(4.1.1)-16限流電抗器及運行

ElectricalEquipmentandOperation12ContentsOverviewOrdinaryCurrent-limitingReactorSplitReactor3OverviewWhatcurrentislimited?Whyisthecurrentlimited?

“Current-limiting”referstothevaluethatlimitstheshort-circuitcurrent;Excessiveshort-circuitcurrentproduceshugethermalandelectrodynamiceffects.Whenthebreakingcapacityofthecircuitbreakerisinsufficientortheequipmentcannotwithstandtheheatingandelectrodynamicforcesoftheshort-circuitcurrent,theshort-circuitcurrentshouldbelimited.Aftertheshort-circuitcurrentislimited,cheaperlight-weightappliancesandwireswithasmallercross-sectioncanbeused.Howdoesacurrent-limitingapplianceplaytheroleofcurrent-limiting?Thecurrent-limitingapplianceisconnectedinseriesinthepowercircuittoincreasetheshort-circuitimpedanceinthepowersupplyline,therebylimitingtheshort-circuitcurrent.4OverviewBasicrequirementsforcurrent-limitingappliances:Whennormalcurrentflows:thevoltagedropgeneratedonitwillnotaffectthequalityofthesupplyvoltage.Whenashort-circuitcurrentflowsthrough:itcanplaytheroleoflimitingtheshort-circuitcurrent.Commonlyusedcurrent-limitingappliances:current-limitingreactorsandsplittransformers5OrdinaryCurrent-limitingReactorWindingCementpillarInterphasepillarinsulatorGroundpillarinsulator1.Structure:Eachoneisasingle-phaseair-coreinductancecoilwithoutatapinthemiddle.Therearethreewaysofarrangingreactors:vertical,horizontalandupsidedownT-shapedarrangement.a)figureisaverticallayout,b)figureisanupsidedownT-shapedlayout,andc)figureisahorizontallayout.Fig.1Reactor’sphysicalmapFig.2Reactor’sstructurediagramFig.3Reactor’slayoutdrawing6OrdinaryCurrent-limitingReactorRatedvoltage:6kVand10kVRatedcurrent:200～4000AReactancepercentage:Thereactancepercentage(XK%)representstheratiopercentageofthereactor'svoltagedroptotheratedvoltagewhenratedcurrentpassesthroughthereactor,namely2.Parameters:％≈Intheequator,INL---Theratedcurrentofthereactor;UNL---Theratedvoltageofthereactor;ZNL---Theratedimpedanceofthereactor;XNL---Thereactanceofthereactor.(XK%)has6sections:4,5,6,8,10and127OrdinaryCurrent-limitingReactor3.Model:XKDGKL---Inwhich:XK—Current-limitingreactorD—Single-phase(three-phaseisrepresentedbyS)GK—Dryair-coreL—Aluminumwire(copperwireisunmarked)

—Systemratedvoltage(kV)

—Ratedcurrent(A)

—Percentreactance(%)123123ModelRatedvoltage(kV)Ratedcurrent(A)Percentreactance(%)Ratedreactance(Ω)Thermalstabilitycurrent(3s)kADynamicstabilitycurrent(kA)Singlephaseweight(kg)XKDGKL-6-3500-46350040.039687.5223.1712XKDGKL-10-3500-410350040.066087.5223.18768OrdinaryCurrent-limitingReactor4.Use:Linereactor:installedbehindtheleadcircuitbreakerAbletolimittheshort-circuitcurrentofthisline,thenthecircuitbreakerandisolatingswitchbeforethereactorcanbechosenforlightelectricalappliancesIncaseofalinefault,thebuscanbemaintainedwithahigherresidualvoltageBusreactor:installedonthebussectionWhenabussectionisshort-circuited,thecurrentflowingfromthenon-faultysectionofthebustotheshort-circuitedbuscanbelimited,increasingtheresidualvoltageofthenon-faultysectionofthebus.Itcanalsolimittheshort-circuitcurrentoftheoutletline(notveryeffective)Theroleandmethodofareactor9SplitReactorThereactorisinstalledinthecircuittolimittheshort-circuitcurrentandmaintaintheresidualvoltageofthebus,sothereactorisrequiredtohavealargereactance.However,innormaloperation,itishopedthatthereactancevalueofthereactorissmaller,resultinginsmallervoltagelossduringnormaloperation.Butthedisadvantageofordinaryreactors:thereactancevalueisdetermined.Thesplitreactorisusedtosolvethiscontradiction.10SplitReactor1.Structure:Thereisatapinthemiddle,andthewindingiscomposedoftwocoaxialwireswiththesamewindingdirection.Generally,1isconnectedtothepowersupply,and2and3areconnectedtotheload.Therefore,splitreactorscanprovidetwiceasmanyoutletsasordinaryreactors.Fig.9.7Splitreactor(a)Electricalsymboldiagram;(b)Circuitdiagram1—Themiddletap;2.3—Theendsoftwoarms11SplitReactor2.WorkingprinciplesDuringnormaloperationWhenthecurrentsofthetwoarmsofthesplitreactorareequal,sincethecurrentsofthetwoarmsareinoppositedirections,themutualinductionpotentialgeneratedbythecurrentineitherarmtotheotherarmisnegative,whichwillreducethevoltagedropofeacharm.X12,X13———EquivalentreactanceofeacharmXL———Self-inductanceofeacharmm———Themutualinductancecoefficientisrelatedtothestructureofthereactor,generally0.5Duringnormaloperation,theequivalentreactanceofeacharmis1/2oftheself-inductance.X12=X13=0.5XLI1+I2I1I212SplitReactorWhenTerminal3isnormalandTerminal2isshort-circuited,theshort-circuitcurrentflowsfromTerminal1toTerminal2.SincethecurrentofTerminal3ismuchsmallerthantheshort-circuitcurrentofTerminal2,thefunctionofTerminal3canbeignored(withoutmutualinductanceeffect).Atthistime,thereactancethataffectstheshort-circuitcurrentofTerminal2isthereactanceXLofonearm,anditsreactancevalueisdoubledcomparedwithnormaloperation.Intimeofshort-circuitTheimpedanceintimeofashortcircuitistwicethatinnormaloperation,whichstrengthensthefunctionoflimitingtheshort-circuitcurrent.X12=XL13SplitReactorConclusion:Theimpedancevalueofthesplitreactorissmallduringnormaloperation,andtheresultingvoltagelossvalueissmall.Th