ML17227A647

Proposed Tech Specs Tables 3.3-3,3.3-4 & 4.3-2 Re Undervoltage Relay Setpoint Changes

ML17227A647
Person / Time
Site:	Saint Lucie
Issue date:	11/30/1992
From:	FLORIDA POWER & LIGHT CO.
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ML17227A646	List: ML17227A645 ML17227A647
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NUDOCS 9212040127
Download: ML17227A647 (18)

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St.LucieUnit1DocketNo.50-335ProposedLicenseAmendmentEmerencBusUndervoltaeRelaSetointChanesATTACHMENT1St.LucieUnit1Marked-upTechnicalSpecificationPages3/4311'/4315'/4319921204OiZT92ii30PDRADOCK05000335P,PDR TABLE3.3-3ContinuedENGINEEREDSAFETYFEATUREACTUATIONSYSTEMINSTRUMENTATION~pFUNCTIONALUNIT5.CONTAINMENTSUMPRECIRCULATION(RAS)a.ManualRAS(TripButtons)b.RefuelingWaterTank-Low6.LOSSOFPOWERa:4.16kvEmergencyBusUnder-voltage(LossofVoltage)b,4.16kvEmergencyBusUnder-voltage(DegradedVoltage)TOTALNO.OFCHANNELS212ygff2/Busa/sos2BusZ/Sos1/Busi/assMINIMUMCHANNELSCHANNELSTOTRIPOPERABLEAPPLICABLEMODES1,2,3,41,2,31,.23ACTION898c.480VEmergencyBusUnder-voltage(DegradedVoltage)7.AUXILIARYFEEDWATER{AFAS)a.Manual'{TripButtons)b.AutomaticActuationLogicc.SGLevel{lA/lB)-Low8.AUXILIARYFEEDWATERISOLATIOHa.SGlA-SGlBDifferentialPressureb.FeedwaterHeaderSG1A-SG1BDifferentialPressure2/Bus4/SG4/SG4/SG4/SG4/SG2/Bus2/SG2/SG2/SG2/SG2/SG1/Bus4/SG3/SG3/SG3/SG3/SG1,2,31,2,31,2,31,2,31,2,312ll8135,1413k',1413/,14 I40TpjI/

1TABLE3.3-4ContinuedIEt(GItlEEREOSAFETYFEATUREACTUATIONSYSTEMINSTRUMENTATIONTRIPVALUESICClPlFUNCTIONALUNIT6.LOSSOFPOWERTRIPVALUEALLOWABLEVALUESCa04.16kvEmergencyBusUndervoltage(LossofVoltage)v900voltswitha>900~voltswitha1+.5secondtimedelay1+.5secondtimedelayb.4.16kvEmergencyBusUndervoltage(DegradedVoltage)t,y15Q,KO03831VoW-swc+4o-)~s8s)vo'L4~ill~LS+2.s~~k~~~deiS+'Zsec~l+Mebetsy.lDO4JlCL3tDOc.480voltsEmergencyBusUndervoltage(DegradedVoltage)7.AUXILIARYFEEDWATER(AFAS)a.Manual(TripButtons)b.AutomaticActuationLogicc.SGlA&18LevelLow8.AUXILIARYFEEDWATERISOLATIONa.SteamGenerator4P-Highb.FeedwaterHeaderHighaP>ciavolts,witha~Q~'econdtimedelayNotApplicableNotApplicable>19.OX<275psid<150.0psid)58voltsw>thasecondtimedelayNotApplicableNotApplicable>18.0X89.2to281psid56.0to157.5psid ph TABLE4.3-2ContinuedENGINEEREDSAFETYFEATUREACTUATIONSYSTEMINSTRUHENTATIONSURVEILLANCEREUIREHENTSFUNCTIONALUNIT6.LOSSOFPOWERa.4.16kvEmergencyBusUnder-voltage(LossoPVoltage)CHANNELCHECKCHANNELFUNCTIONAICALIBRATIONTESTNODESINWHICHSURVEILLANCE-REUIRED1,2,3tb.4.16kvEmergencyBusUnder-voltage(Degi.adedVoltage)~iZ,~If)S<l-~Jndeer~ge=0c.480VEmergencyBusUnder-voltage(DegradedVoltage)7,AUXILIARYFEEOWATER(AFAS)a.Manual(TripButtons)b.SGLevel(A/8)-Lowc.AutomaticActuationLogic8.AUXILIARYFEEDWATERISOLATIONa.SGLevel(A/B)-LowandSGDifferentialPressure(BtoA/AtoB)-Highb.SGLevel(A/B)-LowandFeedwaterHeaderDifferentialPressure(BtoA/AtoB)-HighN.A.N.A.N.A.N.A.N.A.N.A.1,2,31,2,31,2,,31,2,31,2,31,2.3 ISt.LucieUnit1DocketNo.50-335ProposedLicenseAmendmentEmerencBusUndervoltaeRelaSetointChanesATTACHMENT2SAFETYANALYSISIntroductionTheproposedamendmenttoSt.LucieUnit1TechnicalSpecifications(TS)willpermitchangestotheemergencybusundervoltageprotectionschemerelaysettingsatthe480voltand4160voltsystemlevels.TheseprotectionrelaysareinstalledtoinitiateseparationoftheemergencybusesfromtheoffsitepowersystemandpreventdamagetoClass1Eequipmentloadsduringsustainedlowvoltagegridconditions.Therelayingschemeprovidesdetectionoflossofoffsitepowerandasecondlevelofundervoltageprotection(degradedvoltage)atpredeterminedvoltagevs.timesetpoints.Theexistingrelaysettingsareexpectedtobedifficulttomaintaininthefieldduetoverynarrowtolerancesproducedfromapplicationofthelatestsetpointcalculationmethodology.Consequently,FloridaPowerandLightCompany(FPL)conductedrecentanalysesofSt.LucieUnit1systemresponsetodegradedgridvoltageconditions.ItwasconcludedfromtheseanalysesthatchangestoTSTables3.3-3,3.3-4,and4.3-2asshowninAttachment1tothisapplicationwould:(a)enhanceundervoltageprotectionfortheclasslEsystemequipmentand(b)provideforfieldspecificationofconservativecalibrationtolerancesthatwouldnotbedifficulttomaintain.TheproposedTripandAllowableValuesareprovidedina"greaterthan/equal"or"lesserthan/equal"formattospecifyonlythelimitingvaluesfortheundervoltage/degradedvoltageprotectivefunction.ThistypeofvaluespecificationduplicatestheformatpresentlyusedincorrespondingTechnicalSpecificationsforSt.LucieUnit2.DiscussionThepresentSt.LucieUnit1undervoltageprotectiondesign,setpoints,andmethodologywereapprovedbytheNRCandweredevelopedbetweenFPLandtheNRCinaseriesofquestions,responses,andcommitmentsdatingfrom1976through1983.The protectionschemeforthesafetyrelatedelectricaldistributionsystemconsistsofdedicatedrelaysatthe4.16kvand480voltsystemlevels.TripandAllowableValuesarespecifiedinTSTable3.3-4.Thedesignrelaysetpointsandtolerancesemployedinthefieldarecalculatedandincludedincontrolledengineering.drawings.Atthe4.16kvlevel,eachClass1Ebushasthreesetsoftwo(2)relayseachofsolidstateundervoltagedefinitetimerelaysinconjunctionwithsolidstatetimers.Onesetprovidesa"lossofvoltage"function(tripat2900+29volts,1+0.5seconds)andtheothertwosets(UndervoltageDeviceg1andUndervoltageDeviceg2)serveas"degradedvoltage"sensors(tripat3675+36volts,7+1minutes;and3592+36volts,18+2seconds,respectively).Eachofthesetsprovides,uponreachingthevoltageandtimesetpoints,acoincidentlogictripsignalwhichseparatestheClass1Esystemfromoff-sitepower,stripsthebusses,andstarts/enablesconnectionofthediesel-generatorsets.Thisdesignprovidesundervoltage/degradedvoltageprotectionforthe4160and480voltsystemsequipmentundernon-accidentconditions.Atthe480voltlevel,eachClass1Ebushasonesetoftwo(2)'olidstateundervoltagerelayswithinternaladjustabletimersproviding"degradedvoltage"protectionforthe4160and480voltsystemsequipmentduringaccidentconditions.Uponreachingthevoltageandtimesetpoints(429+5,-0volts;7+1seconds)coincidentwithasafetyinjectionactuationsignal(SIAS),busseparationoccursaspreviouslydescribed.Duringrecentcompletionoftheprotectiverelaysetpointdrawings(controlledengineeringdrawings),anewrelaysetpointmethodologywasappliedtothedevelopmentofspecifiedfieldsettings.Baseduponthismethodology,verynarrowcalibrationtolerancerangeswerecalculated.Todetermineifreliefcouldbeprovidedinthecalculatedfieldtoleranceranges,FPLreanalyzedtheresponseofSt.LucieUnit1electricalsystemsduringsustained,degradedgridvoltageconditions.Theseanalysesutilizedaconservativeanalyticalapproachanddemonstratedthattherelaysetpointrangesandtheprotectiverelayingschemecouldberevisedwhilemaintaininganacceptablelevelofprotection.Thereanalysesindicatethatthedistincttrippointsfor4.16kvUndervoltageDeviceglandUndervoltageDeviceg2describedintheSt.LucieUnit1UpdatedFinalSafetyAnalysisReport(UFSAR)asbeingrequiredforequipmentprotectionarenolongerrequired.Rather,asinglesetpointissufficienttoassurethatacceptablevoltagesareavailabletoclass1Eequipmentduringnon-accidentconditionsofdegradedgridvoltage.Therefore,therelaysidentifiedasUndervoltageDeviceglwillbemodifiedtoprovideanalarmfunctiononlyinthemaincontrolroom(awarningnot 1>>'I presentlyavailablewiththeexistingdesign).TherelaysetsidentifiedasUndervoltageDeviceg2willbesettotripatnotlessthan3831voltswithnochangetotheexistingtimedelayrangeof18+2seconds.Thethirdsetofrelaysatthe4.16kvlevelprovidesthelossofvoltagetripfunctionandwilltripatnotlessthan2900voltswithnochangetotheexistingtimedelayof1+0.5seconds.Foraccidentconditions,thedegradedvoltagesensorsatthe480voltlevelwouldbesettotripatnotlessthan415voltsafteratimedelayofnotmorethan9secondsandcoincidentwithaSIAS.SafetAssessmentTheproposedchangetotheemergencybusundervoltageprotectionrelayingschemeestablishesnewsetpointrangestoprovideadequateclass1Eelectricalsystemequipmentprotectionduringbothnon-accidentandaccidentconditions.Toarriveatthenewrelaysetpoints,thelatestknownequipmentoperatingcharacteristicswereemployedtoestablishplantsystemsresponsewitha"lowestexpected"offsitegridvoltageof230kv.Thisvaluewasassumedinordertobeconsistentwiththeanalysesfortheexistingdesignalthoughexperiencehasshownthatsystemimprovementsoverthepast10yearshaveresultedinanormalrangeoftransmissionsystemvoltagesabove236kv.Thereviewofvoltagesconsideredsteady-stateoperation,transients(startingandrun-through),andoperabilityofthecontrolsandnon-motorloads.Minimumvoltagelevelsatwhichprolonged.operationoftheequipmentcouldleadto-possibledamagewereestablished.Systemandequipmentvoltageswereanalyzedforbothsteady-stateandtransientconditionstodeterminetherequiredrelaysetpoints.EbascoServicesIncorporatedComputerProgramAUXSYS4078-12/31/1989wasusedinaconservative"constantkva"approachtostationauxiliarysystemcomputermodeling.Analysisofthe"ArkansasScenario"(NRCInformationNotice79-04),whichpostulatesstartingallSIASinitiatedloadswiththeauxiliarysystemunderfull-poweroperation,wasperformedintwostages:(1)thefirststageassumedsimultaneousstartofallSIASloads.Theresultswereusedtoevaluatetheadequacyofsystemvoltagesforstartinglarge4000voltand460voltmotorsandtoverifythatvoltagesatthe480voltmotorcontrolcenters(MCC)didnotreachcontactordropoutlevels.Thetimeperiodofthefirststagewasconsideredtobeapproximately5seconds(basedonmanufacturer'saccelerationtimedataforthelargemotors);(2)thesecondstageexaminedthestartofsmaller460voltmotorsaftersystemvoltageshadstabilizedfollowingstartofthelargemotors.

Basedontheseanalyses,thelimitingvaluesforundervoltageprotectionwillbespecifiedasTSLimitingConditionsforOperation(LCO).InconjunctionwiththeLCO,anadministrativeupperrangevalueisestablishedbytheanalysesandassuresthatpremature/spurioustripsdonotoccurduringanticipatedoperatingtransients.NominalsetpointsandtolerancesthatconsiderTestInstrument,Relay,andPotentialTransformererrorsarecalculatedfortherelaysettingsinthefieldandwillbespecifiedincontrolledengineeringdrawings.ThesesettingsareboundedbytheTSLCOandtheadministrativeupperrangevalue.Theappropriaterelayrangesaredefinedasfollows:1.The"lossofvoltage"relaysaresetatapproximately704oftheratedbusvoltageof4.16kvpertheexistingdesign.Theadministrativeupperrangevalueisbasedonthe4.16kvbusvoltagedropthatresultsfromstartingthelargestmotor(4000HPcondensatepumpduringfullloadconditionsat230kvtransmissionsystemvoltage)andassuresthatrelayactuationwouldnotoccurforexpectedtransients.2.Thelowerlimitoftheoperatingrangefor4.16kv"degradedvoltage"relayingisconservativelydefinedasavoltagelevelatorabovewhichoperationofallthestationauxiliaryequipmentundernon-accidentconditionsisassured.Thislevelisdefinedas3831volts(equivalentto415voltsatthe480voltLoadCenterbusundernormaloperatingloadconditionsandminimumexpectedtransmissionsystemvoltageof230kv).Thetimedelayrangeallowsstartofthelargest4000voltmotor(4000HPcondensatepump)onthefullyloadedauxiliarysystem(averyconservativeandoperationallyunlikelyscenario)withoutcausingaspurioustrip.Thesesettingsassurethat,theClass1Eequipmentwillnotbesubjecttosustainedinjuriousvoltages.Theadministrativeupperrangevalueisbasedonminimumsystemvoltagesthatwouldexistfornormalloadoperatingconditionsatatransmissionsystemvoltageofapproximately225kv(wellbelowexpectednormaloperatinggridvaluesofmorethan236kv).3.Thelowerlimitoftheoperatingrangeforthe480voltsystemrelaysassuresadequatestartingvoltageandcontinuedsafeoperationofalltheequipmentunderaccidentconditions(415voltsatthe480voltLoadCenterwhichcorrespondsto3850voltsonthe4.16kvbuscoincidentwithSIAS).Thetimedelayrange(7-9seconds)issufficientlylongtoallowbusvoltagerecoveryfollowingstartofallrequiredsafetyinjectionequipment(minimumtransientvoltageisachievedwithinapproximately5seconds)anddoesnotexceedthetimedelayassumedinUFSARaccidentanalysesforconnectingtheemergencybustothedieselgenerators.

~III,lV4s4 Theadministrativeupperrangevalueisdictatedbythevoltagerecovery(atthe480voltlevel)thatoccurswithin1minuteafterreceivingtheSIAS.Thisisaperiodofincreasedloadingduetoallemergencyloads,includingvalves,operating.After1minute,allthevalveswillhavecompletedtheirdesignfunctionsandthevoltagerecoverstoahighersteadystatevalue.Therefore,theadministrativeupperrangevalueisdefinedasthatvaluewhichassuresrelaypickup(reset)atthevoltagelevelavailablewithinthe5-60secondtimeperiodafterSIASandnotcauseanunwantedemergencybusseparationfromoffsitepower.4.Thepresent"UndervoltageDeviceg1"relayswillbemodifiedtoalarmundervoltageconditionsinthemaincontrolroom.Thesetpointwillaccomodatethelowestexpectedvoltageatthe4.16kvbusfornormaloperationat230kvgridvoltageandatimedelaywillpreventrelayactuationpriortobusvoltagerecoveryfromthelongestexpectedequipmentstartingtransients.Thus,operatorswillbeprovidedanearlywarningofsustainedgridvoltagedisturbances.FPLalsoevaluatedtheproposedchangewithrespecttooverloadprotectionofsystemsandmotors.Itwasdeterminedthatthesetpointchangeswillnotresultininadvertentactuationofoverloadprotectivedevicesfortheindividualloadsorforthesystemconnections.Withthenewsettings,allthe480voltsystemmotorswillbeoperatingwithterminalvoltagesnotlessthan400volts(notmorethan1154ofratedcurrent)andsincetheSt.Luciemethodologyofmatchingdriveswithmechanicalloadsassuresthatthemotorsgenerallydonotoperatewithintheirservicefactor,onlythecurrentincreaseduetolowervoltageneedstobeconsidered.Further,sincechoiceoftheoverloadprotectiondevicesisbasedonselectionoftheoverloaddeviceswithratedcurrentsnotlessthanmotorfullloadcurrents,thechosenoverloadheaterswillnottripuntilapproximately1254oftheoverloadheaterratedcurrentisreached.ThisreflectsthemethodologyofoverloadprotectionofGeneralElectric,vendoroftheSt.LucieMCC's.The4.16kvsystemmotorswilloperatewithvoltagesinanormaloperatingrange(morethan90%available)andarethereforenotaffected.Asforthesystemconnections,theoverloadprotectionisbasedonequipmentcapabilities,i.e.,transformercapacities,mainbusampacities,etc.whicharenotapproachedbytheactualloadingoftheplant.Theproposedchangesimplifiestherelayingschemeandestablishessetpointrangeswhichshouldbeeasilyachievableinthefield.FPLhasconcludedthatthesenewsetpointrangesofferfullprotectiontotheClass1Esystemsandequipmentforbothnon-accidentandaccidentconditionsandarebasedonassumptionsand calculationmethodologymoreconservativethantheexistingdesign.Thedegradedvoltageprotectiverelayingschemewillalertplantoperatorstosustainedundervoltageconditionsandwillinitiateseparationfromoff-sitepowerandtransfertotheon-sitesourcesifthevoltagedoesnotrecovertoacceptablelevelswithintheallottedtimeperiods.Thetimedelayrangesassurethatnomomentaryspuriousinitiationorshorttermsystemdisturbancewillcausetransferofpowerfromtheoff-sitetotheon-sitesourceswhenactuallynotrequired.

St.LucieUnit1DocketNo.50-335ProposedLicenseAmendmentEmerencBusUndervoltaeRelaSetointChanesATTACHMENT3DETERMINATIONOFNOSIGNIFICANTHAZARDSCONSIDERATIONTheCommissionhasprovidedastandardfordeterminingwhetherasignificanthazardsconsiderationexists(10CFR50.92(c)).Aproposedamendmenttoanoperatinglicenseforafacilityinvolvesnosignificanthazardsconsiderationifoperationofthefacilityinaccordancewiththeproposedamendmentwouldnot(1)involveasignificant.increaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated;or(2)createthepossibilityofanewordifferentkindofaccidentfromanyaccidentpreviouslyevaluated;or(3)involveasignificantreductioninamarginofsafety.Eachstandardisdiscussedasfollows:Operationofthefacilityinaccordancewiththeproposedamendmentwouldnotinvolveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated.Theproposedchangewillresultinabetteroverallpostureoftheplantunderdegradedvoltageconditions.Thenewsettingswillresultinimprovedprotectionfortheequipmentatallvoltagelevelswhileatthesametimeminimizingthepossibilityofunnecessarychallengestothesafetysystems.Namely,thehighersettingsatthe4160voltelectricalsystemlevelwillenhanceprotectionofferedtothe480voltsystemequipmentunderalloperatingmodesandthelowersettingsofthe480voltsystemprotectiverelayswillnot.initiatethetransferofpowertotheon-sitesourcesunderaccidentconditionsuntilthelevelofvoltagemaybecomeinjurioustotheequipment.Therefore,theproposedchangedoesnotincreasetheprobabilityofaccidentspreviouslyanalyzed.Sincethetimeintervalassumedinthesafetyanalysesforconnectionofthesafety-relatedbusestotheemergencydiesel-generatorsisnotexceededbythenewsettings,theproposedchangedoesnotincreasetheconsequencesofanaccidentpreviouslyanalyzed.

\N~f 2~Operationofthefacilityinaccordancewiththeproposedamendmentwouldnotcreatethepossibilityofanewordifferentkindofanaccidentfromanyaccidentpreviouslyevaluated.Theproposedchangedoesnotchangetheoperation,functionormodesofplantoperation.Theabilityofthedegradedgridvoltageprotectionschemetodetectthedegradedvoltageatanyofthebussesandtotransferthepowerfromtheoff-sitetotheon-sitesourcesisbeingmaintained.Nonewhazardsarecreatedorpostulatedwhichmaycauseanaccidentdifferentfromanyaccidentpreviouslyanalyzed.Thenewrelaysettingsrepresentanenhancementresultinginamoresensitiveprotectiveschemeallowingcontinuousoperationwithoutunnecessarychallengestothesafetysystemswhileofferinganadequateprotectiontoallthesafetyequipment.3~Operationofthefacilityinaccordancewiththeproposedamendmentwouldnotinvolveasignificantreductioninamarginofsafety.Theabilityofthedegradedgridvoltagedetectionsystemisenhancedbythechangesbeingproposedandisconfirmedbytheexistingsurveillancerequirements.Thenewsettingswillresultinamoresensitivedetectionandreducepossibilityofspuriousactuation,thereforethemarginofsafetyisbeingincreased.Further,thenewsettingswillalsoresultinenhancingthemaintenance/calibrationactivities.TheassociatedbasesofthedesignarenotaffectedsincethenewrelaysettingsallowabetterfulfillmentoftheoriginalcriteriaofprotectingtheClass1Eequipmentfromdamageduetoprolongedexposuretodegradedvoltage,and,therefore,theproposedamendmentdoesnotinvolveareductioninthemarginofsafety.Basedontheabove,FPLhasdeterminedthattheproposedlicenseamendmentdoesnot(1)involveasignificantincreaseintheprobabilityorconsequencesofanaccidentpreviouslyevaluated,(2)createthepossibilityofanewordifferentkindofanaccidentfromanyaccidentpreviouslyevaluated;or(3)involveasignificantreductioninamarginofsafety;andthereforedoesnotinvolveasignificanthazardsconsiderationasdefinedin10CFR50.92.

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