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partialdischargesarecomplex,dynamic,non-linearphenomenathatappearinhigh-
-voltageinsulationsystemsandleadtotheirdeterioration.Thechallengewithpartial
dischargesstartswithpulsedetection,astheindividualpulsesusuallylastfornano-or
micro-secondsandoccurwithmagnitudesinthemicro/milivoltrangesuperimposedon
high-voltagesignals.Thismultiplicationfactorshowstherequirementsforsensitivity,
andthetimedomainshowstherequirementsfortheacquisitionspeed.ThePDmech-
anismiscomprisedofagreatvarietyofphysicalphenomenathatrangefromcharge
emissionsfromsurfaces,glowdischarges,chargeinjectionsintoliquidsandsolids,
electrictreeing,streamers,ordry-bandarcs.
AnimportantinnovationinthePDfieldwastheintroductionofphase-resolved
PD(PRPD)acquisition.ThistechniqueallowsfortheregistrationofindividualPD
pulseswithrespecttothephaseangleoftheappliedvoltage.Themeasurementisaccu-
mulatedoverapredefinednumberofcycles.Theideafollowstheunderlyingprinciple
thatdifferentPDsourcesrevealcharacteristicphase-resolvedimages.However,dueto
thecomplexPDmechanismindifferentinsulatingstructures,themainchallengetoday
isintheproperinterpretationofPRPDpatternsandthelocalizationofdischarge
sources.Signal-andimage-processingtechniquesaswellassuchartificialintelligence
(AI)elementsasmachinelearningorautonomousmotiondetectionforPD-pattern
classificationandrecognitionareemployed.
AsanextensionofPRPD,phase-resolvedpulserise-timeacquisitionhasbeenin-
troduced.Thismethodholdsgreatpotentialbecause,inthePDpulse,therisetime
isembeddedinthedischargemechanism(theavalancheformation);thus,aphysical
interpretationcanbedrawnfordifferentdielectricmaterialsanddischargeforms.
Inaharshreal-lifeindustrialenvironment,PDrecordinghastodealwithexten-
sivenoise,disturbances,andharmonics.Sincetheseeffectshaveanenormousimpact
onPDbehavior,wavelet-baseddenoisingalgorithmsareoftenintroduced.
Thedevelopmentofmethodsforpartial-dischargedetection/registrationand
theequipmentcapabilitiesinthisfieldpresentedherearetheresultofprogressinthe
developmentofelectronicsandsoftware.
Theconditionsfortheoccurrenceofpartialdischargesresultfromdefectsinthe
technologicalandmanufacturingprocessesaswellasintheoperationfromelectrical,
thermal,andotherstresses.InvestigationsonPDmechanisms,theirinitiationandde-
velopmentconditions,andtheeffectsofthechangesindielectricstructuresaresub-
jectsofresearchinnumerouslaboratoriesaroundtheworld.Inparticular,thisrefers
totheapplicationofpolymerdielectricsfortheconstructionofhigh-voltageinsulation
systems,theimpactofspacecharge,andthedevelopmentofvariousnon-invasivediag-
nostictechniques.Therulesforselectinginsulationsystemsforhigh-voltageelectrical
devicesrefertotheoperatingconditionsofthesedevices(whichisdefinedasopera-
tionalexposures).
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