheet 5 of 6
Lubricating Oil system : 1 x 100% capacity shaft driven pump and 2x100% AC motor driven main oil pump.
1 Emergency oil pump (EOP), DC motor driven
1 x 100% capacity Jacking Oil Pump (JOP), AC motor-driven
1 x 100% capacity Jacking Oil Pump (JOP), DC motor-driven
Turbine HP-LP bypass system : Capacity : 60% of BMCR steam flow.
Condensing Equipment : One (1) Shell and tube type surface condenser operating on recirculating cooling water with evaporative cooling towers.
Condenser Pressure (mm Hg) : 74.7
Regenerative feed heating arrangement : Three/four stages of LP heaters (U- tube design). One spray-cum-tray type deaerator, two stages of HP heaters either 2x50% or 1x100% configuration.
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Annexure-5.1 Sheet 6 of 6
Boiler feed water pumps : 2×50% nos. steam turbine-driven and 1x50% electric motor-driven barrel type horizontal, centrifugal.
Condensate extraction pumps : 3×50% capacity vertical, centrifugal CAN type construction, electric motor driven.
Generator : 660 MW output at 0.85 power factor (lagging) 3 Ph, 50 Hz and 21 kV rated voltage.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
SECTION-6
AUXILIARY SYSTEMS
6.1 INTRODUCTION
The philosophy of design of the auxiliary system will be pre- dominantly guided by the land features, technology, basic parameters, infrastructure, etc. Adequate redundancy will be adopted to ensure high availability of the plant.
All the systems, sub systems and their components will be designed for simplicity of operation and ease of maintenance so as to call for minimum manual intervention and low degree of supervision. Redundancies in systems and sub-systems will be considered taking into account the experience of similar capacity units being operated elsewhere.
6.2 PLANT WATER SYSTEM
River Bhagirathi is considered to be the source of water for the station. The consumptive water requirement estimated for Phase-II & III together is about 5168 m3/hr. Drawal of water would be done by a new intake pump house under construction for phase-II near Bhagirathi with intake channel. Pump house capacity has been conceived accordingly.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Re-circulating cooling water system using wet evaporative Natural Draft cooling towers will be deployed for the proposed station. It will be used for the condenser and auxiliary equipment cooling in a semi- open cooling water circuit.
The tentative Raw water analysis is furnished as Annexure-3.1. . For the purpose of the present study a single line diagram is presented in Drawing No.16A03-DWG-M-0001 showing plant water system.
For the present study, consumptive water requirement is estimated on the basis of 1% heat cycle make-up, about 1.5% make-up to cooling towers, Bottom Ash and Fly Ash disposal by lean slurry mode with ash water recovery System and other consumptive requirements like different varieties of process and service water etc. It is proposed to utilise cooling tower blow down in ash handling plant and dust extraction and suppression system of the coal handling plant to the extent possible. The break down is furnished as Annexure-3.2 earlier and the Water Balance Diagram is given in Drawing No. 16A03-DWG- M-0002 enclosed.
However, as per MoEFCC stipulation dated 07.12.2015 the specific water consumption limit is 2.5 m3 / MWh. The Plant water and Effluent Treatment systems are designed in such a way that total consumptive water requirement will be within 4150 m3/h for Phase-II & III units
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
together. To achieve this, ash water recovery system would be adopted to recycle ash water from the ash pond to ash water sump after necessary treatment. Other considerations are dry disposal of fly ash and cycle of concentration as 7 in the CW circuit. The representative Water Balance Diagram is given in Drawing No. 16A03-DWG-M- 0002A enclosed.
There (3) nos. vertical wet pit type intake pumps with capacity of 3700 m3/hr have already been installed in the proposed intake pump house of Phase-II. Raw water from the pump house will be conveyed to the in-Plant reservoir through one (1) no. 1200 mm dia. mild steel underground with suitable wrapping & coating.
The Capacity of raw water reservoir developed inside the plant premises adjacent to the existing water reservoirs of Phase-I is of capacity 16,00,000 m3 which can cater raw water requirement of both Phase-II & III units for about 13 days. The reservoir in the raw water system would also functionally assist in removal of substantial portion of suspended solids and will provide redundancy to the system. Raw water will be clarified to remove suspended solids and colloids in clariflocculators or micro sand ballasted flocculation and settling system aided by polymer. Three (3) nos. high rate Solid Contact type clarifiers each having minimum capacity of 2000 m3/hr are being installed under Phase-II to serve the requirement of both Phase-II & III
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units. Lime, alum and other coagulant aids will be dosed in the clariflocculators to accelerate the coagulation process.
RCC (Partly underground) Twin chamber Clarified water reservoir with a storage capacity of 32,000 m3 have been constructed to store clarified water. Clarified water would be supplied as make-up in the cooling tower basin of Phase-II with suitable provision for supply to Phase-III. Other requirement of clarified water for the main plant viz. service water, APH wash water etc. will be supplied to respective terminal points of Phase-II system with suitable provision at Phase-II end for future extension of line for Phase-III.
Clarified water will also cater to the requirement of ventilation system, DG set, service water, CHP wash water, AHP cooling and sealing. A part of the clarified water would be sent to the Ultra filtration plant. Clarified water pump house being implemented for Phase-II will also be utilised for Phase-III. The pump house will comprise of following vertical wet pit pumps :
i) Four (4) nos. cooling tower make-up pumps [3W + 1S] each having capacity of 1300 m3/hr.
ii) Three (3) nos. service pumps [2W + 1S] each having capacity of 400 m3/hr.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
iii) Three (3) nos. clarified water transfer pumps (DMF Feed Pumps) [2W + 1S] each having capacity of 210 m3/hr.
iv) Two (2) nos. AHP wash pumps each having capacity of 320 m3/hr.
. In the Ultra filtration plant being constructed under Phase-II, clarified water will be passed through Ultra Filtration Modules and the outlet water quality shall be maintained as SDI ( Silt density index) <3. Filtered water will be stored in a twin chamber RCC UF Permeate Storage Tank having storage capacity of 700 m3. Filtered water will be required for potable use, AC plant make-up and DM plant feed. Filter water pump house already constructed in Phase-II, comprises of the following set of horizontal centrifugal pumps :
Three (3) nos. RO-DM feed pumps [2W + 1S] each having capacity of 120 m3/hr.
Two (2) nos.[1W + 1S]. 50 m3/hr Potable water pumps
Two (2) nos.[1W + 1S]. 410 m3/hr UF Back Wash pumps
The single line diagram of Plant Water System is presented in Drawing No. 16A03-DWG-M-0001.
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Circulating water (CW) flow through the condenser is estimated at 76000 m3/hr for 1 x 660 MW unit in Phase-III considering temperature rise as 9C. Auxiliary Cooling water (ACW) requirement is estimated at 4000 m3/hr per unit considering temperature rise across coolers as 10 C max. Three (3) Nos.Vertical Wet-pit type CW pumps (2 W + 1 S) and Two (2) nos. Vertical Wet-pit type ACW pumps (1W+1S), located in CW Pump house, have been envisaged for 1x 660 MW unit in Phase- III.
The makeup water requirement for cooling circuit for Phase-II [2 x500 MW] & Phase-III [1 x660 MW] at full load is estimated at 3234 m3/hr. A cycle of concentration of 5 has been considered in the CW circuit. The cooling tower blow down is expected to be about 798 m3/hr for Phase-II & Phase-III units. While major portion of total recoverable blowdown will be fed to Ash water sump, a small quantity of CT blowdown from unit#5 will be used for Coal Handling Plant dust suppression.
Sludge from the clariflocculator would be allowed to settle and only clear water would be sent back to the clariflocculation plant. Backwash from filter beds and re-generation effluent from DM Plant would be neutralised in the neutralising pit before feeding to ash water sump.
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Demineralisation Plant & Heat Cycle Make-up System:
DM Plant consisting of ultra-filtration system, RO units, activated carbon filters, cation exchanger, anion exchanger and mixed bed exchanger are being constructed under Phase-II and are adequate for Phase-II & Phase-III in combine. There are two (2) streams of 100 m3/hr each, RO modules presently installed. DM water would cater the requirement of water for heat cycle make-up, the make-up requirement for primary water circuit of stator cooling system, chemical feed system, hydrogen generation plant, make up requirement for the auxiliary cooling system for Boiler, TG & other common auxiliaries and CPU regeneration.
Filtered water will be pumped to the DM Plant for demineralisation. In the DM Plant, the water will be first filtered through the combination of dual media filter &ultra filter installed within the DM Plant building. Filtered water will subsequently be passed through combination of reverse osmosis (RO) and mixed bed exchanger (MB) system and then the demineralised water would be stored in DM water storage tanks. Acid and alkali handling, storage and feeding system have been installed for the DM Plant resin regeneration. The DM water produced in the plant will then be taken to two (2) DM water storage tanks, each of 2000 m3 capacity to meet the total requirement of Phase-II & Phase-III units. DM water from the storage tanks will be transferred to the unit condensate storage tanks of Phase-II & III units
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by 4x100% capacity DM transfer pumps. Each pump will have the capacity to meet the requirement of one unit. The plant would be equipped with 100% condensate polishing unit for ensuring required water quality for operation of once through steam generator with steam parameter applicable for 660 MW unit.
There will be one common DMCCW circuit for each unit - for both TG auxiliaries and SG auxiliaries. DMCCW system will have 2x100% capacity DMCCW pumps, 2x100% capacity Plate type Heat Exchangers, 2x100% Filters and one expansion tank. Alternatively, separate DMCCW circuit for TG and SG auxiliaries may be provided as per BTG Vendor’s Standard practice.
6.3 COAL HANDLING SYSTEM
The Coal Handling Plant has been designed to cater the requirement for Phase-II & III stations together. Coal would be sourced from a new mine at Pachwara (North) in Jharkhand, being developed by WBPDCL. Merry-go-round rail track is envisaged for the Sagardighi TPS. One (1) track hopper was constructed for Phase-I station. For Phase-II station one additional track hopper of 225 m length and one (1) wagon tippler are under installation. These are considered adequate for Phase-III extension unit#5 also. Further two (2) nos. stacker-cum- reclaimers are being constructed under Phase-II and are adequate for both Phase- II & III units. About 2-3 rake loads of coal would be
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
received per day for Phase-III unit additionally. The capacity of CHP will be adequate to feed Phase-II & III units together by increasing operating hours. For the purpose of equipment selection, raw coal with quality mentioned in Section-3 of the report has been adopted.
The scheme of the proposed Coal Handling System for unit#5 is shown in Drawing No.16A03-DWG-M-0003. Adequate redundancy has been adopted to ensure uninterrupted operation of this vital auxiliary system. The following are the salient points of design basis of the coal handling facilities for Phase-III unit #5 :-
Sl.No. Salient Points Design Coal i) Gross calorific value of coal 3300 kcal/kg ii) Station Heat Rate 2151 kcal/kg iii) Hourly coal consumption (max.) 430 TPH iv) Max. daily consumption of coal (in 10326 TPD MT) @ MCR v) Annual coal requirement @ 90 % 3.4 Million Ton PLF vi) Maximum size of coal delivered (-) 300 mm vii) Mode of coal transportation By rail route from the mine to plant in BOBR/’N’-BOX rakes.
The system design would ensure a margin of 20% in capacity towards presence of shale in raw coal. The plants and equipment of CHP has been designed for three-shift operation for coal receipt and two-shift operation for bunker feeding. The design capacity of Coal Handling System for Phase-II & III units together is 2000 TPH both for receiving
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and handling system. The stacker/reclaimer capacity has been considered as 2000 TPH. Coal, on receipt at plant end, would be fed to the surge hopper of the crusher house. In the crushers coal would be sized to (-)20 mm. The crushing plant is equipped with screens of suitable type and capacity followed by swing hammer type/ring granulator type crushers. Crushed coal would thereafter be led either to the boiler bunkers or to the stack yard. The unidirectional stacker- cum-reclaimer will be rail-mounted, self-propelled unit with 48 m boom length having adequate slewing and luffing provision to stack coal up to a height of 9 m and reclaiming the same afterwards. Two (2) nos. of stacker-cum-reclaimers are planned for Phase-II station. It would cater the requirement of Phase-III unit also. In the main route, coal will be directly taken to the powerhouse bypassing the coal stack. This arrangement would be operational under normal conditions during daylight hours till the bunkers are full. Excess quantity would thereafter be stacked in the yard. In the other route crushed coal from stack would be transported to the coalbunkers through reclaimer. Twin 100% capacity stream of conveying system is proposed to ensure high availability. Bunkers would have a storage capacity of about 12 hours’ coal requirement for the boiler. The bunkers will be provided with SS liners and rod and slide gates, arch breakers etc. to facilitate operation. Necessary belt weighing at bunker level conveyors, electronic type level indicators, coal sampling units, reversible conveyors, flap gates etc. would be provided in the system as required.
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New set of 2000 TPH capacity twin stream conveyors would be installed under Phase-III beyond Transfer Point 19 of unit #4 upto unit #5. Side mill configuration is adopted for the station.
Special precautions will be taken for pollution control by providing dust extraction and dust suppression systems at different transfer points. In addition, roof extraction fans will be provided in key areas like boiler bunker floors.
Necessary water distribution network for drinking and service water with pumps, piping, tanks, valves etc. will be provided for distributing water at the transfer points.
A centralised control room with microprocessor based control system is being constructed under Phase-II near the crusher house for operation of the Coal Handling Plant of Phase- II & Phase-III units. For Coal Handling system for the proposed unit#5, minor modification in the Mechanical System would be taken care of in the existing PLC based control system by using spare I/Os or augmenting I/O cards and modifying the logic. Existing switchgears in the CHP under Phase- II would be suitably modified to suit the requirement of the proposed unit#5.
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The major equipment for the coal handling plant for Phase-II & III is listed below :- 1. a) Track Hopper :5100 Te with paddle feeders to twin stream conveyors.
b) Wagon Tippler : One (1) no. c) Side Arm Charger : One (1) no.
2. Conveyors : Twin stream conveyor line of 2000 TPH.
3. Paddle Feeder : Capacity1000 TPH rated x 2 in each stream of conveyors.
4. Stacker-cum-reclaimer : Two (2) Nos. of 2000 TPH capacity. (Unidirectional)
5. Apron feeder : 2000 TPH capacity 6. Reversible conveyors : As required and belt feeders 7. In-line magnetic separators : Two (2) Nos. 8. Roller screens : Four (4) Nos. 9. Crushers : Four (4) Nos. 10. Metal detectors : Two (2) Nos. 11. Suspended Magnet : Two (2) Nos. 12. Belt weighers : Four (4) Nos. 13. Coal sampling unit : Two (2) Nos.
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14. Flap gates, rack & pinion : As required. gates, etc. 15. Level indicators : Electronic type. 16. Chute liners and chute : One lot supporting structures
17. Wheel mounted loader : One (1) No.
18. Hydraulic Drive for Conveyors : As required. and Stacker-cum-Reclaimers
6.4 ASH HANDLING SYSTEM
Under the proposed system, a wet extraction and wet disposal is considered for bottom ash. For the fly ash, a complete dry extraction and dry as well as wet disposal during exigency has been considered.
Ash handling plant was earlier conceived as lean slurry disposal both for bottom ash (BA) and Fly ash (FA) for 3X500 MW i.e. for Phase-II & Phase-III combined. Accordingly ash handling plant has been designed for Phase-II station, which can also cater the requirement of newly proposed 1X660 MW station under Phase-III. However, with the latest MoEFCC notification for water consumption limitation, it has been decided to consider ash water recovery system under operation from the beginning for Phase-II & III units.
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The quantum of ash generation would depend on the plant load factor and the quality of coal being fed. In keeping with the design system capacity envisaged for coal handling plant, worst coal parameters from the source mentioned earlier is used for equipment selection of the Ash Handling Plant. It has been estimated that with coal available for Phase-III station about 234 tons/hr (max.) of ash would be generated from the proposed extension station at BMCR firing worst coal (GCV-2800 kcal/kg). Assuming the ratio of fly ash to bottom & Eco ash as 100:20, usual for such application, about 58 tons/hr/unit of bottom ash & Eco ash and 234 tons/hr/unit fly ash is required to be removed from the station. In Drawing No.16A03-DWG-M- 0004, the scheme proposed for the Ash Handling Plant is shown. It may be noted while designing ash handling system for units 3 & 4, several provisions/space have been kept in system as well as in the pump house as noted here to combine the system for unit 5 with units 3 & 4.
Bottom Ash Conveying System
Wet Bottom Ash System
Bottom ash from the furnace would be collected in a water-impounded hopper provided with feed gates, feed hoppers and clinker grinders. The bottom ash clinkers will be ground in clinker grinders and will be transported by jet pumps to ash slurry sump (common for bottom ash and fly ash) from where bottom ash slurry will be pumped to ash pond outside the plant boundary. The design capacity of bottom ash conveying system considered should be adequate to clean bottom ash collected in a shift of eight (8) hours within 1 hours and 45 minutes without flushing.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The jet pumps would receive high-pressure water from 2 x 50% capacity H.P. water pumps (These pumps will serve as BAHP & FAHP pumps, each pump set will be able to cater to the total requirement of HP water during Bottom Ash removal of one unit or Fly Ash removal of one unit whatever is higher). 1x100% capacity L.P. water pump will supply water for seal through make-up and refractory cooling of bottom hopper. The H.P. & L.P. water pumps to be located in a common ash water sump which receive make-up water from CT blow down, boiler blow down, recycled ash water from ash pond and raw water system, if required. The seal trough overflow water would be led to the BA overflow tank. In ash water pump house one (1) no. of LP water pump and two (2) nos. of HP water pumps of similar capacity are to be installed for Phase-III unit working in parallel to the existing Phase-II units pumps. However, in case of unavailability of the Phase-III LP water pump, the process requirement can be catered by remaining LP water pumps with moderate rise in BA overflow water temperature (10-15%).In ash slurry pump house, one (1) no. slurry pump chain to be installed for Phase-III units in addition to the existing four (4) (2W+2S) chains presently installed for Phase-II units. One (1) no. seal water pump would be installed in ash slurry pump house for Phase-III unit#5. The pumps to be installed for unit #5 will be installed in the same pump house being constructed for Phase-II units.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Fly Ash Handling System:
Fly Ash Vacuum Conveying System
All air pre-heater hoppers and ESP hoppers will be provided with fly ash vacuum conveying systems having capacity to evacuate fly ash generated in a shift of eight (8) hours within 4 hours and 30 minutes. The vacuum conveying system shall have eight(8) streams operating in parallel, each stream having a conveying capacity of not less than 56 TPH. Below each hopper one Ash intake valve will be provided to discharge fly ash into the ash-conveying pipeline to be conveyed pneumatically. The ash-air mixture flows through the pipeline for collection of fly ash in dry state into an intermediate surge hopper and the other for removal of fly ash in slurry form. The fly ash and air mixture flows into a highly efficient bag filter system where almost entire fly ash is removed and discharged into the intermediate surge hopper located below through separation in filter bags in the filter- separator unit.
Necessary transfer hopper with airlock valves will be provided below the filter separator unit to ensure continuous discharge of fly ash without affecting the operation of the upstream vacuum system. Intermediate surge hopper will have fluidizing pads distributed properly at the bottom to allow smooth flow of fly ash into the downstream pressure conveying system. Suitably sized vent filter will be provided at surge hopper roof along with pressure/vacuum relieving equipment.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Necessary vacuum for the system will be created by water ring type vacuum pumps. Air discharged from bag filter separator will be flown into air washer unit for scrubbing of finer ash particles. Clean air will then flow to the vacuum pump. Total ten (10) nos. vacuum pumps will be provided (1 no. working per stream + 2 nos. as common standby). The standby vacuum pumps would have interconnection facility with each stream.
Intermediate Surge Hopper
Two (2) nos. each 250 Tons capacity Intermediate Surge Hopper (ISH) shall be provided close to the ESP, which will be of MS construction. From intermediate surge hopper, the fly ash would be conveyed through pressurised pneumatic system using air compressor to the terminal silo located on the fringe of the plant boundary wall.
Fly Ash Pressure Conveying System (Dry)
Dry fly ash from the intermediate surge hopper will be conveyed to the terminal fly ash silos by a positive pressure conveying system. Ash feeder vessels would be installed beneath the intermediate surge hopper and fly ash would be transported to the terminal fly ash silos through pipeline from the surge hopper via feeder vessels. The total storage capacity of terminal fly ash silo would be 2400 tonne keeping similarity with existing silos resulting in provision of storage of fly ash generated in 10 hours (Approx.). With interconnection with existing
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silos, the ultimate storage capacity will be even more than 14 hours. Oil free Screw compressors shall provide pressurized air required for conveying. For the proposed unit, four (4) conveying line would be provided for Phase-III unit to transport fly ash at the rate of not less than 112 TPH. A common standby FA transport line will also be provided. Arrangement shall be made such that fly ash conveying line can dump fly ash to either of the terminal fly ash silos. 4x25% capacity screw compressors will be provided keeping similarity with units 3 & 4 compressors, installed in same compressor house already installed for units 3 & 4. Thus the standby compressors provided for units 3 & 4 will be shared by all the three units i.e. 3, 4 & 5.
Fly Ash Conveying System (Wet)
A wet fly ash conveying system shall be provided to meet exigency as an alternate mode of disposal. The wet system shall operate when the terminal fly ash silos are full or there is maintenance/breakdown in the dry fly ash pressure conveying system.
In the system dry fly ash extracted by vacuum conveying system is taken to a wetting unit where it is converted into medium concentration ash slurry by supplying high-pressure water from HP water pumps. Air is separated from the air water separator by the vacuum pumps and the ash slurry is conveyed to the ash slurry sump by gravity. Two (2) (1W + 1S) nos. wetting unit including air water separator shall be provided for each vacuum-conveying stream.
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The ash slurry from the ash slurry sump is transported to ash pond by one (1) no. Slurry pumps chain having 2 nos. ash slurry pumps connected to 4 nos. Slurry discharge pipe headers already provided for units 3 & 4. The ash slurry disposal system is common for wet bottom ash and wet fly ash transportation system. The slurry transportation lines provided for units 3 & 4 will be shared by all the three units i.e. 3, 4 & 5 providing 3 working lines and one standby line for all the three units.
Dry Unloading of Ash in Terminal Silo
In the proposed Phase-III unit, there will be one(1) new terminal fly ash silo having five(5) outlets as follows :-
Two (2) nos. outlet with telescopic spout arrangement with rotary feeder/ orifice feeder for unloading dry fly ash into closed trucks.
One outlet with dust conditioner arrangement with rotary feeder/ orifice feeder for unloading dry fly ash in conditioned form into open trucks.
Two (2) nos. outlet for future use.
Dry fly ash unloaded into enclosed fly ash tankers and open trucks is disposed for the purpose of subsequent use like mine-fill, landfill, cement plant, etc. Each terminal fly ash silo shall be provided with suitably sized vent filter and pressure/vacuum relieving equipment.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Ash Water Recirculation System
The ash water recirculation system being constructed under Phase-II would be utilised for Phase-III unit#5.
Fluidizing Air System
Continuous supply of fluidizing air during ash evacuation has been envisaged in all the hoppers of the ESP, stack and intermediate surge hopper to facilitate smooth and effective ash flow. For this, fluidizing air blowers of adequate capacity and pressure will be provided. The blowers and heaters will be located in vacuum pump house. The terminal fly ash silos will have separate independent fluidizing air system with the blowers & heaters being located in existing silo utility building in the space left for the purpose. Fluidizing pads are distributed properly at the bottom of intermediate surge hopper and terminal fly ash silos to allow smooth flow of fly ash into downstream system. The fluidizing air system would be complete in all respects with necessary electric air heater, insulated piping, valves and instruments to ensure satisfactory system operation.
The intermediate surge hopper will also receive fluidizing air from the ESP hopper-fluidizing blower.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Compressed Air System
One (1) no. additional instrument air compressor with air drying system, piping, valves and instruments would be installed inside AHP Compressor House for Phase-III unit in addition to the existing four (4) (2W+2S) nos. of Compressor- air dryer presently installed for Phase-II
units.
MCC & Control Panel
New equipment/facilities of AHP for the proposed unit#5 would be controlled from the existing control system of Phase-II by adding one new RIO and using the existing HMI.
LT Switchgears for Vacuum pump house and bottom ash system would be located inside a separate room annexed to the vacuum pump house for the proposed unit#5. For AHP compressor house, ash silo area, ash water and ash slurry pump house, existing LT switchgears of Phase-II would be extended to meet the requirement of Phase-III unit.
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6.5 FUEL OIL HANDLING SYSTEM
Both HFO and LDO are envisaged for the proposed Phase-III extension unit#5. LDO would be required for boiler light up and HFO would be used for load carrying purpose and flame stabilization.
HFO and LDO are brought to the plant by railway oil tankers from nearby oil depot. The unloading area has facilities to receive and unload oil from tankers to the headers. There are six (6) HFO and six (6) LDO unloading pumps installed during Phase-I units. The existing two (2) nos. of LDO tanks of 2000 m3 each and two (2) nos. of HFO tanks of 2000 m3 each for the Phase-I and additional two (2) nos. of HFO tanks of 2000 m3 each being constructed under Phase-II project, will cater for storage of LDO and HFO required for start-up and coal firing support purpose of the Phase-II & III units also.
Pressurising pumps will supply oil from the HFO/LDO storage tanks to the burner. Three (3) nos. HFO (2 W+ 1S) & two (2) nos. LDO (1W + 1S) pressurising pumps are being installed under Phase-II system. One additional HFO pressuring pump along with HFO Heater would be installed to cater the requirement of Phase-III unit#5. Installed LDO forwarding pumps of Phase-II can also cater requirement of Phase-III unit#5.
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All instrumentation and control facilities including tank level controllers, pressure/temperature gauges, control valves etc. along with a local control panel in the fuel oil pump house will be provided for safe and reliable operation of the system.
The Auxiliary Oil System and its facilities will be designed as per Pollution Control/Petroleum Rules/Explosion Acts/Fire Rules of Govt. of India. HFO and LDO analysis is given in Section-3 earlier. A flow diagram showing the proposed Fuel Oil System is enclosed in Drawing No.16A03-DWG-M-0005.
6.6 Ventilation & Air conditioning System:
Right environment for operation and maintenance of the plant as well as for proper functioning of the equipment, controls and accessories is an important aspect which has been given due consideration in the proposed Ventilation and Air Conditioning System.
Ventilation System :
Adequate ventilation system has been considered for the powerhouse building, Central Control Building, ESP control building, Vacuum Fly Ash System and other areas like A/C plant room, Switch gear room for Cooling Towers, CW Treatment Building, Elevator Machine rooms and various pump houses like CW/ACW pump house etc. with their
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
associated Electrical rooms, Kitchen/Pantry and Toilet areas of Service building etc. to achieve the following :-
i) Dust-free comfortable working environment.
ii) Scavenging out structural heat gain and heat load from various equipment, hot pipes, lighting etc.
iii) Dilution of air polluted due to generation of obnoxious & hazardous gaseous/aerosol contaminants like acid/chemical fumes, dusts etc.
Ventilation system proposed for important areas are described below :
Ventilation System of Power House and Central Control Building :
Supply/exhaust ventilation system with evaporative cooling arrangement has been recommended for the Powerhouse Building. Ambient air would be drawn through air inlet louver, automatically cleanable water flooded type SS mesh filters, water wetted fill deck and moisture eliminator and will be supplied by means of centrifugal fans to powerhouse through ducting and grilles to achieve proper distribution. The sprayed water over the SS mesh filter will be re- circulated by means of centrifugal pumps, piping, valves and other accessories. Similarly, water dripped over the Fill Deck will also be re- circulated by means of centrifugal pumps, piping, valves and other accessories.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
'Exhaust' system consists of axial flow wall/roof-mounted exhaust fans with rain protection cowl/hood, short duct work etc. Part of the supplied air will be exhausted and the rest will ex-filtrate through the various openings in the structure, preventing infiltration of dusty air.
Following areas of the Power House building are ventilated: a) TG Bay- Steam Turbine & Generator area, HP/LP Heater area, Evaporator & Condenser area, Boiler Feed Pump area, Oil Cooler, Lube Oil Cooler area located within A-B bays.
b) Boiler MCC Rooms c) Cable Vault Rooms d) PRDS Stations e) Vacuum Pump Area f) Chemical Dosing room g) SWAS Room (Wet Panel) h) Switchgear and MCC room i) De-aerator Heater floor, if not open
Exhaust ventilation system shall be provided for the Battery Rooms [Lead acid battery] of the Main Control Block of Power House by installing wall mounted Bi-furcated type Axial Flow Exhaust Fans. All parts of the exhaust system coming in contact with acid fumes shall be epoxy painted. The exhaust air from the Battery rooms shall be discharged at higher level at about 1M from the roof of the control block and away from the nearest steel structures. Foul air of the
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Battery room will be sucked both from top and bottom level to expel acid fumes and Hydrogen.
Pressurized Dry ventilation system with supply Fan-Filter unit and Back draft dampers shall be provided for the Elevator Machine Rooms of the TG Building.
Exhaust ventilation system shall be provided for all the Toilets and Pantries of the TG Building by installing wall mounted Axial Flow Exhaust Fans.
Ventilation Systems for other Auxiliary Buildings
Ventilation provisions for other Auxiliary Buildings in various locations are envisaged as follows :
Sl. Building Area covered and type of Ventilation No. 01. Mill Bay For the Coal Bunker Area of Mill Bay, air shall be exhausted through Roof Extractor Fans and air entry shall be through wall mounted louvers at the floor level from both sides. 02. ESP/AHP For ventilation of these building ambient air will Control be drawn through unitary air filtration unit Building comprising fresh air intake louvers, (except automatically cleanable SS mesh filters (with Control water spray) and moisture eliminator and Room) supplied to the space by means of centrifugal fans. Water sprayed over the filter will be re- circulated by means of centrifugal pumps.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In addition to filter cleaning, the water spray will have an evaporative cooling effect too. This will produce some cooling effect as an additional advantage.
The supplied air will be exhausted through wall mounted gravity operated dampers (Back Draft Dampers) to maintain an overpressure of 1-2 mm of water column to reduce dust ingress.
For Toilets exhaust ventilation system shall be
provided with Wall mounted exhaust fan while
the air entry shall be through door grilles.
03. CW/ACW For Pump House Supply Ventilation shall be Pump House effected by providing Wall mounted supply fans and air exhaust through louver.
For the Electrical Rooms pressurized ventilation system shall be provided by supplying the Filtered Air through wall mounted Fan-Filter unit/s and air exhaust through Back Draft Dampers. 04. Service For Pantry exhaust ventilation system shall be building provided with Wall mounted exhaust fan while air entry shall be through louvers.
For Toilets exhaust ventilation system shall be
provided with Wall mounted exhaust fan while
air entry shall be through door grilles.
For AC Plant room, exhaust ventilation system shall be provided with Wall mounted exhaust fan while air entry shall be through louvers.
For the Electrical Rooms pressurized ventilation system shall be provided by supplying the Filtered Air through wall mounted Fan-Filter unit/s and air exhaust through Back Draft Dampers.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Air Conditioning System
Various control rooms in power station, housing a group of sophisticated and precision control panels and desks call for controlled environment for proper functioning and for personnel comfort.
Some other facilities like Service Building and Administrative Building (if any), etc will also call for comfortable environment for the occupants.
The following areas are proposed to be air-conditioned :-
a) Control room, control equipment room, Shift Charge Engineers’ rooms, computer room, UPS & Battery room, 24V DC & 220V DC Charger Room, SWAS dry panel room, CPU Control room, Laboratory room, located in the Central Control Building/Turbine Building.
b) Electrostatic precipitator control room c) Office areas, lecture rooms etc. in the service building d) AC Plant Control room e) Other Control rooms housing PLC panels
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To cater to the above requirements the following systems are proposed :-
i) A central chilled water plant to cater to the air conditioning requirement for the Central Control Building and Service Building, comprising 1x100%capacityVapour Absorption Chiller and 2 x 50% capacity stand-by Screw Chillers, 3 x 50% capacity (Two nos. working and one no. standby) condenser cooling water circulating pumps, 3 x 50% capacity (Two nos. working and one no. standby) FRP Induced draft cooling towers, 3 x 50% capacity (Two nos. working and one no. standby) chilled water circulating pumps, Non chemical water treatment equipment, one no. make-up water tank, two nos. (one working, one stand-by) make-up water booster pumps, one no. chilled water expansion tank, cooling water and insulated Chilled water piping with valves, accessories, fittings, supports, air distribution system like ducting with thermal and acoustic insulation, grilles/diffusers, volume control dampers, fire dampers, flexible connection, electric strip heater, Electrode type humidifier (wherever applicable), high efficiency filter (wherever applicable), Fresh air system and Smoke Exhaust system (wherever applicable) as applicable, steam piping with fittings, supports, insulation, PRDS and associated Electrical items etc. has been envisaged. The chilled water produced in this central Chilled water plant will be circulated through the
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coils of individual air handling units/Fan-Coil Units for the respective air conditioned rooms/areas. This Central Air Conditioning System will be operated and controlled from the AC plant Control room PLC based panels and two nos. Workstation PCs.
ii) Individual Water Cooled Precision Air Conditioners (PAC) will be provided for ESP Control room, Office and Laboratory. Condenser Cooling water will be supplied to such PAC units from the Plant ACW system. Such PAC units will be operated and controlled from their built-in Microprocessor based Control console.
iii) Air Cooled Non-Ductable Split Air Conditioners will cater to the AC requirement of Weighbridge Control room, AC plant Control room and other small control rooms housing PLC panels. These Air Conditioners will be operated and controlled from their individual hand operated Remote Control Panels.
6.7 COMPRESSED AIR SYSTEM
Compressed air requirement (IA & SA) for phase-III unit would be met by installation of one IA & one SA compressor of higher capacity, in the existing compressor house under Phase-II . The estimated capacity of each air compressor is 55 Nm3/min. (normal) at 8.0 kg/cm2(g)
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
pressure rating. The air compressors will be oil-free dry type screw compressors and will be provided with individual air receivers to absorb pressure pulsations and for acting as reserve supply of compressed air to permit continued operation following failure of the operating compressor until the standby one comes into service. Two (2) nos. HOC type dryers with automatic regeneration facility etc. will be provided for supply of clean, dry air to Control and Instrumentation as well as Service Air System.
The station service air requirement for normal cleaning purposes, atomising air medium for warm-up guns and ignitors, motive power for burner drive mechanism etc. of air pre-heaters will be met from separate plant-air header. A single line diagram of Compressed Air System is given in Drawing No.16A03-DWG-M-0006 enclosed.
6.8 FIRE PROTECTION SYSTEM
Fire protection system designed for Phase-II would be augmented and utilised for Phase-III unit also. For protection of the plant against fire, all yards and plant will be protected by any one or a combination of the following systems:-
a. Hydrant system
b. High velocity & Medium velocity water spray system.
c. Automatic fixed foam system.
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d. Fire Detection and Alarm system
e. Portable and mobile chemical extinguishers
The system will be designed as per the recommendation of Tariff Advisory Committee (TAC) of the Insurance Association of India. Applicable Codes and Standards of National Fire Prevention Association (NFPA), USA, will also be followed.
In view of vulnerability to fire and its importance in the running of the power station, effective measures are to be taken to tackle fire in the following susceptible areas :
i) The cable galleries, and
ii) Coal handling areas, mainly coal conveyors, transfer points and tunnels. For containment of fire and preventing it from spreading in cable galleries, unit-wise fire barriers with self-closing fire resistant doors will be provided. The ventilation systems, if provided in the cable galleries, will be so interlocked with the fire alarm system that in the event of a fire the ventilation system is automatically switched off. Also to avoid spreading of fire, all cable entries/openings in cable galleries, tunnels, channels, floors, barriers etc. will be sealed with non- inflammable/fire resistant sealing material.
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Fire water for Hydrant System and Spray Water System will be tapped off from existing isolating valves provided at units 3 & 4 hydrant system (02 nos. valves) and spray water system (02 nos. valves) on main hydrant and spray water header. Unit 3 & 4 hydrant system will feed pressurised water to hydrant valves located throughout the plant and also at strategic locations within the powerhouse.
Spray system network will be interconnected with hydrant network so that in case spray system network demands water, water can flow from hydrant network to spray network but not the vice-versa.
Automatic medium velocity spray system will be provided for cable galleries, cable trenches/vaults, coal conveyors, HFO/LDO storage tank etc. Automatic medium velocity sprinklers will be used for protection of burner zone of boiler front.
Category-A type automatic high velocity spray system will be provided for the following equipment :
a) Generator transformers
b) Unit auxiliary transformers
c) Station transformers
d) Auxiliary Power transformers
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Category-B type automatic high velocity spray system will be provided for the following areas:
a) Turbine oil storage tanks
b) Boiler burner front
c) Diesel tanks of DG set
d) Oil tanks of BTG auxiliaries
Automatic medium velocity spray system will be provided for the following areas:
a) Cable spreader rooms
b) Switchgear rooms
c) Coal conveyor galleries
Suitable fire detection system as necessary for all the above mentioned fire fighting system with adequate supervisory circuitry will be provided.
Automatic fixed foam installation is envisaged in fuel oil storage and handling areas.
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One centralized total flooding clean inert gas extinguishing system will be provided for Control Equipment room and Central Control room.
In addition to these, adequate number of portable and mobile (wheel mounted) chemical fire extinguishers of foam and soda acid type and carbon-dioxide type will be provided. Portable units will be placed at suitable locations throughout the plant area. The extinguishers may be used during the early stages of fire to prevent spreading.
6.9 PIPING, VALVES, FITTINGS & SPECIALTIES
The scheme of various systems such as, steam, condensate, water, oil, air, etc. have been explained earlier. Piping, valves, fittings, hangers, anchors, supports, guides etc. will be provided as required. All high pressure, medium pressure and low pressure lines will be of proven quality and suitable for conditions of operation encountered at the specific points. Pipelines running outside the powerhouse will be routed over trestles as far as practicable in order to avoid maintenance and other problems encountered with trench piping and buried piping.
Large diameter piping, like raw water, circulating water etc., will be buried. Proper protection by wrapping coating and/or other necessary corrosion protection devices will be taken. For road crossings, in case of buried piping, suitable class of hume pipes shall be used.
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6.10 MISCELLANEOUS AUXILIARIES
Turbine Oil Purification System:
A suitable centrifuge or other type of turbine oil purification plant will be provided as an auxiliary of the turbo-generator to condition the turbine oil continuously, in order to remove the water and other impurities from the system to maintain the turbine oil at the optimum condition. In addition to the above unit system, a central turbine oil storage unit comprising one clean oil tank, one dirty oil tank, one purifier unit and necessary pumps, vent fans etc. will be kept. This will also receive the refill of turbine oil from outside. The purification plant to be provided with the unit system will be complete with oil purifiers, storage tanks, filters, necessary pumping sets, vent fans, etc.
Condensate Polishing System
The proposed 660 MW Phase-III station would be provided with condensate polishing system. Condensate polisher will comprise three (3) demineralizers each operating in parallel. Any two (2) of these units will be capable of treating the full condensate flow at boiler MCR condition. Condensate polishing will ensure elimination of ammonia, silica, sodium or potassium from the condensate before being recycled to the feed water system. During normal operation all the polisher units will remain standby. In case of high condensate conductivity, it
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
will be pressed in service when two (2) of the exchanger vessels will be working in parallel and the third one will remain isolated from the system. The third vessel will act as standby and will be brought into operation when regeneration is required or during any emergency period. The polishing unit would be located at the powerhouse building. The operation of the condensate polishing system will be semi-automatic, remote/manual. Condensate Polishing Unit of Phase- III unit#5 will be controlled from unit#5 DCS.
The regeneration system will be external and located in a building[CPU Regeneration building] close to Power house building.
Chemical Feed System:
Oxygen Injection System
Complete Oxygen Dosing System would be installed for dosing oxygen at two (minimum) locations in the Condensate and in Feed water circuit of the unit, i.e. one at outlet of condensate polishing Plant and the other at deaerator outlet (suction line to feed water pumps
All Volatile type of Treatment (AVT) Systems
LP Chemical Feed System
Residual dissolved oxygen present in feed water at downstream of Deaerator can be detrimental to feed cycle equipment. In order to control the same, continuous injection of dilute solution of hydrazine is envisaged at outlet of Deaerator (suction of Boiler Feed Pumps).
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Provision would be kept to inject hydrazine at outlet of Condensate Polisher & Closed Cooling Water System for Boiler & TG auxiliaries also. However, injection will be done at one place at a time. For this purpose one (1) no. skid mounted Hydrazine Injection Systems have been envisaged.
Condensate or Boiler feed water should have proper pH in order to protect the system from corrosion. In order to control pH, continuous injection of dilute solution of Ammonia is envisaged at outlet of Condensate Polisher. Provision would be kept to inject ammonia at outlet of Deaerator also. However, injection shall be done at one place at a time only. For this purpose one (1) no.skid mounted Ammonia Injection Systems have been envisaged.
Closed Circuit Chemical Dosing System
Sodium Hydroxide from Sodium Hydroxide Preparation/Storage Tank will be dosed by gravity into CCW Make up Tank/CCW Pump Suction as required to raise the pH to the desired value. For this purpose one (1) no. skid mounted Sodium Hydroxide Injection Systems have been envisaged.
Each Skid for Sodium Hydroxide Injection System would comprise one (1) no. Solution Preparation Cum Storage Tank, complete with agitator as well as its drive motor and all other accessories.
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Hydrazine Dosing System
For preparation of diluted hydrazine solution, technical grade concentrated hydrazine liquor will be fed from Barrel to the two (2) nos. Hydrazine Mixing / Metering Tanks by means of a electrically operated Hydrazine Barrel Pump (complete with flexible hose) to be mounted on a Hydrazine Barrel/Drum. Hydrazine will be diluted if necessary, in the Hydrazine Mixing / Metering Tanks with the DM water. For preparation of dilute solution each Mixing / Metering Tank will be provided with stirrer.
From the Hydrazine Mixing / Metering Tanks the hydrazine solution will then be dosed at outlet of Deaerator and Condensate Polishing Plant by means of 2 × 100% Hydrazine Metering Pumps each. Duplex Strainers (2 × 100%) will be provided common for both pumps.
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Ammonia Dosing System
For preparation of diluted ammonia solution, technical grade concentrated ammonia liquor will be fed from Barrel to the two (2) nos. Ammonia Mixing / Metering Tanks by means of a electrically operated Ammonia Barrel Pump (complete with flexible hose) to be mounted on a Ammonia Barrel/Drum. Ammonia will be diluted if necessary, in the Hydrazine Mixing / Metering Tanks with the DM water. For preparation of dilute solution each Mixing / Metering Tank will be provided with stirrer.
From the Ammonia Mixing / Metering Tanks the ammonia solution will then be dosed at outlet of Deaerator and Condensate Polishing Plant by means of 2 × 100% Ammonia Metering Pumps each. Duplex Strainers (2 × 100%) will be provided common for both pumps.
Circulating Water Treatment System
CW and ACW pumping systems for the 1 × 660 MW unit#5, need to have treatment systems for inhibition of micro biological fouling as well as scale formation and corrosion with reference to Circulating Water. Further the control of suspended impurities in CW and ACW Systems should also be given due consideration.
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To inhibit scale formation in the CW and ACW systems, it is proposed to dose Sulphuric Acid (to convert calcium and magnesium bi- carbonate into sulphates which have higher solubility) and a suitable scale inhibitor in the circulating water. Sulphuric Acid and Scale Inhibitor will be dosed at the fore bay of CW/ACW Pump House. For this purpose one (1) no. skid mounted Scale Inhibitor Dosing System has been envisaged.
To inhibit corrosion in the CW and ACW systems, it is proposed to dose a suitable corrosion inhibitor in the circulating water. Corrosion Inhibitor will be dosed at the fore bay of CW/ACW Pump House. For this purpose one (1) no. skid mounted Corrosion Inhibitor Dosing System has been envisaged.
To provide additional protection (in addition to Chlorine dosing) against micro biological growth in CW and ACW Systems, it is proposed to shock dose a suitable Biocide in the circulating water at least once in a week for an hour. Biocide will be dosed at the fore bay of CW/ACW Pump House. For this purpose one (1) no. skid mounted Biocide Dosing System has been envisaged.
Side stream filtration for the CW system to the extent of 2.0% of circulating water flow for CW and ACW Systems is proposed in order to control of suspended impurities in the system.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Air Emission Control System
General
The Plant will be designed to comply with the current emission limits in flue gas promulgated by MoEF viz.
maximum particulate matter < 30 mg per Nm3
3 maximum oxides of Nitrogen (NOX) < 100 mg per Nm
3 maximum Sulphur Dioxide (SO2) < 100 mg per Nm maximum Mercury (Hg) < 0.03 mg per Nm3
The steam-generating unit will be provided with two sets of Electrostatic Precipitators (ESP). Each ESP will have two parallel passes, any of which can be isolated for maintenance as and when required, keeping the other path in operation. Each path will have multiple fields in series for collection of fly ash. The design of ESP will be such that the outlet dust-burden does not exceed 30 mg/Nm3 at 100% BMCR with worst coal firing and one field remaining as operational standby. The ESP will have adequate number of ash hoppers provided with electric heaters. The control of ESP will be based on microprocessor using semi-pulse device.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
To reduce the NOX emission from the Steam Generator necessary provisions in the Steam Generator design and fuel firing system along with Selective Catalytic Reduction (SCR) system will be made such that
3 the outlet NOX emission does not exceed 100 mg/Nm with worst coal
firing. The measures to be taken for NOX emission will include combination of the following methodologies - Low-NOx Burners, Over-Fire Air, Fuel Biasing, Combustion Optimization and Selective Catalytic Reduction as described subsequently.
To reduce the SO2 emission from the Steam Generator, a wet limestone, forced oxidation type Flue Gas Desulphurisation Plant (FGD) will be installed. The system will include rotary Ljungström type Gas-Gas Heater (GGH), absorber and necessary conditioning and conveying systems for Limestone and Gypsum as described subsequently.
The Hg content in Indian coals is usually low and does not require additional measures to limit Hg emission within the limits prescribed by MoEF. However, during implementation of the Project, if requirement for Hg removal is necessary, it shall be carried out along with the equipment installed for removal of particulate matter (PM), sulphur dioxide (SO2) and nitrogen oxides (NOx).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Selective Catalytic Reduction (SCR) System
Selective Catalytic Reduction (SCR) : SCR is a method of converting NOx into nitrogen and water via chemical reactions that utilize ammonia or urea, with the aid of a catalyst. After the reagents are mixed with flue gas in a static mixing device, the flue gas is passed evenly through the catalyst. Effective temperature window for SCR chemical reaction is typically between 280°C to 430° C. However the upper and lower range can vary based on actual flue gas conditions and final catalyst selection.
In this Project, it is proposed to adopt anhydrous ammonia as reagent for SCR application considering its lowest capital and operating cost.
Process Description
In the SCR process, the Reagent is injected into the flue gas downstream of the combustion unit and economizer through an injection grid mounted in the ductwork. The reagent is generally diluted with compressed air or steam to aid in injection. The reagent mixes with the flue gas, and both components enter a reactor chamber containing the catalyst. As the hot flue gas and reagent diffuse through the catalyst and contact activated catalyst sites, NOx in the flue gas chemically reduces to nitrogen and water. The heat of the flue gas provides energy for the reaction. The nitrogen, water vapor, and any other flue gas constituents then flow out of the SCR reactor. The
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
use of a catalyst leads to two primary advantages - higher NOx reduction efficiency and lowering and broadening of temperature range.
The primary components of the SCR system include:
ammonia storage and delivery system
ammonia injection grid
catalyst reactor
soot blowing system
Typical flow scheme of selective catalytic reduction system has been shown in attached Drawing No. 16A03-DWG-M-0007.
Ammonia storage and delivery system
Anhydrous ammonia is received via a tank- truck and stored in a horizontal cylindrical tank. The ammonia storage tank may be sized for 15 days of storage if ammonia distributors located nearby are considered reliable.
The liquid ammonia flows by gravity to a vaporizer and sent to the ammonia/air mixer via the accumulator. Ammonia/ air mixture is then transported to the ammonia injection grid.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Ammonia injection grid
The ammonia-air mixture is directed through a flow-balancing skid to the Air Injection grid (AIG), where it is injected under pressure. The AIG consists of a network of pipes or lances connected in parallel and perforated with several holes or nozzles. The lances are placed in a grid formation across the width and height of the ductwork. Injectors are constructed of stainless steel since they are subject to high temperatures and flue gas impingement, which cause erosion, corrosion and degradation of structural integrity.
Uniform distribution and mixing with flue gas is critical to maintain desired performance of the SCR. Cold gas flow modeling and numerical flow modeling are generally performed for the AIG and SCR system to ensure uniform mixing and dispersion before the gases enter the SCR reactor.
An essential part of an AIG system is the controller used to regulate ammonia injection. Boiler load, inlet NOx, and inlet gas temperatures set the feed-forward signal to establish the base ammonia injection rate. A feedback signal measuring the SCR outlet NOx concentration is used to trim the base ammonia injection rate.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Catalyst reactor
The catalyst itself is the key component of the SCR system. The catalyst composition, type and physical properties affect performance, reliability, catalyst quantity required and cost which will be optimised by the SCR system supplier.
Soot blowing system
Retractable type Soot blowers or sonic horns are installed in the SCR reactor to remove particulates that may mask or block active catalyst surfaces and gas passages.
FLUE GAS DESULPHURISATION
(FGD) General
For this project, in order to restrict SO2 concentration within 100 mg/Nm3, a Lime stone based forced oxidation flue gas desulphurization (LSFOFGD) plant has been selected which is also most popular worldwide for similar applications.
Process Description
The limestone based forced oxidation type Flue Gas Desulphurisation plant basically consists of the following major sub-systems:
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Flue Gas System
Absorber
Process Water System
Limestone System
Gypsum System
Drain Collection System
Typical flow scheme of Flue Gas Desulphurisation Plant has been shown in attached Drawing No. 16A03-DWG-M-0008.
Flue gas system
The raw/untreated flue gas from the ID fan outlet will be led to the rotary Ljungström type, Gas-Gas Heater (GGH) and thereafter to the absorber inlet. From absorber outlet, the Sox cleaned cold flue gas is routed through GGH such that flue gas temperature is raised prior to final exhaust to atmosphere through chimney flue can. Dampers will be installed in the raw, clean gas and bypass ducts for isolating/bypassing the FGD Plant. All raw and clean gas ducts will be adequately insulated to minimize droplet condensation at GGH inlet. The ID fan head will be suitably selected considering additional pressure drop in FGD plant.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Absorber
The raw flue gas enters the spray tower absorber after being cooled in the GGH. In the absorber the cleaning of raw flue gas is performed by spraying the limestone/gypsum slurry as fine droplets into the gas flow. The slurry is pumped through a number of nozzles, where fine droplets are formed. The slurry absorbs the pollutants in the flue gas, drops down through the absorber and is collected in the absorber sump.
The nozzles are arranged in multiple spray banks. Each spray bank is connected to a dedicated recirculation pump. The flue gas flows upwards through the scrubbing section (absorption zone) in a counter current mode and mixes with the recirculated limestone/gypsum slurry.
The absorbed SOxreacts with limestone to form calcium sulphite which is oxidised to calcium sulphate (CaSO4) by air followed by crystallisation of gypsum from the supersaturated solution.
In the top part of the absorber, the gas passes through a mist eliminator where entrained absorber slurry droplets are collected. The Sox cleaned flue gas leaving the absorber at the top with saturated water will be reheated in the GGH and discharged to the atmosphere through the stack.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In the absorber sump the aeration with oxidation air is performed and fresh limestone slurry will be fed according to the actual demand. To prevent solid settling the absorber sump is equipped with a number of agitators which also serve to distribute the oxidation air in the sump.
Process water system
Water will be consumed mainly due to the evaporative cooling of the flue gas at the inlet to the absorber and due to discharge of gypsum slurry. The varying quantities and the required pressure levels will be provided by three (3) Process water pumps (two working, one standby) taking suction from a process water tank.
Limestone system
Limestone from mines (<1000mm) will be transported by truck, unloaded and directly conveyed to the crusher house where one of the two 100% capacity crusher will crush limestone to (-20 mm) size. The crushed limestone will be conveyed to either of the two (2) Limestone silos by Bucket elevators. Crushed limestone will be transported from silo to the wet ball mills (one working, one standby).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
In the wet ball mills, limestone will be ground and mixed with water to form slurry. Limestone slurry produced in the wet mills will be stored in limestone slurry tanks and from there transported to the absorbers by pumps by Two (2) nos. limestone slurry pumps (one operating, one standby).
Gypsum system
To regulate the solids content in the absorber, gypsum slurry is discharged from the absorber by means of absorber bleed pumps. When the solid concentration rises above a preset value, the bleed pumps will start automatically. In case the solid concentration falls below the preset value, the pumps will be shut down.
The gypsum slurry from the absorber sump will be pumped out by two (2) absorber bleed pumps per absorber (one in operation and one standby) to the gypsum hydrocyclone station for the purpose of dewatering.
The gypsum slurry underflow from the hydrocyclone station will be fed to the vacuum belt filter. Overflow of the hydrocyclone stations will be split into two parts: the larger portion will be stored in a common reclaim water tank and the smaller portion will be led to waste. From the reclaimed water tank, reclaimed water will be pumped back to the absorbers.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The gypsum formed, having moisture content about 10%, will be transported to the gypsum storage by belt conveyors. The gypsum will be stored under a closed storage shed having stacking / reclaiming/ conveying system and finally loaded on to trucks for disposal.
Drain collection system
When the absorber is taken out of operation, all slurry lines will be automatically flushed with process water. In addition, splash and leak water may occur in the absorber, limestone slurry preparation and gypsum dewatering areas. These will be collected in drain pits and sent back into the FGD system.
Mill Reject Handling System
Dense phase pneumatic conveying system would be employed for handling of the mill rejects. Each mill reject discharge hopper shall be fitted with a positive pressure pneumatic conveying vessel which shall discharge the mill rejects through pipe lines in the storage silo(s). The proposed 660 MW unit#5 shall be provided with silo(s) having collection capacity of 24 Hours. The transmitting vessel shall operate on level probe mode with timer back up.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
. Two nos.[1W + 1S] 20 m3/min capacity MRS conveying compressors have been installed under Phase-II in the Plant Air Compressor House. One additional compressor of identical capacity would be installed in the compressor house to meet the requirement of unit#5.
For the Steam Generator of extension unit#5, coal mills would be arranged either on each side of the boiler or on the Front side of boiler. Each mill shall be provided with collection and transportation equipment comprising of Pyrite Hopper with water spray arrangement, plate valves at inlet & outlet and a denseveyor or similar pneumatic bulk conveying equipment/ vessel. Each vessel shall be connected to a storage bunker/silo via conveying pipeline having mild steel construction with Alloy CI bends. The storage silo in MS Construction & 3 mm SS Liner on conical portion shall be provided with a hand lever operated bunker discharge gate at its outlet to discharge mill rejects into a truck. Mill rejects collection & discharge system shall be designed to ensure sequential automatic operation of the coal mill discharge gates for flow of rejects into the reject spout. The necessary mill isolation dampers/valves, to facilitate automatic continuous or automatic intermittent discharge of rejects to the storage silo will be provided.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Mill Reject Handling System (MRHS) for unit#5 would be controlled from the existing Phase-II MRHS control system by using spare I/Os or augmenting I/O cards and modifying the logic.
Hydrogen Generation Plant
The hydrogen generation plant provided for Phase-II units will be used for the proposed Phase-III station to meet the requirement of hydrogen gas required for cooling the generator.
Elevators
One (1) goods-cum-passenger elevator will be installed for the boiler. One (1) elevator for ESP control room building and one (1) for ESP roof would be provided. In addition, one goods-cum-passenger elevator will be installed at the end of the powerhouse building. Besides, an elevator of rack and pinion type would be provided for the 275 m single-flue stack.
Cranes & Hoisting Equipment
Two (2) EOT cranes suitable for handling the heaviest equipment (except Generator stator) are proposed to be installed in the turbine hall and will be used for erection/maintenance of the TG hall equipment. Estimated rating of the crane is 110/25 Tonnes. The Generator stator is lifted from outside ‘A row’ and moved inside the
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Power House Building with the aid of a moving trolley and erected on the Generator Foundation.
Conventional and special type of cranes required for maintenance of certain SG and TG equipment such as FD/PA/ID fans, condenser water box, ESP transformer rectifier sets, etc. will be supplied by the respective equipment supplier. EOT/ Under slungcranes as required for maintenance would be provided in the circulating water (CW) pump house, store and workshop.
Maintenance hoists of suitable capacities have been considered for all other pump houses and other places such as coal handling plant transfer points, water treatment plant, ash handling facilities etc. Monorails for lifting heavy motors and other equipment within the powerhouse not covered by EOT crane such as miscellaneous pumps, heat exchangers, etc. will also be provided. Suitable rails will be provided, if necessary, on floor for bringing the horizontal feed water heaters under the approach of EOT crane.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
6.11 ASSOCIATED FACILITIES
Workshop For achieving higher availability of the plant, the plant maintenance will be done following a concept of unit exchange system for repair and maintenance.
Under this system, the defective components will be replaced immediately by sound ones from the stores. The defective components will thereafter be repaired in the workshop and sent back to the stores. Following this system, two types of activities namely maintenance and reconditioning will be physically separated thereby speeding up maintenance activity.
Existing workshop would be utilised for Phase-III extension unit.
General Stores
Both covered and open space will be required for storage of various materials required for construction as well as operation and maintenance of the plant. While the construction stores will be temporary, the other stores will be permanent. Consumables, tools and tackle and other relevant items required for the 660 MW unit size will also be kept in the stores.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The stores will broadly have the following divisions to house material of different categories :
1. Heavy materials store will house boiler tubes of various sizes, boiler and auxiliary parts, turbine heavy parts, stainless steel plates, conveyor belt and other coal handling equipment spares, dumper and dozer spares, motors, transformer windings, fire fighting equipment, insulators and hardware connectors, copper and aluminium conductors and similar heavy items.
2. Mechanical, electrical and instrument stores will accommodate small spare parts for mechanical and electrical equipment and instruments respectively.
3. Fast moving spares store will house electrodes and welding materials, blow lamps, bulbs and light fittings, grease, soap, battery, cotton waste and cloth, brooms, motor vehicle spares, gas cylinders, gloves, aprons, safety belts, goggles, ropes, refill for the fire fighting equipment etc.
4. Chemical stores will house alum, lime, morpholin/hydrazine resin, spirit and other chemicals required for steam, feed water and condensate system and chemical laboratory.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
5. Civil engineering store will accommodate cement, sanitary materials, filtering sand and filters, pipe and pipe fittings etc. for water supply.
6. Refractories and lubricants will be stored under separate covered sheds.
New stores both covered and open shall be constructed. Open storage- yard will be provided to store structural steel, rail, sleeper, heavy castings, cable reels etc.
Suitable enclosures will be provided for storing the insurance spares. Arrangements will be made for storing items like relays, motors, and instruments under controlled atmospheric conditions.
Thermal Insulation
Adequate insulation will be provided to reduce heat losses from the equipment, piping and ducts and to ensure adequate personnel protection in critical areas. Insulation will be so selected that the covering jacket surface temperature does not exceed the surroundings ambient temperature by more than 15 °C.
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Pollution Monitoring System
Monitoring of various environmental aspects is of prime relevance in setting-up the proposed units. The following aspects will be critically monitored :-
• To keep watch on the state of pollution • To generate data for predictive and corrective measures • To quantify environmental impacts
The important area requiring periodic/conditions monitoring are:- • Stack emission • Ambient air quality • Disposed water quality
Electronic smoke density analyser and gas analyser equipment is proposed to be provided for continuous monitoring of particulate
matters at the outlet of ESP. Sample analysis of SO2 and other pollutants from chimney will be carried out. Wastewater will be checked for any harmful pollutants before discharging to outfall.
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An oil/water separation unit has been installed near fuel oil tank/pump house area under Phase-II in order to reclaim waste oil as far as practicable. Oil thus separated will be returned to the fuel oil tank and used. Water separated out from the oil-water separation unit will be suitably treated for further use in CHP dust suppression, horticulture etc.
Coal Handling and Ash Handling Plants will be equipped with dust extraction/suppression system to combat fugitive dust.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Annexure-6.1 Sheet 1 of 9
SALIENT FEATURES OF AUXILIARIES PLANT & EQUIPMENT
1. Intake/Plant Water System (For Phase-II & III units together)
Intake Raw Water Pumps :
Source : From Bhagirathi River. Type : Vertical wet pit mixed flow multi-stage. Fluid Handled : River water Capacity : 3700 m3/hr each Number : Three (3) [2 working + 1 operational standby]. Drive : Electric motor, 3.3KV/415 V, 3 Ph., 50 Hz.
Raw Water Reservoir :
Type : Clay lined. Number : Three (3) Capacity : 1601182 m3
Raw water Pumps : 4 (3W+1 S) – capacity 1600 m3/hr
Clariflocculator :
Type : High Rate Solid Contact Clarifier Capacity : 2000 m3/hr. Number : Three (3) Construction : RCC for conventional clariflocculator.
Clarified Water Storage Tank :
Type : RCC (Partly underground) Twin chamber Capacity : 63,000 m3
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Annexure-6.1 Sheet 2 of 9
DM Plant :
Type : Combination of RO, MB system.
Control Room : Indoor
Capacity : Two (2) streams of 100 m3/hr each, RO stream consisting of ultra-filtration, units activated carbon filters, and mixed bed exchanger. A common atmospheric degasser is also provided. The system would also include acid and alkali handling and storage facilities.
Operation : PLC based from control room.
DM Water Storage Tanks :
Type : Vertical cylindrical steel tank with inside rubber lining. Capacity : 2000 m3 Numbers : Two (2)
Condensate Storage Tank :
Type : Vertical steel tank with inside rubber lining. Capacity : 750 m3 Numbers : Three (3) [ One for each unit of Phase-II & Phase-III]
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Annexure-6.1 Sheet 3 of 9
Cooling Water Circuit : (For Phase-III unit)
Cooling Tower :- Type : Natural Draft Nos. : One (1) Cooling Water Quality : Clarified water Total circulating water flow : 80,000 m3/hr. Design cooling range : 43 °C to 33 °C i.e. 10 °C Approach : 5 °C
Cooling Tower make-up Pumps:- Type : Vertical, centrifugal Fluid Handled : Clarified water Capacity : 1300 m3/hr. each Number : 4 (3W+1S) for Phase-II & III
Circulating Cooling Water Pumps :- Type : Vertical Wet Pit Fluid Handled : Clarified water Capacity : 40,000 m3/hr. each Number : 2 W+ 1 S
Auxiliary Cooling Water Pumps :- Type : Vertical wet pit installation. Flow : 4000 m3/hr. Fluid : Clarified water Number : Two (2) [1 working + 1 standby]
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Annexure-6.1 Sheet 4 of 9
2. Coal Handling Plant (For Phase-II & III units together)
Conveying System :
Type : Twin stream conveying system, hydraulic motor driven.
Capacity : 2000 Tons/hr.
Crushers :-
Type : Ring granulator
Number : Four (4) (2 working + 2 standby)
Capacity : 1000 TPH each
Input coal size : (-)300 mm
Output coal size : (-) 20 mm
Vibrating Screen :-
Type : Roller screen type.
Number : Four (4) (2 working + 2 standby)
Capacity : 1000 TPH
Stacker-cum-Reclaimer :-
Type : Hydraulic motor-driven rail-mounted unidirectional having slewing and adequate lifting arrangement.
Stacking Capacity : 2000 TPH
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Annexure-6.1 Sheet 5 of 9
Reclaiming Cap : 2000 TPH Number : Two (2) Coal size : (-) 20 mm
3. Solid Waste Handling System Equipment (For Phase-III unit)
Ash Handling System :
Basic Design Parameters : Max. Bottom Ash generation 46.8 Tons per hour. Eco Ash- 11.7 TPH
Max. Fly Ash generation–234 Tons/hr.
Type : Water impounded/extraction and wet disposal for Bottom Ash and dry extraction and dry/MCS disposal of fly ash. MCS during exigency only.
Bottom Ash cleaning : Intermittent (2 hrs. of operation per shift including flushing)
Fly Ash cleaning : Auto-sequential operation with 5 hours of operation per shift.
Fly Ash Handling System :
Intermediate Surge Hopper :-
Type : MS construction
Number : Two (2)
Capacity : 250 T each
Outlet : Six (6) [4W + 2S] for Pneumatic conveying to terminal silos.
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Annexure-6.1 Sheet 6 of 9
Fly Ash Terminal Silo:-
Type : RCC construction
Number : One (1)
Capacity : Ten (10) hours’ storage capacity each unit considering fly ash generation for the station at rated load with worst coal – 2400 MT.
Outlet : Two (2) for closed truck disposal. One (1) for open truck disposal. Two (2) spares
4. Main and Start-up Fuel Oil System (For Phase-III unit)
LDO Storage Tanks : (Common For Phase-II & Phase-III)
Capacity : 2000 m3 Number : Two (2)-Existing
LDO Unloading Pump
Type : Positive Displacement Type Number :4 x 100 m3/hr + 2 x 25 m3/hr.
LDO Pressurising Pump
Type : Positive Displacement Type Number : 2 x 24 TPH
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Annexure-6.1 Sheet 7 of 9
HFO Storage Tanks : (Common For Phase-II & Phase-III)
Capacity : 2000 m3
Number : Two (2) - Existing + Two (2)-Under Phase-II
HFO Unloading Pump
Type : Positive Displacement Type
Number : 4 x 100 m3/hr + 2 x 25 m3/hr.
HFO Pressurising Pump
Type : Positive Displacement Type
Number : 3 x 50 TPH[Phase-II] + 1 x 55 m3/hr.[Phase-III]
5. Auxiliary Equipment
Turbine Hall EOT Crane :
Capacity :-
Main Hook : 110 T Auxiliary Hook : 25 T Number : One (1)
CW Pump House EOT Crane :
Number : One(1)
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Annexure-6.1 Sheet 8 of 9
Fire Protection System :
Fire Hydrant System :-
Type : Common for Phase-II & III units Hydrant Pumps :
Main PlantAir Compressor : (For Phase-III unit)
Type : Screw type – oil-free, dry type. Number : 2 (1 IA + 1 SA) Estimated Free air capacity : 55 Nm3/min. each At normal pressure and Temperature
Rated discharge pressure : 8.0 kg/cm2) (g) Location : Indoor Assumed inlet air temp. : 45 °C (max.) Air Receiver : One(1) per compressor. Air Drying Plant : One stream of capacity 55 Nm3/min. fully automatic type.
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Annexure-6.1 Sheet 9 of 9
Hydrogen Generation Plant : (For Phase-II & Phase-III units)
Type : Bipolar Electrolytic module or equivalent. Electrolyte : KOH Capacity : 2 units of 10 m3/hr.
Accessories : Bottling arrangement of H2 & O2 in cylinders.
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SECTION-7 ELECTRICAL SYSTEM & EQUIPMENT
7.1 INTRODUCTION
The Thermal Power Station at Sagardighi is proposed to be expanded by one (1) more generating unit of 660 MW in addition to the 2 x 500 MW unit nos. 3 & 4 of Phase-II.
Power from the proposed power station will be available at 400 kV level at the bus bars of the existing 400 KV EHV switchyard of the power plant. Power from this switchyard would be evacuated at 400 kV level through existing lines / new double circuit line of WBSETCL.
The existing 400 KV switchyard of Phase-II will be extended to accommodate the following bays:
(a) 1 No. Generator Transformer (b) 1 No. Station Transformer (c) 2 Nos. future Lines/bays
The 400 kV switchyard of the Phase-II has spare space for accommodating bays for use in Phase-III. So the implementation of Phase-III calls for procurement of 400 kV bay equipment and foundation for the new generator transformer (GT-5) and new station transformer (ST-5).
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Generator will be directly coupled to the steam turbine and will have a nominal rating of 660 MW at 0.85 (lag). Generation voltage will be 21 kV or as per the manufacturer’s standard with variation in frequency of +3% and –5%, 3 Phase. The generator will be connected to the 400 kV switchyard bus through 3x270 MVA, 420/3 kV/21 kV generator transformer (GT). Connection between generator and GT low-voltage terminal will be done by isolated phase bus duct and that between the high voltage terminals of GT and the 400 kV switchyard will be done by ACSR Moose conductor.
Three voltage levels viz. 11000 V, 3300 V and 415 V have been envisaged to supply power to unit and station auxiliaries. Scheme of the entire electrical power distribution arrangement to the plant including auxiliaries has been shown in Drawing No.16A03-DWG-E- 0001 and a brief technical particular of major equipment is given in Annexure-7.1.
During normal operating condition of generator, the power supply to unit auxiliaries will be either from the generator terminal through two (2) unit transformers (UT) or from the grid through existing station transformers of unit 3 &4 as well as proposed station transformer (ST- 5) of unit 5. UT will be directly connected to generator bus duct and will be rated for 40/50 MVA, 21 kV/11.5 kV and with ONAN/ONAF cooling. In order to take care of grid voltage variation, the transformer will be provided with On-Load tap changer.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
UT will supply power to unit auxiliaries like ID fan, FD fan, PA fan, CW pump etc., through required number of 11 kV breakers. Balance HV motors like Mill, Compressor, CE pumps, DMCW pump & ACW pumps will be fed from 3300 V unit and station auxiliary switchgears. The MDBF pump shall be fed from 11 kV station switchgear. Ash slurry, etc will be fed from 3300V station auxiliary switchgear.
Power supply to station load as well as start-up power will be drawn from the 400 kV grid using existing two (2) nos. 80/40/40 MVA three- winding Station Transformer (ST-3 & ST-4) & through proposed one (1) no. 90/45/45 MVA three-winding Station Transformer (ST-5). Power for station and unit auxiliaries will be supplied through 11 kV switchgear, 11 kV/3.3 kV & 11 kV/433 V transformers, 415 V power and motor control centres. After synchronisation of the unit, unit transformer will take over the load barring those systems meant for feeding from station transformer. All electrical equipment shall be rated for 50 C ambient air temperature.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
7.2 DESIGN PARAMETERS
Following criteria / data will be used in engineering the electrical system and equipment for 1x660 MW power plant.
System Configuration
The basic system connection is shown in the Single Line Diagram for 400kV Substation (Drawing No. 16A03-DWG-E-0002) and Single Line Diagram for Auxiliary Power Distribution (Drawing No. 16A03- DWG-E-0001). The scheme has been developed considering the requirement of efficient and reliable operation of the plant under normal as well as adverse system conditions.
The system configuration is based on the concept of single contingency of operation, i.e. failure of any auxiliary transformer or supply feeder pertaining to any sub-system will not affect the full load operation or start- up/shut down operation of any unit.
400 kV System Data
a. Maximum short circuit level : 50 kA for 1 sec.
b. Maximum system voltage : 420 kV
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Voltage at Load Terminal
a. At full unit load, the voltage will not drop below 90% of the rated voltage. b. At light unit load, the voltage will not exceed 110% of the rated voltage. c. During starting of large motor, the voltage will not drop below 80% of the rated voltage.
System Parameters & Variations
System parameters for utility systems are detailed below:-
System Voltage & Sl.No. Fault level Grounding Frequency
Non 11000 V ± 10%, 3Ph, 3-wire, 40 KA a. effectively 50 Hz - 5% to +3% (3 sec) earthed
Non 3300 V ± 10%, 3Ph, 3-wire, 40 KA b. effectively 50 Hz - 5% to +3% (3 sec.) earthed
415 V ± 10%, 3Ph, 4-wire, 50 KA Effectively c. 50 Hz - 5% to +3% (1 sec) earthed
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
240 V ± 10%, 1Ph, 2-wire, 50 KA Effectively d. 50 Hz - 5% to +3% (1 sec) earthed
Combined voltage and frequency variation 10% (Absolute sum)
220 V DC (–) 15% to (+) 10%, 25 kA e. Unearthed 2-wire (1 sec)
Environmental Condition
Electrical equipment will be installed in a hot, humid, and tropical atmosphere, heavily polluted at places with coal dust and/or fly ash and will be designed accordingly.
The equipment will be capable of continuous full load operation under the following site conditions:-
Finished Grade Level : 34.5 M above MSL Annual Ambient Air Temperature : (+) 46.1C (Max.) (+) 3.9C (Min.) Relative Humidity : 87% (Max.) 40% (Min.) Wind Velocity : 47 km/hr. in accordance with I.S.: 875 Seismic Zone : Zone-III in accordance with I.S.: 1893, Part-3
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Sensitive electrical and electronic devices will be placed in controlled environment such as control room, electronic equipment room, etc. as required.
Codes and Standards:
Electrical equipment will be designed in accordance with the latest applicable Indian Standards (IS), International Electro-Technical Commission (IEC) standards and publications of Central Board of Irrigation & Power (CBIP).
Electrical installation work will conform to the provisions of Indian Electricity Act, relevant I.S. Codes of practice, CEA regulations and also comply with other statutory rules and regulations, as applicable.
7.3 ELECTRICAL SYSTEM
7.3.1 Generation System & Power Evacuation:
Proposed power station will have 1 x 660 MW STG unit generating power at 21 kV. These units will be connected to 400kV outdoor switchyard in the plant for evacuation of generated power. The electrical single line diagram (Drawing No. 16A03-DWG-E-0002) indicates the arrangement of evacuation of power from the proposed
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
1x660 MW unit through proposed extension of existing 400 kV switchyard. The switchyard will include one additional feeder each for Generator Transformer and station transformer of Phase-III. The station layout considers power evacuation through present line feeders and proposed D/C 400kV line feeder of WBSETCL at 400 kV level from the switchyard. The existing switchyard already has spare space for bays for the above line feeders. Details are shown in the Drawing No.16A03-DWG-E-0002.
Existing switchyard control building will be used to house equipment associated with substation automation system, AC/DC auxiliary system. AC Kiosk will be provided in the switchyard which will house the control, metering and protective equipment. For reliable communication and carrier aided distance protection of 400kV remote end breakers, power line carrier communication equipment (PLCC) / (FOTE) system will be installed in the switchyard.
In the Power House, each generator will be directly coupled to the steam turbine and will have a nominal rating of 660 MW at 0.85 p.f. (lag). Generation voltage will be 3-phase, 21 kV with variation of ±5%, at frequency 50 Hz with variation of + 3% to - 5%. The excitation system will be static/brushless type and will be selected for an ideal rate of response, accuracy and sensitivity during normal as well as transient state of operation. The generating unit will be connected to 400kV switchyard through a three-phase bank of three (3) single phase,
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
21/(420/√3) kV step-up generator transformers (GT) of 270MVA each, having the total capacity of GT as 810MVA. Connection between generator and generator transformer low voltage terminals will be through isolated phase generator bus duct and between the high voltage terminals and the switchyard by outdoor overhead ACSR conductors.
7.3.2 Power Distribution System: Three voltage levels viz. 11000V, 3300V and 415V have been envisaged to supply power to the unit and station auxiliaries in the power plant. According to the kW rating of motor, its rated voltage will be as follows: kW rating of AC Motor Rated Voltage Motor kW 0.2 kW 240 V , 1 phase 0.2 kW Motor kW 200 kW 415 V, 3 phase 200 kW Motor kW 2000 kW 3300 V, 3 phase Motor kW 2000 kW 11000 V, 3 phase
During starting of the unit the start up power will be drawn from 400 kV bus through 420/11.5/11.5 kV station transformer. The generator will then be synchronized to the 400 kV system through generator transformer breaker and will gradually take over the unit loads, as part of normal operation. In the event of unit trip, power will be drawn from 400 kV bus through this station transformer for coasting down of
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
the unit. One (1) station transformers will be provided to feed the station auxiliaries and unit start up / shutdown facilities. During complete blackout, emergency DG set will be automatically started and will provide power to essential loads for carrying out safe shutdown of the unit.
The power supply to unit auxiliaries will be from the 11kV unit switchgears fed by the unit transformers (UTs). UTs will be directly connected to the generator bus duct. The capacity of the unit transformers (UTs) has been selected on the basis that the unit auxiliary load corresponding to the maximum continuous rating of the unit with due consideration to the starting of the largest motor, system fault level, available breaker capacity and voltage regulation requirement.
The station auxiliary loads will be fed from the 11kV station switchgear. Separate 3.3kV and 415V switchgears will feed the loads for Ash Handling Plant, WT Plant etc., located in the respective plants as required.
Motors rated 200 kW and below will be supplied from 415 Volts system. For this purpose, 11kV/433Volts, 3 phases, 50 Hz, dry-type LV auxiliary transformers rated 2.5 MVA, 2 MVA, 1.6 MVA and 1 MVA will be used as required. These transformers will receive power from the 11kV buses. The LV side of these transformers will be connected to
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
the respective LV Switchgear / Power Control Centre (PCC) / Power- cum-Motor Control Centre (PMCC) through non-segregated phase bus duct. These transformers will be provided with off-circuit tap changing device in five (5) equal steps to take care of voltage variation to the extent of ± 5% in steps of 2.5% per tap.
Brief technical particulars of major equipment associated with the Electrical System are given in Annexure-7.1.All electrical equipment shall be rated for 50C ambient air temperature.
7.3.3 Electrical Equipment
Generator
The generator will be a two-pole, three-phase unit rated for 660 MW at 0.85 p.f. lag, 50 Hz. The nominal voltage rating will be 21 kV or as per manufacturers’ standard.
The generator shall be capable of continuous safe operation at rated output and power factor under any of the following conditions:-
a. Terminal voltage variation of ± 5% of the rated value. b. Frequency variation within -5% to +3% Hz. c. Absolute sum of combined voltage and frequency variation of 5%.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The generator neutral will be grounded through a distribution transformer having a secondary loading resistor limiting the ground fault current to 5-10 amps.
Excitation system shall be of state-of-the-art microprocessor based system of latest version. The generator stator will be water cooled and stator core & rotor winding will be hydrogen cooled. The generator excitation system will be selected to provide the following basic requirements.
a. Maintain the generator terminal voltage constant within 0.5% of the pre-set value over the entire load range of the machine.
b. The response time must be short so that the automatic voltage regulator (AVR) can control the generator during system disturbances or transients in which rapid changes in excitation are required to maintain system stability margins both in steady state and transient condition.
c. The AVR shall be PLC based, designed for continuous acting and high speed with 100% redundancy. The AVR shall have two (2) Auto and one (1) Manual channel with facility of automatic changeover from Auto-1 to Auto-2 or from Auto to Manual.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
d. Each excitation system channel shall be designed to continuously carry at least 110% of the rated machine excitation current at the rated output of the machine and higher currents for short time duty. The rated voltage shall be at least 140% of the machine excitation voltage.
e. The excitation system shall be provided with power system stabilizer for achieving the dynamic stability of the system under most stringent conditions of operation in the phase of disturbance created by short circuits conditions, load rejections, switching on/off of transmission lines.
Transformers
Generator Transformer
The generated voltage of 21 kV will be stepped-up and fed to 400 kV switchyard by a step-up two-winding generator transformer (GT) connected to the generator through isolated phase bus duct. GT will be a bank of three single-phase units each rated for 270 MVA. The transformer will have OFAF type of cooling with ‘Off-circuit’ tap change system having taps (+) 5% to (–) 5% in 4 equal steps on HV side. Vector group will be YNd11. The high voltage terminals of the transformer will be connected to the 400 kV outdoor switchyard by overhead conductors. Lightning arresters will be provided on primary terminals of the transformer to protect it from atmospheric disturbances.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Selection of the rating of generator transformer has been done considering that the full generated power can be transmitted by GT if it is required at any time. The rated short–circuit withstand capability at its terminals shall be considered as 2 seconds.
One spare 270MVA, 21 kV / 420/√3 kV single-phase, 50Hz generator transformer, without external cooler bank, will be kept as reserve for use in contingency. This spare unit will be located in the transformer yard and will be kept charged.
Unit Transformer
During normal operating condition of generator under unit concept, the power supply to unit auxiliaries will be given from the generator terminals through the unit transformers (UT). UTs will be directly connected to the generator bus-duct. The Each unit transformer will be rated 40/50 MVA, 21/11.5 kV, ONAN/ONAF cooled, 3-phase, 50 Hz, provided with On-Load tap change system on the high voltage side to take care of voltage variation to the extent of ±10% in 16 equal steps for OLTC. The capacity of the unit transformer has been selected on the basis of the unit auxiliary load with due consideration to the starting of the largest motor, available breaker capacity and voltage regulation requirement.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Estimated short circuit capability to withstand rated short–circuit at its terminals for a time duration considering the actual duty to which the transformer is subjected depending upon the generator’s initial loading and other design parameters under AVR / Manual mode of operation have been considered as 3 seconds.
Station Transformer:
Power requirement for 5th unit start-up or shutdown and station auxiliaries will be drawn from the 400 kV grid thru’ the existing two (2) nos. Station Transformer (ST-3 & ST-4) as well as from proposed one (1) no. Station Transformer (ST-5). Station Transformer (ST-5) will be connected to the 400kV switchyard through ACSR Moose conductor and LV sides of ST-5 will be connected to station switchgear through segregated phase bus duct. The station transformer will be three winding rated 90/45/45 MVA, 400/11.5/11.5 kV, ONAN/ONAF cooled, 3-phase, 50 Hz, provided with On-Load tap change system on the high voltage side to take care of voltage variation to the extent of ±10% in 16 equal steps @ 1.25% per step.
Selection of the rating of station transformer has been done considering that, if one ST is out of service other STs will be capable of sharing total station loads of three units. The rated short–circuit withstand capability at its terminals shall be considered as 2 seconds.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Bus Duct
Generator Bus duct (Isolated Phase):
The generator will be connected with the generator transformer and unit transformer through bus duct. The bus duct will be of isolated phase, continuous type with aluminium conductor in aluminium enclosure, partially indoor & partially outdoor. Lightning arrestors and surge protection cubicle (where recommended by generator manufacturer) of proper rating will be provided at a location as close as practicable to the generator terminals. Delta run of bus duct will be achieved prior to connection with 1-phase GTs. Neutral side bus duct run from generator terminals will terminate at the Neutral Grounding Transformer (NGT) cubicle. CTs will be provided at both phase & neutral sides of bus duct
The main section of bus from generator to generator transformer will be suitable for 25000 Amp. The tap-off connection to the unit transformer will be suitable for 1600 A. Generator Bus duct shall be capable of withstanding short circuit current for 3 sec. The maximum temperature of the bus conductor will be limited to 105 °C for silver plated joints and 90 °C for other joints and that of enclosure will be limited to 80 °C.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The short circuit rating of the generator main bus duct will correspond to higher of the fault current contributions from generator or transformer side while the tap-off bus ducts will be designed for sum of the fault contributions from generator and GT side.
11/3.3 kV Bus Duct (Segregated-phase):
The 11 kV side of Unit Transformer (UT) and station transformer (ST- 5) will be connected with the associated unit switchgears and station switchgear through phase segregated bus duct. The maximum temperature of bus conductor will be limited to 105 °C for silver plated joints and 90 °C for other joints. In case of enclosure the maximum temperature will be limited to 80 °C.
Similarly the LV side of unit and station auxiliary transformers will be connected to 3.3 kV switchgears through 3.3 kV segregated phase bus ducts. The rating of bus duct for connection of unit transformer with 11 kV unit switchgear is envisaged as 3000 Amp and station transformer with 11 kV station switchgear is envisaged as 2800 Amp.
Tie connection between existing station switchgears and proposed station switchgear will be done through segregated phase bus duct of suitable rating.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Switchgears
The drives for auxiliary equipment, having capacity above 200 kW will be fed either from 11 kV or from 3.3 kV system and those with capacity 200 kW and lower will be fed from 415 V, 3-phase, 4-wire system. Suitable HV and LV switchgears, as described below, will be provided for operation of these motors.
a. 11 kV & 3.3 kV Switchgears
Power received at 11 kV from unit transformer will be fed to the respective 11 kV unit switchgear through circuit breakers for further distribution to high voltage motors and also to transformers intended to step down this voltage to 3.3 kV & 415 volts. These feeders will be controlled by vacuum circuit breakers. Two (2) nos. 11 kV station switchgear will be required to provide start up power and station auxiliaries. This switchgears will be fed from proposed station transformer (ST- 5) and also from existing station transformers (ST-3 & 4) via existing station switchgear. This new station switchgear will also be located in power house switchgear room and will be connected to 11 kV unit switchgear through bus ducts. There will be one (1) 3.3 kV unit switchgear and one (1) 3.3 kV station switchgear to provide power to all 3.3 kV common auxiliary load such ac conveying compressor, HP ash water pumps, IA and SA compressors etc.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The 11 kV & 3.3 kV system will be designed for 40 kA fault level. The interrupting capacity of 11 kV & 3.3 kV breakers has been selected as 40 kA considering the maximum possible fault contribution from the system and also the motors under the most severe fault condition. Motors rated above 200 kW shall be connected to 11 kV & 3.3 kV switchgear. Short-circuit withstand capability of 11 kV & 3.3 kV equipment shall be 3 second. Inter-changeability will be possible with breakers having identical rating. Duplicate feed will be provided for 11 kV & 3.3 kV switchgears where considered necessary.
b. 415V Switchgears
415 volts supply from LV auxiliary transformers will be fed to the respective 415V switchgear bus through air circuit breaker to facilitate power distribution to different motors and other electrical loads at the downstream. LT Motors of rating 100 KW and higher will be controlled by 415 V circuit breakers. The rupturing capacity of all 415 V circuit breakers will be 50 kA. Short-circuit withstand capability of 415 V equipment shall be 1 second. Duplicate feed will be provided for 415 V switchgears where necessary.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Motor control centres (MCCs) will be provided for the control of LV motors below 110 kW. Magnetic contactors with required protection and MCCB will control the motors. MCCs are envisaged to be located at respective load centres as far as possible.
415 V Emergency System :
The emergency power system provides power to essential auxiliary loads required, to permit a safe shut down of the unit in the event of a plant blackout. In addition, power is provided for auxiliaries and services required for personnel safety and equipment safety during the blackout. The bearing cooling pumps, seal oil pumps, barring gear, emergency lighting for the station, etc. would be fed from the emergency power supply system.
In order to meet the above requirement and as per CEA recommendation one(1) no.1600 kVA Diesel Generator will be installed in existing DG room in addition to three(3) nos. 1500 kVA diesel generator sets already installed for phase II, for meeting the requirement of emergency load for the Phase-II and Phase-III units.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
220 V DC System:
A reliable DC power source would be provided to supply those loads, which are required to function for security, protection and safe shutdown of plant in the event of failure of normal AC power supply. Present unit will have one (1) 220 V battery set of adequate capacity. One (1) no. 220 V battery as standby has been already installed for Phase-II. DC power supply system for said unit comprises:
220 Volt DC battery Battery chargers (float and boost charger) DC distribution and sub-distribution boards
Basis of selection of the above items will be as follows:-
a. Battery
Normal requirement of the battery is to supply power for the following:- Control and monitoring of the plant Alarm and annunciation of plant condition under emergency.
During the first one minute after occurrence of emergency, the battery will be called on to supply the following loads:
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Tripping power for all major circuit breakers simultaneously Starting of emergency drives to protect the machines from damage Plant emergency DC illumination system Other miscellaneous loads
Battery would be PLANTE type and the capacity of the 220 V battery set would be such that it will meet the above requirement of one unit and the requirement of common services.
As the battery sets for the 220 kV and 400 kV switchyards of Phase-I & II are sized for Phase-I & II equipment only, separate battery sets may be required for operation, control, indication, emergency lighting etc. of new 400 kV switchyard equipment of Phase-III. This requirement will be decided during detailed engineering time.
b. Battery Charger
Battery chargers of suitable capacity will be provided with quick boost and trickle charging facility for each of the aforesaid battery sets. Completely automatic and self-regulating type of battery charger will comprise one float charger and one float-cum-boost charger for each of the battery set.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The float charger will be capable of floating the battery at 2.15 volts per cell and at the same time supplying the normal DC load.
The boost charger will be capable of quick charging the battery at 2.75 volts per cell and will have the capacity to restore a fully discharged battery to a state of fully charged condition in 10-12 hours.
c. DC Distribution Board
One main DC distribution board for each of the battery sets will be provided with DC sub-distribution boards as required. The main DC distribution board will have two incomers having switch-fuse units and required number of outgoing switch-fuse units which will be selected to have a continuous current rating of not less that 125% of the nominal load current. DC distribution boards will be used to give DC power supply as required to plant auxiliary systems like DM plant and various pump houses. Separate battery with charger will be used to give DC power supply to equipment located in remote areas.
UPS System
Two (2) sets of uninterruptible power supply (UPS) systems of continuous duty have been envisaged to supply regulated, filtered and uninterrupted 240 V, 50 Hz, single phase power within acceptable tolerances to critical AC loads like computerised data acquisition
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
system, microprocessor based control and instrumentation system, analog control system, burner management system, annunciation system, indicators/recorders mounted on unit control boards and other critical loads of such nature. The system would comprise static inverters, static transfer switches, UPS system battery, float-cum-boost chargers for the battery, step down transformer, voltage stabilizer, AC distribution boards etc. Both automatic and manual mode of operation will be provided.
7.4 CONTROL OF ELECTRICAL SYSTEM
In line with the present-day practice centralised control of the electrical system / equipment has been envisaged for the plant from main plant central control room. There will be one separate main plant central control room for 5th unit due to non availability of space in existing common control room.
Generator synchronisation and its control will be done from this Control Room. However, bus selection for generator transformer breaker and outgoing 400 kV feeders control shall be done from existing Switchyard Control Room. Operation of 400 kV disconnecting switches shall also be done from existing switchyard control room. Existing SAS will be used for control, protection and metering for new extended 400 kV switchyard. There will be hook-up between existing 400 kV switchyard, extended 400 kV switchyard part and Power
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
House Control Room. Control, relay and other panels for new 400 kV bays will be located in the existing switchyard control room by suitable modification. BCU concept will also be applicable like in existing unit 3&4 switchyard.
Control and metering of generator, generator transformer, station transformer and unit transformers will be from Central Operating Console located in Unit Control Room. No Back-up panels are envisaged. The energy meters mentioned elsewhere shall be used for energy accounting and audit purposes and shall be located at a point after the generator stator terminals and before the tap-off to UATs and shall comply with the requirements of CEA regulations on Metering.
Control, indication, metering and monitoring of the electrical auxiliary power distribution system comprising of 11 kV and 3.3 kV circuit breakers (except those for motor feeders), LT transformers, 415 V switchgear breakers for incomers and bus couplers etc. shall be achieved from operator’s consoles through DCS. For details relevant section of C&I shall be referred.
Control panels for common service system like CHP, AHP, Plant Water System shall be located in the respective control room. However for Unitised services like C.W. pumps and ACW pumps etc. Control panels shall be located in the respective new control rooms. For details relevant section of C&I shall be referred. In addition, some local panels
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
will be provided near respective system/ equipment such as boiler feed pump, hydrogen seal oil system, electrostatic precipitator, etc.
Control of diesel generator for Unit # 5 and common standby DG will be from AMF panel in DG room. Remote control provision for the above DGs will also be provided in DCS through CRT operator interface in central control room.
7.5 METERING
Plant electrical parameters will be metered to the extent required for proper operation and monitoring of plant conditions. The same will be provided as per requirement.
Separate Main and Check meters will be provided in outgoing lines for tariff metering for import and export of power. The meters will be ABT (availability based tariff) compatible, static type, composite meters. These are self-contained devices for measurement of active and reactive energy. Separate CT & PT cores with accuracy class 0.2S will be provided for connection to these meters. The meters will be of accuracy class 0.2S.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Energy Management System Energy Management System (EMS) will be provided for accounting of the electricity to various segments of electrical system.
EMS will measure, record and display Apparent Power, Phase wise voltage, kW & kVA (reactive) at peak kVA, Power Down Time, Average Power Factor, Line Currents etc. Data collected from various meters will be displayed through various MMI pages of the EDMS system in Control Room.
The location of these meters will be as under following the Central Electricity Authority Regulation guideline:
At a point after the generator stator terminals and before the tap-off to the UTs. On each incoming feeder (excluding tie feeders) of HT buses. On LV side of each incoming transformer feeder of LV buses. On each incoming feeder of emergency MCC buses from DG PCC and On all HT motor feeders.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
EMS will generate Power Generation/Consumption and PLF Reports (Shift wise, Daily, Weekly, Monthly & Yearly basis), Single Line Diagram, Breaker on/off status and Load Flow and Reactive Power Flow Report as the minimum.
The system will be complete with all necessary equipment and accessories like meters as mentioned above, Communication Servers, Data Viewers / Operator Console with Printer, RS 485 to TCP/IP Converter, TCP/IP to FO Converter with FO Outputs, Interface Unit, Fibre Optics & HDPE Cables, TCP/IP Switches, CAT 5 HUB Cable, Twisted RS 485 Cable etc.
7.6 PROTECTION SYSTEM
For protection of equipment against abnormal system conditions, adequate protective devices will be installed in the respective switchgears and/or control and relay panels. A group of such protective devices will be necessary to protect the equipment under different abnormal conditions arising in the system. Microprocessor based Numerical relays with 100% redundancy through different algorithm also will be used for protection of equipment. For line protection, numerical relays with different algorithm will be provided as back-up. All relays shall be IEC 61850 compatible and shall communicate with central SCADA.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
The following protections are envisaged for major electrical equipment:- a. For Generator
i) Generator differential ii) Generator inter-turn fault iii) 100% stator earth fault/95% stator E/F protection iv) Standby stator earth fault v) Rotor earth fault (2 stage) vi) Loss of excitation vii) Negative sequence current viii) Pole-slipping ix) Back-up impedance x) Over voltage/Under voltage xi) Low forward power and reverse power xii) Under-frequency and over-frequency xiii) Generator Overload Relay xiv) Check Synchronizing Relay xv) Dead Machine Protection xvi) Over fluxing Protection xvi) Voltage operated Earth Fault Relay xvii) Neutral displacement relay
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
b. For Generator Transformer (GT) :
i) Overall differential ii) Restricted earth fault (HV Side) iii) Back-up earth fault (HV Side) iv) Overcurrent (HV Side) v) Overfluxing vi) Local breaker back-up vii) Buchhloz protection viii) Winding temperature protection ix) Oil temperature protection x) Pressure relief during protection
c. For Unit Transformer (UT) :
i) Transformer differential ii) Back-up over current with high set inst. unit (HV side) iii) Restricted earth fault (LV side) iv) Back-up earth fault on LV-neutral v) Buchhloz protection vi) Winding temperature protection vii) Oil temperature protection viii) Pressure relief during protection
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
d. Aux. Power Transformer:
a. Transformer differential (87T) b. Buchholtz/Winding/Oil temperature/PRV operated (63) c. Restricted earth fault (64) d. HV Back-up over current with high set instantaneous unit (50/51) e. LV standby inverse time earth fault for Transformer (51N)
e. For Station Transformer (ST) : i) Transformer differential ii) Back-up over current with high set inst. unit (HV side) iii) Restricted earth fault (HV, LV-1, LV-2 side) iv) Back-up earth fault on HV, LV-1& LV-2-neutral iv) Overcurrent (HV Side) v) Overfluxing vi) Local breaker back-up vii) Buchhloz protection viii) Winding temperature protection ix) Oil temperature protection x) Pressure relief during protection
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
f. 400 kV Bus Bar: i) Bus differential
g. 400 kV Line Feeder:
i) Non-switched Distance Main – 1 with inbuilt directional earth fault (21,67N) ii) Non-switched Distance Main – 2 with inbuilt directional earth fault (21,67N) iii) Breaker failure (50Z) iv) Check synchronization (25) v) Auto re-closing (79) vi) Overvoltage protection
The protections provided for different kind of feeders in 11 kV & 3.3 kV switchgears are as follows:
a. Incomer / Tie / Feeder:
i) Inverse time overcurrent relay for phase fault ii) Definite time overcurrent relay for earth fault iii) Instantaneous short-circuit protection (where applicable) iv) Under-voltage protection (where applicable) v) Synchronising relay with synchronising selector switch
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
b. Motors:
i) Comprehensive motor protection relay ii) Differential protection for motors rated 1000 kW and above. iii) Under-voltage protection (where applicable)
c. LV Auxiliary Transformer:
i) Inverse time over-current relay with high set instantaneous unit for phase faults. ii) Definite time over-current relay for earth fault. iii) Differential protection (for transformer 5 MVA and above) iv) Stand by earth fault relay v) Buchholtz protection (for oil type) vi) Winding temperature protection vii) Oil temperature protection viii) Pressure relief during protection ix) Magnetic oil level gauge
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
415 V Switchgear/PMCC:
Incomer / Bus-coupler
a. Inverse time over current for phase fault (51) b. Inverse time over current for earth fault (51N) c. Check synchronization (25) d. Under voltage (27) (wherever applicable)
Outgoing Feeders
a. Inverse time over current for phase fault (51) b. Inverse time over current for earth fault (51N)
415 V Breaker Controlled Motor Feeders (110 KW & above ):
a. Integrated motor protection relay (99) for the following functions: Thermal overload Phase fault (short circuit) Unbalance (Negative Sequence) Locked rotor Earth fault
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
415 V MCC
Incoming/Outgoing Feeders:- a. Short circuit protection through fuse/MCCB
415 V Contactor Controlled Motor Feeders (below 110 KW):-
a. Thermal overload with in-built single phasing protection. b. Short circuit protection through fuse/MCCB
DC System:
a. Short circuit protection with earth fault alarm.
Diesel Generator:
a. Voltage restrained over current (51VR) b. Reverse power (32) c. Negative phase sequence (46) d. Under frequency (81) e. Over voltage (59) f. Under voltage (27) In all cases, proper discrimination would be achieved so as to isolate the faulty elements only, keeping the healthy part of the system in service.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
7.7 PLANT ILLUMINATION
Suitable illumination is necessary to facilitate normal operation and maintenance activities and to ensure safety of working personnel. This would be achieved by artificial lighting. Required illumination levels in different areas as per standards/code of practice would be provided.
For outdoor yard illumination, floodlights would be installed at suitable locations to provide requisite level of illumination. Pole- mounted high- pressure sodium vapour lamp fixtures will be used for approach and work roads. Photocell will be used for controlling chimney lighting/boiler lighting/streetlights/yard lighting with provision for manual over ride.
Generally energy efficient fluorescent fixtures will be used for indoor illumination. Combination of sodium vapour, fluorescent, Clustered LED lighting fixtures and incandescent fixtures would be used for turbine hall and boiler platforms/galleries as may be necessary. For hazardous location appropriate type of fittings would be used.
The lighting system design would ensure uniform illumination at working levels. Illumination levels as per standard will be followed for illumination system design.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
Power for the illumination system would be supplied from 415 V switchboard through lighting distribution boards and lighting panels. Lighting distribution boards would be located in different buildings as per the requirements.
Suitable number of lighting panels will be located in each area, power to which will be supplied from lighting distribution boards. The lighting panels will be installed at convenient locations for ease of operation. In addition to normal illumination scheme, emergency AC and DC lighting scheme would be provided in the powerhouse complex. Emergency AC lighting would be supplied from AC emergency lighting boards, which would be connected to the AC emergency MCC. The AC emergency MCC would be energised from diesel generator during emergencies. The station emergency DC lighting will be provided in critical and safety related areas and would be fed from station 220 Volt DC distribution system during extreme emergencies. On failure of the AC supply, these lights will glow from DC system. For isolated buildings in remote areas where station 220 V DC is not available, DC lighting will be derived from self-contained battery with charger units, energised upon loss of normal AC supply in such isolated areas.
EXIT sign fixtures with built-in battery will be provided in strategic location.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
7.8 GROUNDING & LIGHTNING PROTECTION
Comprehensive grounding system will be provided in the power plant. A ground mat will be laid below ground level in switchyard and powerhouse mainly. This new ground grid shall be interconnected to the existing ground grid mat. The mat will be laid up to the fence and 1.5 meter beyond it on all sides. Suitable ground electrodes shall be provided at intervals. All metallic part of switchyard equipment, structures of equipment and towers shall be connected to this ground mat by means of suitable risers.
The grounding requirement of a power station complex could be divided into the following two main categories: System Grounding Equipment Body Grounding
The system grounding is adopted to facilitate ground fault relaying and to reduce the magnitude of transient over voltage. The system grounding involves primarily the grounding of the generator and transformer neutrals. The generator neutral will be high resistance grounded through distribution transformer and secondary loading resistor. 400 kV system will be effectively grounded.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
For 11 kV & 3.3 kV system of the proposed 660 MW unit high resistance grounding will be provided to limit the fault current to the order of 300 Amp. 415 V power supply system will be solidly grounded. DC system will be ungrounded. Necessary annunciation will be provided for detection of first earth-fault on positive or negative pole. The equipment body grounding will be provided to protect personnel from potential hazard caused by ground faults and lightning discharges by providing a low resistance, conducting path to the ground. A suitable ground grid will be provided for grounding of equipment and structures maintaining the step and touch potentials within safe limits.
The earth mat as provided will be buried at a suitable depth below the ground and provided with ground electrodes at suitable intervals. All metallic parts of equipment supposed to be at earth potential will be connected to the ground mat including structures, buildings, trans- mission towers, plant rail-road tracks, the perimeter fencing etc.
For lightning protection, lightning mast/shield wires would be provided on towers to cover the switchyard area for protection of the switchyard equipment against lightning. Similar protection will be provided for powerhouse transformer yard also. Besides, this lightning arrestor at required locations will be provided to protect the outdoor equipment from lightning and switching surges. Lightning protection system will be installed for protecting the buildings/structures against
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
lightning discharge. This would be achieved by providing lightning masts on stacks, powerhouse building, towers in switchyard, floodlight towers etc. and connecting them with the ground grid. Grounding and lightning protection for the entire power plant, switchyard and other areas or buildings will be provided in accordance with IS:3043, IS:2309, IEEE 80 and IEEE 665.
7.9 IN –PLANT CABLING
Main factors which are considered for selection of sizes for power cables are as follows: System short circuit current and allowable withstand time. Derating factors due to higher ambient temperature and grouping of cables. Continuous current rating. Voltage-drop during starting and under continuous operation. Standardisation of the cable sizes.
11 kV & 3.3 kV cables will be of heavy duty stranded aluminium conductor, XLPE insulated, extruded PVC inner sheathed, each core screened on conductor as well as on insulation, single round galvanized steel wire armoured (for multi-core cables only) and with fire resistant low smoke (FRLS) extruded PVC outer sheath. The cables will be suitable for non-effectively earthed system. For single core cables, single round aluminium armour wire will be used.
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Detailed Project Report 1 X 660 MW Phase-III Extension Unit#5, Sagardighi, West Bengal
LT power cables will be 1100 V grade with heavy duty stranded aluminium conductor. XLPE insulated, extruded PVC inner sheathed, galvanized steel wire armoured (for multi-core cables only) and with FRLS extruded PVC outer sheath. The cables would be suitable for effectively earthed system. Control cables will be multi-core 1100 V grade heavy duty PVC insulated, PVC sheathed, round steel wire armoured and with FRLS PVC outer sheath having 2.5 sq. mm stranded copper conductors. Fire survival cables (FS) will be used for system, which are necessary for protection and safe shutdown of plant in case of fire.
Cables provide means of carrying electrical power and also conveying signals for various control, protection and monitoring functions.
Cable Routing Cables will generally be laid on ladder type prefabricated GI cable trays either in trenches or overhead steel/structures supported from building. For inter plant connections, cables may be directly buried or routed through overhead cable bridge. Separate trays will be used for HV, LV, control and instrumentation cables. AC and DC circuit will not run in the same cable tray. For underground crossing of railways, roads, etc. protection will be provided in the form of hume pipe or concrete encased rigid steel conduits, depending on application.
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