Whatislockoutrelayfunctionwhyitisneeded?LockoutRelayistheMasterTriprelay(Itisalatchrelayonceoperatedwehavetoresetitbymanual)WhichisusedforGeneratorprotection,Transformerprotection,Turbineprotection(FixedinindoorPanel,Standardmanufactureronlymakingthoserelays)ifitoperatedbecauseofanyfaultinabovetheafterclearingallthefaultwehavetoresetitbyhand(normallyavailable110Voltsor220VoltsDC).Generatorlock-outrelayThedescriptionofan86deviceisa"locking-out"or"lock-out"relay.Ingeneral,the86G-1and86G-2relaysontheGeneratorProtectionPanelareactuatedbyoneofseveralgeneratorprotectionrelays--usually,87devices(differentialcurrentdetectiondevices--andoccasionally,othersasspecifiedbytheowner,insuringagency/company,localregulations,orutilityrequirements.Sometimes,numerousdeviceswere"grouped"toactuate86G-1OR86G-2inordertoprovidesomedifferentiationastotheexactcauseofthetrip.Whenan86G-nrelayisactuatedbyoneormoregeneratorprotectiverelays/devices,thedevice/relaywhichactuatedthelock-outshouldhavea"flag"orilluminatedindicatinglighttosignifywhichdevice/relaydetectedaseriousproblemwhichcouldcausedamagetothegenerator.Whentheactuatingdeviceisidentified,thecauseshouldbeinvestigatedandunderstoodBEFOREtheunitisre-started.Whenan86G-ndeviceisactuated,thegeneratorbreakerisopened(tripped),excitationisusuallyde-energized,andtheturbineisusuallytripped(emergencyshutdown).The86G-nrelaysrequireamanualreset(theymustbemanuallyrotatedtoreturntotheresetposition)inordertopermitaturbinere-start--hencethe"lock-out"function.RefertotheGeneratorProtectionPanelelementarydrawingsfortheexactdetailsofwhatdevicesactuatethe86G-nrelaysatyoursite.86Lockoutrelayisanelectricallyoperatedhandorelectricallyresetauxiliaryrelaythatisoperatedupontheoccurrenceofabnormalconditionstomaintainassociatedequipmentordevicesoutofserviceuntilitisreset.94Trippingortrip-freerelayFunctionstotripacircuitbreaker,contactor,orequipment,ortopermitimmediatetrippingbyotherdevices;ortopreventimmediatereclosingofacircuitinterrupterifitshouldopenautomatically,eventhoughitsclosingcircuitismaintainedclosed.Whatisthedifferencebetweenthe94lockoutrelayand86lockoutrelay?Ihavenoticedthatthe94lockoutrelayisactivatedwhenthedistancerelayisactivatedand86isactivatedwhenthe87Tdifferentialisactivated.Butwhycan'tthesamelockoutsbeusedforboththeprotectionschemes.86lockoutrelayishandresetusedformechanicalprotection(permanentfault)&94lockoutrelayisselfresetusedfortransientfault(temporaryfaultcondition)thisismajordifferentbetween86and96lockoutrelay.94lockoutrelayisforlinefaultonly.86lockoutrelayismastertriprelay.Ittripsbothprimaryandsecondaryofthetransformerasthefaultisofseriousnature.86lockoutrelayisanelectricallyoperatedhand,orelectricallyresetrelayordevicethatfunctionstoshutdownorholdanequipmentoutofservice,orboth,upontheoccurrenceofabnormalconditions.94trippingrelayishavingfunctiontotripacircuitbreaker,contactororequipment,ortopermitimmediatetrippingbyotherdevices.ortopreventimmediatereclosingofacircuitinterrupterifitshouldopenautomaticallyeventhoughitsclosingcircuitismaintainedclosed.Lockoutrelayishandresetrelayinthiscaseboththerelaysarehandresetrelay.Onlydifferenceisthat94lockoutrelayisusedforlineprotectionandcanalsobeprovidedwithautoreclosingfacility.Iftheautoreclosingisnotsuccessfultheninthatcase94goestoLockoutstateandshallbemanuallyreset.Incaseof86thereisnoAutoreclosingfeatureavailable.Itgoestolockoutstatedirectly.86isactuallyanelectrically/HandresetMastertriprelaythattripsboththeprimary&SecondaryofaTransformerwhereas94isalockoutrelaythatisusedintransmissionlineprotectioneg.inanAutorecloser.IncaseofafaulttheAutoeclosershallstartitsO-t-CO-T-CO-T-CO-T-COoperation.Afterunsuccessfullytryingtoreclosetheline,the94Lockoutrelayshallactafterthetimedurationset&willputtheAutorecloserinanLockoutconditionsothattherearenofurtherreclosingattempts.86Lockoutrelaysareusedbymanyutilitiesinelectricalpowertransmissionsubstationstotripandholdoutofequipmentservicewithinaprotectedzoneontheoccurrenceofprotectionrelayoperationwhichrequiresinspectionand/orrepairbeforethezonemaybesafelyplacedbackinservice.Theoriginalintentoflockoutwasthatonoperation,maintenanceoroperatingpersonnelwouldinspectandrepairasrequiredthelocked-outzone,andwhenclear,wouldresetthelockoutallowingoperatorstoplacetheelementbackinservice.Howeverinrecentdecades,ithasbecomenormaltoremotelycontrolsubstations,resultingintheabsenceofon-sitepersonneltoresetalockoutinanemergencysituation.Ontheotherhand,94inter-triprelayisusedforupordownstreambackupprotectiontopreventtheothersidebreakerfromsupplyingthefaultyzone.Theinter-tripsignalshallbeclearedasthefaultclearedandassociatedrelayhasbeenreset.
