TI Designs High-Resolution, Fast Start-Up, Delta-Sigma ADC-Based AFE for Air Circuit Breaker (ACB) Reference Design TIOverview DesignFeatures Thisdesignhighlightsasignalprocessingfrontendfor • ThreeVoltageandFiveCurrentInputsInterfaced anelectronictripunit(ETU)forusewithanaircircuit to8-Channel,SimultaneousSampling,24-Bit ∆∑ breaker (ACB).Thissubsystemusesahigh-resolution ADCADS131E08SWithFastStart-Up(<3ms) delta-sigma(∆∑)ADCformeasuringwidecurrentand • MeasurementofACCurrentInputsWithDynamic voltageinputswithinaspecifiedaccuracy;the Rangeof ≤500Within ±1%WithFixedPGA Gain subsystemcanmeasureuptoeightsimultaneous • MeasurementofACInputFrom10Vto750 V inputswith24-bitresolution.TheADCinterfaceswith Within±1%WithFixedPGAGain anMSP430MCUforinputprocessing.Thisdesignis poweredwithrectifiedcurrentinputorauxiliaryDC • OnboardPotentialDivider toMeasureVoltage and inputpower supplies.Thedesignofferstwooptionsto BurdenResistorsfor CurrentMeasurement generatepositive andnegativepowersupplies,one • TotalStart-upTimeof <4msfor ∆∑ADC usingtheLM5017andtheotherwiththeLM5160 (ADS131E08S)toMeasureWithin±2%ofInput configuredinFly-Buckmode.Thepurposeofusingan VoltageAfterApplicationofAuxiliaryDCInput ETUinanACB istoachievefastandrepeatabletrip • CurrentMeasurementAccuracyof ±0.2%Achieved performanceforwidecurrentinputsandwide WithADS131E08for 0.2-to100-AACInput temperatureinputs.TheACBtripswithin <mswhen poweredwithafault. • VoltageMeasurementAccuracyof ±0.2%Achieved WithADS131E08for 5-to1000-VACInput DesignResources • DC-DCConvertersConfiguredinFly-Buck™ ConfigurationtoGenerateSupplyOutputs TIDA-00661 ToolFolderContainingDesignFiles • AccuracyMeasurementWithLowPowerCurrent ADS131E08S ProductFolder Transformer(LPCT)From0.6mVto333V(>500 MSP430F5969 ProductFolder DynamicRange)Within±0.2% LM5160 ProductFolder • SubsystemConfigurablefor 2-or8-WPower LM5017 ProductFolder Output TPS73201-Q1 ProductFolder • ProvisiontoMeasureThreeCurrentInputsWith TPS72301-Q1 ProductFolder SingleGainInterfacedto12-Bit InternalADCof TPS73230-EP ProductFolder MCUfor EarthCurrentMeasurement TPS7A6533-Q1 ProductFolder • ModularDesignProvidesOptiontoInterfaceADC LMV614 ProductFolder BoardtoADS131EVMorMSP430MCU LM2903 ProductFolder LMT87 ProductFolder • OnboardLDOstoGenerate3.3Vand5VforMCU andADCBoards,±2.5Vand3Vfor ADCAnalog LM4041-N ProductFolder Supply LM8364 ProductFolder ADS131E08 ProductFolder • ADCInputsProtectedAgainstESD FeaturedApplications • ACB ASKOurE2EExperts • MCCB • Recloser • FeederProtectionRelay TIDUB80B–January2016–RevisedSeptember2016 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit 1 SubmitDocumentationFeedback Breaker(ACB)ReferenceDesign Copyright©2016,TexasInstrumentsIncorporated www.ti.com VDC_PRI TPS7A6550 5.0 V_REG ENBCRLEOASKUERR E (CLoMmp2a9ra0to3r) 12.0 V (LDO) 12.0 V_RELAY TPS7A6533 3.3 V_DVDD AUCOXR.T DC RECTIFIER CS(DN 1C8h.5 M3o7sFNEKT)CS L(SMtep5 D1o6w0n D(8C -WDC)) 5.5 V (LDO) MOSFET based LM5160 (2 W) TPS73201 2.5 V_AVDD Shunt Regulation (Step Down DC-DC) TP(SLD7O3)230 3.0 V_AVDD (LDO) –5.5 V TPS72301–2.5 V_AVSS (LDO) On MSP430 Board On ADS131E08S Board ADS131E08S Board AVDDAVSS 3.3 V_DVDD ADS131E08S Current Input RBE1US6RI.S5DT E(cid:159)ON(cid:3)R V i n = - V - -D2-I-F-F-- E PPGGAA ßß(cid:8)(cid:8)(cid:3)(cid:3) SePcr:i :(0 15(:.5C100la 0 smm Ts uA0Ar.n2 ttRCooaT t)i84o)00 mAA (PIFnaispltseuivrte ) MRETLFII PPPGGGAAA ßßß(cid:8)(cid:8)(cid:8)(cid:3)(cid:3)(cid:3) CAOONNLDTR S+GP5PI.,5I OI 2VC INATDECR/MFACCUE 5V VoRlMtSa tgoe 7 5I0n pVRuMtS PO1T.E2N 0T(cid:159)IA(cid:3):L 1 D.2IV .ID(cid:159)E(cid:3)R V i n = - V - -D2-I-F-F-- MNDUAX PPGGAA ßß(cid:8)(cid:8)(cid:3)(cid:3) SPI +5.+0-53 V..53_ RVVEG (TMLPM STEN8S7OR) PGA ß(cid:8)(cid:3) 2.4I NVT o Rr E4.F0 V CLK EXCTLEORCNKAL MSP430 Board 3.3 V_DVDD 3.3 V_DVDD 3.3 V_DVDD LMV614 MSP430F5969IRGZ (L1.M65-4V0 R4E1F) V i n = - -V -2-D-D-- (xA1) (opamp) EVMSPI/ I2C (+SI5NPA.5TID, E VIC2R,C /–MF, A5CG.C5UP E IVO, B 3.3 V, 5V_REG) (x5.7) EaCruthrr Fenatult (xC5.7) 1AS2DA-BRCit UGAPRIOT C(EOxNpNaEnCsiToOnR) D CLK CRYSTAL (x5.7) RST (ULLMV D8e3te6ct4or) NOTE 1: Voltage & Current input is converted to ±1.2-V peak at Max input NOTE 2: ADC PGA Gain Setting = 2 for all inputs JTAG CONNECTOR NNOOTTEE 34:: OA/PDA c (oBn,nCe,Dc)t sG taoi nM =C U5. 7board through the ADC/MCU Interface connector A (14 PIN) AnIMPORTANTNOTICEattheendofthisTIreferencedesignaddressesauthorizeduse,intellectualpropertymattersandother importantdisclaimersandinformation. 2 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit TIDUB80B–January2016–RevisedSeptember2016 Breaker(ACB)ReferenceDesign SubmitDocumentationFeedback Copyright©2016,TexasInstrumentsIncorporated www.ti.com DesignTheory—CircuitBreaker 1 Design Theory—Circuit Breaker Acircuitbreakerisanautomatically-operatedelectricalswitchthat hasbeendesignedtoprotectan electricalcircuitfromdamagecausedbyoverload.Anoverloadoccurswhentoomanydevicesare operatingonasinglecircuit,orwhenforcingapieceofelectricalequipmenttoworkbeyonditsdesigned capabilities.Ashortcircuitoccurswhentwobareconductorstouch.Whenashortcircuit occurs, resistancedropstoalmostzero.Short-circuitcurrentcanbethousandsoftimeshigher thananormal operatingcurrent).Thebasicfunctionof acircuit breakeristodetectafaultconditionand,byinterrupting continuity,immediatelydiscontinueelectricalflow. Breakersareavailableindifferent types. • Low-voltagecircuitbreakers:These breakersarecommonlyusedindomestic,commercial,and industrialfields.Miniaturecircuitbreakers(MCB),molded-casecircuit breakers(MCCB), andaircircuit breakers(ACB)arecommonexamplesoflow-voltagecircuit breakers. • Medium-voltagecircuitbreakers:Thesebreakerscanbeassembledintometal-enclosedswitchgear lineupsforindoorapplicationsorasindividualcomponentsfor outdoorapplicationslikesubstations. Vacuumcircuitbreakers,aircircuitbreakers,andSF6circuit breakersareexamplesofmedium- voltagecircuitbreakers. • High-voltagecircuitbreakers:Thesebreakershelptoprotectandcontrolelectricalpower transmission networks.Thesebreakersareusesolenoidsfor operationandemploytheuseofcurrentsensing protectiverelaysthatfunctionthroughcurrent transformers. Vacuum circuit breakersandSF6circuit breakersareexamplesofhigh-voltagecircuit breakers. Circuitbreakersperformthefollowingfunctions: • Sensing–Whenanovercurrentoccurs • Measuring– Theamountofovercurrent • Acting– Bytrippinginatimelymannertoprevent damagetothecircuit breakerandtheconductors thatthe breakerprotects Thecurrent-carryingcapacity(inA)ofthebreakermust behigher thantheexpectedloadinthecircuit. 1.1 Circuit Breaker Construction Circuitbreakersareconstructedfromthefollowingfivemajorcomponents: • Frame(moldedcase) • Contacts • Arcchuteassembly • Operatingmechanism • Electronictripunit(ETU) TheconstructionandoperationofACBsandMCCBssharecommon features,suchasacontactsystem withanarc-quenchingmechanismtooperatethebreakerandanelectronicsystemtoprovideprotection, control, andindication. MCCBsareavailableupto4000Abutbecomelesscost-effectivefor verylargeratings(2000Aand above). TheadvantageofMCCBswithlargeratingsisacompactsize. Inashortcircuit,thecontactsof MCCBsopenbeforethefirstpeakofthecurrent waveform(withinfivemsina50-Hzsystem).The fault currentflowingthroughanMCCBneverreachesitspeakandthefaultenergyalloweddownstreamis limited. Thisfaultlimitationprotectssensitiveequipmentthat isnotratedtowithstandfaults. AnACBisphysicallylargerbutmorecost-effectivefor higher ratings.ACBsareselectedbecausethey havetheabilitytowithstandfaultcurrent ratherthanlimitit.AtypicalACBopensashort circuit within 40msto50ms,allowingbetweenoneandtwocyclesoffaultcurrent throughbeforeopening. Aload protectedbyanACB(transformersorbusbars, for example)must beratedtowithstandfaultcurrentfora shortduration. TIDUB80B–January2016–RevisedSeptember2016 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit 3 SubmitDocumentationFeedback Breaker(ACB)ReferenceDesign Copyright©2016,TexasInstrumentsIncorporated DesignTheory—CircuitBreaker www.ti.com 1.2 Circuit Breaker—Sensor Selection Circuitbreakerscombinethefollowingsensorsfor operation: • Ironcoresensorforthepowersupplytotheelectronics • Air coresensor(Rogowskicoils)formeasurement,whichguaranteeshighaccuracy Considerthefollowingparameterswhenselectingbreakers: 1. Ratedcurrent – Thisisthemaximumvalueofcurrentthat acircuit breaker(fittedwithaspecified overcurrenttrippingrelay)cancarryindefinitelyatanambienttemperaturestatedbythemanufacturer withoutexceedingthespecifiedtemperaturelimitsofthecurrentcarryingparts. 2. Short-circuitcurrent(faultcurrent) – Theshort-circuitcurrent-breakingratingofacircuit breakeristhe highest(prospective)valueofcurrentthat thecircuit breakeriscapableofbreakingwithoutbeing damaged.Thevalueofcurrentquotedinthestandardsistheroot meansquare(RMS)value of theAC componentofthefaultcurrent,thatis,theDCtransientcomponent,whichisalwayspresent inthe worstpossiblecaseofshortcircuit.Whencalculatingthestandardizedvalue, theDCtransient componentisassumedtobezero. 3. Ratedvoltage– Thisisthevoltageatwhichthecircuit breakerhasbeendesignedtooperateinnormal orundisturbedconditions. 4. Systemfrequency– Thesystemfrequencyisnormally50Hzor60Hzandcanevenbe400Hzin someapplications.Thenextsubsectionprovidesfurtherinsightonthefaultcurrent. Thesystemfrequencyisnormally50Hzor60Hzandcanevenbe400Hzinsomeapplications.The next subsectionprovidesfurtherinsightonthefaultcurrent 1.2.1 FaultCurrent Acircuitbreakermustbecapableofsafelyinterruptingthemaximumratedshort-circuitcurrentat their locationinthecircuit.Notethatthecostofcircuit breakersislowerwithalowerbreakingcapacity. Potentialshort-circuitcurrentisdeterminedby: 1. Theavailablepowerfromthetransmissionnetwork 2. Transformercharacteristics 3. Impedanceofconductorsinthedistributionsystem Afaultlevelstudythataccountsfortransformer characteristicsandconductorimpedanceatallcircuit- breaker installationpointsallowsforaselectionofbreakerswithanoptimumbreakingcapacity. 1.3 Next-Generation Circuit Breakers Thepreviousgenerationsofbreakershavebeenthermal-magneticbreakers. Thenewgenerationof circuit breakersisbasedontheETU.CircuitbreakersbasedonETUprovidehighlyaccurateprotectionwith widesettingrangesandcanintegratemeasurement,metering,andcommunicationfunctions.Designers cancombinethesecircuitbreakerswithaswitchboarddisplayunit toprovideallofthefunctionsof a powermeteraswellasoperatingassistance.Throughdirectaccesstoin-depthinformationand networkingthroughopenprotocols,thesebreakersallowoperatorstooptimizethemanagementof their electricalinstallations. Thenewgenerationofcircuitbreakershasbeenspecificallydesignedtoprotectelectricalsystemsfrom damagecausedbyoverloads,shortcircuits,andequipmentgroundfaults.Circuitbreakersaredesigned toopenandcloseacircuitmanuallyandtoopenthecircuit automaticallyatapredeterminedovercurrent setting. Circuitbreakerscanalso: • Enhancecoordinationbecauseoftheir levelofadjustability • Provideintegralground-faultprotectionfor equipment • Providehighinterruptingratingsandwithstandratings • Providecommunicationsandpowermonitoring • Provideprotectiverelayingfunctions • Providezone-selectiveinterlocking(ZSI),whichcanreducedamageintheeventofafault • Provideameansofconnectiontoanexternaltest device, allowingfor periodicaltestsofthestatusof 4 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit TIDUB80B–January2016–RevisedSeptember2016 Breaker(ACB)ReferenceDesign SubmitDocumentationFeedback Copyright©2016,TexasInstrumentsIncorporated www.ti.com DesignTheory—CircuitBreaker theETUusedinbreakers • Allowallsettingstobeprogrammedinthefield, without theuseofanyexternaldevice • AllowtheETUtosealuponadjustment (keylockorseal) behindatransparentdoororplate,which allowstheusertoviewthesettingsandprotect against unauthorizedtampering 1.3.1 ElectronicTripUnit(ETU) Thetripunitsintegratedintocircuitbreakersarecalledelectronictripunits(ETUs).ETUsintegrateinto the circuitbreakerasanadd-onsystemtomaintain thecompactsizeofacircuit breaker. ETUsare microcontroller(MCU)basedandareusedtomeet abroadrangeofmonitoringandprotection requirements,suchascurveshaping,zoneselectiveinterlocking,arcflashreduction,diagnostics,system monitoring,andsystemcommunications.TrueRMSsensingoffersincreasedaccuracyandreliability. Tripunitsusingdigitalelectronicsarefasterandmore accurate.Designedwithsignalprocessing capabilities,ETUscanprovidemeasurement informationanddeviceoperatingassistance.Someof the functionsthatETUsofferare: • MCUandmicroprocessorunit(MPU)basedtrueRMSmeasurement • Fourtofivecurrentsensing • Optionalvoltagemeasurement • Protectionfunctionsandpowermeasurements • Self-poweredwhenphasecurrent> 20%to25%nominalcurrent (In)orauxiliarypowered(DCinput) • Makingcurrentrelease(MCR) • Fault recordingandeventlogging • Digital outputsandinputsforcoordination • Parameterizationanddisplay • Networkcommunication • Thermalmemoryandovertemperatureprotectivetrip • Zoneselectiveinterlocking(ZSI)andisolatedalarmsprovision • Unitstatuslight-emittingdiodes(LEDs) andcauseoftripLEDs • Liquidcrystaldisplay(LCD),resetpush-button,andtest push-button • Discreterotary orkey-basedprogrammablesettings • Auxiliary modulesincluding – Analogoutput – Digital input – Tripcircuitsupervision(TCS)module – Powersupplymodule 1.4 Summary of Electronic Trip Unit (ETU) Features 1.4.1 Measurements TheETUcalculatesalltheelectricalvaluesinrealtime,suchastheV,A,W,VAR,VA,Wh,VARh,VAh, andHzpowerfactors.TheETUalsocalculatesdemandcurrentanddemandpower overanadjustable timeperiod.Intheeventoftrippingonafault,theinterruptedcurrentisstored.Theoptionalexternal powersupplyenablestheETUtodisplaythevaluewiththecircuit breakeropenornotsupplied. Instantaneousvalues Thevaluedisplayedonthescreenisrefreshedatsomefixedtimeinseconds.Minimum andmaximum valuesofmeasurementsarestoredinmemory. TIDUB80B–January2016–RevisedSeptember2016 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit 5 SubmitDocumentationFeedback Breaker(ACB)ReferenceDesign Copyright©2016,TexasInstrumentsIncorporated DesignTheory—CircuitBreaker www.ti.com Demandmetering Thedemandiscalculatedoverafixedorslidingtimewindow,whichcanbeprogrammedfrom5min to 60min.Accordingtothecontractsignedwiththepower supplier, anindicatorassociatedwithaload sheddingfunctionenablestheETUtoavoidorminimizethecostsofoverrunningthesubscribedpower. Maximumdemandvaluesaresystematicallystoredandtimestamped. 1.4.2 FaultRecording,EventLogging,andDisplay Eventlogsandtablesarecontinuouslyactivated.Providingawealthofinformation,thesemetricsenable userstoensurethattheinstalledequipmentbaseoperatescorrectlytooptimize settingsandmaximize energyefficiency. Localorremotedisplaysoffereasyaccesstooperatorsandprovidethemainelectricalvalues:I,U,V,f, energy, power,totalharmonicdistortion, andsoforth.Theuser-friendlyswitchboarddisplayunitwith intuitivenavigationismorecomfortabletoreadandoffersquickaccesstoinformation. 1.4.3 Communication Fourlevelsofcommunicationfunctionalitiesexist: • Devicestatus:onandoffposition,tripindication,andfault-tripindication • Commands:open,close,andreset • Measurements:mainlyI,U,f,P,E,andTHD • Operatingassistancedata:settings,parameters,alarms,histogramsandeventtables,and maintenanceindicators CommoncommunicationinterfacesincludeEthernet,RS485,Profibus,andRS232. 1.4.4 I/OModules Inputandoutput(I/O)modulesareavailabletoexpandthecapabilitiesofthecircuit breaker. Thefollowing descriptionssummarizethecapabilitiesofthesemodules: • Thedigitaloutputmoduleallowstheconnectionofuptosixbinarysignalstoexternalsignaling devices.Themodulecanbealternativelyutilizedtocontrolother equipment.Solid-stateandrelay outputversionsofthismoduleareavailable. • Thedigitalinputmodulecanconnect toamaximumofsixdigital(24-VDC)inputs.Thisspecification enablesthestatusofaswitchorthecubicledoortobecommunicatedtothecircuit breaker. • Theanalogoutputmodulecanbeusedtooutput avarietyofmeasuredvalues(amps, volts,power, powerfactor,andsoforth)toanalogdisplaydevicesonthecubicledoor. • Zoneselectiveinterlocking(ZSI)isamethodthat allowstwoormore circuit breakerstocommunicate witheachothersothatashortcircuitorgroundfaultisclearedbythebreakerclosest tothefaultinthe minimumamountoftime. SomeoftheothercommonlyusedI/Omodulesinclude: • Communicationmodule • Powersupplymodule • Analoginputmoduleforinputmeasurementofresistance-temperaturedetectors(RTDs) • Communicationmodule • Displaymodule • EarthLeakagemodule 6 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit TIDUB80B–January2016–RevisedSeptember2016 Breaker(ACB)ReferenceDesign SubmitDocumentationFeedback Copyright©2016,TexasInstrumentsIncorporated www.ti.com DesignTheory—CircuitBreaker 1.4.5 Time-CurrentCurvesandCircuitBreakerAdjustments Time-currentcurvesshowhowfastabreakertripsatanymagnitudeofcurrent.AnETUprocessesthe inputsignals(voltageandcurrent)andprovidesthetripsignalstoasolenoidorfluxshiftdevice(FD) basedontheconfiguredtripsettings.Someofthetripcurvesthat canbeconfiguredare: • L=Longtime • S=Shorttime • I=Instantaneous • G=Groundfault(equipment) 1.4.6 CircuitBreakerAdjustments Table1.BreakerTripParameters FUNCTION DESCRIPTION Variesthelevelofcontinuouscurrentthecircuitbreakercarrieswithouttripping.The Continuousampere(Ir) continuouscurrentisadjustablefrom20%to100%ofthecontinuousampereratingofa breaker(Ir=%ofIn).Thisisalsoknownaslong-timepickup. Referredtoasthe"overload"position,thisfunctioncontrolsthe"pause-in-tripping"timeofa Long-timedelay breakertoallowlowlevelortemporaryoverloadcurrents.Thisfunctionallowsadjustable settingsfrom3sor25sat6×Ir. Determinesthelevelatwhichthecircuitbreakertripswithoutanintentionaltimedelay.The instantaneouspickupfunctionisadjustablefrom2to40timesthecontinuousamperesetting Instantaneouspickup (Ir)ofabreaker.(Anytimeanoverlapexistsbetweentheinstantaneousandshort-timepickup settings,theinstantaneousautomaticallytakesprecedence). Controlstheamountofhighcurrentthebreakerremainsclosedagainstforshortperiodsof Short-timepickup time,whichallowsbettercoordination.Thisfunctionisadjustablebetween1.5to10timesthe continuousamperesetting(Ir)ofacircuitbreaker. Controlstheamountoftime(from0.05to0.2sinfixedtime,or0.2sat6×IrintheI2tramp mode)abreakerremainsclosedagainstcurrentsinthepickuprange.Thisfunctionisusedin Short-timedelay conjunctionwiththeshort-timepickupfunctiontoachieveselectivityandcoordination.(A predeterminedoverrideautomaticallypreemptsthesettingat10.5timesthemaximum continuousamperesettingIn). Controlsthelevelofgroundfaultcurrentthatcausescircuitinterruptiontooccur.Thisfunction Groundfaultpickup isadjustablefrom20%to70%ofthemaximumcontinuousamperesetting(In)ofabreaker. Addsapredeterminedtimedelaytothetrippointwhenthegroundfaultpickuplevelhasbeen Groundfaultdelay reached.AninverseI2trampisstandardandprovidesabettertrippingselectivitybetweenthe mainandfeederorotherdownstreambreakers. 1.4.7 ElectricMotor Operator Theelectricmotoroperatorisdesignedtoopen,close,andremotelyreset acircuit breaker. Theelectric motoroperatorismountedonthefaceofacircuit breakersothat itcanengagetheoperatinghandleof a breaker.Thebuilt-inmotorisconnectedtoremotepushbuttonsorcontacts.Pressingthe “ON”pushbutton orclosingthe“ON”contactscausestheelectricmotortomovethecircuit breakertothe “ON” position. Pressingthe “OFF”pushbuttonorclosingthe “OFF” contactscausestheelectricmotortomovethe circuit breaker to the“OFF” position.Toresetthecircuit breakerfromthetrippedposition, theelectricmotormust first movethecircuitbreakerhandletothe “OFF”positionandthentothe “ON”position, just asthisaction isperformedmanually. 1.4.8 Discriminatoror Making CurrentRelease(MCR) Thediscriminator(alsoknownasamakingcurrent release(MCR)),isasettingprovidedwitheachtripunit andisbasedonthespecificcircuitbreakersizeandprotectsthecircuit against closingonhighmagnitude faults. TheMCRfunctionimmediatelytripsandopensthecircuit breakerifhigh-magnitudefaultcurrentis sensedat theinstantthecircuitbreakercloses. Thediscriminatorissetat ≥tentimestheratingplugampereratingandisenabledfor approximatelythe first tencyclesofcurrentflow.Incaseswhereafaultconditionexists,thebreakertripswithnointentional timedelayonclosing,whichprotectstheuserfromapotentiallyunsafecondition. TIDUB80B–January2016–RevisedSeptember2016 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit 7 SubmitDocumentationFeedback Breaker(ACB)ReferenceDesign Copyright©2016,TexasInstrumentsIncorporated DesignTheory—CircuitBreaker www.ti.com 1.4.9 InstantaneousOverride Instantaneousoverrideisafixedcurrent levelatwhichanadjustablecircuit breakeroverridesallsettings andtripsinstantaneously.Theinstantaneous(INST)tripfunctiontripstheMCCBorACBwhentheshort- circuitcurrentexceedsthepickupcurrentsetting,irrespectiveofthestate.Theinstantaneousoverride is factorysetnominallyjustbelowthebreakerwithstandrating. 1.4.10 TripUnitOvertemperature Electronictripunitscanoperatereliablyinambienttemperaturesthat rangefrom –20°Cto70°C.Breakers arederatediftheyareabove70°C.Intheunlikelyeventthat temperaturesexceedthisambient temperaturerange,thetripunithasabuilt-inovertemperature triptoprotectthetripunit. 8 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit TIDUB80B–January2016–RevisedSeptember2016 Breaker(ACB)ReferenceDesign SubmitDocumentationFeedback Copyright©2016,TexasInstrumentsIncorporated www.ti.com ACBRatings 2 ACB Ratings Avoltageratingcircuitbreakerhasavoltageratingthat designatesthemaximumvoltageitcanhandle. Thevoltageratingofacircuitbreakercanbehigher thanthecircuit voltage,butneverlower. Forexample, a480-V ACcircuitbreakercanbeusedina240-VACcircuit,buta240-VACcircuit breakercannot be usedina480-VACcircuit Table2.CommonBreakerVoltageRatings ACVOLTAGE 230 380 400 415 440 500 525 690 RATINGS(V) Continuouscurrentrating Everycircuitbreakerhasacontinuouscurrentrating,whichisthemaximumcontinuouscurrentacircuit breaker isdesignedtocarrywithouttripping.Theratedcurrentfor acircuit breakerisoftenrepresented as In.Thisdesignationisnottobeconfusedwiththecurrentsetting(Ir), whichappliestothosecircuit breakersthathaveacontinuouscurrentadjustment.Ir isthemaximumcontinuouscurrent that acircuit breaker cancarrywithouttrippingforthegivencontinuouscurrentsetting.Ir maybespecifiedinampsor asapercentageofIn. Table3.CommonBreakerCurrent Ratings ACCURRENT 200 250 400 630 800 1000 1250 1600 2000 2500 3200 4000 5000 6300 RATINGS(A) 80 100 160 250 320 400 500 630 800 1000 1280 1600 2000 2500 IrTHRESHOLD to to to to to to to to to to to to to to SETTINGS(A) 200 250 250 630 800 1000 1250 1600 2000 2500 3200 4000 5000 6300 Pickup(A)=Irx…1.5 – 10 Currentsetting(A)Ir=Inx …0.4 –1.0 NOTE: ThepickupcurrenthastheoptiontobeIr×15orIr×20. • ICW is theshort-circuitwithstandratingofaparticularcircuit breakerinamperes.Thewithstand rating isdefineddifferentlywithindifferentstandards, butitisalwaysthevalueofcurrent that acircuitbreaker canwithstandforsomeperiodoftimewithout interrupting. • ICS,ortheservicebreakingcapacityperIEC60947-2,isthebreakingcapacitythat abreakercan safelyinterruptandbeoperationalafterinterruptingatleastonetime. • ICU,ortheultimatebreakingcapacityperIEC60947-2,isthebreakingcapacitythat abreakercan safelyinterrupt,butmaynotremainoperationalafterinterruptingonetime. Interruptingrating Circuitbreakersarealsoratedaccordingtothemaximumlevelofcurrenttheycaninterrupt.Thisisthe interruptingratingorampereinterruptingrating(AIR).Theinterruptingratingsfor acircuit breakerare typicallyspecifiedinsymmetricalRMSamperesfor specificrated voltages.Thetermsymmetrical indicatesthatthealternatingcurrentvaluespecifiediscenteredaroundzeroandhasequalpositive and negativehalfcycles. Circuitbreakershaveinterruptingratingsasfollows: • 25kA– Standard,lowshort-circuitlevelapplications(forexample:servicebusinesses) • 36kAto50kA –Standardapplications(forexample:industrialplants,buildings,andhospitals) • 70kAto100kA– Highperformanceatcontrolled cost • 150kA– Demandingapplications TIDUB80B–January2016–RevisedSeptember2016 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit 9 SubmitDocumentationFeedback Breaker(ACB)ReferenceDesign Copyright©2016,TexasInstrumentsIncorporated ACBRatings www.ti.com 2.1 Air Circuit Breaker (ACB)—Operating Time AnimportantspecificationforACBsistheoperatingtime.Thespecificationsfor operatingtimeinclude breakingtimeandclosingtime.Breakingtimeincludesthemeasurementofinput current andprocessing ofthesamplestoprovidethesolenoidtripcommand,whichbreaksthefaultcurrent. Breaking(maximum)time(instantaneousbreaktimeatshort-circuitinterruptioncurrent):If theload current isgreaterthanthesetinstantaneouspickupvalueisdetected,theACB-electronictripunit willinitiatea trippulsewithinMaximumbreaktimeofhavingseenthecurrent.Themaximumbreakingtimeisspecified bydifferentACBmanufacturersintherangeof 30msto50ms. Toachieveafasterbreakingtime,theETU(includingthepower supply, MCU, andADCs)must have a faststart-upcapability. 2.2 TIDA-00661 Advantages ThisTIDA-00661designprovidesasolutiontosomeofthecriticalrequirementsofanACB,suchas: 1. Fast start-up:ACBsarespecifiedtotripwithin35msto40mswhentheyarepoweredwithafault.The start-uptimeincludesthesystempowerup,ACinput currentmeasurement,andbreakingofthefault current. 2. Wideinputmeasurement:Thefaultcurrentinput rangevariesfrom0.3Into12Inormoreforagiven currentbreakerrating.Thecircuitbreakersareavailableinmultiplecurrent ratings.AnADCwith high resolutionensurestheuseofthesametripunit for multiplecurrentratings. 3. Accuratemeasurementofvoltageandcurrent inputs:Theaccuratemeasurementofinput current ensuresarepeatabletriptimeperformancefor protectionandanaccuratemeasurementofdifferent parametersformetering. 4. Increasedreliabilityandtemperatureperformance:Theintegrationofreferenceandprogrammable gainamplifier(PGA)reducestheexternalcomponentsrequirement,improvestemperature performance,andincreasesreliability. TheTIDA-00661designprovidesasolutionfor alloftheabovecriticalrequirementsofacircuit breaker. ThedesigncontainsanAFEboardandaninterfaceboard. 2.3 TIDA-00661 System Description and Functionality 2.3.1 AFEBoard(With ADCandLDOsforAnalogSupply) Theanalogfrontend(AFE)boardusesafast start-up ∆∑ADCwithastart-uptimeof <3ms. The ∆∑ ADChaseightsimultaneoussamplingADCswith24-bitresolution.Additionally,theADChasaPGA, whichcanbeusedtoimproveaccuracywhilemeasuringwideinput currents.TheAFEhasaprovisionto measurethreevoltagesandfivecurrents. TheAFEboardusestheinternalreferenceoftheADC.A provisionforanexternalclockhasbeenprovidedinthisdesigntomeetthemeasurementaccuracy requirementoverawidetemperaturerange.TheADCinput hasbeenconfiguredfor a ±2.5-Vinputrange. ThePGAhasbeensetforafixedgainof2for most measurementapplications.Anexternal,onboard temperaturesensorhasbeenprovided.Thedigitalinterfaceispoweredby3.3-Vsupply. TheADCis interfacedtoanMSP430F5969basedinterfaceboardorMMB0DSPboard. TheAFEboardfortheTIDA-00661designfeaturesthefollowing: 1. Fast start-up(<3ms)∆∑ADCADS131E08Switheight simultaneousinputsfor measuringupto five currentsandthreevoltages;onboardpotentialdividerfor measuringupto900V 2. LDOtogenerate ±2.5V,3VforADCanaloginput 3. Temperaturesensortomeasurelocalonboardtemperature 4. ExtensionconnectorsforinterfacingtoMMB0digitalsignalprocessor(DSP)boardofan MSP430F5969interfaceboard 10 High-Resolution,FastStart-Up,Delta-SigmaADC-BasedAFEforAirCircuit TIDUB80B–January2016–RevisedSeptember2016 Breaker(ACB)ReferenceDesign SubmitDocumentationFeedback Copyright©2016,TexasInstrumentsIncorporated