電力電容器的局部放電測量

Lecture7

PDDetectioninPowerCapacitors電力電容器的局部放電測量1Contents1.PartialDischargeinPowerCapacitors電力電容器中的局部放電2.ParametersandStandard測試參數(shù)及相關(guān)規(guī)程3.ElectricalDetectionofPDinCapacitor電力電容器的局部放電電測法21.PartialDischargeinPowerCapacitors1.1thecharacteristicsofpowercapacitorsInsulationstructureofcapacitors:oil-impregnatedpapers,oil-impregnateddielectricmembraneandtheircombination.絕緣結(jié)構(gòu)：油浸紙，浸漬薄膜及其組合Extremelyhighelectricalfieldstressexistsincapacitorsandpartialdischargesareverypossibletooccurinside.介質(zhì)工作場強特別高，內(nèi)部特別容易發(fā)生局部放電電力電容器的特點31.2InceptionanddamageofPDinpowercapacitor1.PartialDischargeinPowerCapacitorsThelifetimeofcapacitorsufferingfromPDdecreasesexponentially.

PDisakeyfactorthatresultsinexpandingandincipientfaultofpowercapacitor.在局部放電作用下，壽命是隨著電場的增加而呈指數(shù)形式下降的局部放電是造成電容器膨脹和早期損壞的一個重要因素42.ParametersandSpecification2.1ParameterstoestimatethePDofcapacitorApparentcharge,qInceptionvoltage,UiTheACvoltageacrossthecapacitoratwhichthedischargemagnitudeexceedsagivenvalueqg.視在放電量升壓過程中，觀測到的放電量超過某個規(guī)定值時的最低電壓Inceptionvoltage(stress):TheACvoltage(stress)acrossthesampleatwhichdischargesstarttooccurwhenthevoltageisincreased.5Extinctionvoltage,Ue降壓過程中，觀測到放電量低于某個規(guī)定值的最高電壓值。TheACvoltageacrossthecapacitoratwhichthedischargemagnitudeislessthanthegivenmagnitudeqg.aisbetterthanb2.ParametersandSpecificationChangeofqwithvoltageapplyingtime放電量隨加壓時間的變化62.2ProcedureofPDdetection2.ParametersandStandardsU1:pre-appliedVoltage預(yù)加電壓

Type

U1(kV)

U2(kV)

U3(kV)

Requirement

Note

Shunt

capacitors

2.15un,1s

1.2un,10min

1.5un,10min

Series-connectedcapacitors

4.5un,1s

1.6un,10min

Breakercapacitors

1.8un,1s

1.1un,10min

Duringlast10min,noPDimpulseswithincreasedmagnitudeareobserved.

un

isworkingvoltage.

U1

U2

U3

t1

t2

t3

U2:holdingvoltage保持電壓U3:measuringvoltage測量電壓7Powersource:sinewave,50Hz,60HzThecapacitancedifferencebeforeandaftertestshouldnotexceedthedifferencecausedbyafuseburningout.Asimulatingsmallcapacitorscanbeusedwhensensitivityorcapacitycouldnotmeetthetestrequirements.2.ParametersandStandards試驗電壓為正弦波，頻率為50或60Hz測試前后測量電容，兩次測量值之差不能超過一根熔絲斷開的差值如果被試電容器的電容值太大，在整臺上不能得到滿意的精度或設(shè)備容量不夠的時候，用模擬的較小電容器進行試驗。83.ElectricalDetectionofPDinCapacitorThecapacityofapowercapacitorismuchlargerthantheusualHVequipments.LargecapacityofthepowersourceisrequiredforPDexperimentofcapacitors.

3.1PowerSourceandCircuits(1)PowersourceCompensationreactorisusedinseriesorparallelwithCxsothattodecreasethecapacityoftestingtransformerCurrentsthroughLandCwhilethetwoelementsconnectedinparallelVoltagesacrossLandCwhilethetwoelementsconnectedinseries試驗電源及回路電容器的容量比其他普通高壓設(shè)備大很多，因此所需的試驗設(shè)備容量也很大采用補償電抗器與試品串并聯(lián)的方式滿足實驗變壓器的容量要求9(2)Detectioncircuitse.g.Ck↗qs↘Cv↘3.ElectricalDetectionofPDinCapacitorsensitivity10ABalanceddetectioncircuitisrecommended3.ElectricalDetectionofPDinCapacitorThestraightdetectioncircuitsmaybeused.Inordertoobtainhighsensitivity,thecouplingcapacitorshouldbeatleastaslargeasthesample.Asecondsampleisusedasthecouplingcapacitor,Ck=Cx.采用直接測量回路，并用另外一個試品作為耦合電容使用平衡檢測回路11(2)Theinfluenceofinternalinductance3.2Someproblemsneedtobenoticed(1)RequirementsofdetectionimpedancesThecapacitancerangeofpowercapacitorsislargerthanthatofmanyotherHVequipments，severaldetectionimpedancesareneededtomatchthecapacitorsamples,sothattogettheproperfrequency-bandandsensitivity.3.ElectricalDetectionofPDinCapacitor電力電容器的電容量比其它高壓設(shè)備電容量的變化范圍大,需要準(zhǔn)備多個檢測阻抗，以匹配不同電容量大小的試品.以便得到合適的檢測頻帶和靈敏度。Detectionimpedancesisrequiredtowithstandlargecurrent.檢測阻抗需要承受較大的電容電流對檢測阻抗的要求注意的問題12(2)Connectiontypesofcapacitorelementsinfluencedetectionresults.3.ElectricalDetectionofPDinCapacitor電容器元件的連接形式會影響檢測結(jié)果。13(3)TheinfluenceofinternalinductancePowercapacitorisnotpurecapacitance.Theinternalinductancecomesfrom:internalleads,leadingoutwires,capacitorelementsconnectinginseriesorparallel.L≈0.1~0.3μH電力電容器不是純電容設(shè)備，內(nèi)部電感來自于：內(nèi)部引線，引出線以及以串