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2012InternationalConferenceonHighVoltageEngineeringandApplication,Shanghai,China,September17-20,2012978-1-4673-4746-4/12/$31.00©2012IEEE523NumericalSimulationofDCPositiveCoronaDischargeunderAtmosphericEnvironmentFeifeiWu1*,RuijinLiao1,XinghuaLiu1,2,FanYang1,LijunYang1,ZhiZhou1,YeLuo31.StateKeyLaboratoryofPowerTransmissionEquipment&SystemSecurityandNewTechnology,ChongqingUniversity,Chongqing,P.R.China2.ZiboPowerSupplyCompany;ShandongElectricPowerCorporation;Zibo,P.R.China.3.DazhouPowerSupplyCompany;SichuanElectricPowerCorporation,Dazhou,P.R.China.*Email:[e-mail]-Thispaperpresentsanimprovedself-consistent,multi-componentandtwo-dimensionalplasmahybridmodelforthesimulationofDCpositivecoronadischargeunderatmosphericenvironment.Themodelisbasedontheplasmahydrodynamicsandthechemicalmodles,itincludes12speciesand27reactions.Besides,thephotoionizationeffectisalsoconsideredintheproposedmodel.Basedonthismodel,thevolumeofdynamicschargedspeciesgeneration,thedischargecurrentwaveform,electrontemperature,andelectricfieldvariationsareinvestigatedindetails.Theresultsindicatethatthemodelprovidesvaluableinsightstothephysicsofaircoronadischarge.IndexTerms-coronadischarge,hybridmodel,ions,electrondensitiesⅠ.INTRODUCTIONCoronadischargesareusuallygeneratedonsharppoints,edgesoronthinwireswheretheelectricfieldisstronglyconcentrated.Withtherapiddevelopmentofextraandultrahigh-voltagetransmissionlines,theaircoronadischargebecomesoneofthecriticalproblemsassociatedwithhigh-voltagelines,whichwouldleadtothedeteriorationofinsulationsystems,powerloss,radionoise.Theyhavereceivedtheattentionofmanyresearchers.Despitetherecentimprovements,thephysicalmechanismassociatedwiththedynamicsofcoronadischargeisstillunclear.Aeffectivetooltoinvestigatethecoronadischargeindetailsistheintroductionofnumericalmodeling.Nahomy[1]whoadopted430chemistryreactionsinairdischarge,presentedoneofthemostcomprehensivecompilationsofchemistrymechanism.ThemathematicalmodelingofDCorimpulsedischargewasutilizedtoexplorethephysicalmechanism,andtheoriesofthechemicalreactionsduringthedischargeprocesstendtobecleargraduallyaftertheabovemilestonepaper.Macheretetal.[2]demonstratedtheairplasmagenerationthroughrepetitivehigh-voltagenanosecondpulses.Pancheshnyietal.[3]developedareducedairmodelwith10speciesbasedonthemechanismofNahomy[1]tosimulatethestreamerdischargesatthepressureof1atm.Morrow[4]investigatedthecoronadischargeinoxygenandothergasesusingthefinite-elementmethod.Gordiets[5]developedareducedairchemistrymodeltoinvestigatetheroleofexcitedneutralmoleculesandatomsintheairdischarge.Recently,Liangetal.investigatedtheinfluenceofreducedelectricfieldontheevolvementcharacteristicsofplasmaforN2/O2discharge.Yinetal.simulatedthereactiondiffusionprocessofairdischargeintheopenatmosphericenvironment.Inthispaper,aself-consistent,multi-componentandtwo-dimensionaldischargehybridmodelisdevelopedtosimulatetheatmosphericenvironmentDCpositivecoronadischarge,whichisbasedonthedischargehydrodynamicsandthechemicalmodel.Andthephotoionizationeffectisalsoconsidered.Theaimofthisworkistoreportthedetailsofthedevelopeddischargehybridmodel,andtrytounderstandtheelectricalandthephysicalcharacteristicsofDCpositivecoronadischargeinair.Inthefollowingsections,detaileddescriptionswillbepresentedfortheairdischargemathematicalmodelandthedischargechemistrymechanism.ThecorrespondingresultsanddiscussionsaregiveninSection3andtheconclusionsaregiveninSection4Ⅱ.MATHEMATICALMODELAirdischargeisdescribedasacontinuummedia,consistingofcoupledelectroncontinuityequations,heavyspeciesmulti-componentdiffusiontransportequations,momentumbalanceequations,electronenergybalanceequationandPoisson'sequationforelectricpotential.UsingtheobtainedelectronenergydistributionfunctionasasolutionoftheBoltzmannequation,theelectronmobility,diffusioncoefficientandcollisionratecoefficientswerecalculated.A.GoverningequationsThebalancegoverningequationforelectrondensityis(())eeeeeennDnRtμφ∂+∇⋅−⋅∇−∇=∂（1）det0eeeeeeiepnphRnwnwRnnvnSSαη=−−+++（2）wherene,np,andnndenotesthenumberdensitiesoftheelectron,positiveionandnegativeionrespectively.μeiselectronmobilitycoefficient,Deiselectrondiffusioncoefficient,φistheelectricpotential,Reisthenetrateofproductionofelectronsduetochemicalreactions,weisthedriftvelocitiesoftheelectron,αistheionizationcoefficient,ηisthenetattachmentcoefficient,Reiisthecoefficientsof2012InternationalConferenceonHighVoltageEngineeringandApplication,Shanghai,China,September17-20,2012978-1-4673-4746-4/12/$31.00©2012IEEE524electron–ionrecombination,υdetisthedetachmentcoefficient,S0istherateoftheappearanceoftheinitialelectron,andSphistherateofphotoionizationcalculatedbythefollowingequation:q3ion1ph112q1()1()4VPSSdPpPπ=⋅Ψ−⋅+−∫rrrrrr（3）Intheaboveequation,1/4πisthenormalizingconstant;pisthegaspressure;Pqistheattenuationpressureofexcitedstatenitrogenatomsandissetat30Torrforair;Ψ(r-r1⋅P)isthecoefficientofabsorptionoftheionizingradiation;risthedistancebetweenpointofradiationandabsorptiontophoton.Fortheheavyspecies(i.e.,positiveions,negativeionsa