高電壓設備測試（High Voltage Equipment Testing）（英文版） 課件 Worksheet 1 DC Resistance Test

《HighVoltageEquipmentTesting》DCResistanceTest主講人：何發(fā)武（副教授）OperatingWorksheet：OperatingWorksheet：TableofContents01Followme02Workshop03Training01FollowmeFollowMeDCresistancetestisanecessarymeasurementitemduringtheproductionoftransformersemi-finishedproducts,factorytests,commissioningtest,majorrepairs,andtapswitchchanges.Figure3-1isshowingthetransformerwithneutralpointtapdamagedbylightning.Figure3-1

TransformerwithneutralpointtapdamagedbylightningⅠ.SignificanceofMeasuringDCResistanceAftertheinstallationofatransformer,itsinternalstructureissealedwithinsulationmaterials.BymeasuringtheDCresistanceofthetransformer’sthreephases,thefollowingdefectscanbedetected:①Checktheweldingqualityofinternalwindingwiresandleadwires.②Checkthecontactqualityofthetapswitchatvariouspositions.③Checkforanybreakageinthewindingsorlead-outwires.④Checkthecorrectnessofparallelbranchesandmeasureifthereareanybrokenconnectionsinmultipleparallel-woundwindings.⑤Checkforshortcircuitsbetweenlayersorturns.Ⅱ.TestStandardsTheteststandardsarebasedonthe“StandardforElectricalEquipmentHandoverAcceptanceTestinElectricalInstallationEngineering”(GB50150–2016).TheDCresistanceorloopresistanceofpowerequipmentisshowninTable3-1below.Ⅱ.TestStandardsTable3-1

QualifiedstandardsforDCresistanceorloopresistance02WorkshopⅠ.DCResistanceTestofTransformer(Ⅰ)WiringForsingle-phasemeasurement,takethemeasurementofthetransformerABphaseasanexample.ThethickredwireisthepositiveelectrodeofthecurrentterminalandisconnectedtoI+.ThethinredwireisthepositiveelectrodeofthevoltageterminalandisconnectedtoV+,andthetestclampcorrespondingtotheredlineisconnectedtothetransformerAphase.ThethickblackwireisthenegativeelectrodeofthecurrentterminalandisconnectedtoI－.ThethinblackwireisthenegativeelectrodeofthevoltageterminalandisconnectedtoV－,andthetestclampcorrespondingtotheblacklineisconnectedtothetransformerBphase.,asshowninFigure3-2.AftermeasuringtheABphase,measuretheBCphase,CAphase,abphase,bcphase,andcaphaseinturn.Ifthetransformerhasatapswitch,theDCresistanceshouldbemeasuredateachpositionofthetapswitch.(Ⅰ)WiringFigure3-2

TransformerDCresistancetestingwiringdiagramofthehigh-voltageside(A-Bphase)(Ⅱ)OperationStepsforDCResistanceTestingAfterpoweringon,enterthemaininterfaceforparametersettings.Movethecursortoselectsettings,querydata,andselectcurrentforfunctionselection.Clickthe“SelectCurrent”buttontochoosedifferentselectabletestcurrentvaluesrange(Auto,10

A,5

A,1

A,200

mA,40

mA,<5

mA),asshowninFigure3-3.Figure3-3

MaininterfaceandrangesettingofDCresistancetester(Ⅱ)OperationStepsforDCResistanceTestingAfterdeterminingthetestcurrentbasedonthecapacityofthetransformer,presstheConfirmkeytostartthemeasurement.Whenauto-testisselected,theinstrumentwillautomaticallychoosetheappropriatecurrentfortestingbasedonthesample.Afterstartingthemeasurement,thescreenwilldisplaythechargingandtestingprocess,andthendisplaythemeasuredresistancevalue.RecordtheDCresistancemeasurementvalueafterthevaluestabilizes.Thelargerthecapacityofthetransformer,thelongerthechargingtimeandthestabilizationtime,whichmaytakebetween5and30minutes.ThemeasurementprocessisshowninFigure3-4.(Ⅱ)OperationStepsforDCResistanceTestingFigure3-4

DCresistancetestprocessandvalue(Ⅱ)OperationStepsforDCResistanceTestingInthefigure,Ristheactualmeasuredresistance,andRtistheconvertedresistance.Afterthetestresultisstable,theinstrumentautomaticallysavesthetestdata.Fortheconvertedtemperature,pleaserefertothetemperaturesetting.Ifnotemperaturesettingismade,itdefaultstothelastsetting.Afterdisplayingthetestresult,pressandholdtheselectkeytoprintthetestresult.Afterthetestiscompleted,presstheresetkey.Theinstrumentwillstopoutputtingcurrent,andthescreenwillreturntoitsinitialstate.Afterdischarging,changethewiringmethodaccordingtothetapswitchforthenextsetoftestmeasurements.Ⅱ.PrecautionsforTestingDuetodifferenttestcurrentscorrespondingtocertainresistancemeasurementranges,itisnecessarytoselectanappropriatetestcurrentduringmeasurement.Excessivecurrentmaycausethewindingtoheatup,leadingtoincreasederrorinresistancevalues.Itmayalsoresultinsignificantresidualmagnetisminthetransformercore.Ontheotherhand,toosmallatestcurrentmayprolongthemeasurementtime.Therefore,whenselectingthetestcurrent,itisnecessarytoconsiderthecorrespondingresistancemeasurementrange,thedurationofmeasurement,andthepotentialimpactofresidualmagnetismonthetransformer.Ⅱ.PrecautionsforTestingItisprohibitedtodisconnectthecurrentorvoltagetestleadsduringthemeasurementprocess.Afterthetestiscomplete,presstheresetkeyfirst.Onlyaftertheinstrumentandthetransformeraredischargedcanthepowerbedisconnectedandtheconnectionsberemoved.Otherwise,thereisapossibilityofelectricshocktopersonnel.Ⅱ.PrecautionsforTestingThree-channeldirectresistancemeasurementcansimultaneouslymeasuretheDCresistanceofthree-phasewindings.Forthetransformerwithon-loadtapchangeronthehigh-voltageside,theDCresistancemeasurementcangreatlyshortenthetestingtime.However,sincethethree-channelmeasurementdoesnotincludetheneutralpointleadresistance,itlackscertaintyinjudgingtheconditionoftheneutralpointleadcontactinthetransformer.Beforethethree-channelmeasurement,itisadvisabletousesingle-channelmeasurementtomeasureoneortwotappositionsinordertocomparethesingle/three-channelmeasurementvaluesandchecktheconditionoftheneutrallead.Itshouldbenotedinthetestreportthatathree-channeltestwasperformedforthepurposeofcomparisonandreference.Ⅱ.PrecautionsforTestingTherefore,thethree-channelmeasurementmethodisnotsuitableforuseinthetransformermanufacturingprocess.Thethree-channelmeasurementtakeslongerforthethree-phaseresistancetestofasingle-positionYNwindingcomparedtothetraditionalfour-terminalmethodanddoesnothavetheadvantageofshorteningthetestingtime.Forthetransformerwithon-loadtapchangersonthehigh-voltageside,itisrecommendedtousethetraditionalfour-terminalmethodfortesting.Ⅱ.PrecautionsforTestingForDCresistancemeasurementoftractiontransformerwindingsinrailwayapplications,thethree-phaseVVconnectiontransformer(ratedvoltage:110/27.5

kV,connectionmethod:Vv0/Vv6)forconventional-speedrailwayorthesingle-phasetransformer(ratedvoltage:220/2×27.5

kV)forhigh-speedrailwaymaylooklikeathree-phasetransformerfromanexternalview,butitisessentiallycomposedoftwosingle-phasetransformers.Therefore,whenmeasuringtheDCresistance,themeasurementshouldbeperformedaccordingtothestepsforasingle-phasetransformer.Ⅱ.PrecautionsforTestingFortheconventional-speedrailwayVvconnectiontransformer,theDCresistancevaluesoftheABandBContheprimarysideandT1-x1,T2-x2onthesecondarysideshouldbemeasuredseparately.Forthehigh-speedrailwaysingle-phasetransformer,theDCresistancevaluesoftheA-Xsideontheprimarysideanda1-x1,a2-x2onthesecondarysideshouldbemeasuredseparately.Whenusingathree-channeldirectresistancetester,thethree-channeltestcannotbeused,andsingle-channelmeasurementsshouldbeperformedontheABandabends,asshowninFigure3-5.Ⅱ.PrecautionsforTesting(a)Vv-connectedthree-phaserailwaytractiontransformer(b)220

kVcombinedthree-phaseVv-connectedtractiontransformerⅡ.PrecautionsforTesting(c)Nameplateof110

kVSingle-phasetransformerforconventional-speedrailway(d)Nameplateof220

kVSingle-phasetransformerforhigh-speedrailway(e)Nameplateof110

kVon-loadtapchangertransformerFigure3-5

DCresistanmeasurementoftractiontransformerwindingsinrailwayappicationsⅢ.JudgmentofTestResultsForthetransformerwithon-loadtapchanger,theDCresistanceshouldbemeasuredatalltappingpositions.ForthetransformerwithNo-loadtapchangeraftermajoroverhaul,theDCresistanceshouldbemeasuredatalltappingpositionsofeachwindingonbothsides.Preventivetestsareusuallyconductedonlyintheoperatingrange.Iftappingpositionischangedduringoperation,theDCresistancemustbemeasuredagain.Ⅲ.JudgmentofTestResultsSomefactorsthatcanaffectthemeasurementoftransformerDCresistanceinclud