Distribution Transformers -Impact of Harmonics, Estimation of Losses and Life expectancy & Mitigation of ill effects

Diesel GeneratorsM. Nageswar Rao, Sr.Mgr.(EMD), NTPC-Simhadri

Date: 08.06.2016

ContentsNeed for DG setsPrinciple & OperationDG set partsDG sets startingAuto startRemote startLocal StartingVoltage/speed biasProtections & Alarms2Need for DG sets3DG sets are the backbone of the emergency supply equipment of the power plant.Safe isolation/ shutdown of the Unit in case of AC failure Grid failure 11kV unit bus faultDC failureUnit 220V dc failure.Switchyard 220V dc failureStation C&I 24V dc failure (Stage#2)Emergency equipment (EOP, DC SOP, DC JOP, DC scanner air fans) will start with battery back up.For long time operation, DG sets to be started to charge Emergency bus.DC battery banks are sized for providing DC supply for 30min to all the mentioned critical DC drives. To supplement this, DG sets are provided.Provided with safe shutdown of the unit (to provide lubrication and avoid metal to metal contact during coasting down period).

3Principle & Operation4DG sets Working PrincipleDiesel engine is the prime mover, which drives an alternator to produce electrical energy.DIESEL ENGINEALTERNATORLOADchemicalmechanicalelectricalDG set system6

Parts of DG setDiesel EngineAlternatorPCC (power command)Local control PanelBattery & Battery chargerDay tankRadiatorStack

7Pros & ConsAdvantagesDisadvantagesLow operating costs Easily available in the market Portable Least inflammable Maintenance is easy

Sound (However, one can even buy silent generators) Produces higher smoke

8DG set RatingPrime Power Rating (PRP)Stand by Power Rating (ESP)Applicable for supplying electric power in lieu of commercially purchased power. installations served by a reliable utility source. Power availability at variable load forunlimited number of hours. the duration of power outageOverload capacity at intermittent periods.10%NilTA Turbocharged Aftercooled50 50.3ltr (3067 cub.inch dispacement)9DG sets in NTPC-Simhadri10DG sets in SimhadriStage#1Stage#211

DG sets in SMPPStage#1Stage#2DG set SupplierPowericaJaksonsPrime Power Rating415V, 1500kVA, 415V, 1250kVA, Diesel EngineCumminsAlternatorStamford-New Age, U.K.Stamford, IndiaControlPLC basedMicroprocessor based Power CommandEnclosureOpen typeAccoustic enclosureTA Turbocharged Aftercooled50 50.3ltr (3067 cub.inch dispacement)12Diesel Engine specsStage#1Stage#2MakeCumminsModelKTA-50-G8 KTA-50-G3No. of cylinders16 VeeAspirationTurbocharged-AftercooledMethod of cooling of Engine &lubrication oilRadiator cooled, Water cooledDisplacement50.3 ltrs (3067 cub.inch)Output - Prime1735 bhp (1294 kWm)1470 bhp (1097 kWm)Fuel consumption @100% load301.7 ltr/hr251.8 ltr/hrOil consumption @100% load0.35 ltr/hr0.3 ltr/hrGovernor / ClassElectronic / A1Lubricating oil system capacity177 ltrsCoolant capacity (engine + radiator)510 ltrs440 ltrsWeight6580 kg (dry)TA Turbocharged Aftercooled50 50.3ltr (3067 cub.inch dispacement)1500 rpmGovernor class-A1: Speed variation is limited to 1% for any steady state load from no load to full load.(full load thrown off/ full load put on)EFC: Electronic Fuel Control (for isochronous and voltage droop characteristics)Fuel: HSD as per IS:1460Lube oil: Grade CF-4, 15W40 Valvoline CumminsDiesel engine standard: is 304613Alternator specsStage#1Stage#2Rating1500 kVA1250 kVAVoltage, p.f.3-ph ,415V, 0.8 pf lagStator current2086 A1739 ARated overload capacity110% for 1 Hr. in every 12 Hrs Operation.Stator winding2/3 pitch, Double Layer LapClass of insulationClass HTemperature rise over 50 degC at rated currentClass HMakeStamford-New Age, U.K.Stamford, IndiaFrame size / Model No.HC-74GPI-734C2Voltage regulation 0.5%WindingStar 12 windingStar- 6 windingAlternator standardIS 4722, IEC 60034-1EnclosureIP 22IP 23Max. permissible unbalance electrical loading25% unbalance in electrical loading is allowed provided none of the phases exceeds the rated currentBearingDE (BALL. 6228 C3)NDE(BALL. 6319 C3)Weight4022 kgTA Turbocharged Aftercooled50 50.3ltr (3067 cub.inch dispacement)2/3 pitch eliminates all triplen harmonics in output voltage, also reduces neutral current.14Parts of DG set15DG set parts16

Diesel EngineIn the diesel engine, air is drawn into the cylinder and is compressed to a high ratio (14:1 to 25:1). During this compression, the air is heated to a temperature of 700900C. A metered quantity of diesel fuel is then injected into the cylinder, which ignites spontaneously because of the high temperature. Hence, the diesel engine is also known as compression ignition (CI) engine.17

AlternatorSynchronous generator brushless with rotating magnetic field

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Alternator naming

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ExciterAlternator is separately excited by the PMG. This is a shaft mounted, high frequency, pilot exciter which provides a constant supply of clean power via the Automatic Voltage Regulator (AVR) to the main exciter. The main exciter output is fed to the main rotor, through a full wave bridge rectifier, protected by surge suppression.20Stage#1Stage#2TypeBrushlessRating10.3 kVA, 3.6A, 0.8pf

Genset controlAVR ControlPCC control21

ECPThe ECP controls the engine speed at the set reference speed (for e.g. 1500 RPM) from No load to full load (Isochronous operation).22

AVR- MX321 3 phase rms sensed with a voltage regulation of 0.5% rms (see the note on regulation). The UFRO circuit has adjustable slope and dwell for controlled recovery from step loads. An over voltage protection circuit will shutdown the output device of the AVR, it can also trip an optional excitation circuit breaker if required.Generator mounted current transformer to provide quadrature droop characteristics for load sharing during parallel operation.Provision is also made for the connection of the STAMFORD power factor controller, for embedded applications, and a remote voltage trimmer.23PCCPCC is a microprocessor based generator set monitoring, metering, and control system designed to mount directly on the generator set. 24

Power Command ControlAlternator data- Line-to-neutral and line-to-line AC volts- 3-phase AC current- Frequency- kW, kvar, power factor kVA (three phase and total)Engine data- DC voltage- Engine speed- Lube oil pressure- Coolant temperature/ low level- Comprehensive FAE data (where applicable)Other data- Genset model data- Start attempts, starts, running hours, kW hours- Load profile (operating hours at % load in 5% increments)- Fault history- Data logging and fault simulation (requires InPower)

24Turbo charger25

After coolerLarge capacity integral aftercoolers are supplied with cooling water separate from the engine jacket. This provides cooler, denser intake air for more complete combustion and reduced engine stresses for longer life and low exhaust emissions. 26

RadiatorA two pump, two loop system must be employed; i.e. the engine jacket is cooled by one radiator or heat exchanger and the aftercoolers are cooled by a separate radiator or heat exchanger.

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Fuel filterDual spin on paper element fuel filters with standard water separator

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Fuel supply controlFuel pumpActuatorFuel shut off valve

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Lub-oil filterLub oil filterSuper bypass lub-oil filter30

Starter motor31

Battery charging alternator32

Air filter33

Lub-oil priming pump34

Alternator terminalsPhase sideNeutral side35

DG set starting36DG set startingRemote starting37DG starting (St#1)EMCC normally fed from USS Section#1. In case of failure of incoming supply from 1DA/2DA bus, on sensing of under voltage, tie breaker gets opened Main DG takes auto-start & DG incomer auto-closes.If Main DG fails to start, start S/B DG manually.38

Time taken to start the DG and closing of DG breaker is 12-14 sec, during this time bus will not be available.The Main DG set will start in auto when DG bus is dead or DG bus senses under voltage (V