commissioning generators and its auxiliary system

7/31/2019 Commissioning Generators and Its Auxiliary System

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24 May 2012 PMI Revision 00 1

COMMISSIONING OF

GENERATOR AND

ITS AUXILIARY

SYSTEM


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GENERATORS AND ITS AUXILIARYCAN BE BROADLY DIVIDED INTOTHREE SYSTEMS

A) Stator water system B) Seal oil system

C) Gas system

D) Generator


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STATOR WATER SYSTEM


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STATOR WINDINGWATER SYSTEM

DIFF PRESSSWITCH

VACUUMPUMPS

POLISH UNIT

FILTERS

COOLERS

PUMPS

GAS TRAP

FLOWMETERS

CONDUCTIVITY

EXPANSIONTANK

MAKEUP

FSI

IDIFF PRESS.

MAGNETFILTER


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Stator water cooling is a closed loop system.

There are two full capacity single stagecentrifugal pumps with change over facility.

The pumps are driven by 3Ph. 415V A.C.

motors. The stator water cooler is shell and tube type

heat exchanger.

DM water flows through shell.


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There are two mechanical filters and one

magnetic filters. Mechanical filters are of wire mesh type.

Magnetic filter is having permanent magnet.

The expansion tank is a hermetically sealedcontainer made of S.S.


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Float valve in the expansion tank maintains

water level in the tank which act as suctionstorage tank for stator water pumps.

Polishing unit (mixed bed ion exchanger)

maintains conductivity of stator water to desiredlevel.


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For commissioning, first the system has to be

filled up.

Prerequisites for filling the cooling circuits:

a) complete circuit should be flushed,

b) hydraulic testing,

c) installation of pump and motors after O/H,

d) filters cleaned and boxed up,


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e) coolers and all other components are boxed

up,f) ion exchanger is ready and is in service,

g) all instruments and measuring devices are in

position after calibration.


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System should be lined up for filling.

Complete stator water system should be filledwith DM water having required quality.

All air should be vented from the system before

starting of the pump.


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Trial run of the stator water pumps is

satisfactory. Check the stand by pump for automatic starting

on all interlocks and protections,

Adjust level regulator in the expansion tank, Check all the signaling, indicating, recording,

event logging, metering instruments, alarms and

annunciating devices for proper functioning.


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Adjust make up water pressure around

2.0Kg/cm2

Adjust small water flow through the gas trap

Check there is no leakage of water in the

system Take ejector into service

Take one cooler into service


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Check emergency switching in circuit of the stand

by water pump Check high and low alarm of the expansion tank

Check high conductivity alarm and tripping

Check pump discharge pr., filter diff. pr.,conductivity, flow, inlet winding pr., winding diff. pr.,vacuum in expansion tank, motors current.


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SEAL OIL SYSTEM


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SEAL OIL SYSTEM

OILCOOLER

FILTERS

DPRV

CONSTANT PRESS. REGULATORSWITH ORFICE PLATES

VACCUM

PUMP

BEARG

DRAINS

TG

1 2

EE

BEARING

TEBEARING

GASEXHAUST

FROM GAS

SYSTEM

IOT

VACUUM

TANK

SOST

SOPSOP-3

DC

DPSW

TS ES

FR

FLOW M.PS PG


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Generator shaft seals are supplied with

pressuerised seal oil to prevent hydrogenescape at the shaft.

Oil pressure is kept higher than the gas

pressure. AC seal oil pump one number and DC seal

oil pump- one number are provided which

feed the oil to the seal through cooler andfilter.


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Both the AC seal oil pumps are 100%

capacity screw type pumps. A vacuum pump is provided to maintain

vacuum in seal oil tank.

There is a additional facility to supply seal oilfrom governing oil.

The seal oil pressure to the seal is controlled

by DPR which maintain specified DPbetween oil and hydrogen.


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Thrust oil holds the seal ring in position

against gas pressure. Two seal oil coolers each having 100%

capacity is provided to cool the oil.

Duplex filter is provided in the oil line.

Vacuum pump evacuates gases from SOT.


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Seal oil system will be commissioned when the

following system is ready1) Generator ready to be filled with hydrogen or air.

2) Machine (TG) ready to be put on barring gear.

Prior to commissioning make ensure properfunctioning of all the signaling, indicating, recording,event logging, metering instruments, alarms andannunciating devices.


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Seal oil system has to be filled with oil

Prerequisite for oil filling

1) set all level switches

2) close all stop and non-return shut offvalves

3) open all pressure gauge and pressureswitches isolating valves


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4) open pressure transducer isolatingvalves

5) open isolating valves of impulse lines

of differential pressure regulator6) bearing lube oil system is in service


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Open isolating valve of seal oil storage tank

to seal oil system. Oil will start filling the sealoil system

Open valves in oil flow path

Take coolers and filters into service

After oil is filled up into the system level willbe visible in the gauge glass of the SOT


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Take governing oil system into service

Start AC seal oil pump

To clear air locking seal oil pump should be

switched on and off till its discharge pressuregauges shows a constant pressure

Vent DPRV-A and DPRV-B


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Vent both the coolers one by one

Vent filters

Vent pressure gauges, pressure switches

and transmitters

Set seal oil pressure by DPRV-A

Stop AC seal oil pump and set DPRV-B

(


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Set thrust oil pressure (0.5 Kg/cm2 more than

seal oil pressure) Take vacuum pump into service and adjust

SOT vacuum as recommended

Check all the meter readings are within limit

Check seal oil flow is as per systemrequirement


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Check automatic starting of stand by DC seal oil

pump by different interlocks including alarm Check function of level switch of SOT, seal oil

storage tank and pre-chambers

After seal oil temperature reaches 30

0

C startcooling water flow to seal oil cooler and adjustthe flow in such a way so that the seal oiltemperature is maintained at 400C


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HYDROGEN GAS SYSTEM


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H2DISTRIB

HYDROGEN

CO2VAPOURIZER

TO

SEALOIL

DPT

H2 DRIER

HYDROGEN GAS SYSTEM

CO2

ANALYZER

DRAIN

AIR

FILTER

OP

DPI


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Overhauling of gas drier has been carried

and the drier is boxed up Check all instruments are in position after

calibration

Functionally check the gas drier system Check the availability of adequate no of CO2

filling point and adequate no of CO2 cylinders


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Check availability of adequate no of

Hydrogen filling points and cylinders

Functionally check the LLD system

Check whether the relief valves in the highpressure valves are alright

Check the generator is completely boxed up

Check the seal oil system is in service


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Check generator air tightness test is

successfully completed.

Start purging air with CO2 till the purity ofCO2 inside casing reaches above 95%.

After CO2 purity reaches as desired startpurging CO2 with Hydrogen.

Continue purging till hydrogen purity reaches

above 98%.


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GAS SYSTEM

Pressurise generator casing with hydrogenup to its design value

Recheck hydrogen leakages by detector

Take drier into service

Take gas coolers into service

Vent the coolers and establish flow


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TESTS ON GENERATOR


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The field tests of the generator include theacceptance tests and periodic tests.The Acceptance tests are performed during

the erection and after completion of theerection.

The periodic tests are carried out duringoverhauls, routine repairs and during the time

between repairs.


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Measurement of Insulation ResistanceEach phase relative to

the earthed casing (frame) and other phasesearthed. Bus-duct shall be disconnected.IR measurement at 2500Volts

After

the water connections are mounted and before

the external parts of the cooling system isconnected.IR measurement at 2500Volts


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a) The insulation resistance of the stator winding

shall be measured with distillate drained from thestator winding, the water headers being connectedto the ohmmeter screen and isolated from theexternal cooling systems.


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b) The value of the ratio R60/R15 shall be at

least 1.3 at a temperature of +10 C to +30

C. If the value of the resistance R60 or ratioR60/R15 is below the permissible value, the

stator winding shall be dried out accordingto the appropriate instructions, remove

moisture from the winding by blowing it out

with dry compressed air then recheck itsinsulation resistance.


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c) Prior to measuring the insulation resistance of

the stator windings make sure that there was noingress of water to it during storages transit and

erection of the stator (the condition of packagingwill show it.)


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3. Rotor winding: IR measurement at 1000Volts.4. Bearing: Insulation resistance is measuredrelative to the base-plate, with oil pipingcompletely assembled, with no contactbetween the bearing and the rotor shaft

journal. IR measurement at 1000 Volts.


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5. Resistance temperature detectors:Insulation resistance of RTDs is

measured together with the wiring from,

the measuring instrument to the RTDS,including that running within thegenerator. IR measurement at 1000 Volts.

6. Insulation of oil catcher and the

outer end shields of at the exciter end. IRmeasurement at 1000 Volts.


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Shaft seal at the exciter end: Insulation

resistance as is measured between theshaft seal housing and the outer endshields, with oil piping completely

assembled. IR measurement at 1000

Volts.


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Measurement of A.C. Impedance ofRotor-winding This should be made with apower-frequency voltage of 220 V at differentrotor speeds varied in steps from 500 rpm to

3000 rpm and on the stationary rotor. Theresults shall be compared with those obtainedpreviously, the condition of the generator

during the compared measurements being thesame (the rotor is inside or outside thegenerator, the stator winding is open-circuitedor short-circuited, etc).


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Leakage Test on Bearing and Shaft-Seal

Housings The leakage test should be

conducted with the use of white wash andkerosene, the leaks being detected by visualexamination. The shaft-seal housings shouldbe also tested for leakage with the use of

kerosene . No leaks are permitted, The testduration is 24 h.


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Leakage Test on Stator WindingTerminals and Water Connections Theleakage test on the stator winding terminals

should be done in several steps.First the terminal bars should be separatelytested for leakage and for strength. The test is

conducted with water at a pressure of 2450kPa (25 kgf/cm2) applied for 1 h. No waterleaks are permitted.


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Leakage Test on Stator WindingTerminals and Water Connections When

assembling, the terminal bushings, test themfor leakage in a special fixtures (tank) with airat a pressure of 490 kPa (5 kgf/cm2), gauge,applied for 1 h. The test shall be made on the

completely assembled terminal bushing, Noleaks are permitted.


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Hydraulic Pressure Test on Gas CoolersPrior to mounting the gas coolers in the statorcasing, rust-preventive coatings should be

remove from their surfaces and the tube finsblown with compressed air.The gas coolers are tested with a hydraulicpressure of 784 kPa (8.0 kgf/cm2) applied for60 min. No reduction of the test pressure andleaks should take place during the test.


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Hydraulic Pressure Test on Gas CoolersIn the gas coolers with installed protectors areliable contact between the protectors andprotected surface should be ensured. Theresistance shall not be greater than 0.1 ohm,

The protectors shall not have a joint coating.


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Hydraulic Pressure Test an StatorWindingThe hydraulic pressure test on the statorwinding is made with DM water at a pressure

of 764 kPa (8 kgf/cm ) applied for at least 24 h.Before the distillate pressure is increased, tothe required value, the air shall be fully

expelled from the system. No reduction of thetest pressure, no signs of moisture an thewinding, headers, flexible tubes and theirsections are permitted during the test.


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Gas Leakage Tests on Rotor, Stator andAssembled Generator

After the generator erection / overhauls /routine repairs wherever dismantling of theouter end shields or removal of the gascoolers is involved, the generator and its

separate parts should be subjected to a gasleakage test.


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Gas leakage Test on the current carryingbolts (Rotor)The test should be performed before the rotoris inserted into the stator. Air is applied in turn

to the gland seals of each current-carryingbolt through special radial holes in the rotorshaft, Gas leakage is determined from a dropof the test pressure.The detected leaks should be eliminated by re-packing or replacement of the gland seals bytheir.


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Gas Leakage Test on AssembledGeneratorThe leakage test is aimed at tracing and

stopping air leakage in the stator casingassembled with the terminals, gas coolers,shields, water connections. The air used forthe test shall be dry and clean. The leaks

should be located with the help of soapsolution applied to the welds and to all jointsof the parts and comments.


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After the traced leaks are stopped, the secondstep of testing determines the leakage rateand is per formed at an air-pressure equal tothe rated hydrogen pressure applied for 24 h.


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Note: It should be noted that a 1 Cchange in the air temperature inside thegenerator part under will result in a 1.6

kPa change in the air pressure, the testpressure being 392 kPa (4 kgf/cm2),gauge. Therefore, when the leakage tests

are conducted, special attention shouldbe paid to the variation of airtemperature inside the part under test.


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Testing of rotor vent ducts for freepassage of airMark out the rotor slots in a clockwise

direction (as viewed from the slip rings

end), starting from the big pole tooth

located in that part of the rotor where thefield current lead is connected to the

inner slip rings. Number the vent ducts

in the wedges of each slot, starting fromthe retaining ring located at the slip-ring

end.


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TESTING

(1) Using the stoppers, plug all the holesin the seat wedges(2) Take out the stoppers from the inlet

and outlet holes of the vent duct betested.(3) Fit the nipple of the inlet nozzle into

the inlet hole of the vent duct, and that ofthe outlet nozzle into the outlet hole, the

liquid-filled column micro-manometerbeing connected to the outlet nozzle.


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EXAMINATION OF ROTOR RETAINING

RINGS BY DYE-PENETRANT METHODThe dye-penetration method of surfaceexamination is used for detecting cracks

and other types of discontinuities on thesurface of the rotor retaining rings. Themethod is based on the ability of some

aniline dye solutions to penetrate intothe various types of discontinuities in

materials.


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Clean the surface to be examined to amirror-like condition. Polish out roughmarks or, otherwise, they may affect the

examination results directly beforeapplication of the dye-penetrant solution,de grease the examined surface area. Applya continuous coat of the dye penetrationsolution to the examined surface. As the

solution coat dries out, apply another coat.


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After 15-20 min, remove quickly and

thoroughly the dye-penetrant solutionwith soft clean cloth. Using a spraygun or a flat brush, apply a smooth

coat of whitewash. Examine thesurface 5 min after the white wash hasbeen applied. Appearance of red veins

on the surface is indicative of thepresence of cracks.


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The dry-penetrant solutions shall be

prepared and applied in the open air or in aproperly ventilated room as all the dry-penetrant solution components are fire-

hazardous. Therefore, no smoking, no openflame, no sparking and no switching on ofelectric device are allowed near the placewhere the solution is prepared orexamination is conducted. Rubber glovesare to be used when preparing for andconducting the examination.


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ELCID (Electrical Core ImperfectionDetection) test on Stator Core: This test is

conducted to assess the condition of thestator core by testing for location of anyinter-turn shorting in the stator corelamination. This test is repeated in everyoverhaul involving rotor thread out.


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Prior to the initial start of the generator, thefollowing shall be done:(1) All civil construction work according to thedesign documents shall be completed, the

general and local lighting systems shall beinstalled.(2) Erection of the generator, installation of theauxiliary equipment, primary and secondary

switching circuits and their associated equipmentshould be completed, the completion of the workrecorded.


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(3) All pre-operational electrical measurementsand tests included in the generatoracceptance test program shall be performed.

(4) Water-, gas- and oil-supply systems,thermal-control, delaying, alarm and indicationcircuit shall be adjusted and tested, non-electrical protections shall be put on guard.

(5) All safety and fire prevention measuresshall be taken.


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The initial start and initial operation of thegenerator shall be performed in accordance

with the test and commissioning program. Allwork on the initial start and operation shouldbe done in accordance with this instructionmanual, the relevant operating rules and the

directions of the generator manufacturer.


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Initial Start of GeneratorWith the rotor stationary, proceed as follows:(1) Supply oil to the generating unit bearingsand shaft seals and make sure that the oil isflowing to the drain pipes normally.(2) Fill the generator with hydrogen so that thehydrogen pressure reaches the rated value.

Use carbon dioxide or nitrogen to purge airfrom the generator before filling it withhydrogen.


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(3) Ensure that the differential pressurebetween the seal oil and gas inside thegenerator, as specified, is maintainedautomatically. During the initial start (while

accelerating the generator to the rated speed),measure the vibration on the bearings andensure that there is no unusual noise, rubbing,

etc. in the generator. Go rapidly through thecritical speeds at which the highest vibrationson the rotor are observed.


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With the rotor at the rated speed,check the following:(1) Temperature of oil at outlets of all thebearings, and temperature of the bearingliners and shaft-seal bushes, vibration on thegenerator supports,

(2) Operation of the generator and exciterbrush gear.


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(3) Generator phase sequence and phasing onthe power system, residual voltage, withoutapplication of field excitation of the rotor).4) Proper circulation of water in the cooling

circuits of, the stator, gas coolers, heatexchangers.Abnormalities revealed (if any) after the initial

start and mechanical run may be eliminated bystopping the generator and inspection of thebearings.


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The electrical tests on the generator

should be conducted in accordance withthe acceptance test program.

No limitation is imposed on the rate ofraising the generator terminal voltage for

starts form both cold and hot conditions.

There is no need to warm-up the

generator before raising the voltage.


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No specific limit is placed on the extent ofdeviation of the obtained characteristic fromthose determined earlier. The test should beconducted at the rated hydrogen pressure.

During this test, measure and record all the PToutput voltages. Also ensure, measure andrecord availability of PT voltages at all voltage

/ impedance operated relays.PT Voltages in the synchronising circuit to beverified.


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Three-Phase short-circuitCharacteristic of Generating Unit

This characteristic should be determined withthe stator current reaching the rated value.Prior to obtaining the characteristic, a shortinglink should be installed behind thetransformer. The hydrogen pressure should be

equal to the rated value.


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The deviation of the obtained short circuitcharacteristic from those determined earliershould be within the accuracy of

measurements.

During the SCC testing, measure and recordthe reflection of the CT secondary of all the

CTs. Ensure the CT juice is available at all therelevant relays.


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Safety precautions including fire fighting

equipments are available. Oil supply to generator bearing and seal

has been established and quality/flow of

oil is as per specification. Generator is filled with hydrogen of

desired purity and up to rated pressure.


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Generator stator winding is charged with

distillate of desired quality. The otherparameters of distillate is as per norms

Generator gas coolers are charged and the

parameters are normal Generator circuit breaker is in open

condition after testing

All switchyard equipments has been testedand normalised


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All protection and control schemes are in

service after callibration and testing Excitation system has been tested,

normalised and field breaker has been kept

in open condition. Mode of excitation system has been

selected (auto/man)


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When generator reaches rated speed check

the followinga) bearing and seal temperatures

b) performance of brush gear

c) vibrations

d) any gas, oil or water leakages

e) any abnormalities in generator

performance


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Switch on excitation system and check forvarious parameters and functioning of excitation

system After ensuring all parameters are all right and

machine behavior is normal match thegenerators electrical parameters with the gridand synchronise the machine when permissivefor the same is available. The generator shall beswitched into the power system at precisesynchronizing.

Load the machine gradually. During loading alsomonitor all parameters.


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Inspection after Initial Operation Under

Load

The initial operation under load is considered tohave been accomplished if the generator hasshown normal performance during continuousoperation for 72 hours of switching thegenerator into the power system.


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After the 72-h operation, make inspection ofthe generator. During the inspection,disassemble the bearing and shaftirrespective whether any abnormalities have

been noted or in their performance duringadjustment and testing. The inspectioninvolves the visual examination of the shaft

journals, babbit-lined faces of the bearingliner an shaft-seal bushes.


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Clean the filters of the oil system and statorwinding cooling system. Remove scratches,marks, etc. on the shaft journals and babbit-lined faces by polishing or scraping. Stop theleaks detected in valves, flange joints, etc.

The generator is to be placed in commercialoperation after completion of the adjustmentand testing, and upon elimination of defectsand workmanship faults revealed during the

inspection.


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commissioning generators and its auxiliary system

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