ACKNOWLEDGEMENTS

I would firstly wish to thank Mr. M.K. SHARMA for allowing me to undergo summer training at NTPC AURAIYA, AND SPECIALLY TO THE DEPUTY GENERAL MANAGER , at NTPC .I would also wish to convey my warm regards to Mr. C.K. MISHRA (O&M-EM)for providing me with all the knowledge & GUIDANCE database that I needed for this report.

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S.NO. DESCRIPTION PAGE NO.

(1) ABOUT THE COMPANY 5

(2) NTPC SUBSIDARIES 7

(3) NTPC HUMAN RESOURCES 8

(4) AWARDS 8

(5) INSTALLED POWER PLANTS 10

(6) NTPC STRATEGIES 13

(7) BRIEF DESCRIPTION OF THE PLANT 15

(8) ELECTRICAL MAINTENANCE 21

(9) GENERATOR SYSTEM 36

(10) STATION TRANSFORMER 42

(11) AUXILIARY MOTORS 44

CONTENTS

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ABOUT THE COMPANY

 Corporate Vision:

“A world class integrated power major, powering India’s growth, with increasing global presence”

 Core Values:  B- Business Ethics C- Customer Focus O- Organizational & Professional pride M- Mutual Respect and Trust I- Innovation & Speed T- Total quality for Excellence

NTPC Limited is the largest thermal power generating company of India. A public sector company, it was incorporated in the year 1975 to accelerate power development in the country as a wholly owned company of the Government of India. At present, Government of India holds 89.5% of the total equity shares of the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and others. Within a span of 31 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.

 

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EVOLUTION OF NTPC

1975NTPC was set up in 1975 with 100% ownership by the

Government of India. In the last 30 years, NTPC has grown into the largest power utility in India.  

  1997In 1997, Government of India granted NTPC status of

“Navratna’ being one of the nine jewels of India, enhancing the powers to the Board of Directors.

2004NTPC became a listed company with majority

Government ownership of 89.5%. NTPC becomes third largest by Market Capitalisation of listed companies

  2005 

The company rechristened as NTPC Limited in line with its changing business portfolio and transform itself from a thermal power utility to an integrated power utility.

2010

Government of india granted NTPC the status of maharatna company.

  

NTPC is the largest power utility in India, accounting for about 20% of India’s installed capacity.

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Human ResourcesPeople before PLF (Plant Load Factor) is the guiding philosophy behind the entire gamut of HR policies at NTPC. We are strongly committed to the development and growth of all our employees as individuals and not just as employees. We currently employ approximately 24500 people at NTPC.Competence building, Commitment building, Culture building and Systems building are the four building blocks on which our HR systems are based.

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AwardsNTPC has a glorious record of excellence in every field of its activities ever since its inception in 1975. Leading the country’s power sector with a vision to become a 75,000 MW company by 2017, we take pride in our people and their performance which has been acknowledged time and again at various national and international fora.•NTPC named in Platts Top 250 Global Energy Company Rankings 2009•Business Standard Award - Star Company (Public Sector Undertaking) of the year, Business Standard•‘Water Digest Water Awards 2008-09, Water Digest •'Golden Peacock Environment Management Award - 2008’ Institute of Directors•NTPC Baged 4 awards at the Great Places to Work Awards-2009•NTPC bags Gold Trophy at India Pride Awards•‘International Gold Star Award for Quality 2009’ for NTPC–CenPEEP Conferred at International Star Quality Convention Geneva 2009•ICAI Award for Excellence in Financial Reporting, The Institute of Chartered Accountants of India•International Project Management Award 2008, International Project Management Association (IPMA)•CII-Exim Excellence Award 2008, Confederation of Indian Industry•India Power Awards 2008, Council of Power Utilities•Enterprise Excellence Award 2007, Indian Institution of Industrial Engineering•Golden Peacock Award for Occupational Health & Safety -2008’ Institute of Directors

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INSTALLED POWER PLANTS

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NTPC Auraiya Plant

Location Auraiya, Dibiyapur, Uttar Pradesh

Govt. Approved Date

17th January, 1987

Plant Capacity

662 MW

Land Availability

Available

Fuel Used

Natural Gas, Naptha

Turbines Gas turbines, Steam turbines

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Basic parts of power plants

1.Gas turbine: In the gas turbine, the power for driving both the compressor and the generator is produced.2. The energy is supplied to the turbine in the form of hot gases as they come from the combustion chamber. The kinetic energy of the gases is transferred to the rotor in the turbine by means of rotating blades. The combustion gases, come from the preceding stage, are accelerated in the stator blade while, simultaneously the inlet pressure is reduced by vectorial addition with circumferential speed. The relative speed is obtained for starting the generator, there is a high torque requirement and therefore we used a starting unit for starting a gas turbine. Gas turbine starting unit consists of Pony motor, which provides starting torque to generator for rotation. There is a turning motor in starting unit, which provides lubrication of oil in the bearing. In this unit an oil tank is also present to provide oil. Here we use a pressure gauge for measurement of pressure. We use a pressure transmitter which transmits a current signal. The GT starting unit is joined to generator through a shaft. This generator is joined to a gas turbine which is joined to combustion chamber. This gas turbine exhaust has temperature from range 500 to 550 degrees Celsius. This exhaust is used for generation of steam for steam turbine through Waste heat recovery boiler (WHRB). This gas turbine operates on Brayton cycle.

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2. Steam turbine: There are 2 steam turbines in number, present in the full AuGPP (Auraiya Gas power project). The two waste heat recovery boilers combined their output to one turbine.The turbine gets its feed from two drums. These drums are low pressure (LP) and high pressure (HP) drums. The low pressure drums give its output directly to the turbine but the HP drums give its output to the supper heater and then to the turbine. In this way, steam turbine consists of two turbines. These are as follows-a) Low pressure (LP)b) High pressure (HP)The low pressure turbine also gets the raw material from the HP exhaust. The left out steam in the LP steam turbine goes to the condenser and then again to the drums. The numbers of stages that are present in the high pressure (HP) turbine are total 12 in number and that in the LP turbine are 6*2 stages. This low pressure turbine is directly connected to the generator. The steam turbine operates on Rankine cycle.3. Fuels: In the plant, mainly two fuels are used. They are as follows:a) Natural gasb) NaphthaGas turbine is capable of burning a range of fuels including naphtha, distillates, crude oil, and natural gas. Selection of fuels depends on several factors including fuel availability, fuel cost and cleanness of fuel.

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Natural gas is ideal fuel because it provides high thermal efficiency and reliability with two operation and maintenance cost. Liquid fuels, particularly heavy oils, usually contain contaminants, which cause corrosion and fueling in the gas turbine. Contaminants, which cannot be removed from the fuel, may leave deposit in the gas turbine, which reduces performance and adds to maintenance costs.Dual fuel systems are commonly used enabling the gas turbine to burn back up fuels. When the primary fuel source is not available, dual fuel systems can be used fire both fuels simultaneously.

LIQUID FUEL SYSTEM: it consists of the liquid fuels storage and handling system. The liquid fuel storage and handling system provides means for unloading storage and distribution of the fuel oil within the plant and typically composed the following major components.a) Fuel oil unloading pumpsb) Fuel oil transfer pumpsc) Fuel oil storage tanksd) Flow motore) Strainersf) Pressure and level control

NAPHTHA PRESSURING SYSTEM: By the forwarding pumps Naphtha is pumped up to the GTs and kept under recirculation for firing, separated pressure pump sallied filters and measurements and recirculation system is used. This pressurizing is required because in the naphtha burner this fuel is mechanically atomized. 14

4. Heat exchanger: It is a device in which heat is transferred between two moving fluids. Heat exchanger may be parallel flow. Counter flow or cross flow, depending upon the direction of the motion of the two fluids. If both fluids move in the same direction, it is parallel flow heat exchanger and if fluids move in the opposite direction, it is a counter flow heat exchanger. If they flow normal to each other, it is a cross flow heat exchanger. There are 4 types of heat exchanger-a) Shell typeb) Single typec) Double typed) Plate type

5. Compressor: In the gas power plants, the main function of the compressor is to increase the pressure of the air and its temperature is also increased in the compressor room, first of all there is a silicon tank which is used for absconding the moisture contents of air and then this air is compressed and sent to the combustion chamber for the combustion. The number of stages involved in the compressor chamber is 19. 6. Combustor: In the combustor chamber, combustion takes place between fuel and compressed air from compression room. The combustion is a chemical reaction between a fuel and oxygen, which proceeds at the fast rates with the release of energy in the room of the heat. The temperature of the combustor chamber is usually 1100 degree Celsius. This temperature heat energy is sending to the turbine. The number of thermocouples in the combustor chamber is 18. They are used for the measurement of the temperature indication of the combustor chamber.

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7. Condenser: The exhaust steam of the steam turbine condenses into water in the condenser where cooling water circulates. After heat reflecting from the condenser chamber, this water is sent to the pump. A condenser could be a reversible constant pressure heat rejection. 8. Nozzle: A nozzle is a device which increases the velocity or kinetic energy of a fluid at the expense of its pressure drop. When air pressure, at nozzle end is very low, then there is less leakage to the surrounding and back pressure will be high. But as we increase the air pressure, then there is more leakage to the surrounding and the back pressure decreases.

9. Filters: For combustion process in the combustion, there is requirement of oxygen. We take oxygen from atmosphere as air in the atmosphere contains impure particles (dust particles). Therefore we use a filter, for removal of dust particles from the atmosphere air and to get pure oxygen for combustion in the combustor chamber.

10. Generator: In gas power plant, generators are used for generation of electricity. Basically generator has two parts:a) Statorb) RotorStator is the stationary part of the generator on which field winding is present. Rotor is the rotating part of the generator on which armature winding is present. When the rotor rotates, the flux linked with the conductors changes. Therefore EMF is induced based on the principle of Faraday’s laws.In gas power plant, total six generators are used (one for each turbine). 16

11. Valves: In gas power plant, valves are used to control the flow. On the basis of activating, control valves are classified as follows:a) Pneumatic valves- These type of valves are operated by air. These are fast controlling valves. These are as follows:(i) Diaphragm actuated:--- Position control type (can be adjusted to various levels)--- On soft type

b) Position type:Air to case- fails safe openAir to open- fails safe closeAir to close means gas pipe is connected to the upper surface of the diaphragm.(ii) Piston (cylindrical) actuated:--- Electric valve: these are operated by electricity and are slow--- Manual valve: these are operated by humans --- Hydraulic valve: these are operated by liquids.On the basis of mechanical construction:

a) Globe valve: these are also called control valves.b) Gate valve: these are called on/off valve.c) Needle valve: these are used for small flow.d) Non-return valve: these are used for unidirectional flow.e) Butterfly valve: these are used for large flow.

12. Pump: After heat rejection, in the condenser the water is sent to the pump. For the pump, the ideal process would be reversible adiabatic compression of this liquid ending at the initial pressure (increase its pressure).In the gas power plant, there is centrifugal type pump. In this type of pump, inlet and outlet are connected to the peripheral of the pump. After pumping, outlet water is sent to the boiler.

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ELECTRICAL MAINTENANCESWITCH GEAR

A Switch gear is one which makes or breaks an electrical circuit.

The devices which comes under this category are:

1.Isolator

2.Circuit Breaker

3.Earth switch

4.Load Break Switch

5.Switching Isolater

An Isolator is one which can break an electric circuit when the circuit is to be switched on no load.These are normally used in various circuits for the purposes of isolating a certain portion when required for maintenance.

A Circuit Breaker is one which can break or make the circuit on load and even on faults. Normally Circuit Breakers are installed accompanied by isolators.

Earth switches are devices which are normally used to earth a particular system to avoid accident , which may happen due to induction on account of live adjoining circuit . These do not handle any appreciable current at all.

Load break switches are those interrupting devices which can make or break circuits at 8 times the rated current . These are normally installed on the same circuit or on the circuits which are backed up by circuit breakers.

Switching isolators are capable of 1. Interrupting transformer magnetize current and line charging

current2. Load transfer switching its main application is in connection with transformer feeder

as this unit makes it possible to switch out one transformer while the other is still on load 18

A VIEW OF THE 220 KV SWITCHYARD

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CIRCUIT BREAKER

Classification based on medium used for arc quenching

1.Minimum oil circuit breaker 2. Bulk oil circuit breaker

3.Sulphur hexafluoride (SF6) circuit breaker

4. Air blast circuit breaker

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Arc extinction in air break circuit breaker

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SWITCH YARD AND TRANSMISSION EQUIPMENTS

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Lightening arrester:They are provided at the terminals of the transformers for protection against lightening or any surges developing in the system.

Current transformer:They are single phase oil immersed type.The secondary current is generally 1 amp but also 5 amp in certain cases.

Capacitor voltage transformer: They are used at 220kv and above.For the lower voltages electromagnetic typeof voltage transformers are mostly used.

Bus bar arrangement:They are single bus single main and transfer bus,main I and main II with transfer bus.The type of arrangement depends uponthe reliability of supply from the substation.

Bus bar supporting structures:They are generally of steel latticed type.Recent trend is to adopt RCC structures for supporting the buses.

Earthing resistance of the substation:For substaion it is of the order of .5 ohms and for transmission lines it varies from 10 to 20 ohms.Earthing of the substation is done by laying mat in and around the switch yard area.Normally ungalvanised mild steel flats are used for earthing and risers.

Soak pits: They are provided in respect of all the transformers where the quantity of oil exceeds 2000 litres.

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List of Equipment 400 KV Switch-Yard------------------------------------------------------------------------------------------------Name of Equipment, Equipment detail, No. of Equipment------------------------------------------------------------------------------------------------Air Blast Circuit Type DIVF, 400 KV, In = 3000 A, 7 Set

Breaker If=40 KA, Operating pressure 27To 31 Kg/cm2 , ABB make

Air Break Isolator Voltage = 420 KV, Rated Amp = 20 Set2000 A, 40 KA for 3 Sec.Type : RC 500Make : S & S Power Switch gear.

Current Transformer Type NPOULVZ Insulation level 24 Nos.630/1425 KV, system voltage420KV, 5 Core, Core 1 & 2 : 2000-1000/1Core 3 : 2000-1000-500/1Core 4 & 5: 2000-1000-500/1CVT Type CVE/420/110 V, 300VA, 3 core 12 Nos.25

Each of ratio 400 KV/110V. Make WSI

Lightening Arrester 360 KV, 10 KA, Make : BBC 12 Nos.

Earth Switch Type RC-E, 420 KV, S&S PowerSw/Gr make 22 Nos.

Wave trap 0.5 mH, 2000 A, WSI makeHV LV TV92

Auto Transformer 315 MVA with OLTC V = 400 : 220 : 33 2 Nos.MVA = 315 : 315 : 105I = 455 : 827 : 1837

Above rating for OFAF cooling TELK Make

Shunt Reactor 33 KV Core type, 33 KV, I = 437.4 A, 25 MVAR 2 Nos.

Cooling ONAN BHEL make

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33 KV MOCB Type HLR 84/2501B V = 72.5 KV 3 Nos.

Insulation level 325/140 KVNormal current – 2500 AFault current – 40 KABHEL make

66 KV PT BHEL make, current ratio 1000/1 Amp 6 Nos.5 core66 KV PT BHEL make, 66 KV/110 V, 3 core 6 Nos.66 KV Isolator S&S make RC 300, I = 1250 A 8 Nos.Voltage 245 KV

66 KV Earth switch S&S make for Isolators RC 300, 12 Nos.I = 1250 A, V = 245 KV93

Surge Capacitor BHEL make 40 KV, 0.125 6 Nos.40 KV Rated V = 40 KV, I = 1.57 A

Lightening Arrester Elpro international make Type 9L 9 Nos.111 AH/A / 18.5 KV each stack.

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Diagram of 400 KV Switch Yard

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6.6 KV Switchgear

(1) Incomer/Bus Tie /Bus Tie Isolator BreakerMake MELCOType 6-SFG-40KRated Voltage 7.2 KVRated Breaking Current 40 KARated Making Current 100 KARated Normal Current 2850 AmpsRated control Voltage DC 220 Volts

(2) Feeder Breaker/Cooling Water P/H BreakerMake MELCOType 6-SFG-40KRated Voltage 7.2 KVRated Breaking Current 40 KARated Making Current 100 KARated Normal Current 570 AmpsRated control Voltage DC 220 Volts(3) 6.6 KV Bus BarRated Voltage 6.6 KV, 3 , 3 Wire ,Rated Current 2370 Amps 94

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Single Line Diagram of 6.6 KV Switch Yard

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415 Volts Switchgear

(1) Incomers/Bus Tie Breakers-1Type AE 3200 SRated Voltage 660 Volts (AC)Rated Normal Current 2800 AmpsRated Breaking Current 40 KAMaking Capacity (Peak) 105 KAShort Time Rating 65 KA, 1 sec.Application GTSWGR #1 & #2,WHRB/ST SWGR,BC # 1 & #2 SWGR

(2) Incomers/Bus Tie Breakers-2Type AE 4000 SRated Voltage 660 Volts (AC)Rated Normal Current 3550 AmpsRated Breaking Current 65 KAMaking Capacity (Peak) 143 KAShort Time Rating 85 KA, 1 sec.Application STATION COMMON SWGR

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Diagram Of 415 Volts Switch Yard32

GENERATOR SYSTEM

GeneratorThe generator is of hydrogen cooled (rated hydrogen pressure=2 Kg/cm2)3000 rpm, 50 Hz with static excitation system.The rated output of gas turbine generator is 141.08 MVA (at cooling watertemperature 32 0 C) at power factor 0.8 with rated terminal voltage 11.5kV.The rated output of steam turbine generator is 144.19 MVA (at coolingwater temperature 37 0C) at power factor 0.8 with rated terminal voltage11.5kV.The insulation of stator winding is of Class F (type of insulation:impregnated epoxy resin mica). The impulse voltage strength is 115 LVP.The insulation of rotor winding is of class F (type of insulation: impregnatedepoxy resin mica).

Excitation SystemStatic excitation system (MEC-3400) is adopted for both gas turbinegenerator and steam turbine generator.Basically, the excitation system consists of the following cubicles:a) AVR cubicle (with Power System Stabilizer PSS)b) Thyristor cubicle.c) Surge absorber cubicle.d) Field breaker cubicle.

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The power for initial excitation of the generator is obtained from the station220 V DC system.Under normal operation, the power source of the excitation system is fromthe associated excitation transformer, which is of dry type (natural aircooling)11.5 kV/360 V star/delta connected and nominal output capacity1200 kVA. The excitation transformer is protected by duplicatedinstantaneous and inverse time over current relays. Each relay leads to theoperation of its associated lockout relay (relay 186 or 286).The excitation system and PSS can be controlled and monitored from theelectrical control board (ECB) in the central control room.

NGR CubicleThe neutral point of the generator is earthed through grounding transformer.Grounding resistor is connected at the secondary side of the groundingtransformer.The grounding transformer is of single phase, encapsulated winding drytype, indoor type, with class F insulation, rated capacity 40 kVA (10-minuterating), rated voltage 11.5 kV/ 190 V.The grounding resistor is of 110 V rated voltage. 195 A (10 min.) and 0.563ohms.The generator neutral grounding cubicle is rated at 12 kV with lighteningimpulse withstand voltage 95 kV and to IP23.

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Generator Main CircuitIsolation phase busduct (IPB) is used to transmit power produced by thegenerator to the generator transformer excitation etc., which consists of thefollowing buses:a) Main BusBetween the generator and generator transformer. The aluminum conductoris of circular shape.b) Tee-off Bus :Between main bus and PT & SA cubicle. The aluminum alloy conductor isin channel shape.c) Tee-off Bus :Between the main bus and excitation transformer cubicle. The aluminumalloy conductor is in channel shape.d) Neutral Bus :Between the generator and generator NGR cubicle. The aluminum alloyconductor is in channel shape.

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Generator Transformer

The gas turbine generator transformers are supplied by MELCO, which arerated at 148 MVA (at 270 C), 235/11.5 kV (Yd11) and with OFAF. Thetransformer is of shell type.The short time rating of the transformer is 31.5 kA 3 second.Each transformer has an automatic TCG (Total Combustible Gas) analyzer,which takes oil sample automatically from the transformer tank at pre-settime interval. The combustible gas content of the oil sample is analyzed. Ifthe gas content or the trend of gas content exceeds certain level, an alarmwould be given to the control center. After the analysis, the oil samplewould be returned to the transformer tank automatically and the TCGanalyzer is ready for the next sample check. The transformer is equippedwith wheels with rail gauge 1676 mm.The transformer has two radiator banks (each bank has 50% coolingcapacity). Each bank has:- 6x10% fans (1x10% as spare )- 3x25% oil pump (1x25% as spare)Impact recorder was mounted on the tank during transportation.The steam turbine generator transformers are supplied by Crompton greaveslimited. They are shell type transformers (Rating =144.19). Each transformerhas 2 radiator banks.

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Potential Transformer and surge Absorber CubicleSurge absorbers are provided to protect the generator from lightening. Thelightening surges flow through the transmission lines to the generatortransformer.A surge absorber consists of a surge capacitor and lightening arrester.a) Surge Capacitor- Type : Synthetic liquid filled- Rated : 11.5/Ö3 kV- Rated capacity : 0.13 mFb) Lightening Arrester- Type : Metal oxide type- Rated Voltage : 12 kV- Power frequency-starting voltage: 15 kV (crest)- Max. discharge Voltage for : 25.2 kV (crest)1500A discharge currentThere are 3 potential transformers for generator protection and meteringpurpose.

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a) Potential transformer for voltage balance relay and reverse powerrelay (or low forward relay for steam turbine generator andperformance test at ECB).Connection : Star/starVoltage : (11500/Ö3) 110/Ö3 VCapacity : 100 VAAccuracy class : 0.2b) Potential transformer for various protection and metering purposesConnection : Star/star/Open DeltaVoltage : (11500/Ö3)/Ö3/)(190/3) VCapacity : 100 VA/ 200 VAAccuracy : 0.5/ 3Pclassc) Potential transformer for AVR :Connection : Star/StarVoltage : 11500/Ö3)/110/Ö3VCapacity : 200 VAAccuracy : 1.0ClassThe surge absorber and potential transformers are housed inside PT &SA cubicle, which is to IP52. The cubicle is of isolated phase type, which issuitable for connection on to the IPB. The impulse withstand voltage of PT& SA cubicle is 95 kV.

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STATION TRANSFORMER

The auxiliary power of the power station is supplied by two 220/6.9 kV(star-star connection) 27 MVA ONAF station transformers. The capacity ofeach station transformer is sufficient for all auxiliaries of the power stationoperating at the same time. So switching out of one station transformer willnot affect the normal operation of power station.The station transformer is equipped with on load tap changer at HV sidewith range ±10% in 1% step.Each station transformer is also with an automatic TCG analyser formonitoring the transformer oil at pre-set interval.Full wave lightening impulse withstand levels for HV and LV winding are950 kV and 60 kV respectively.Station transformer is of core type.HV side of the transformer is connected to 220 kV switchyard by overheadline. LV side is connected to 6.6 kV switchgear through non-segregated busduct.Nominal voltage rating of LV winding is 6.9 kV to take into considerationthe voltage variation (+10%) at 220 kV system and voltage drop at 6.6 kVand 415 V side.Neutral point of HV side is solidly earthed. Neutral point of LV side isearthed through neutral grounding resister.

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The capacity of 6.6 kV neutral grounding resistor is 400 A 10 seconds. Inthe design of the resistance grounding system, the following is considered:a) Co-ordination of protection relays.b) Overvoltage during single line to earth fault condition.c) Fault currentA 6.6 kV/415 V AUXILIARY TRANSFORMER AT415 V POWER CENTER

(i) The auxiliary transformer is of encapsulated dry type for indoor purpose,class F insulation and AN cooling. The winding of transformer is delta/star(6.6 kV/415 V) connected. The neutral point at LV side is solidly earthed.The transformer is mounted in the panel of 415 V power center. HV side isconnected to 6.6 kV switch board by cable. LV side is terminated with 415V busbar. Each transformer has a winding temp. indicator and with thecontacts for alarm and tripping.(ii) 6.6 kV/415 V station service transformers are of oil cooled outdoor type,class F insulation and having ON AN cooling. Transformers are located nearrespective load centers.40

6.6 kV AUXILIARY MOTOR AND 415 V AUXILIARY MOTORS

Motors with rating over 200 kW are fed directly from 6.6 kV switch-board,namely1) Gas turbine starting motor (1450 kW)2) Gas Turbine main fuel oil pump (210 kW)3) Waste Heat Recovery Boiler HP feed water pump (720 kW)4) Circulating water pump (770 kW)6.6 kV auxiliary motors are with class F insulation and enclosure to IP54(indoor motors). The starting current of 6.6 kV is 600% of full load current.In the power station, the rating of the gas turbine starting motor (1450 kW)is the highest. However, in the study of voltage drop during starting ofmotor, the starting current of circulating water pump (770kW) is considered.It is because the gas turbine starting motor (4-pol) is accelerated from zeroto synchronous speed by pony motor (90 kW). Furthermore, type of gasturbine starting motor is of short time rating (30 minutes- for 2 times startingin succession). The gas turbine starting motor is equipped with insulatedbearings to prevent flow of the shaft current.All 6.6 kV motors have stator winding temp. detectors (4 R.T.D’s perphase). Auxiliary motors with rating less than 200 kW are of 415 V withclass B insulation and enclosure to IP54 and IP55 for indoor and outdoorservice respectively

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. For motors with rating larger than 100 kW, the startingcurrent is 720% of full load current. For motors with rating less 100 kW, thestarting current is 800% of full load current. All motors rated above 30 kWare provided with spare heaters.

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