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Modern Electrical Technology for Water Treatment Plants

Modern Electrical Technology for Water Treatment Plants

Modern Electrical Technology for Treatment Plants

Yoshinori Nagakura Masayoshi Tokuhiro Kouji Akiyama

1. Introduction 2. New Energy in Plants

Global environmental problems such as global Most of the energy consumption in waterworks warming and rain originate from dioxide and sewerage facilities is electric power consumption. and nitrogen oxide, which are generated mostly from To reduce the power consumption it is effective to the energy consumption of fossil fuels. To solve these accelerate application of dispersed power generation problems there are two methods, one is to restrict the of new energy. consumption of fossil fuels and change to clean As alternative energy sources to fossil fuels, there energy, and the other is to reduce energy consumption exists solar energy, hydraulic power energy, wind itself. force energy and biogas ( digestion gas). A This paper will introduce: comparison of the CO2 emission corresponding to (1) New energy technology and each of the power generation systems is shown in Fig. (2) Energy saving technology 1. available for the above-mentioned methods in water treatment facilities, and 2.1 Photovoltaic power generation system (3) Recent initial electric power receiving, transform- It is said that the amount of solar energy irradiat- ing and powering equipment and their applica- ed upon the surface of the earth for only 40 minutes tions can supply the energy consumed by mankind in one that support the above technologies. year. However, it is difficult to use this energy steadily

Fig.1 Comparison of power generation systems and CO2 emission

300 270 CO2 emission during lifetime 250 (Facilities construction+Facilities operation CO2 emission unit +Fuel for power generation+ Methane leakage) requirement (g-C/kWh) = 200 Generated energy during lifetime 200 178 Fuel Facilities and operation 150

100 New energy

emission unit requirement (g-C/kWh) 58 2 50 40

CO 36 35 34 34 24 12 16 5 6 3 to 6 0 nd force Tidal current force Nuclear power Geothermal power Ocean thermal energy Solar thermal power Medium and small-type hydraulic power Photovoltaic power (for business) LAG thermal power Coal thermal power Oil thermal power Photovoltaic power (for household) Wi

[Reference] Survey of Central Power Research Institute

110 Vol. 45 No. 4 FUJI ELECTRIC REVIEW Fig.2 Basic configuration of photovoltaic power generation Fig.3 Applicability of water turbine system

1000 Sunshine DC load AC load

System 500kW Solar DCDC-to-AC ACconnecting AC 100 Pelton battery converter equipment turbine array (Inverter) Filter,

protective ower system P 50kW Francis Electricity storage equipment, turbine equipment etc. 10 Effective head (m)

1 0.1 1 10 100 3 Table 1 Proposed applications of photovoltaic power genera- Water turbine flow rate (m /s) tion systems to waterworks and sewerage

Features of Applied photovoltaic Installation location waterworks power generation of solar battery and sewerage system ™Upper space of water ™Medium and large of solar energy, water treatment plants are highly basin, filter capacity facilities bed ™Connected to adaptable to energy applications. The main system Available ™Upper space of first commercial power applications are listed below. upper space sedimentation, last system (usually is wide. sedimentation and without storage (1)A system linked to the electric power system aeration tank [Cover] battery) (2)A system that independently operates as dis- ™Roof of facilities house persed power generation using a storage battery Some ™Small capacity (3)A system in which wind force power generation, facilities such facilities as a service ™Connected to small-type hydraulic power generation, etc. are are commercial power used in combination. located among system Proposed applications to a waterworks plant are mountains. ™Roof of facilities house (Storage battery is ™Special mounting used in case of shown in Table 1. Detection frame (such as a pole) power outage) elements for pressure, flow 2.2 Small-type hydraulic power generation system rate, water This system converts the kinetic energy of are scattered. into electricity, and the quantity of power generation is determined by the head and flow rate of the water. The advantages are listed below. (1) The construction is simple and compact in com- because its density is low and the quantity of power parison with other power generation systems. generation depends on seasonal and meteorological (2) Power generation is practical if the water has a conditions such as sunlight and the weather. On the head and flow rate. other hand, solar energy generates no atmospheric (3) Maintenance is unnecessary. pollutants and no noise that can to disruption of (4) Among power generation methods, hydraulic pow- the earth’s environment. Solar energy is a clean and er has the lowest emission of . quiet energy source that can be utilized anywhere on 2.2.1 Applicability of small-type hydraulic power generation the earth. The basic configuration of a photovoltaic Fuji Electric provides a series of models widely power generation system is shown in Fig. 2. applicable for power generation with generated out- 2.1.1 Principle of power generation puts ranging from 50kW to several thousand kWs. A solar battery is configured with pn-junction Figure 3 shows a graph of power generation quantity structure, joining a p-type semiconductor with an n- related to the effective head and flow rate. For type semiconductor, and a pair of electrodes for example, a head of 10m with a flow rate of 42m3/min extracting electricity. When light is irradiated upon allows a generated power of 50kW. the junction, electrons (negative charge) and holes 2.2.2 Application to water treatment plants (positive charge) are generated by the photoelectric Hydraulic systems can be employed in water effect, and their movement creates an electromotive conduction and distribution systems of waterworks force between the electrodes. and in water discharge systems of sewerage systems. 2.1.2 Application to water treatment plants Hydraulic systems are highly adaptable to water Because there is much available space at the upper treatment plants because the variation in quantity of part of water treatment facilities, such as at a water both the conduction water and the distribution water service reservoir, and the energy consumption pattern is similar to that of the electric load in water treatment of water treatment is similar to the irradiation pattern plants.

Modern Electrical Technology for Water Treatment Plants 111 Table 2 Supply list of wind power generation facilities

Specifications Year Customer name End-user name Windmill/generator System connecting Note delivered Capacity manufacturer equipment mfr. 1993 Toyo Engineering Co. Yamagata Prefecture 1000kW × 3 US Wind Power Fuji Electric Tachikawa Town 1994 Power Development Wakamatsu Thermal 22kW Isobe Steel Co. Fuji Electric Co. Power Station (Darius type windmill) 1997 NTT Facilities Co. NTT Kumejima Radio 225kW × 1 Ebara Works Fuji Electric Relay Station 1997 Tohoku Electric Megawa Nuclear Power Wind: 17.5kW Yamaha Motors Co. Fuji Electric Hybrid system of Power Co. Station PR Center Solar: 3kW Fuji Electric wind and solar power 1999 Shikoku Electric Tohmen Co. 1000kW × 20 BONUS Fuji Electric (planned) Power Engineering Hokkaido Tomamae Co. Wind Park

Fig.4 Configuration of wind power generation system Fig.5 Overview of photovoltaic power generation system in Murasakigawa Water Source Station

Remote monitoring system 150kW Solar battery array

Commercial power system Slow filtration Power company’s (Kyusyu Electric bed distribution line Power Co.) Telephone line DC DC Murasakigawa Water Source Station

20kW Storage 10kW battery inverter inverter 13 1-phase 3-line 210/105V Windmill control House load panel (Inside of pole) Inverter panel Circuit breaker panel Transformer panel System 3-phase System connection 3-phase connection Load protection panel, etc. 3-line 3-line protection 210V during 6,600V equipment disaster

20kW inverter panel Transformer 2.3 Wind power generation system This power generation system utilizes wind energy. The advantages are listed below. power generation that use biogas (digestion gas gener- (1) There is no emission of air pollutants. ated in the sewerage plant) as the fuel. The fuel cell (2) Large-capacity power generation is possible. has the following advantages. (3) Installation is practical if there is an average wind (1) Efficient high power generation. speed of greater than 6 m/s. (2) Constituents of the discharged gas are clean Factors to be considered when determining the (NOx: below 5ppm, CO2: 60 to 70% of conven- installation location are listed below. tional generators). (1) There are no obstructions in the surrounding (3) The overall efficiency reaches 80% by utilizing the neighborhood that would create turbulance in the heat generated from the process of its electro- wind flow. A laminar flow is best if possible. chemical reactions. (2) There is no radio wave interference such as microwave, radiotelegraphy and televisions sig- 2.5 Application of new energy systems to water treatment nals in the neighborhood. plants The system configuration is shown in Fig. 4, and a Applications of new energy systems to water list of customers to whom systems have been deliv- treatment plants are introduced below. ered is shown in Table 2. 2.5.1 Application of photovoltaic power generation system (1) Delivery example to the Murasakigawa Water 2.4 Biogas utilizing power generation system Source Station of the Waterworks Bureau of Kita- Biogas systems include fuel cell and digestion gas Kyusyu City

112 Vol. 45 No. 4 FUJI ELECTRIC REVIEW Fig.6 System configuration of photovoltaic power generation equipment in Ogochi Reservoir

Solar battery (Polycrystal type) 125kW Solar battery Solar battery Tokyo Electric (Polycrystal type) (Amorphous type) Power Co. 25kW 1.5kW [Parking space] DC Initial power DC DC to AC receiving and converter DC transforming Storage battery Inverter equipment DC to AC AC for powering converter and disaster [Switch room] DC DC DC to AC Storage battery AC to DC Inverter converter for electrically- converter for disaster AC driven vessel Inverter Battery AC charger Load during Water quality disaster maintenance Load during Exhibition device disaster facilities (Power supply AC for illumination) [Machine room] (Power supply for illumination) [OKUTAMA MIZU [Offshore [Kawano parking TO MIDORI NO based water area of Tokyo FUREAI KAN ] quality main- Metropolis] [Land based equipment] For natural education tenance equipment] Driving motor for electrically- driven vessel M [Electrically-driven vessel “Hidamari” ] Waterweed salvaging pump 2

Fig.7 Appearance of vessel for conveying salvaged waterweed inverter and a storage battery, the system can be used as an emergency power source. Growth of waterweeds in the slow filtration bed is prevented by the covering effect of the solar battery array. (2) Delivery example to the Ogochi Reservoir of the Tokyo Metropolitan Waterworks Bureau The reservoir covers a vast area of a and is suitable for the installation of a large-scale photovoltaic power plant. It is believed that the growth of waterweeds due to water inflows into , marshes and dams may influence the water quality. A system that operates on energy obtained from photovoltaic power generation and maintains the water quality by salvaging the waterweed, has been delivered to the Ogochi Reservoir. The system configuration is shown A7530-19-19 in Fig. 6 and the appearance is shown in Fig. 7. The generated outputs are 125kW from the land- based equipment, 25kW from the offshore equipment In this system, a 150kW solar battery array is and 1.5kW from the electrically driven vessel. Each installed at the upper side of the slow filtration bed, piece of equipment is used jointly with a storage and DC electric power generated from the solar battery to implement a hybrid system for disasters battery is converted to AC with an inverter and used and emergencies. as a power source after being connected to the initial 2.5.2 Application of small-type hydraulic power genera- electric power receiving and transforming equipment. tion systems An overview of the power source system is shown in As application examples there are several plants of Fig. 5. When a commercial power source is shut down, various capacity from the 20kW micro-hydraulic tur- because of its self-sustaining function with a 20kW bine generator for the Tainai of Niigata Prefec-

Modern Electrical Technology for Water Treatment Plants 113 Fig.8 840kW horizontal shaft Francis turbine hydraulic gener- Fig.9 Circuit configuration of VVVF with harmonic restrained ator for Ken’o 1st Waterworks of Gumma Prefecture PWM converter

Power source

Power supply unit

Converter unit

Control IGBT circuit

Frequency Inverter unit setting

Control IGBT circuit Control signal ture to the 840kW horizontal axis Francis turbine M Motor hydraulic generator (Fig. 8) for the Ken’o 1st Water- works of Gumma Prefecture. The historical annually generated energy of the power plant delivered to the Ken’o 1st Waterworks of Gumma Prefecture is 6,303MWh (an average output ing to the rated water (or gas) volume. of 755kW) and the utilization factor is high. However, the pumps and blowers are often driven In a small-type hydraulic power plant, now under at less than their rated values. As a result, convention- construction at the Higashi-Murayama Water Purifi- al operation by driving at a fixed speed will restrain cation Plant of the Tokyo Metropolitan Waterworks the flow rate of discharge valves, etc. and thus some Bureau, an S-type tubular turbine is to be installed in energy will be lost in the discharge unit. the existing conduit, and the power plant is to operate On the contrary, unnecessary energy consump- while connected to the power system of an electric tion can be limited if the motor is driven with variable power company. speeds. The generator will output a rated power of The primary frequency control system (VVVF: 1,400kW and feed approximately 90% of the usual Variable Voltage Variable Frequency) and the second- power demand in the plant by parallel operation of 2 ary excitation control system (Scherbius), variable sets of 2,000kW co-generating equipment. It is also speed control systems used for energy saving in many planned to use this system as an emergency power water treatment plants, are introduced in the follow- source during service outages of the electric power ing. company. 3.1.1 VVVF with harmonic restrained PWM (pulse width 2.5.3 Application of biogas utilizing power generation modulation) converter systems In this system, the converter unit of a variable A system among water treatment plants generates speed controller (VVVF) used for driving 3-phase electricity by using the digestion gas originated in the 200V and 3-phase 400V squirrel-cage induction motors treatment plant as fuel. There is also a system is modified to the PWM type (sine wave input type). that produces by using the DC The advantages of this system are listed below. electric power generated from a fuel cell directly for Figure 9 shows the circuit configuration. the electrolysis of salt water. (1) Countermeasures against harmonics are unneces- sary 3. Energy Saving Technology in Water Treat- Because the current at the power source side is ment Plants made into a sine waveform by the PWM control, few harmonics are generated. 3.1 Variable speed control system (2) Miniaturization is possible Pump or blower motors consume most of the Because the power factor control creates a current electric power in water treatment plants. Therefore, flow that is in-phase with the source phase voltage, energy saving by these motors allows the whole plant driving at a power factor of approximately 1 becomes to effectively conserve energy. Usually the pumps and possible, and thus the power transformer and other blowers are manufactured at a rated capacity accord- apparatus can be miniaturized.

114 Vol. 45 No. 4 FUJI ELECTRIC REVIEW Fig.10 Circuit configuration of harmonic restrained PWM Fig.12 Ideal operation region for high-efficiency number of Scherbius pumps

52M 52C

PG 1234 5 67 or TG IM

STMC Head Initial charging DC chopper circuit RNMC DCL PWM inverter

Diode ACL rectifier +

Flow rate

6 Detection of synchronized DDC controller DDC controller power source ASR+ACR AVR Speed command of the inverter is approximately 2/3, the efficiency of the wound-rotor-type motor is higher than that of the squirrel-cage type, and thus the running efficiency is higher by about 2 to 3%. 3.1.3 High-voltage direct drive VVVF This system directly controls the speed of a high- Fig.11 Circuit configuration of high-voltage directly driving voltage induction motor from a high source voltage VVVF using high-voltage diodes and high-voltage IGBT elements. The advantages are as follows. The circuit configuration is shown in Fig. 11. (1) High-voltage motor is directly driven A 3kV high-voltage motor can be directly driven from a high source voltage. (A 6kV system will be soon introduced to the marketplace.) (2) Miniaturization is possible A step-up transformer becomes unnecessary, and Same as above IM miniaturization and improved reliability are achieved. (3) Countermeasures against harmonics are unneces- sary Same as above Adoption of a multiphase diode rectifying system (3 × 12-phase rectification) eliminates the necessity for countermeasures against harmonics. (4) Extended-life and reduced noise of the motor are realized (3) Maintenance is easy Stress to the motor is reduced, because the output The intelligent functions allow easy referencing of current waveform becomes almost a sine wave fault histories, thereby simplifying the maintenance. through employment of PWM control. 3.1.2 Harmonic restrained PWM Scherbius (5) Maintenance is easy The Scherbius system controls the speed of a high- Operations and failure diagnosis can be easily voltage wound-rotor-type motor by returning its sec- carried out by the intelligent functions. ondary power to the power source through an invert- er. Because a PWM inverter is employed instead of 3.2 Energy saving control the usual thyrister inverter, this system has the The usual energy saving operation of pumps is following advantages. The circuit configuration is implemented using a combination of the “number of shown in Fig. 10. pumps” control and the “variable speed” control (1) Countermeasures against harmonics are unneces- corresponding to increases or decreases of the flow sary rate and level of water. The resulting energy saving Control at a power factor of approximately 1 is effect is approximately 20%. possible, and the percentage of harmonic components As methods to increase the energy saving effect can be limited to less than 5%, too. even more, two systems will be introduced here. One (2) Operating efficiency is high is the high-efficiency number of pumps control system, Compared with the VVVF, the equipment capacity in which a pump head is used as the criteria to

Modern Electrical Technology for Water Treatment Plants 115 Table 3 Main energy saving apparatus in water treatment plant

Apparatus Classification SummaryApplication Effect Misc. name ™Restricts loss and influence ™Harmonics generat- ™Restricts overcurrent due to harmonics, such as ing apparatus such due to harmonics Active filter overheat, noise, vibration as variable speed ™Reduces power ™Compensates reactive controllers, non- charge by improved power interrupting power power factor supplies, rectifiers Demand ™Supervises control of ™Receiving point ™Reduces contract controller contract demand power demand demand ™Prevents excessive Power contract demand equipment Automatic ™Reduces ohmic loss due to ™Compensation of ™Reduces power ™Reduced voltage drop power factor reactive power transformer excitation charge and increased capacity regulator ™Induction motor ™Reduces power loss factor. Molded ™Extensively reduces loss by ™Initial power receiving ™Compared with usual ™Changeover operation transformer core material and mold and transforming dry type, no load loss of working number of technology equipment, powering is reduced by approx. units equipment, illumina- 2/3 and load loss by ™Operation at highest tion equipment 1/2 to 2/3. efficiency Variable speed ™Realizes high-efficiency ™General-use type controller operation by changing squirrel-cage induc- VVVF frequency and voltage tion motor ranging from 0.2kW to 900kW ™ Reduces approx. 65%

Thyrister ™Realizes high-efficiency ™Wound-rotor type of loss at 70% speed Pumping Scherbius operation by returning induction motor from equipment secondary slip power to approx. 100kW to power source 5,000kW High-efficiency ™Achieves high-efficiency by ™Maintains high- ™Induction motor motor using latest design and low- efficiency at light loss material load (above 50%) Power saving ™Saves excessive power by ™Low voltage powering ™Reduces working ™Apparatus lifetime is Illumination device restraining excessive voltage and illuminating power by 10 to 20% expected to increase equipment to appropriate value equipment also Reduced ™Applies Energy Star logo to ™Computer, display ™Widely used by most Logo Miscellaneous stand-by power energy-saving apparatus, device, printer, of OA devices according to International facsimile, copy Energy Star Program machine

determine whether the number of pumps should be ning pumps, an energy saving effect of 2% or more was changed. The other is the efficiency-increasing achieved in comparison with the conventional system (equalizing) pump driving system, which uses the for controlling the number of pumps. quantity determined based on predicted 3.2.2 Efficiency-increasing (equalizing) pump driving demand. system by operation program 3.2.1 High-efficiency number of pumps control system This system aims to save energy through limiting Energy saving for the whole plant is attempted by the energy loss during pump changeover by reducing driving the number of pumps that will result in the the unnecessary of pumping operation. greatest saving of electric power. In such a water supply program, the water The electric power Pm at the time when m pumps volume required for a service reservoir is supplied in operate to supply water at the flow rate Q and head H advance based on predicted demand so that the is calculated and compared with the electric power at pumps may be evenly driven, and changeover of the the time when (m+1) and (m-1) pumps run. Then if running pumps is controlled. the value of least power is chosen as the number of Employment of this system can expect to yield an driving pumps, operation with the greatest power energy saving effect of approximately 1% or greater savings can be achieved. than the conventional pump number changeover meth- As shown in Fig. 12, the region corresponding to od based on the water level of the service reservoir. the number of ideal driving pumps is established in advance, and the number of pumps can be controlled 3.3 Energy saving apparatus by comparison to this region. Summaries of various energy saving electrical Employment of this system in a water purification apparatus and their effects are shown in Table 3, and plant equipped with approximately 3,000kW of run- their applied system configurations are shown in

116 Vol. 45 No. 4 FUJI ELECTRIC REVIEW Fig.13 System configuration of energy saving apparatus The unit circuit modules can be completely assem- bled in the factory and then transported to the site. Therefore, the fieldwork can be finished by connecting only the modules. Demand controller (3) Maintenance can be reduced Since the components themselves are enclosed in Automatic power factor regulator SF6 gas sealed containers, there is no need to worry about degradation caused by and oxidation. The age deterioration of parts is also much decreased. (4) Harmony with environment is obtained There are no steel supports as in substations with Capacitor Molded air insulation systems and the appearance is excellent. transformer M (5) Safety is high High-voltage Every container is completely grounded and there directly driving PWM VVVF is no fear of electric shock. Active converter Power saving filter device 4.1.1 Front access type GIS (72/84kV) Under the concepts of “more compactness”, “easi- High-efficiency er use” and “greater safety”, further miniaturization, motor VVVF front access and completely oil-free equipment are

M achieved. (1) Installation area can be extensively reduced The skeletal diagram and comparison with a Fig. 13. conventional device are shown in Fig. 14. The mount- ing area is extensively reduced by about 50% in the 4. Recent Initial Power Receiving, Transforming case of a 2-circuit, 2-bank and 1-VCT system. and Powering Equipment in Water Treatment (2) Maintainability is drastically improved Plants As shown in Fig. 15, all the manipulating and monitoring functions such as manipulators, monitor- Equipment recently used for initial power receiv- ing instruments and gas components are mounted on ing, transforming and powering facilities in many the front panel of the equipment. There is no need to water treatment plants will be described here. turn the equipment to access the side or the back. As forms of extra-high-voltage substations, there Thus, daily maintenance can be performed as if this are steel structure types, housing types and gas was an ordinary switchboard. insulation types. Recently, the gas insulation type (3) High safety has become frequently used since it allows substan- Completely oil-free equipment is achieved by tially reduced installation space and high reliability. making electrically-driven -manipulation type Fuji Electric has delivered this type to many foreign circuit breakers. countries including China and the Southeast Asia 4.1.2 Super-miniaturization by replacing extra-high- area. voltage circuit-breaker with vacuum circuit breaker (VCB) 4.1 Gas-insulated switchgear (GIS) The gas-insulated switchgear is super-miniatur- This equipment compactly encloses charged parts ized by replacing the usual 72/84kV gas circuit breaker of circuit-breakers, disconnectors, instrument current with a vacuum circuit breaker. This also achieves a and voltage transformers, arresters, buses, etc. in cost reduction. several metal containers that are filled with SF6 gas (6 fluorine sulfur gas), having excellent insulation char- 4.2 Digital multi-function relay acteristics, and are then sealed. Fuji Electric is The digital multi-function relay is an integrated providing a series of GIS devices ranging from rated compact module with functions of protection, manipu- voltages of 72kV to 300kV and rated breaking currents lation, instrumentation, monitor and transmission for of 25kA to 50kA. SF6 gas insulation has the following initial power receiving and distribution facilities, and advantages in comparison with a conventional air has the following advantages. Table 4 shows the insulation system. specifications and Fig. 16 shows the appearance of the (1) Substantial reduction of onsite space is possible relay. The equipment is made compact in size, as various (1) System is readily made intelligent individual power apparatus are unified by SF6 gas With its transmission function, the relay can insulation. connect to upper level computers through a network. (2) Shortened fieldwork term and highly reliable So in addition to the normal operation and supervisory equipment can be achieved control functions, intelligent functions such as support

Modern Electrical Technology for Water Treatment Plants 117 Fig.14 Space comparison of front access type GIS

VCT

Skeletal diagram Conventional type GIS Front access type GIS

Fig.15 Appearance of front access type GIS Fig.16 Appearance of digital multi-function relay

AM180975 N99-2332-4

of the operation and maintenance are readily achieved. by replacing its control unit with an electronic unit. (2) Fault analysis is easy The intelligent control center has the following advan- Data at the occurrence of a fault such as currents, tages and its specifications are listed in Table 5. voltages, zero sequence currents, zero sequence volt- (1) Extensively reduced external wiring and short- ages, etc. are automatically preserved and the instru- ened construction period mentation results can be displayed in the relay itself. Because the equipment has a transmission func- Fault analysis is easy, even at a central location, by tion, a total networked system can be built ranging viewing the transmitted fault data. from upper level systems, such as PLCs (programma- (3) Reduced labor for maintenance ble logic controllers) and CRT supervisory controllers, In addition to the continuous fault monitoring to the fields of local operator panels. This enables function of the relay itself, the relay is provided with higher maintenance with detailed data, extensive an automatic checking function which verifies accura- reduction in the number of external wires and a cy of the analog input parts and responses of the shorter onsite construction period. output relays, and a circuit breaker monitoring func- (2) Faults are preventable tion which observes breakage of trip coils and open- The protection performance is dramatically en- ing/closing times of the circuit breakers. This achieves hanced by new functions such as an overload pre- a reduction in the labor for maintenance. alarm, ground fault pre-alarm, detection of blocked opening/closing of MCs (magnet contactors) and detec- 4.3 Intelligent control center tion of abnormally configured MC main circuit, togeth- The intelligent control center is a multistage er with conventional functions such as overload, open stacked power board that is a modified conventional phase, ground fault, instantaneous overcurrent and control center made highly functional and intelligent undercurrent protection. This enhanced protection

118 Vol. 45 No. 4 FUJI ELECTRIC REVIEW Table 4 Function list of digital multi-function relay ○ : With function, - : Without function Feeder unit (shared Item Content Bus unit combination unit) Current value indication (A) - ○ Voltage value indication (V) ○ -

Zero sequence current value indication (MA0) - ○

Zero sequence voltage value indication (MV0) ○ - Power value indication (W) - ○ Instrumentation Reactive power value indication (var) lag power factor functions - ○ Power factor indication (cos φ ) - ○ Frequency indication (Hz) ○ - Watt-hour indication (Wh) - ○

Fault record (measured value at fault) indication MA, MA0 - ○

MV, MV0 ○ - Open/close manipulation of line switch - ○ Control functions Remote/direct changeover (control right) - ○ Open/close remote control (external contact and transmission) - ○ Short circuit protection (INST: instantaneous) - ○ Overcurrent protection (OC: inverse time-lag) - ○ Directional ground protection (DG) - ○ Overvoltage protection (OV) ○ - Protection functions Undercurrent protection (UV) ○ - Ground overvoltage protection (OVG) ○ - Voltage recognition (VR) ○ - Remote trip (external trip) - ○ Reverse phase and open phase - ○ Relay setting value indication ○ ○ Relay operation indication ○ ○ Display functions Line switch status indication - ○ Control right status indication (remote/direct) - ○ Monitoring functions CB trip coil breakage monitoring - ○ (maintenance support) CB opening/closing time monitoring - ○ Constant monitoring function ○ ○ Automatic checking (initiated at fixed cycles every 24 hours) ○ ○ Self-diagnostic Manual test (initiated anytime) functions ○ ○ Lamp test ○ ○ Forced operation (each element individually) ○ ○ Reception of line switch open/close signals Transmission of measured value data to upper system Transmission of protective relay operation signals to upper system Transmission of setting values of protective relays and timers to Transmission upper system, and reception of setting values functions (T-Link) Only for types with T-Link Transmission of line switch status indication signals and control right status indication (remote/direct) signals to upper system Transmission of switchgear side signals (CB draw-out position, etc.) to upper system Transmission of system failures and ID data to upper system

performance allows the prevention of faults. (3) Switch room space is saved 5. Conclusion The direct connection of control signals with PLCs through transmission lines eliminates the necessity for New energy technology and the energy saving installation of conventional auxiliary relay panels, and technology have been introduced and applications to thus space saving of the switch room can be achieved. water treatment plants have been explained. It will be

Modern Electrical Technology for Water Treatment Plants 119 Table 5 Function list of intelligent control center

Item Content Item Content Applied Inverter, 1-phase or 3-phase general low-voltage load ™Protection: circuit with inching manipulation CT rating, rated current, overload protection mode, instantaneous operat- Overload ing current of overcurrent, instanta- Open phase neous operating time of overcurrent, Direction ground operating current of undercurrent, Protection Instantaneous overcurrent operating time of undercurrent, ground Undercurrent fault sensitive current, ground fault Overloard pre-alarm operating time, ground fault changeover, Direction ground pre-alarm open phase protection valid/not valid, MC fault overload pre-alarm operating current, ™Load current ground fault pre-alarm operating ™Leakage current current, overload protection reset Monitor, Monitor ™Fault current Setting Item method, starting lock time display display ™Fault condition ™Control: ™Setting value Momentary interruption compensation ™Operating record time, momentary interruption restart time, sequence number, application ™Selector switch: REM-DIR-TEST Operation sorting of fault output contact, process- ™Push button switch: ON, OFF, REV Manipula- ing during CPU error tion ™Push button switch: ™Transmission: Instrumenta- MODE SELECT, SET/FLT, RESET, Transmission address, processing tion, setting ∧, ∨, ENTER during upper system error ™Operation record: Initial value ™ Main circuit: ™Setting protection: Sequence Automatic setting (Non-reversible, Provided with locking function of reversible, power source feed) setting value ™Control circuit: 256-pattern ™Protection function: ™Compensation time: Restart after Overload, ground fault 0.5 to 5.0 s (in 0.5 s steps) TEST mode momentary ™Control function: ™Restart: 0 to 60 s (in 1 s steps), power inter- Center (via transmission), onsite, MCC Instant restart if interruption is ruption shorter than 0.2 s. ™Normally: CPU monitor, Test Communication monitor Control ™Control signal: 4-point (88F, 88R, ™During operation: interlock, external fault) CPU Input ROM monitor, RAM monitor, EE-ROM ™Manipulation signal: self-diagnosis monitor, Analog input value monitor 4-point (ON, OFF, REV, center) ™During test: ™Operation signal: Analog input value monitor 3-point (ON, OFF, REV) ™F-NET: ™Fault signal: Normally provided with T-Link Output 2-point (Element can be selected) ™Transmission rate: 500kbs ™Contact capacity: ™Transmission distance: 1km Rated current 1 A, maximum System ™Transmission line: switching capacity 250V AC, 5A 2-wire twisted pair cable ™ ™ Fault current Overload: 0 to 1000%A Number of terminals that can be ™Ground fault: 0 to 500mA connected: 32/1-link to 128/4-link Setting value ™All setting items ™Transmission quantity: Transmis- Digital 26-items, analog 4-items ™Operating time sion Transmission ™Data contents: ™MC close/open data Operation signal, fault signal, ™Trip measured value, setting value, ™Overload present value of operation record Memory ™Open phase ™ Operation Ground fault ™ record Instantaneous overcurrent ™Reception quantity: ™ Undercurrent Digital 22-items ™ Reception External fault ™Data contents: Operation signal, ™ data Momentary interruption restart setting value, initial value of operation ™ MC failure record ™Maximum load current ™Minimum load current

appreciated if this information is helpful in the technology still has some subjects that should be implementation of measures to counteract environ- improved upon in the future, such as cost reduction mental problems, such as reducing fossil fuel consump- and higher efficiency, Fuji Electric will continue to tion by accelerating applications of new energy and make efforts to provide systems in response to require- energy saving apparatus. Although the new energy ments of the age and society.

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