158948170 transformer testing
Post on 19-Oct-2015
71 Views
Preview:
DESCRIPTION
TRANSCRIPT
-
TRANSFORMERTESTINGVIVEK JHA
1VIVEK JHA
-
Transformers:coreofelectricitysupply
Transformer:mostvitalequipmentofthesupplysystem
Types: EHVTransformer HTTransformer LTTransformer InstrumentTransformers
2VIVEK JHA
-
Toprovethatthedesignmeetsthespecifiedjobrequirementsandtoobtaintransformercharacteristics.
Tocheckthatthequalityrequirementshavebeenmetandthatperformanceiswithinthetoleranceguaranteed.
TestsperformedfortheformerpurposearereferredtoasTypetests andthatforthelaterpurposearereferredtoasRoutinetests (carriedoutoneveryunitmanufactured).
InAdditiontothesetwocategoryoftests,specialtestsMayalsobeperformedtoobtaininformationusefultotheUserduringoperationormaintenanceofthetransformer.
NECESSITYOFTESTS
3VIVEK JHA
-
TransformerTests
EXAMPLE:ROUTINETESTS Measurementofwindingresistance Measurementofvoltageratio,polarityandcheckofvoltagevectorrelationship Measurementofnoloadlossandexcitationcurrent Measurementofshortcircuitimpedanceandloadloss Measurementofinsulationresistance Switchingimpulsevoltagewithstandtest Lightningimpulsevoltagewithstandtest Magneticcircuit(isolation)test
EXAMPLE: TYPETESTS
Meaurementofpowertakenbycoolingcircuits
TempRiseTest
Reference standard : IEC 60076
4VIVEK JHA
-
ADDITIONALTESTS
TESTWITHLIGHTNINGIMPULSECHOPPEDONTHETAIL
MAGNETICCIRCUIT(ISOLATION)TEST
MAGNETICBALANCETESTONTHREEPHASETRANSFORMERS
DISSOLVEDGASANALYSIS(DGA)OFOILFILLEDINTHETRANSFORMER
DETERMINATIONOFCAPACITANCESANDTANDELTABETWEENWINDINGTOEARTHANDBETWEENWINDINGS
MECHANICALTESTS
MEASUREMENTOFVIBRATIONONTRANSFORMERTANK
VACUUMTESTONTRANSFORMERTANK
OILPRESSURETESTONCOMPLETELYASSEMBLEDTRANSFORMER
JACKINGTESTANDDYEPENETRATIONTEST
PRESSURERELIEFDEVICETEST
5VIVEK JHA
-
TestsonTransformers
Erectiontests(installationTests) Precommissioningtests CommissioningTests
Erection tests: Thorough checking for any damage Verification of technical specifications Foundation etc
6VIVEK JHA
-
ERECTIONATSITE:INSPECTION
y Makevisualinspectionforanytransitdamagey Checknitrogenpressure.y Checkvariousaccessoriesforanytypeoftransitdamage.y Makeinternalinspectionofthetransformertotheextent
possibleforanyvisiblediscrepancy.
7VIVEK JHA
-
OILFILLING
y Beforefillingtheoilintotransformerchecktheoilcarefullyfory Breakdownvoltagey Moisturecontenty Tandeltaandcapacitance
y Iftheoilisnothavingthepropertiesasrecommendedbythestandards,itmustbefilteredwithfilterswithbuiltinheaters andvacuumpumpsforimprovingthequalityofoil.
y Fortransformersdispatchedgasfilled,oilfillingmustalwaysbedoneundervacuum.
8VIVEK JHA
-
GENERALTESTSAFTERTRAFOINSTALLATION
(GetClearanceforTesting&Commissioningactivities) Physicalinspection Fireprotectionsystemavailable Oillevelchecking,nooilleakage Powerandcontrolcablingchecking, CoolerfanandPumpcontrolcktchecking Buch.Relaycorrectlymounted,airreleasedfromBuchrelay, Coolingsystem&radiators,OLTC BreatherinstallationOk,silicagelcolourblue OTI&WTICalibration
9VIVEK JHA
-
IRvalueoftransformerandcables WindingResistance TransformerTurnsRatio PolarityTest MagnetizingCurrent VectorGroup MagneticBalance Bushing&WindingTanDelta(HV) Protectiverelaytesting Transformeroiltesting Hipottest
PrecommissioningTests
10VIVEK JHA
-
CommissioningTests:
RemoteAnnunciationandcontrolschemes PowercableIdentification&Tests Chargingthetransformer:noloadandfullloadoperationandObservationforanyabnormality
Confirmingtheoperationofallprotection,interlocksandmeteringschemes
11VIVEK JHA
-
VIVEK JHA 12
1.ChecktheoperationoftheBuchholtzalarmandtripbyinjectingairthroughthetestpetcock.2.TesttheOTIforalarmandtrip.3.TesttheWTIforalarmandtrip.4.ChecktheworkingoftheWTI/RTD(ResistanceTemperatureDevice)repeatersatthecontrolroom.5.TesttheOLTC Oilsurgerelayfortrip.6.Checkalarmforlowoillevel.7.Checkvariousrelaysforcurrent×ettings8.Checkthecoolerunitfor
overcurrentsettingoffansandoilpumps coolersupplyfailurealarm fan/pumptripalarm.anymal operationofthetransformerBuchholtzrelaywhenalltheoilpumpsareswitchedonsimultaneouslyinforcedoilcooledtransformers
-
FIELDTESTS:
NoLoad Windingresistance TurnsRatio. Polarity, connectiongroupand Excitationcurrent.Onload shortcircuittest, Impedancemeasurement
13VIVEK JHA
-
InsulationResistance
y Thistesthasbeenthemostusualhistorically,beingcalledtomegger thetransformer(thetermcomesfromthefirmofthefirstIRsystems).
14VIVEK JHA
-
InsulationResistanceandPolarizationIndex
Equivalent diagram of the dielectric circuit of a transformer. Ri is the insulation resistance, Cg the geometric capacitanceand the different Ra/Ca emulate the equivalent dielectric absorption circuit.
15VIVEK JHA
-
WindingResistance
y Thisisnothingbuttheresistancemeasurementofthewindingsbyapplyingasmalld.cvoltagetothewindingandmeasuringthecurrentthroughthe same
y Themeasuredresistanceshouldbecorrectedtoacommontemperaturesuchas75Cor85Cusingthefollowingformula:
where
y RCisthecorrectedresistance,RMisthemeasuredresistancey CFisthecorrectionfactorforcopper(234.5)oraluminum(225) windingsy CTisthecorrectedtemperature(75Cor85C)y WTisthewindingtemperature(C)attimeoftest
16VIVEK JHA
-
WindingResistance.
y Withthistestwedeterminatethepureohmicresistancefromeachphasewindingsbothinhighandlowvoltageandeachpositionoftapchanger.
y inafirstapproachseemseasytomeasure,itsnotso,becauseitisnecessarytomakeflowrelativelyhighcurrentstoregistertheusuallowresistancevalues/m / withtherequiredprecision.Thiscurrentsmustalsoflowthroughtheequivalentinductanceofthetransformer.
17VIVEK JHA
-
18VIVEK JHA
-
TransformerTurnsRatio(TTR):
Transformer Turns Ratio (TTR): quotient between high voltage / low voltage. Must match with protocol /nameplate values.
In the power transformer with tap changer, take readings for each position (giving extra information on its status and that of the On Line Tap Changer (OLTC)
19VIVEK JHA
-
20VIVEK JHA
-
Transformer Turns Ratio: Doble kit
21VIVEK JHA
-
22VIVEK JHA
-
23VIVEK JHA
-
PolarityTest
24VIVEK JHA
-
Opencircuittest&Excitationcurrent
y Excitationcurrentisthecurrentflowingintothehighvoltagewindingwiththelowvoltagesideopen.
25VIVEK JHA
-
FIELDTESTS:Loadtest
y shortcircuittest,y Impedancemeasurement
26VIVEK JHA
-
ShortCircuittest
27VIVEK JHA
-
ShortCircuittest
y shortcircuittest isbasedintheapplicationofavoltageinonewinding(highvoltageone)withtheotherwindingshortcircuited.Itisusualtoregisternominalandextremepositionsifthetransformerhadan OLTC.
28VIVEK JHA
-
Impedancemeasurement
y Shortcircuitvoltage:voltagerequiredtocirculatefullloadcurrent.y shouldbeneartheprotocol/nameplatevaluefromthetransformer.y Itschangewillindicateirregularitiesinthemagneticcore,winding,
displacement,shortcircuits,mechanicaldeformations
29VIVEK JHA
-
30VIVEK JHA
-
FrequencyResponseAnalysis
y Themainpurposeofthistestistodeterminatethefrequencyresponsegraphoftheequivalentelectric/dielectric/magnetic/mechanicaltogetherevaluated.
31VIVEK JHA
-
FrequencyResponseAnalysis
32VIVEK JHA
-
DIELECTRICSYSTEMTESTS.Liquiddielectric(usuallymineraloil)ORsoliddielectric(usuallypaper)
Dielectriccircuittests.y InsulationResistanceandPolarizationIndex(IR,PI).y Capacitance,Dissipation(power)factor(tan)andinsulationlosses
indielectricbushing.y PartialDischarge(PD).
Oilsampling.y DielectricStrength.y Moisturecontent.y DissolvedGases.y FuranAnalysis.
33VIVEK JHA
-
Oiltestingandmaintenance
Therearethreeimportantpurposesoftheoilinatransformer:
1.Gooddielectricstrength2.Efficientheattransferandcooling3.Topreservethecoreandassemblyy Byfillingvoids(toeliminatepartialdischarge)y Bypreventingchemicalattackofcore,copperandinsulationbyhaving
y lowgascontentandnaturalresistancetoageing.
-
OilTesting
y Visualchecks
y OilBDVtest
y Powerfactor(tandelta)test
y Aciditytest
y Moisture(ppm)
y DGA
35VIVEK JHA
Transformer BDV test set
-
Breakdownvoltage.
y Oildegradationcanbeeasilyappreciatedwiththisparametertested.Thetestisbasedintheinsertionofelectrodesimmersedinoilandincreasingvoltageuptobreakdown.
y Testisrepeatedsixtimestogetarepeatablemeasurement.y Theonlydisadvantageisthatitisnecessarytoextractfromthe
transformerasignificantsample(testcellwillhave350...600ml).
36VIVEK JHA
-
37VIVEK JHA
IEC 156
-
TransformerOilSpecificationsTransformerOilSpecifications
Characteristics Requirementasper
IS:18661983
Breakdownvoltage 50KV(min)for>145KV
40KV(min)for72.5KVto145KV
30KV(min)for145KV
35ppm(max)for145KV
1.0(max)for0.1X10E12
NeutralizationvaluemgKOH/gm 140
38VIVEK JHA
-
Capacitance/Tandelta(DissipationFactor)
39VIVEK JHA
-
Capacitance/Tandelta(DissipationFactor)
y Anotherusualapproachwhenperformingdielectricevaluationistandelta.ThistestusesACandpursuestoknowlossangleofthetestedelement.
y Thismeasurementincludesinformationofthemoistureandcontaminationdegreeandemulatesthebehaviourandvoltageaggressionssimilartoserviceones.
y Itisimportanttotakenoteoftransformertemperatureandenvironmentalmoisture(surfaceleakage).
40VIVEK JHA
-
VectorGroupTest:Dy11
41VIVEK JHA
-
VectorGroupTest:Dy11
42VIVEK JHA
Dy11
-
Vectorgrptest
43VIVEK JHA
-
VectorGroupDy1
44VIVEK JHA
-
VectorGroupDy1
45VIVEK JHA
-
PartialDischargetest.
y Partialdischargearesmalldischargesthatappearinsideofthe dielectricasasignofitsdegeneration.Theyappearasaresultoftheincreaseoftheelectricfieldinsmallgaseousvoidsinsidetheoilandalsoinsidethepaper,epoxyor asaresultofthepresenceofmetalliccontamination,etc.Thisdischargeacceleratethethermaldegradationeffectsandleadsometimesexponentiallytothepowertransformerdestruction.
y Therearetwousualdetectionsystems,y Acousticsystemusessoundmechanicmanifestation(inultrasonicrangey Electric systemsdeterminatesdischargesandcorrelatesthemwithInsulation
healthiness.
46VIVEK JHA
-
SomeotherTests,normallyperformedatManufacturersworks
TemperatureRiseTest LighteningImpulseTest VacuumAndPressureTest LightningImpulseWithstand SwitchingImpulseWithstand
47VIVEK JHA
-
History/Trending
48VIVEK JHA
-
49VIVEK JHA
-
50VIVEK JHA
-
51VIVEK JHA
-
Conclusion
Testingisanart&scienceofmanagingMachine,Manpower,Material,Quality,Time
y Peopleresponsibleforupkeepofelectricalapparatusneedtocultivateawatchfulattitudeto
y Look (eye) Listen (ear)y Smell (nose) Feel (finger/skin)
forsymptomsofimpendingtroubley Adaptnewtechniques.y Keeponlearningfromtheexperiencesworldwide,avoid
obsolescencey DevelopIntegratedPredictiveDiagnosticSystemy KeepitSystemOrientedtoensuresustainabilityy (Avoidsubjectivity&individualbias)
52VIVEK JHA
-
Conclusion
y SafetyFirsty GoodTestequipmenty peopletohaveadeepknowledgey Takecareofenvironmentalconditionswhilecomparingresultsy Workpressureandshortdowntimey Keepyourmindcool
53VIVEK JHA
-
SomeReferences
y NATIONALSTANDARDSIS2026(PARTIII)y IEC600765:2000.Powertransformers.Part5:Abilitytowithstandshortcircuit.y IEC60726:2003.Drytypepowertransformers.y IEC600763Testlevels&testmethodrequirementfordifferenttestsy ANSI/IEEEStd621995.IEEEGuideforDiagnosticFieldTestingofElectricPowerApparatus
Part1:OilFilledPowerTransformers,Regulators,andReactors.IEEEPowerEngineeringSociety1995.y ANSI/IEEEStdC57.12.901993.IEEEStandardTestCodeforLiquidImmersedDistribution.Power
andRegulatingTransformersandIEEEGuideforShortCircuitTestingofDistributionandPowerTransformers.
y ANSI/IEEEStd.C57.12.001993.IEEEStandardGeneralRequirementsforLiquidImmersedDistribution,PowerandRegulatingTransformers.
y EN601561995.Insulatingliquids.Determinationofthebreakdownvoltageatpowerfrequency.Testmethod..
y EN608141997.Insulatingliquids.Oilimpregnatedpaperandpressboard.DeterminationofwaterbyautomaticcoulometricKarlFischerTitration.
y EN605671992.Guideforthesamplingofgasesandofoilfromoilfilledelectricalequipmentandfortheanalysisoffreeanddissolvedgases .
y EN60599:1999.Mineraloilimpregnatedelectricalequipmentinservice Guidetotheinterpretationofdissolvedandfreegasesanalysis..
y EN61620:1999.Insulatingliquids.Determinationofthedielectricdissipationfactorbymeasurementoftheconductanceandcapacitance.Testmethod.
y EN61198:1994.Mineralinsulatingoils.Methodforthedeterminationof2furfuralandrelatedcompounds.
54VIVEK JHA
-
y LIGHTNINGIMPULSETEST
TESTING OF TRANSFORMERS
TosimulatethesystemdisturbancesduetoLightningstroke Canberepresentedbythreebasicwaveshapes
FullwaveLI Choppedwave(Choppedontail) Choppedwave(Choppedonfront)
Lightningdisturbancesdonotalwayshavethesebasicwaveshapes.However,bydefiningtheamplitudeandshapeofthesewaves,itispossibletoestablishaminimumimpulsedielectricstrengththatatransformershouldmeet.
y Ifalightningdisturbancetravelssomedistancealongthelinebeforeitreachesatransformer,itswaveshapeapproachesthatofthefullwave.Itisgenerallyreferredtoas1.2/50wave.Awavetravelingalongthelinemightcauseflashoveracrossaninsulatorafterthepeakofthewavehasbeenreached.Thiswaveissimulatedbyachoppedwavewhichisofthesamemagnitudeasthefullwave.Ifalightningstrokehitsdirectlyatorveryneartoatransformerterminal,theimpulsevoltagemayrisesteeplyuntilitisrelievedbyaflashover,causingsudden,verysteepcollapseinvoltage.Thisconditionisrepresentedbythefrontofwave
55VIVEK JHA
-
TESTSONTRANSFORMERS
y LIGHTNINGIMPULSETEST
1.2/50SLIWAVE CURRENTWAVEFORMDURINGLI
TYPICAL TEST LEVELS FOR LI TEST :H1 : 1300 kVp,
56VIVEK JHA
-
TESTSONTRANSFORMERS
y LIGHTNINGIMPULSETEST
1.2/50SLIWAVECHOPPEDAT3.7S CURRENTWAVEFORMDURINGCHOPPEDLI
57VIVEK JHA
-
SWITCHINGIMPULSETEST
y SwitchingimpulselevelisconductedtoverifytheintegrityoftransformerundervariousswitchingsurgesonAC/DCline.
y ThetypicalwaveshapeofSwitchingimpulseis250/2500SasperIEC60060&itsmagnitudeislowerthanthecorrespondingLIwavebutforlongerduration.
y Inviewofthedifficultiesingeneratingthesewaveshapesinlaboratoriesandmoretominimizethecoresaturationduringtestingoftransformers,IEC60076Part3hasspecifiedaswitchingimpulsewavehavingavirtualfronttimeofatleast100s,durationabove90%ofthespecifiedamplitudeofatleast200sandatotaldurationtothefirstzeropassageofatleast1000s.
y Unlikeinthecaseofacwinding,boththeterminalsofvalvewindingexperiencefulldcvoltageofthebridgetowhichtheyareconnected.Thereforevalvewindingistestedtoprovetheinsulationofthewindingwiththerespecttoground.Switchingimpulsesareappliedtothevalvewindingterminalsconnectedtogether.Theotherwindingterminalsnotundertestareshortcircuitedandgrounded.
58VIVEK JHA
-
SWITCHINGIMPULSETEST
y WAVESHAPEOFSWITCHINGIMPULSEASPERIEC60060
STANDARD250/2500SSWITCHINGIMPULSEWAVE
TYPICAL SWITCHING IMPULSE LEVELS : H1 : 1080 kVp,X1-X2 : 1290 kVp, X3-X4: 980 kVp
59VIVEK JHA
-
SWITCHINGIMPULSETEST
y SwitchingimpulselevelisconductedtoverifytheintegrityoftransformerundervariousswitchingsurgesonAC/DCline.
y ThetypicalwaveshapeofSwitchingimpulseis250/2500SasperIEC60060&itsmagnitudeislowerthanthecorrespondingLIwavebutforlongerduration.
y Inviewofthedifficultiesingeneratingthesewaveshapesinlaboratoriesandmoretominimizethecoresaturationduringtestingoftransformers,IEC60076Part3hasspecifiedaswitchingimpulsewavehavingavirtualfronttimeofatleast100s,durationabove90%ofthespecifiedamplitudeofatleast200sandatotaldurationtothefirstzeropassageofatleast1000s.
y Unlikeinthecaseofacwinding,boththeterminalsofvalvewindingexperiencefulldcvoltageofthebridgetowhichtheyareconnected.Thereforevalvewindingistestedtoprovetheinsulationofthewindingwiththerespecttoground.Switchingimpulsesareappliedtothevalvewindingterminalsconnectedtogether.Theotherwindingterminalsnotundertestareshortcircuitedandgrounded.
60VIVEK JHA
-
SWITCHINGIMPULSETEST
y WAVESHAPEOFSWITCHINGIMPULSEASPERIEC60060
STANDARD250/2500SSWITCHINGIMPULSEWAVE
TYPICAL SWITCHING IMPULSE LEVELS : H1 : 1080 kVp,X1-X2 : 1290 kVp, X3-X4: 980 kVp
61VIVEK JHA
-
62VIVEK JHA
-
Magnetic balance test Done on TRANSFORMER to see whether the transformer core is magnetically balanced or
not...AND ALSO WINDING CONDITION.... for example we r having delta HV and star winding LV side ... HV SIDE WE WIL BE HAVING
THREE BUSHINGS....THOSE R 1U,1V,1W.. HV SIDE WE WIL BE HAVING FOUR BUSHINGS.....2U,2V,2W,2N... WE CAN DO THIS MBT (MAGNETIC BALANCE TEST)WITH 1PHASE SUPPLY(1PHASE AND NEUTRAL(230V)) OR WITH 2-PHASE SUPPLY(2-PHASES(440V)) 1ST STEP OF MBT: GIVE POWER SUPPLY 1-PHASE OR 2 PHASE BETWEEN 1U AND 1V ,MEASURE THE VOLTAGES BETWEEN 1V-1W AND 1U-1W AND ALSO 2U-2N,2V-2N,2W-2N.. SO HERE IF THE CORE IS CORRECTLY BALANCED THEN WE WILL GET RESULTS AS FOLLOWS 1U-1V 1V-1W 1U-1W 2U-2N 2V-2N 2W-2N 440 300 140 90 50 40 THAT MEANS HV SIDE : 1U-1V = 1V-1W + 1U-1W I.E 440V = 300 + 140 AND ALSO LV SIDE : 2U-2N = 2V-2N + 2W-2N 90 = 50 + 40 STEP 2: AFTER DOING THIS ..INTERCHANGE THE CONNECTIONS BETWEEN 1V-1W AND MEASURE THE VALUES AS ABOVE... STEP 3: AFTER DOING THIS ..INTER CHANGE THE CONNECTIONS BETWEEN 1U-1W AND MEASURE THE VALUES AS ABOVE... IF ANY FAULT IS THERE IN TRANSFORMER WE CAN NOT FIND GOOD RESULTS.... IF THE WINDING IS DAMAGED .... WE WILL GET ZERO VALUES .... ex: HV SIDE 1U-1V = 1V-1W + 1U-1W 440V = 440 + 0 AND ALSO LV SIDE : 2U-2N = 2V-2N + 2W-2N 90 = 90 + 0 THIS IS THE ACTUAL APPLICATION OF MANGNETICA BALANCE TEST...
VIVEK JHA 63
-
64VIVEK JHA
top related