ASTM D2275-2001(2008)e1 固体电绝缘材料表面对局部放电(电晕)的耐电压性标准试验方法

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【英文标准名称】:StandardTestMethodforVoltageEnduranceofSolidElectricalInsulatingMaterialsSubjectedtoPartialDischarges(Corona)ontheSurface
【原文标准名称】:固体电绝缘材料表面对局部放电(电晕)的耐电压性标准试验方法
【标准号】:ASTMD2275-2001(2008)e1
【标准状态】:现行
【国别】:美国
【发布日期】:2001
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D09.12
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:partialdischarge;surfacedischarge;thresholdvoltage;voltageindurance;voltagestressx2013;timecurve;voltx2013;timecurve;Corona;Electricalinsulatingsolids;Electricalproperties;S
【摘要】:Thistestmethodisusedtocomparetheenduranceofdifferentmaterialstotheactionofcoronaontheexternalsurfaces.Apoorresultonthistestdoesnotindicatethatthematerialisapoorselectionforuseathighvoltageorathighvoltagestressintheabsenceofsurfacecorona.Surfacecoronashouldbedistinguishedfromcoronathatoccursininternalcavitiesforwhichnostandardizedtesthasbeendeveloped.Evaluationofendurancebycomparisonofdataonspecimensofdifferentthicknessisnotvalid.Theprocessingofthematerialmayaffecttheresultsobtained.Forinstance,residualstrainsproducedbyquenching,orhighlevelsofcrystallinitycausedbyslowcoolingmayaffecttheresult.Also,thetypeofmoldingprocess,injectionorcompression,maybeimportantespeciallyifthemixingoffillersortheconcentrationandsizesofgas-filledcavitiesarecontrolledinanydegreebytheprocess.Indeed,thistestmethodmaybeusedtoexaminetheeffectsofprocessing.Thedataaregeneratedintheformofasetofvaluesoflifetimesatavoltage.ThedispersionoffailuretimescanbeanalyzedusingWeibullorextremevaluestatisticstoyieldanestimateofthecentralvalueofthedistributionanditsstandarddeviation.Thisisparticularlyrecommendedwhenthedispersionoffailuretimesislarge,andacomparisonoflifetimesoftwomaterialsmustbemadeataspecifiedlevelofconfidence.Thistestisoftenusedtodemonstratethedifferencesbetweendifferentclassesofmaterials,andtoillustratetheimportanceofeliminatingcoronainanyapplicationofaparticularmaterial.Whenthetestisusedforsuchpurposesorothersimilarones,theneedforprecisionisreduced,andcertaintimesavingtechniques,suchastruncatingatestatthetimeofthefifthfailureofasetofnine,andusingthattimeasthemeasureofthecentraltendency,arerecommended.Twosuchtechniquesaredescribedin10.2.Bothtechniquesremovethenecessityoftestingbeyondmedianfailure,andreducetherequiredtestingtimetoapproximatelyhalfofthatrequiredtoobtainfailuresonallspecimens.Insulatingmaterialsoperatinginagaseousmediumaresubjectedtocoronaattackatoperatingvoltageonsometypesofelectricalapparatusinthoseregionswherethevoltagegradientinthegasexceedsthecoronainceptionlevel.Onothertypesofequipment,wheredetectablecoronaisabsentinitially,itmayappearlaterduetotransientover-voltagesorchangesininsulationpropertiesattendingaging.Certaininorganicmaterialscantoleratecoronaforalongtime.Manyorganicmaterialsaredamagedquicklybycorona,andforthese,operationwithnodetectablecoronaisimperative.Thistestmethodintensifiessomeofthemorecommonlymetconditionsofcoronaattacksothatmaterialsmaybeevaluatedinatimethatisrelativelyshortcomparedtothelifeoftheequipment.Aswithmostacceleratedlifetests,cautionisnecessaryinextrapolationfromtheindicatedlifetoactuallifeundervariousoperatingconditionsinthefield.Thefailureproducedbycoronamaybeduetooneofseveralpossiblefactors.Thecoronamayerodetheinsulationuntiltheremaininginsulationcannolongerwithstandtheappliedvoltage.Thecoronamaycausetheinsulationsurfacetobecomeconducting.Forinstance,carbonizationmayoccur,sothatfailureoccursquickly.Ontheotherhand,compoundssuchasoxalicacidcrystalsmaybeformed,aswithpolyethylene,inwhichcasethesurfaceconductancewillvarywithambienthumidity,andatmoderatehumiditiestheconductancemaybeattheproperleveltoreducethepotentialgradientattheelectrodeedge,andthuscauseeitherareductionintheamountofcorona,oritscessation,thusretardingfailure.Thecoronamaycauseax201C;treeing