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变压器油中微水含量在线监测研究 Introduction Transformeroilservesasanexcellentinsulatingandcoolingmediumfortransformers,butitsperformancecanbedegradedbythepresenceofwater,whichincreasestheriskoftransformerfailure.Theamountofwaterpresentintransformeroilisusuallyverylow,typicallylessthan50ppm,butevensmallamountsofwatercancausesignificantchangesintheelectricalandphysicalpropertiesoftheoil. Therefore,itisessentialtomonitorthewatercontentintransformeroiltoensurethesafeandreliableoperationoftransformers.Traditionally,watercontentintransformeroilisdeterminedbytheKarlFischertitrationmethod,whichisanofflineandtime-consumingprocess.Recently,thedevelopmentofonlinemonitoringtechnologyhasmadeitpossibletomeasurewatercontentintransformeroilinreal-time,whichgreatlyenhancesthesafetyandreliabilityoftransformers. Thispaperreviewsrecentprogressinonlinemonitoringtechnologyforwatercontentintransformeroilanddiscussesitspotentialapplications. Methodology Onlinemonitoringtechnologyforwatercontentintransformeroilhasbeenextensivelystudiedinrecentyears.Severalmethodshavebeenproposedanddeveloped,includinginfrared(IR)spectroscopy,microwaveabsorption,capacitance,andopticalsensing. IRspectroscopyisawidelyusedmethodformeasuringwatercontentintransformeroil.ItworksbydetectingtheabsorptionofspecificwavelengthsofIRradiationbywatermoleculesintheoil.Thismethodhashighaccuracy,butitrequiresexpensiveequipmentandisvulnerabletointerferencefromothercompoundsintheoil. Microwaveabsorptionisanon-invasivetechniquethatmeasuresthechangesinthedielectricpropertiesoftheoilcausedbythepresenceofwater.Thismethodishighlysensitiveandcandetectwatercontentaslowas10ppm,butitisexpensiveandrequirescalibrationwithtransformeroilsamplesofknownwatercontent. Capacitancesensingisanothercommonlyusedmethodformonitoringwatercontentintransformeroil.Itworksbymeasuringthecapacitanceofacapacitorwiththeoilasthedielectric.Whenwaterispresentintheoil,itincreasesthedielectricconstantandcausesthecapacitancetochange.Thismethodisinexpensiveandeasytouse,butithaslowa