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.
To:
Shared Package
ML17227A646	List: ML17227A645 ML17227A647
References
NUDOCS 9212040127
Download: ML17227A647 (18)

Text

St.LucieUnit1DocketNo.50-335ProposedLicenseAmendment EmerencBusUndervolta eRelaSetointChanesATTACHMENT 1St.LucieUnit1Marked-up Technical Specification Pages3/4311'/4315'/4319921204OiZT 92ii30PDRADOCK05000335P,PDR TABLE3.3-3Continued ENGINEERED SAFETYFEATUREACTUATION SYSTEMINSTRUMENTATION

~pFUNCTIONAL UNIT5.CONTAINMENT SUMPRECIRCULATION(RAS)a.ManualRAS(TripButtons)b.Refueling WaterTank-Low6.LOSSOFPOWERa:4.16kvEmergency BusUnder-voltage(LossofVoltage)b,4.16kvEmergency BusUnder-voltage(Degraded Voltage)TOTALNO.OFCHANNELS212ygff2/Busa/sos2BusZ/Sos1/Busi/assMINIMUMCHANNELSCHANNELSTOTRIPOPERABLEAPPLICABLE MODES1,2,3,41,2,31,.23ACTION898c.480VEmergency BusUnder-voltage(Degraded Voltage)7.AUXILIARY FEEDWATER

{AFAS)a.Manual'{TripButtons)b.Automatic Actuation Logicc.SGLevel{lA/lB)-Low8.AUXILIARY FEEDWATER ISOLATIOH a.SGlA-SGlBDifferential Pressureb.Feedwater HeaderSG1A-SG1BDifferential Pressure2/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/

1TABLE3.3-4Continued IEt(GItlEEREO SAFETYFEATUREACTUATION SYSTEMINSTRUMENTATION TRIPVALUESICClPlFUNCTIONAL UNIT6.LOSSOFPOWERTRIPVALUEALLOWABLE VALUESCa04.16kvEmergency BusUndervoltage (LossofVoltage)v900voltswitha>900~voltswitha1+.5secondtimedelay1+.5secondtimedelayb.4.16kvEmergency BusUndervoltage (Degraded Voltage)t,y15Q,KO 03831VoW-swc+4o-)~s8s)vo'L4~ill~LS+2.s~~k~~~deiS+'Zsec~l+Mebetsy.lDO4JlCL3tDOc.480voltsEmergency BusUndervoltage (Degraded Voltage)7.AUXILIARY FEEDWATER (AFAS)a.Manual(TripButtons)b.Automatic Actuation Logicc.SGlA&18LevelLow8.AUXILIARY FEEDWATER ISOLATION a.SteamGenerator 4P-Highb.Feedwater HeaderHighaP>ciavolts,witha~Q~'econdtimedelayNotApplicable NotApplicable

>19.OX<275psid<150.0psid)58voltsw>thasecondtimedelayNotApplicable NotApplicable

>18.0X89.2to281psid56.0to157.5psid ph TABLE4.3-2Continued ENGINEERED SAFETYFEATUREACTUATION SYSTEMINSTRUHENTATION SURVEILLANCE REUIREHENTS FUNCTIONAL UNIT6.LOSSOFPOWERa.4.16kvEmergency BusUnder-voltage(LossoPVoltage)CHANNELCHECKCHANNELFUNCTIONAI CALIBRATION TESTNODESINWHICHSURVEILLANCE

-REUIRED1,2,3tb.4.16kvEmergency BusUnder-voltage(Degi.aded Voltage)~iZ,~If)S<l-~Jndeer~ge=0 c.480VEmergency BusUnder-voltage(Degraded Voltage)7,AUXILIARY FEEOWATER (AFAS)a.Manual(TripButtons)b.SGLevel(A/8)-Lowc.Automatic Actuation Logic8.AUXILIARY FEEDWATER ISOLATION a.SGLevel(A/B)-LowandSGDifferential Pressure(BtoA/AtoB)

-Highb.SGLevel(A/B)-LowandFeedwater HeaderDifferential Pressure(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.50-335ProposedLicenseAmendment EmerencBusUndervolta eRelaSetointChanesATTACHMENT 2SAFETYANALYSISIntroduction Theproposedamendment toSt.LucieUnit1Technical Specifications (TS)willpermitchangestotheemergency busundervoltage protection schemerelaysettingsatthe480voltand4160voltsystemlevels.Theseprotection relaysareinstalled toinitiateseparation oftheemergency busesfromtheoffsitepowersystemandpreventdamagetoClass1Eequipment loadsduringsustained lowvoltagegridconditions.

Therelayingschemeprovidesdetection oflossofoffsitepowerandasecondlevelofundervoltage protection (degraded voltage)atpredetermined voltagevs.timesetpoints.

Theexistingrelaysettingsareexpectedtobedifficult tomaintaininthefieldduetoverynarrowtolerances producedfromapplication ofthelatestsetpointcalculation methodology.

Consequently, FloridaPowerandLightCompany(FPL)conducted recentanalysesofSt.LucieUnit1systemresponsetodegradedgridvoltageconditions.

Itwasconcluded fromtheseanalysesthatchangestoTSTables3.3-3,3.3-4,and4.3-2asshowninAttachment 1tothisapplication would:(a)enhanceundervoltage protection fortheclasslEsystemequipment and(b)provideforfieldspecification ofconservative calibration tolerances thatwouldnotbedifficult tomaintain.

TheproposedTripandAllowable Valuesareprovidedina"greaterthan/equal" or"lesserthan/equal" formattospecifyonlythelimitingvaluesfortheundervoltage/degraded voltageprotective function.

Thistypeofvaluespecification duplicates theformatpresently usedincorresponding Technical Specifications forSt.LucieUnit2.Discussion ThepresentSt.LucieUnit1undervoltage protection design,setpoints, andmethodology wereapprovedbytheNRCandweredeveloped betweenFPLandtheNRCinaseriesofquestions, responses, andcommitments datingfrom1976through1983.The protection schemeforthesafetyrelatedelectrical distribution systemconsistsofdedicated relaysatthe4.16kvand480voltsystemlevels.TripandAllowable Valuesarespecified inTSTable3.3-4.Thedesignrelaysetpoints andtolerances employedinthefieldarecalculated andincludedincontrolled engineering.

drawings.

Atthe4.16kvlevel,eachClass1Ebushasthreesetsoftwo(2)relayseachofsolidstateundervoltage definitetimerelaysinconjunction withsolidstatetimers.Onesetprovidesa"lossofvoltage"function(tripat2900+29volts,1+0.5seconds)andtheothertwosets(Undervoltage Deviceg1andUndervoltage Deviceg2)serveas"degraded voltage"sensors(tripat3675+36volts,7+1minutes;and3592+36volts,18+2seconds,respectively).

Eachofthesetsprovides, uponreachingthevoltageandtimesetpoints, acoincident logictripsignalwhichseparates theClass1Esystemfromoff-sitepower,stripsthebusses,andstarts/enables connection ofthediesel-generator sets.Thisdesignprovidesundervoltage/degraded voltageprotection forthe4160and480voltsystemsequipment undernon-accident conditions.

Atthe480voltlevel,eachClass1Ebushasonesetoftwo(2)'olidstateundervoltage relayswithinternaladjustable timersproviding "degraded voltage"protection forthe4160and480voltsystemsequipment duringaccidentconditions.

Uponreachingthevoltageandtimesetpoints (429+5,-0volts;7+1seconds)coincident withasafetyinjection actuation signal(SIAS),busseparation occursaspreviously described.

Duringrecentcompletion oftheprotective relaysetpointdrawings(controlled engineering drawings),

anewrelaysetpointmethodology wasappliedtothedevelopment ofspecified fieldsettings.

Baseduponthismethodology, verynarrowcalibration tolerance rangeswerecalculated.

Todetermine ifreliefcouldbeprovidedinthecalculated fieldtolerance ranges,FPLreanalyzed theresponseofSt.LucieUnit1electrical systemsduringsustained, degradedgridvoltageconditions.

Theseanalysesutilizedaconservative analytical approachanddemonstrated thattherelaysetpointrangesandtheprotective relayingschemecouldberevisedwhilemaintaining anacceptable levelofprotection.

Thereanalyses indicatethatthedistincttrippointsfor4.16kvUndervoltage DeviceglandUndervoltage Deviceg2described intheSt.LucieUnit1UpdatedFinalSafetyAnalysisReport(UFSAR)asbeingrequiredforequipment protection arenolongerrequired.

Rather,asinglesetpointissufficient toassurethatacceptable voltagesareavailable toclass1Eequipment duringnon-accident conditions ofdegradedgridvoltage.Therefore, therelaysidentified asUndervoltage Deviceglwillbemodifiedtoprovideanalarmfunctiononlyinthemaincontrolroom(awarningnot 1>>'I presently available withtheexistingdesign).Therelaysetsidentified asUndervoltage Deviceg2willbesettotripatnotlessthan3831voltswithnochangetotheexistingtimedelayrangeof18+2seconds.Thethirdsetofrelaysatthe4.16kvlevelprovidesthelossofvoltagetripfunctionandwilltripatnotlessthan2900voltswithnochangetotheexistingtimedelayof1+0.5seconds.Foraccidentconditions, thedegradedvoltagesensorsatthe480voltlevelwouldbesettotripatnotlessthan415voltsafteratimedelayofnotmorethan9secondsandcoincident withaSIAS.SafetAssessment Theproposedchangetotheemergency busundervoltage protection relayingschemeestablishes newsetpointrangestoprovideadequateclass1Eelectrical systemequipment protection duringbothnon-accidentandaccidentconditions.

Toarriveatthenewrelaysetpoints, thelatestknownequipment operating characteristics wereemployedtoestablish plantsystemsresponsewitha"lowestexpected" offsitegridvoltageof230kv.Thisvaluewasassumedinordertobeconsistent withtheanalysesfortheexistingdesignalthoughexperience hasshownthatsystemimprovements overthepast10yearshaveresultedinanormalrangeoftransmission systemvoltagesabove236kv.Thereviewofvoltagesconsidered steady-state operation, transients (starting andrun-through),

andoperability ofthecontrolsandnon-motor loads.Minimumvoltagelevelsatwhichprolonged.

operation oftheequipment couldleadto-possibledamagewereestablished.

Systemandequipment voltageswereanalyzedforbothsteady-state andtransient conditions todetermine therequiredrelaysetpoints.

EbascoServicesIncorporated ComputerProgramAUXSYS4078-12/31/1989 wasusedinaconservative "constant kva"approachtostationauxiliary systemcomputermodeling.

Analysisofthe"Arkansas Scenario" (NRCInformation Notice79-04),whichpostulates startingallSIASinitiated loadswiththeauxiliary systemunderfull-power operation, wasperformed intwostages:(1)thefirststageassumedsimultaneous startofallSIASloads.Theresultswereusedtoevaluatetheadequacyofsystemvoltagesforstartinglarge4000voltand460voltmotorsandtoverifythatvoltagesatthe480voltmotorcontrolcenters(MCC)didnotreachcontactor dropoutlevels.Thetimeperiodofthefirststagewasconsidered tobeapproximately 5seconds(basedonmanufacturer's acceleration timedataforthelargemotors);(2)thesecondstageexaminedthestartofsmaller460voltmotorsaftersystemvoltageshadstabilized following startofthelargemotors.

Basedontheseanalyses, thelimitingvaluesforundervoltage protection willbespecified asTSLimitingConditions forOperation (LCO).Inconjunction withtheLCO,anadministrative upperrangevalueisestablished bytheanalysesandassuresthatpremature/spurious tripsdonotoccurduringanticipated operating transients.

Nominalsetpoints andtolerances thatconsiderTestInstrument, Relay,andPotential Transformer errorsarecalculated fortherelaysettingsinthefieldandwillbespecified incontrolled engineering drawings.

ThesesettingsareboundedbytheTSLCOandtheadministrative upperrangevalue.Theappropriate relayrangesaredefinedasfollows:1.The"lossofvoltage"relaysaresetatapproximately 704oftheratedbusvoltageof4.16kvpertheexistingdesign.Theadministrative upperrangevalueisbasedonthe4.16kvbusvoltagedropthatresultsfromstartingthelargestmotor(4000HPcondensate pumpduringfullloadconditions at230kvtransmission systemvoltage)andassuresthatrelayactuation wouldnotoccurforexpectedtransients.

2.Thelowerlimitoftheoperating rangefor4.16kv"degraded voltage"relayingisconservatively definedasavoltagelevelatorabovewhichoperation ofallthestationauxiliary equipment undernon-accident conditions isassured.Thislevelisdefinedas3831volts(equivalent to415voltsatthe480voltLoadCenterbusundernormaloperating loadconditions andminimumexpectedtransmission systemvoltageof230kv).Thetimedelayrangeallowsstartofthelargest4000voltmotor(4000HPcondensate pump)onthefullyloadedauxiliary system(averyconservative andoperationally unlikelyscenario) withoutcausingaspurioustrip.Thesesettingsassurethat,theClass1Eequipment willnotbesubjecttosustained injurious voltages.

Theadministrative upperrangevalueisbasedonminimumsystemvoltagesthatwouldexistfornormalloadoperating conditions atatransmission systemvoltageofapproximately 225kv(wellbelowexpectednormaloperating gridvaluesofmorethan236kv).3.Thelowerlimitoftheoperating rangeforthe480voltsystemrelaysassuresadequatestartingvoltageandcontinued safeoperation ofalltheequipment underaccidentconditions (415voltsatthe480voltLoadCenterwhichcorresponds to3850voltsonthe4.16kvbuscoincident withSIAS).Thetimedelayrange(7-9seconds)issufficiently longtoallowbusvoltagerecoveryfollowing startofallrequiredsafetyinjection equipment (minimumtransient voltageisachievedwithinapproximately 5seconds)anddoesnotexceedthetimedelayassumedinUFSARaccidentanalysesforconnecting theemergency bustothedieselgenerators.

~III,lV4s4 Theadministrative upperrangevalueisdictatedbythevoltagerecovery(atthe480voltlevel)thatoccurswithin1minuteafterreceiving theSIAS.Thisisaperiodofincreased loadingduetoallemergency loads,including valves,operating.

After1minute,allthevalveswillhavecompleted theirdesignfunctions andthevoltagerecoverstoahighersteadystatevalue.Therefore, theadministrative upperrangevalueisdefinedasthatvaluewhichassuresrelaypickup(reset)atthevoltagelevelavailable withinthe5-60secondtimeperiodafterSIASandnotcauseanunwantedemergency busseparation fromoffsitepower.4.Thepresent"Undervoltage Deviceg1"relayswillbemodifiedtoalarmundervoltage conditions inthemaincontrolroom.Thesetpointwillaccomodate thelowestexpectedvoltageatthe4.16kvbusfornormaloperation at230kvgridvoltageandatimedelaywillpreventrelayactuation priortobusvoltagerecoveryfromthelongestexpectedequipment startingtransients.

Thus,operators willbeprovidedanearlywarningofsustained gridvoltagedisturbances.

FPLalsoevaluated theproposedchangewithrespecttooverloadprotection ofsystemsandmotors.Itwasdetermined thatthesetpointchangeswillnotresultininadvertent actuation ofoverloadprotective devicesfortheindividual loadsorforthesystemconnections.

Withthenewsettings, allthe480voltsystemmotorswillbeoperating withterminalvoltagesnotlessthan400volts(notmorethan1154ofratedcurrent)andsincetheSt.Luciemethodology ofmatchingdriveswithmechanical loadsassuresthatthemotorsgenerally donotoperatewithintheirservicefactor,onlythecurrentincreaseduetolowervoltageneedstobeconsidered.

Further,sincechoiceoftheoverloadprotection devicesisbasedonselection oftheoverloaddeviceswithratedcurrentsnotlessthanmotorfullloadcurrents, thechosenoverloadheaterswillnottripuntilapproximately 1254oftheoverloadheaterratedcurrentisreached.Thisreflectsthemethodology ofoverloadprotection ofGeneralElectric, vendoroftheSt.LucieMCC's.The4.16kvsystemmotorswilloperatewithvoltagesinanormaloperating range(morethan90%available) andaretherefore notaffected.

Asforthesystemconnections, theoverloadprotection isbasedonequipment capabilities, i.e.,transformer capacities, mainbusampacities, etc.whicharenotapproached bytheactualloadingoftheplant.Theproposedchangesimplifies therelayingschemeandestablishes setpointrangeswhichshouldbeeasilyachievable inthefield.FPLhasconcluded thatthesenewsetpointrangesofferfullprotection totheClass1Esystemsandequipment forbothnon-accidentandaccidentconditions andarebasedonassumptions and calculation methodology moreconservative thantheexistingdesign.Thedegradedvoltageprotective relayingschemewillalertplantoperators tosustained undervoltage conditions andwillinitiateseparation fromoff-sitepowerandtransfertotheon-sitesourcesifthevoltagedoesnotrecovertoacceptable levelswithintheallottedtimeperiods.Thetimedelayrangesassurethatnomomentary spuriousinitiation orshorttermsystemdisturbance willcausetransferofpowerfromtheoff-sitetotheon-sitesourceswhenactuallynotrequired.

St.LucieUnit1DocketNo.50-335ProposedLicenseAmendment EmerencBusUndervolta eRelaSetointChanesATTACHMENT 3DETERMINATION OFNOSIGNIFICANT HAZARDSCONSIDERATION TheCommission hasprovidedastandardfordetermining whetherasignificant hazardsconsideration exists(10CFR50.92(c)).

Aproposedamendment toanoperating licenseforafacilityinvolvesnosignificant hazardsconsideration ifoperation ofthefacilityinaccordance withtheproposedamendment wouldnot(1)involveasignificant.

increaseintheprobability orconsequences ofanaccidentpreviously evaluated; or(2)createthepossibility ofanewordifferent kindofaccidentfromanyaccidentpreviously evaluated; or(3)involveasignificant reduction inamarginofsafety.Eachstandardisdiscussed asfollows:Operation ofthefacilityinaccordance withtheproposedamendment wouldnotinvolveasignificant increaseintheprobability orconsequences ofanaccidentpreviously evaluated.

Theproposedchangewillresultinabetteroverallpostureoftheplantunderdegradedvoltageconditions.

Thenewsettingswillresultinimprovedprotection fortheequipment atallvoltagelevelswhileatthesametimeminimizing thepossibility ofunnecessary challenges tothesafetysystems.Namely,thehighersettingsatthe4160voltelectrical systemlevelwillenhanceprotection offeredtothe480voltsystemequipment underalloperating modesandthelowersettingsofthe480voltsystemprotective relayswillnot.initiatethetransferofpowertotheon-sitesourcesunderaccidentconditions untilthelevelofvoltagemaybecomeinjurious totheequipment.

Therefore, theproposedchangedoesnotincreasetheprobability ofaccidents previously analyzed.

Sincethetimeintervalassumedinthesafetyanalysesforconnection ofthesafety-related busestotheemergency diesel-generators isnotexceededbythenewsettings, theproposedchangedoesnotincreasetheconsequences ofanaccidentpreviously analyzed.

\N~f 2~Operation ofthefacilityinaccordance withtheproposedamendment wouldnotcreatethepossibility ofanewordifferent kindofanaccidentfromanyaccidentpreviously evaluated.

Theproposedchangedoesnotchangetheoperation, functionormodesofplantoperation.

Theabilityofthedegradedgridvoltageprotection schemetodetectthedegradedvoltageatanyofthebussesandtotransferthepowerfromtheoff-sitetotheon-sitesourcesisbeingmaintained.

Nonewhazardsarecreatedorpostulated whichmaycauseanaccidentdifferent fromanyaccidentpreviously analyzed.

Thenewrelaysettingsrepresent anenhancement resulting inamoresensitive protective schemeallowingcontinuous operation withoutunnecessary challenges tothesafetysystemswhileofferinganadequateprotection toallthesafetyequipment.

3~Operation ofthefacilityinaccordance withtheproposedamendment wouldnotinvolveasignificant reduction inamarginofsafety.Theabilityofthedegradedgridvoltagedetection systemisenhancedbythechangesbeingproposedandisconfirmed bytheexistingsurveillance requirements.

Thenewsettingswillresultinamoresensitive detection andreducepossibility ofspuriousactuation, therefore themarginofsafetyisbeingincreased.

Further,thenewsettingswillalsoresultinenhancing themaintenance/calibration activities.

Theassociated basesofthedesignarenotaffectedsincethenewrelaysettingsallowabetterfulfillment oftheoriginalcriteriaofprotecting theClass1Eequipment fromdamageduetoprolonged exposuretodegradedvoltage,and,therefore, theproposedamendment doesnotinvolveareduction inthemarginofsafety.Basedontheabove,FPLhasdetermined thattheproposedlicenseamendment doesnot(1)involveasignificant increaseintheprobability orconsequences ofanaccidentpreviously evaluated, (2)createthepossibility ofanewordifferent kindofanaccidentfromanyaccidentpreviously evaluated; or(3)involveasignificant reduction inamarginofsafety;andtherefore doesnotinvolveasignificant hazardsconsideration asdefinedin10CFR50.92.

~rt