译文DLT 722014 变压器油中溶解气体分析和判断导则

DL/T722—2014

ICS29.040.10

E38

Filingnumber:47903-2015

ElectricPowerIndustryStandardofthePeople'sRepublicofChina

DL/T722—2014

ReplaceDL/T722—2000

GuidetotheAnalysisandtheDiagnosisofGasesDissolvedinTransformerOil

（ExposureDraft）

Issuedate:2014-10-15Implementationdate:2015-03-01

IssuedbyNationalEnergyAdministration

DL/T722—2014

II

Foreword

ThisstandardisdraftedinaccordancewiththerulesgivenintheGB/T1.1-2009Directivesforstandardization—Part1:Structureanddraftingofstandards.

ThisstandardreplacesDL/T722-2000Guidetotheanalysisandthediagnosisofgasesdissolvedintransformeroilinwhole.Exceptforeditorialrevisions,thefollowingtechnicaldeviationshavebeenmadewithrespecttoDL/T722-2000:

——The"dissolutionanddiffusionofgasesinoil"wasadded(seeArticle4.4ofthisstandard);

——Thespecificrequirementsforshorteningthecyclein"detectionunderspecialcircumstances"wereadded(seeArticle5.4ofthisstandard);

——Thespecificcontentof“takeoilsamplefromoil-filledelectricalequipment”in“sampling”wasdeleted,andonly“takegassamplefromgasrelayventnozzle”wasretained,andotheroriginalspecificcontentsaresubjecttorelevantregulationsinGB7597(seeChapter6ofthisstandard);

——Theoriginalcontentsin"removalofdissolvedgasfromoil"and"gasdetectionmethod"weredeleted,andtherelevantregulationsinGB/T17623shallprevail(seeChapter7andChapter8ofthisstandard);

——Thetitleof"Ex-worksandnewlycommissionedequipment"(see9.2ofthisstandard);

——Thegascontentrequirementsofvarioustypesofequipmentnewlycommissionedweremodified,itwasclassifiedintovoltagelevels"330kVandabove"and"220kVandbelow",andthecontentrequirementsweremodifiedaccordingly(see9.2ofthisstandardand8.4.4of2000edition)；

——Thevoltageclassclassificationoftheinstrumenttransformerandthecorrespondingattentionvaluesweremodified,andtheattentionvaluesofthebushingweremodified(see9.3.1ofthisstandard);

——The"Principlesfortheapplicationofattentionvalues"wasadded,andsomecontentsweremodified(see9.3.3ofthisstandard);

——Apartofthecontentof"Characteristicgasmethod"wasrevised(see10.1ofthisstandard);

——Thecodeof"low-temperatureoverheating(below150℃)"wasrevised(see10.2.1ofthisstandard);

——Thestructureandcorrespondingcontentof"faulttypejudgment"wererevised(seeChapter10ofthisstandard);

——AnnexA"SampleLabelFormat"andAnnexD"ApplicableConcentrationofStandardMixture"weredeleted(seeAnnexof2000Edition);

——"Othertestitemsrecommendedwhenjudgingfaults"wasadded(seeAnnexDofthisstandard);

——Thedescriptionoftypicalfaultswasrevisedandfaultexampleswereadded(seeAnnexEofthisstandard);

——Aninformativeannex"GasDistributionCoefficient"wasadded(seeAnnexFofthisstandard).

ThisstandardwasproposedbytheChinaElectricityCouncil.

ThisstandardwaspreparedbytheTechnicalCommitteeforStandardizationofPowerTransformerinthePowerIndustry(DL/TC02).

Thisstandardwasdraftedby:ChinaElectricPowerResearchInstitute,StateGridOperationBranch,StateGridHubeiElectricPowerCompanyElectricPowerResearchInstitute,StateGridLiaoningElectricPowerCo.,Ltd.,StateGridJiangsuElectricPowerCompanyElectricPowerResearchInstitute,StateGridElectricPowerResearchInstituteWuhanNARICo.,Ltd.,StateGridGansuElectricPowerCompanyElectricPowerResearchInstitute,GuangdongPowerGridCompanyElectricPowerResearchInstitute,StateGridJilinProvinceElectricPowerCo.,Ltd.ElectricPowerResearchInstitute,StateGridEastChinaBranch,StateGridShanghaiElectricPowerCompany,StateGridSuzhouPowerSupplyCompany,StateGridJiangsuElectricPowerCompanyMaintenanceBranch,StateGridHenanElectricPowerCompanyElectricPowerResearchInstitute,StateGridShanghaiElectricPowerCompanyElectricPowerResearchInstitute,ShenyangTransformerResearchInstituteCo.,Ltd.Company,TBEAShenyangTransformerGroupCo.,Ltd.,ChinaYangtzePowerCo.,Ltd.MaintenancePlant,NynasPetroleum(Shanghai)Co.,Ltd.

Maindraftersofthisstandard:WangJianyi,LingMin,LiJinzhong,SheZhenqiu,WangRuizhen,WangShige,WuYihua,LiangZhiyu,FuQiang,LiShouxue,JiangYimin,ChenJiangbo,ZhangShuzhen,CaiShengwei,LiaoWenfeng,ZhouXiaofan,XuWanda,XuJiangang,HanJinhua,LiHonglei,PengWei,ChenKui,LiuFeng,WangWeiguo,LiYongchun.

ThisstandardreplacesDL/T722-2000.

Thisisthesecondrevisededition.

Thepreviouseditionsofthisstandardareasfollows:

——SD187—1986；

——DL/T722—2000。

PleasesendanyopinionsorsuggestionsputforwardduringtheexecutionofthisstandardtotheStandardizationManagementCenterofChinaElectricityCouncil(No.1,Lane2,BaiguangRoad,Beijing,100761)

TranslationunitofEnglishversionofthisstandard:

Maintranslatorsandeditorsofthisstandard:

GuidetotheAnalysisandtheDiagnosisofGasesDissolvedinTransformerOil

1 Scope

Thisstandardspecifiesthemethodforfaultidentificationandfaulttypejudgmentofoil-filledelectricalequipmentbasedonthedissolvedandfreegasesintransformeroil(mineralinsulatingoil),andrecommendsfurthermeasures.

Thisstandardisapplicabletoelectricalequipmentthatusestransformeroilandpaper(board)asthemaininsulatingmaterials,includingtransformers,reactors,instrumenttransformers,andbushings.

2 NormativeReferences

Thefollowingreferenceddocumentsareindispensablefortheapplicationofthisstandard.Fordatedreferences,onlytheeditioncitedapplies.Forundatedreferences,thelatesteditionofthereferenceddocument(includinganyamendments)applies.

GB/T7597 Methodofsamplingfortransformerandturbineoilsinelectricpowerindustry

GB/T17623Determinationofcomponentcontentsofgasesdissolvedininsulatingoilbygaschromatographymethod

DL/T984 Guideforthediagnosisofinsulationaginginoil-immersedpowertransformer

IEC60599 Mineraloil-impregnatedelectricalequipmentinservice-Guidetotheinterpretationofdissolvedandfreegasesanalysis

3 TermsandDefinitions

Forthepurposesofthisdocument,thefollowingtermsanddefinitionsapply.

3.1

characteristicgas

Gasesthatarevaluableforjudgingtheinternalfaultsofoil-filledelectricalequipment,i.e.hydrogen(H2),methane(CH4),ethane(C2H6),ethylene(C2H4),acetylene(C2H2),carbonmonoxide(CO),carbondioxide(CO2)

3.2 totalhydrocarbon

Totalamountoffourhydrocarboncharacteristicgases,i.e.CH4,C2H6,C2H4andC2H2.

3.3 freegas

Gasinsolubleinoil(suchasthegasintheupperpartoftheoilsurfaceoftheequipmentandthegasinthegasrelay).

4 SourcesofGasesDissolvedinOil

4.1 Decompositionoftransformeroil

Transformeroilisamixtureofmanyhydrocarbonmoleculeswithdifferentmolecularweights.ElectricorthermalfaultcanbreaksomeC—HbondsandC—Cbonds,whichisaccompaniedbythegenerationofasmallnumberofactivehydrogenatomsandfreeradicalsofunstablehydrocarbons.ThesehydrogenatomsorfreeradicalsquicklyrecombinethroughcomplexchemicalreactionstoformH2andlow-molecularhydrocarbongases,suchasCH4,C2H6,C2H4,C2H2,etc.,andmayalsogeneratecarbonsolidparticlesandhydrocarbonpolymers(X-wax).TheoxidationofoilwillalsogenerateasmallamountofCOandCO2,whichcanaccumulatetoasignificantamountoveralongperiodoftime.

AnnexAofthisstandardshowstherelationshipbetweenthegasformedinthethermalequilibriumstateandthetemperaturecalculatedbyHalsterdinthethermodynamicequilibriumtheory.

4.2 Decompositionofsolidinsulatingmaterials

Solidinsulationmaterialsrefertopaper,laminatedcardboardandwoodblocks,etc.,whicharecelluloseinsulationmaterials.Celluloseisalong-chainhighlypolymerizedhydrocarbon(C6H10O5)ncomposedofmanyglucosemonomers.ThethermalstabilityoftheC—ObondandglucosidebondisweakerthanthatoftheC—Hbondinoil.Thepolymerwillbecrackedabove105°C,andcompletelycrackedandcarbonizedabove300°C.Alongwithwater,alargeamountofCOandCO2,asmallamountoflow-molecularhydrocarbongases,furfuralanditsseriesofcompoundswillbegeneratedduringinthepolymercracking.

4.3 Othersourcesofgas

ThewatercontainedintheoilcanreactwithirontogenerateH2;whenthetemperatureishighandthereisO2dissolvedintheoil,somepaint(alkydresin)intheequipmentmaygeneratealargeamountofH2underthecatalysisofsomestainlesssteel,orthecatalyticreactionofstainlesssteelwithoilcanalsogeneratealargenumberofH2;newstainlesssteelmayalsoadsorbH2duringprocessingorgenerateH2duringwelding;somemodifiedpolyimideinsulatingmaterialscanalsogeneratecertaincharacteristicgaseswhencontactedwithoil;oilcanalsogeneratecertaincharacteristicgasesundersunlight.

Thesourceofgasalsoincludessomegasintheinjectedoilitself;aftertroubleshooting,thegasadsorbedinthedevicebodyisnotcompletelyremoved,butslowlyreleasedintotheoil;Theoilintheoilchamberoftheswitchoftheon-loadvoltageregulatingtransformerleakstothemaintankofthetransformer,andelectricsparksareformedwhentheselectiveswitchoperatesatacertainposition(suchaspolarityconversion),whichwillgenerateC2H2intheoilofthetransformerbody;Thegasgeneratedbythefaultoftheauxiliaryequipmentofthecoolingsystem(suchassubmersibleoilpump)willalsoentertheoiloftransformerbody;Repairingweldingofoiltankwillleadtooildecompositionandgenerategases.

4.4 Dissolutionanddiffusionofgasesdissolvedinoil

Thegasgeneratedbythedecompositionofoilandpaperinsulationmaterialsiscontinuouslydissolvedintheoilthroughconvectionanddiffusionintheoil.Whenthegasgenerationrateisgreaterthanthedissolutionrate,apartofitwillgatherintofreegasandenterthegasrelayoroilconservator.Therefore,whenthereisgasaccumulatedinthegasrelayoroilconservator,detectingthegasesinitwillhelptomakeajudgmentontheinternalconditionoftheequipment.

5 DetectionCycle

5.1Detectionbeforecommissioning

Neworoverhauled66kVandaboveequipmentshallbedetectedatleastoncebeforebeingputintooperation.Detectionisnotrequiredforfullysealedinstrumenttransformersandbushingsthatarenotsampledasrequiredbythemanufacturer.Iftheinducedvoltagewithstandandpartialdischargetestsarecarriedoutonsite,andetectionshallbeconductedbeforeandafterthetest,andtheoilsampleshallbetakenatleast24hoursafterthetestiscompleted.

5.2Detectionduringnewcommissioning

Neworoverhauledtransformersandreactorsof66kVandaboveshallbedetectedatleastonceevery1day,4days,10days,and30daysafterbeingputintooperation.

Neworoverhauledinstrumenttransformersof66kVandaboveshouldbedetectedoncewithin3monthsafterbeingputintooperation.Detectionisnotrequiredforfullysealedinstrumenttransformersthatarenotsampledasrequiredbythemanufacturer.

5.3Periodicdetectionduringoperation

TheperiodicdetectioncycleoftheequipmentinoperationshallbecarriedoutinaccordancewiththeprovisionsofTable1.

Table1Periodicdetectioncycleofequipmentinoperation

Equipmenttype

Equipmentvoltagelevelorcapacity

Detectioncycle

Transformersandreactors

Voltage330kVandabove

Powerplantstep-uptransformerswithacapacityof240MVAandabove

3months

Voltage220kV,capacity120MVAandabove

6months

Voltage66kVandabove,capacity8MVAandabove

1year

Instrumenttransformer

Voltage66kVandabove

1~3years

Bushing

—

Whennecessary

Note:Thedetectioncyclesofothergradesoftransformers,reactorsandinstrumenttransformersisself-regulated.Thefullysealedinstrumenttransformersandbushingswhicharenotsampledasspecifiedbythemanufactureraregenerallynotdetectedduringthewarrantyperiod.Afterthewarrantyperiodhasexpired,itmaybedeterminedbytheactualsituation,butitisnotappropriatetotakesamplesundernegativepressure.

5.4 Detectionunderspecialcircumstances

Underspecialcircumstances,detectionshallbecarriedoutaccordingtothefollowingrequirements:

a) Whentheequipmenthasexceptionalconditions(suchastransformergasrelayaction,differentialprotectionaction,pressurereleasevalveaction,andhighcurrentimpact,over-excitationoroverload,instrumenttransformerexpanderaction,etc.),oilsamplesshallbetakenfordetection.Intheeventofgasaccumulatedinthegasrelay,agassampleneedstobetakenfordetection.

b) Whenthefollowingexceptionalitiesaresuspectedintheequipment,thedetectioncycleshallbeshortenedaccordingtothesituation,soastomonitororexitoperation.Duringthemonitoringprocess,ifthegrowthtrendisobvious,othercorrespondingmeasuresmustbetaken;ifthecontentisstableafterthreetimesoftestsundersimilaroperatingconditions,thetestcyclecanbeappropriatelyextendeduntilthenormaltestcycleisrestored.

1) Overheatfaults.Whenitissuspectedthatthemainmagneticcircuitorthemagneticleakagecircuitisfaulty,thecyclecanbeshortenedtoonceaweek;whenitissuspectedthattheconductivecircuitisfaulty,itshouldbeshortenedtoatleastonceaday.

2) Dischargefaults.Whenlow-energydischargeissuspected,itshouldbeshortenedtoonceaday;whenhigh-energydischargeissuspected,carryoutfurtherdetectionorexitoperation.

6 Sampling

6.1 Takeoilsamplesfromoil-filledelectricalequipment

AccordingtotherelevantregulationsofGB/T7597fortheanalysisandsamplingofgasesdissolvedintransformeroil.

6.2 Takegassamplefromtheventnozzleofthegasrelay

6.2.1Overview

Whengasaccumulatesinthegasrelay,agassampleshallbetakenfordetection.Thecompositionandcontentofthesegasesareoneoftheimportantcriteriaforjudgingtheequipmentfaultandthenatureofthefault.Inordertoreducetheimpactofdifferentre-dissolutionratesofdifferentcomponents,thegassamplemustbetakenoutinthetimeasshortaspossibleanddetectedassoonaspossible.

6.2.2Containerfortakinggassample

Awell-sealedglasssyringeorgassamplingbagshallbeused.Theglasssyringe,ifused,shallbelubricatedbytheequipmentbodyoilbeforesamplinginordertoensurethesyringeissealedwell.

6.2.3Methodoftakinggassample

Whentakinggassamples,putasmallpieceoflatextubeontheventnozzleofthegasrelay,andconnectasmallmetalthree-wayvalvetothesyringeattheotherendofthelatextube(payattentiontotheinnerdiameterofthelatextube,thejointbetweenthedeflatingvalveofthelatextubeandthegasrelayandthemetalthree-wayvalveshallbesealed).Fortheoperationstepsandconnectionmethods,seetherelevantregulationsontheanalysisandsamplingofgasesdissolvedintransformeroilinGB/T7597.

Thefollowingstepscanbeused:

a) Turnthethree-wayvalve,flushtheconnectingpipelineandthesyringewiththegasinthegasrelay(thisstepisnotnecessarywhenthegasvolumeislow);turnthethree-wayvalvetoemptythesyringe;turnthethree-wayvalveagaintotakeagassample;Inthecaseofdown-drawingofgasrelaypipe,themethodisthesame,butoilshallberemovedfromthesyringe.

b) Aftersampling,closetheventnozzle,turnthethree-wayvalvetosealthesyringeport,removethesyringetogetherwiththethree-wayvalveandthelatextube,thenremovethethree-wayvalve,andimmediatelysealthesyringewithasmallrubberhead(exhausttheairinthesmallrubbertipasmuchaspossible).

7 RemovetheGasDissolvedinOil

SubjecttotherelevantregulationsinGB/T17623.

8 GasComponentContentDetectionMethod

SubjecttotherelevantregulationsinGB/T17623.

9 FaultIdentification

9.1 Overview

Theoil-paperinsulationmaterialinsidetheoil-filledelectricalequipmentwillgraduallyageanddecomposeundertheactionofheatandelectricityduringnormaloperation,andgenerateasmallamountofH2,lowmolecularhydrocarbongases,CO,andCO2etc.;Incaseofthermalandelectricalfault,thesegaseswillalsobegenerated.Thetwosourcesofgascannotbedistinguishedtechnically,andtherearenostrictlimitsinvalue.Inaddition,itisrelatedtomanyvariablefactorssuchasload,temperature,O2contentandwatercontentinoil,oilprotectionsystemandcirculationsystem,etc.Therefore,whenjudgingtheequipmentfaultandtheseverityofthefault,acomprehensivejudgmentshallbemadebasedontheabsolutevalueofthegascontent,thegrowthrate,theoperatingstatus/structuralcharacteristicsoftheequipment,andtheexternalenvironment.Sometimesthereisnofaultintheequipment,buttheabove-mentionedgasesmayalsoappearintheoilduetootherreasons.Therefore,payattentiontothesourcesofthesegasesthatmaycausemisjudgment.Fordetails,see4.3ofthisstandard.

Inordertoidentifyfaults,attentionvaluesforgascontentandgasgenerationrateareproposed.Attentionvaluereferstothevalueofthecontentorincrementofthecharacteristicgastowhichattentionshallbepaid,anditisactuallynotastandardforclassifyingequipmentstatus.Whentheattentionvalueisexceeded,thedetectioncycleshallbeshortenedaccordingtotheprovisionsof5.4ofthisstandard,andacomprehensiveanalysisshallbecarriedouttogetherwithotherjudgmentmethods.

9.2 Requirementsforcontentofgasdissolvedinoilbeforenewequipmentisputintooperation

Beforethenewequipmentisputintooperation,thecontentofgasesdissolvedintheoilshallmeettherequirementsofTable2,andthereshallbenoobviousdifferencebetweenthetwodetectionresultsbeforeandaftertheoperation.

Table2Requirementsforcontentofgasesdissolvedinoilbeforenewequipmentisputintooperation

μL/L

Equipment

Gascomposition

Content

330kVandabove

220kVandbelow

Transformersandreactors

Hydrogen

<10

<30

Acetylene

<0.1

<0.1

Totalhydrocarbons

<10

<20

Instrumenttransformer

Hydrogen

<50

<100

Acetylene

<0.1

<0.1

Totalhydrocarbons

<10

<10

Bushing

Hydrogen

<50

<150

Acetylene

<0.1

<0.1

Totalhydrocarbons

<10

<10

9.3 Attentionvaluesofgasesdissolvedinequipmentoilduringoperation

9.3.1Attentionvaluesofgasesdissolvedinoil

WhenthecontentofgasesdissolvedintheequipmentoilexceedsthevaluelistedinTable3duringoperation,attentionshallbepaidtoit.

Table3Attentionvaluesofcontentofgasesdissolvedinequipmentoilinoperation

μL/L

Equipment

Gascomposition

Content

330kVandabove

220kVandbelow

Transformersandreactors

Hydrogen

150

150

Acetylene

1

5

Totalhydrocarbons

150

150

CO

(See10.2.3.1ofthisstandard)

(See10.2.3.1ofthisstandard)

Carbondioxide

(See10.2.3.1ofthisstandard)

(See10.2.3.1ofthisstandard)

Currentinstrumenttransformer

Hydrogen

150

300

Acetylene

1

2

Totalhydrocarbon

100

100

Voltageinstrumenttransformer

Hydrogen

150

150

Acetylene

2

3

Totalhydrocarbons

100

100

Bushing

Hydrogen

500

500

Acetylene—

1

2

Totalhydrocarbon

150

150

Note:Thevalueslistedinthistablearenotapplicabletothegassamplestakenfromthegasrelay(seeChapter11ofthisstandard).

9.3.2 Attentionvalueofgasgrowthrate

Thegasgrowthrate(gasgenerationrate)isdirectlyrelatedtothefaultenergy,thetemperatureofthefaultpoint,andthescopeofthefault.Therateofgasgenerationisalsorelatedtothetypeofequipment,loadconditionsandthevolumeoftheinsulatingmaterialusedanditsagingdegree.Whenjudgingtheseriousconditionofequipmentfault,theescapelossofgasshallalsobetakenintoconsideration.Itshallbenotedthatthegasgenerationtimemayonlybeacertainperiodoftimewithinthetwodetectioncycles,sothecalculatedvalueofthegasgenerationratemaybelessthantheactualvalue.

Thegasgenerationrateiscalculatedinthefollowingtwoways:

a) Absolutegasgenerationrate,thatis,theaveragevalueofacertaingasgeneratedperoperatingday,iscalculatedasfollows:

γa=Ci,2−Ci,1∆t×mρ (1)

Where:

γa——Absolutegenerationrate,mL/day;

Ci,2——Concentrationofacertaingasintheoilmeasuredduringthesecondsampling,μL/L;

Ci,1——Concentrationofacertaingasintheoilmeasuredduringthefirstsampling,μL/L;

∆t——Actualrunningtimeinthetwosamplingintervals,indays;

M——Totaloilvolumeofequipment,t;

ρ——Densityofoil,t/m3.

b) Relativegasgenerationrate,thatis,thepercentageofacertaingascontentincreaserelativetotheoriginalvaluepermonthofoperation(orconvertedtoamonth),iscalculatedasfollows:

γr=Ci,2−Ci,1Ci,1×1∆t×100% (2)

Where:

γr——Relativegasgenerationrate,%/month;

Ci,2——Concentrationofacertaingasintheoilmeasuredduringthesecondsampling,μL/L;

Ci,1——Concentrationofacertaingasintheoilmeasuredduringthefirstsampling,μL/L;

∆t——Actualrunningtimeinthetwosamplingintervals,indays;

Fortransformersandreactors,theattentionvaluesofabsolutegasgenerationratesareshowninTable4;theattentionvalueofrelativegasgenerationrateoftotalhydrocarbonis10%(forequipmentwithverylowinitialcontentoftotalhydrocarbon,thiscriterionshouldnotbeused).

Forequipmentwithaslowincreaseingascontent,thegasgrowthoftheequipmentcanbemonitoredbythegasonlinemonitoringdeviceatanytime.

Table4Attentionvaluesofabsolutegasgenerationratesofgasesdissolvedinequipmentoilinoperation

mL/d

Gascomposition

Sealedtype

Opentype

Hydrogen

10

5

Acetylene

0.2

0.1

Totalhydrocarbon

12

6

Carbonmonoxide

100

50

Carbondioxide

200

100

Note1:Whenacetylene<0.1μL/Landtotalhydrocarbonislessthanthenewequipmentcommissioningrequirements,theabsolutegasgenerationrateoftotalhydrocarbonmaynotbeanalyzed(judged).

Note2:Attheinitialstageofoperationofthenewequipment,thegasgenerationrateofCOandCO2mayexceedtheattentionvaluesinthetable.

Note3:Whenthedetectioncyclehasbeenshortened,theattentionvaluesinthistableareforreferenceonly,andtheyarenotapplicablewhenthecycleisshort.

9.3.3 Applicationprincipleofattentionvalues

Theapplicationprinciplesofattentionvaluesofgascontentandgasgenerationrateareasfollows:

a) Theattentionvalueofgascontentisnotthesolebasisforjudgingfaultinsidetheequipment.Whenthegascontentexceedstheattentionvalue,thedetectionperiodshallbeshortenedaccordingto5.4b)ofthisstandard,andthejudgmentshallbemadebasedonthegasgenerationrate.Ifthegascontentexceedstheattentionvaluebutisstableforalongtime,itcanbeoperatedundertheconditionofexceedingtheattentionvalue;inaddition,ifthegascontentislowerthantheattentionvalue,butthegasgenerationrateexceedstheattentionvalue,thedetectionperiodshallalsobeshortenedaccordingto5.4b)ofthisstandard.

b) Forequipmentwithavoltagegradeof330kVandabove,attentionshallbepaidwhenC2H2(≥0.lμL/L)isdetectedintheoilforthefirsttime.

c) Whenthegasgenerationrateincreasessuddenlyorthenatureofthefaultchanges,necessarymeasuresmustbetakenasappropriate.

d) TherearemanyfactorsthataffecttheH2contentintheoil(see4.3ofthisstandard).IfonlytheH2contentexceedstheattentionvalue,butnoobviousgrowthtrendexists,itcanalsobejudgedasnormal.

e) Payattentiontodistinguishinggassourcesundernon-faultconditions(see4.3ofthisstandard).

10 JudgmentofFaultType

10.1Characteristicgasmethod

AccordingtothebasicprinciplesdescribedinChapter4ofthisstandard,themaincharacteristicgasesandsecondarycharacteristicgasesgeneratedbydifferenttypesoffaultsaresummarizedinTable5,andthetypesofequipmentfaultscanbeinferredaccordingly.

Table5Gasesgeneratedindifferentfaulttypes

Faulttype

Maincharacteristicgases

Secondarycharacteristicgases

Oiloverheating

ch4，c2h4

H2，c2h6

Oilandpaperoverheating

ch4，c2h4，CO

H2，c2h6，cO2

Partialdischargeinoil-paperinsulation

H2，ch4，CO

c2h4，c2h6，c2H2

Sparkdischargeinoil

H2，c2H2

Arcinoil

H2，C2H2，C2H4

ch4，c2h6

Electricarcinoilandpaper

H2，c2H2，c2h4，CO

ch4，c2h6，CO2

Note1:Oiloverheating:Thereareatleasttwocases,i.e.,mediumandlow-temperatureoverheating(below700°C)andhigh-temperatureoverheating(above700°C).Forexample,ifthetemperatureislow(below300℃),therearemoreCH4andC2H6inhydrocarbongascomponents,andC2H4islessthanC2H6orevendoesnotexist;asthetemperatureincreases,C2H4increasessignificantly.

Note2:Oilandpaperoverheating:TheoverheatingofsolidinsulatingmaterialswillgeneratealargeamountofCOandCO2.Aftertheoverheatedpartreachesacertaintemperature,thecellulosewillbegraduallycarbonizedandtheoiltemperatureoftheoverheatedpartwillincrease,whichwillincreasethegasessuchasCH4,C2H6andC2H4.Therefore,thelow-temperatureoverheatingofsolidinsulatingmaterialsdoesnotincreasesignificantlytheinitialhydrocarbongascomposition.

Note3:Partialdischargeinoil-paperinsulation:itmainlygeneratesH2andCH4.Whenthesolidinsulationisinvolved,COisgenerated,anditisrelatedtotheoriginalCOandCO2intheoil,featuringprimarilyingeneratingnoorverylittleC2H4.

Note4:Sparkdischargeinoil:Itisgenerallyintermittent,featuringthatincreaseofC2H2isfasterthanthatofothercomponents,whilethetotalhydrocarbonisnothigh.

Note5:Arcdischarge:high-energydischarge,whichgeneratesalargeamountofH2andC2H2andaconsiderableamountofCH4andC2H4.Whenthesolidinsulationisinvolved,COincreasessignificantly,andpaperandoilmaybecarbonized.

10.2 Gascontentratiomethod

10.2.1Three-ratiomethod

Thethree-ratiomethod,whichwassummarizedonthebasisofthermodynamicsandpractice,judgesthetypeoffaultviathecombinationofcodesofthethreeratios(C2H2/C2H4,CH4/H2,C2H4/C2H6)offivegases(CH4,C2H4,C2H6,C2H2,H2),anditisgenerallyusedafterthecharacteristicgasesexceedtheattentionvalues.Tab