高电压设备测试（High Voltage Equipment Testing）（英文版） 课件 Worksheet 2 Loop Resistance Test

《HighVoltageEquipmentTesting》LoopResistanceTest主讲人：何发武（副教授）OperatingWorksheet：OperatingWorksheet：TableofContents01Followme02Workshop03Training01FollowmeFollowMeThedifferencebetweenloopresistanceandDCresistanceliesintheelectricalequipmentandtherangeoftestcurrentsused.Aloopresistancetestercanmeasurewithintherangeof100–600

A,whileaDCresistancetestertypicallymeasuresatthepositionof1/3/5/10/30

A.DCresistanceismainlyusedintransformertesting,whileloopresistanceisprimarilyappliedtodevicessuchascircuitbreakersanddisconnectswitches.Ⅰ.PurposeofLoopResistanceTestingTheconductivecircuitofhigh-voltageswitchgeariscomposedofmultipleconductorsthatallowelectricalconductionthroughcontact.TheDCresistanceoftheconductivecircuitincludesnotonlytheDCresistanceoftheconductormaterialitselfbutalsothecontactresistanceofvariouselectricalcontacts.TheconductivecircuitofGasInsulatedSwitchgear(GIS)isevenmorecomplex.Theresistanceoftheconductoritselfdependsontheresistivityoftheconductormaterialanditsgeometricdimensions.Ⅰ.PurposeofLoopResistanceTestingInthelong-termoperationofelectricalswitchequipment,thecontactresistanceisaffectedbychemicalcorrosion,mechanicalwear,electricalwear,shortcircuitcontactweldingandotherfactors.Ifthecontactresistanceistoolarge,theheatgeneratedunderthelong-termoperatingcurrentwillincreasewiththeincreaseinresistance,thetemperatureoftheelectricalcontactrisessharply,whichmayresultinadeclineintheinsulatingpropertiesoftheinsulatingmaterialandmechanicalstrength,Theoxidationofthecontactsurfaceleadstofurtherdeterioration.Inseverecases,itmaycausepartialweldingofthecontact,affectingthenormalopeningandclosingoftheswitch.Whenpassingtheshort-circuitcurrent,itwillalsoaffectthedynamic,thermalstabilityandinterruptionperformanceoftheswitch.Ⅰ.PurposeofLoopResistanceTestingIfthecontactresistanceistoohigh,theheatgeneratedbytheworkingcurrentwillincreasewiththeincreasingresistanceovertime.Thetemperatureoftheelectricalcontactwillsharplyrise,whichmaycausetheinsulationperformanceandmechanicalstrengthoftheinsulatingmaterialtodecrease,andthecontactsurfacetooxidizefurther,resultinginmoreseveredeterioration.Inseverecases,localweldingofthecontactmayoccur,whichcanaffectthenormalswitchingoftheswitch.Whenshort-circuitcurrentflowsthrough,itcanalsoaffectthedynamicandthermalstabilityperformanceandbreakingperformanceoftheswitch.Ⅰ.PurposeofLoopResistanceTestingContactresistanceisaffectedbyfourmainfactors:materialproperties(aluminum,copper,silver,tin),contactform(pointcontact,linecontact,surfacecontact),contactpressure,andprocessingtechnologyofcontactsurfaces.Therefore,currentandresistancemeasurementsoftheconductivecircuitareastandardtestingitemintypetests,factorytests,handoveracceptancetests,andpreventivetestsofhigh-voltageswitches.Theresistancevalueofeachphase’sconductivecircuitofelectricalswitchgearisanimportantdataforinstallation,maintenance,andqualityacceptance.Bymeasuringthecontactstateofelectricalcontacts,safeoperationoftheswitchgearcanbeensured.TakeFigure3-6asanexample.Ⅰ.PurposeofLoopResistanceTestingFigure3-6

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kVcircuitbreakeranddisconnectswitchⅠ.PurposeofLoopResistanceTestingTheloopresistancetestistomeasurethecontactresistanceoftheconductivecircuitoftheswitchwhenitisintheclosedposition.Itchecksforanycontactdefects,whetherthecircuitiswell-connected,andifthereisanyoxidationonthecontactsurface.Theresistanceoftheconductivecircuitoftheswitchgearmainlydependsonthecontactresistancebetweenthemovingandstaticcontactsofthecircuitbreaker(disconnectswitch).Thepresenceofcontactresistanceincreasesthelossoftheconductorduringpowertransmission,raisingthetemperatureatthecontactpoint.Themagnitudeoftheresistancedirectlyaffectsthecurrent-carryingcapacityduringnormaloperation,andtosomeextent,theabilitytointerruptshort-circuitcurrents.Ⅱ.ConductiveCircuitTestinHighVoltageSwitchElectricalswitchgearrequiresthatthetemperaturerisedoesnotexceedacertainvaluewhentheelectricalcontactpassesthroughtheratedcurrentforalongtime,andthecontactresistancemustbestable.Whenashort-circuitcurrentpassesthroughtheswitchgearforashortperiod,itisrequiredthattheelectricalcontactdoesnotresultinweldingorsplashingofcontactmaterials.Duringtheclosingandopeningprocessoftheswitch,thecontactshouldbeabletohandletheshort-circuitcurrentwithoutcausingweldingorseveredamage.Duringtheopeningprocess,itisrequiredthatthecontactwearshouldbeminimizedasmuchaspossiblewhenbreakingthecurrent.Ⅱ.ConductiveCircuitTestinHighVoltageSwitchTheDCresistancevalueoftheconductivecircuitinahigh-voltageswitchisdeterminedthroughtypetestingoftheproduct.AccordingtotheGB/T11022standard,DCresistancemeasurementshouldbeconductedbeforeandaftertemperature-risetests.Themeasurementshouldbetakenunderthesameconditionsasthetestcycle’stemperatureofthetestconductorandambientairtemperature.Thedifferenceinresistancebetweenthetwomeasurementsshouldnotexceed20%oftheresistancevalueobtainedbeforethetemperature-risetest.Ⅱ.ConductiveCircuitTestinHighVoltageSwitchThisregulationrequiresthattheDCresistancevaluemustbedeterminedbyactualmeasurementstoensurelong-termcurrent-carryingcapacityandperformancewhenpassingthroughextremeshort-timecurrents.WhenmeasuringDCresistanceduringfactorytests,itisnecessarytoobtainameasurementassimilaraspossibletothetypetestconditions(ambientairtemperature,locationofthemeasurement).Themeasuredresistanceshouldnotexceed120%oftheresistanceobtainedbeforethetemperature-risetest.Ⅱ.ConductiveCircuitTestinHighVoltageSwitchThemeasurementmethodmainlyadoptsthedirectcurrentvoltagedropmethod.Acertaindirectcurrent(generallynotlessthan100

A)ispassedthroughtheconductivecircuit,andthevoltagedropoftheconductivecircuitismeasuredusingadirectcurrentvoltmeter.ThedirectcurrentresistanceoftheconductivecircuitisthencalculatedusingOhm’sLaw.Sincethecurrentpassingthroughthetestspecimenisrelativelylarge,itissufficienttobreakdownthemetaloxidefilmonthecontactsurface,therebyreducingmeasurementerrors.Thedataobtainedfromthemillivoltmeterinthecircuitresistancemeterisrelativelyaccurate.TheprincipleofthedirectcurrentvoltagedropmethodisshowninFigure3-7.Ⅱ.ConductiveCircuitTestinHighVoltageSwitchFigure3-7

SchematicdiagramofthedirectcurrentvoltagedropmethodⅡ.ConductiveCircuitTestinHighVoltageSwitchWhenmeasuringtheDCresistanceoftheconductivecircuitinopen-typehigh-voltageswitchgearsuchasvacuumcircuitbreaker,SF6circuitbreaker,anddisconnectswitch,pleasenotethefollowing:Thevoltageleadsshouldbeconnectednearthecontactside.Thecurrentleadsshouldbeconnectedtotheoutsideofthevoltageleads.Ensuregoodcontactbetweenthevoltageandcurrentleads.Ifnecessary,polishthecontactsurfacewithsandpaper.Beforemeasuring,theswitchshouldbeoperatedseveraltimesatitsratedoperatingvoltageandgaspressure(oroilpressure)toensuregoodcontactwiththecontacts.Ⅱ.ConductiveCircuitTestinHighVoltageSwitchThisallowsthemeasurementresultstoreflecttheactualconditions.Theshort-circuitbreakingcurrentsthattheSF6circuitbreakercanhandlearerelativelylarge.Thenameplateofa220

kVSF6ZF16-252GCBcircuitbreakerisshowninFigure3-8.(a)220

kVSF6

CircuitBreakerZF16-252GCBNameplate(b)220

kVDisconnectorZf16-252DSNameplateⅡ.ConductiveCircuitTestinHighVoltageSwitch(c)

220

kVEarthSwitchZF16-252ESNameplateFigure3-8

TheNameplateⅡ.ConductiveCircuitTestinHighVoltageSwitchThewiringdiagramfortheloopresistancetestisshowninFigure3-9.Figure3-9

WiringDiagramforLoopResistanceTestⅡ.ConductiveCircuitTestinHighVoltageSwitchThetestprocedureisshowninTable3-3.Table3-3

PreventiveTestProcedureforConductiveCircuitResistance02WorkshopⅠ.MethodformeasuringthemainloopresistanceofGISThemainloopresistanceofGISismainlymeasuredusingthegroundingswitchcircuit.Ifthereisinsulationattheconnectionpointbetweenthegroundingswitchandtheshell,themeasurementcanbetakenbyopeningtheconnection.Ifthereisnoinsulationattheconnectionpointbetweenthegroundingswitchandtheshell,firstmeasuretheresistanceR1oftheGISshell,thenmeasuretheresistancevalueR2afterthecircuitisinparallelwiththeshell,andthencalculatethemainloopresistanceR=R1R2/(R1－R2).Forasleevewithoverheadlinesenteringit,themeasurementcurrentcanalsobeinjectedfromthesleeveside,andthemeasurementpointsshouldbeasdenseaspossible.Ⅰ.MethodformeasuringthemainloopresistanceofGISFigure3-10showsahigh-precisioncircuitresistancetester.Figure3-10

HighPrecisionLoopResistanceTesterⅠ.MethodformeasuringthemainloopresistanceofGISThewiringprincipleformeasuringtheGISloopresistanceisshowninthefigure3-11.(a)Schematicdiagramofresistancemeasurementwiring(b)WiringdiagramforinjectingcurrentfromthesleeveandmeasuringvoltagefromthegroundingswitchⅠ.MethodformeasuringthemainloopresistanceofGISThewiringprincipleformeasuringtheGISloopresistanceisshowninthefigure3-11.(c)Wiringdiagramforinjectingcurrentfromthegroundingswitchandmeasuringvoltagefromthegroundingswitch(d)WiringdiagramforinjectingcurrentandmeasuringvoltageatthesamelocationFigure3-11

ThewiringprincipleformeasuringtheGISloopresistanceⅡ.LoopResistanceMeasurementAftercorrectwiring,themeasurementmaininterfacewillbedisplayedwhenthedeviceisturnedon.ThisisshowninFigure3-12.Figure3-12

MeasurementmaininterfaceⅡ.LoopResistanceMeasurementClickthe“Measure”buttontostartthemeasurement.Themeasuredresultis20,indicatingthatthedataisqualified.ThisisshowninFigure3-14.Figure3-14

MeasurementresultsⅡ.LoopResistanceMeasurementTheloopresistancetestprocedureisshowninTable3-4.Table3-4

LoopResistanceTestProcedureⅡ.LoopResistanceMeasurementTestNotes:(1)ApplyanyvalueofDCcurrentbetween100

Aandratedcurrentinthecircuitandmaintainitfor1minute.(2)Measurementshouldbeperformedusinginstrumentsthatreflectaveragevalues,withaprecisionofnotlessthan0.5gradeformeasuringmeters.(3)Thevoltmeterisconnectedontheinnersideofthetestedcircuitandisswitchedonafterthepowercircuitisconnected,topreventmeasurementinterruptioncausedbysuddentrippingofthecircuitbreakerorsuddendisconnectionofthemeasurementcircuitthatmayresultindamage.Ⅱ.LoopResistanceMeasurement(4)Iftheinfraredthermalimagingdisplaysabnormaltemperaturesatfracturesurfaces,abnormaltemperaturedifferencesbetweenphases,oriftherehavebeenmorethan100switchingoperationsofthecircuitbreakerafterthetest,thistestshouldalsobeconducted.(5)Theloopresistancetestinginstrumentshouldbereliablygrounded.Ensuregoodcontactontheclampingsurfaceofthemeasurementcable,andthetestcurrentshouldnotbelessthan100

A.Removepaintandmetaloxidelayersfromthecontactsurfacesofthetestedequipment’sterminalconnections.Performseveralopeningandclosingoperationsonthecircuitbreakerbeforethetesttominimizetheimpactoftheconductivecircuitoxidefilmonthetestresults.Ⅱ.LoopResistanceMeasurementItisnotallowedtoenergizewhenthetestcableisopen-circuited,asitmaydamagetheinstrument.Tominimizevoltagedropinthemeasurementcable,trytoreducethelengthofthecableandusethecablewithasufficientlylargecross-sectionalarea.(6)Duringthemeasurement,preventsuddentr