2552IEEETRANSACTIONSONPOWERDELIVERY,VOL.20,NO.4,OCTOBER2005OnPowerQualityIndicesandRealTimeMeasurementTaoLinandAlexanderDomijanAbstract—Powerquality(PQ)indicesareusedtoquantifytheThereareseveralaspectstoapowerqualitystudy:1)Sensi-qualityofthepowersupplyandserveasthebasisforcomparingtivedetectionofpowerdisturbances.2)Realtimemeasurementthenegativeimpactsofdifferentdisturbancesonpowernetworks.oftheparametersofsignalcomponentsinpowerdisturbances,Toovercomethelimitationsanddeficienciesofthepracticalnamelymonitoringthepatternfeaturesofpowerdisturbances.applicationsofsomepowerqualityindicesincommonuse,asetofthreenewindices,namelythefundamentalfrequencydeviation3)Quantificationoftheextentofpowerdisturbances(orwave-ratio(FDR),waveformdistortionratio(WDR),andsymmetricalformdistortions)andtheirnegativeimpactsonpowersystems.componentsdeviationratio(SDR)areproposedinthispaperto4)Identificationofthetypesandcausesofpowerdisturbances.summarizedifferenttypesofpowerdisturbancesinacompre-5)Locationofthesourcesofpowerdisturbancesinelectrichensivemanner.Asinstantaneousquantities,thesenovelindicespowernetworks.Thethirdobjectivecanbefulfilledusingpowercanrevealthetimevaryingcharacteristicsofpowerdisturbancesquality(PQ)indices,whicharetheconcisenumericalrepresen-inrealtime.Hence,thenewPQindicescanwellaccommodatetationscharacterizingthenatureofaPQeventbasedonthetimepracticalwaveformdistortionsinpowernetworks,whichmaybecausedbymultipletypesoftimevaryingpowerdisturbances.Theyand/orfrequencyinformationofthedisturbancewaveform.PQcanthereforebefurtherusedtoevaluateboththeeffectivenessindicesalsoserveasthebasisforcomparingthenegativeim-anddynamicresponsesofPQmitigationequipmentinpracticalpactsofPQeventsonpowersystems/customersinaquantita-applications.tivemanner.TheeffectivenessofPQindicesunderpracticalcir-TofullyrealizetheadvantagesofthenewPQindices,anovelcumstancesisdeterminedbytheapplicabilityofboththeirdef-Atom(transformkernel)basedtimefrequencytransformanditsinitionsandth