HazardBasedSafetyEngineering

-Touch(Leakage)CurrentOverallSessionObjectives:1.TounderstandtherationalefortheTouch(leakage)CurrentTest,instrumentation,connections,testproceduresandlimits2.TounderstandlimitationsoftestandalternativeapproachesTouch(Leakage)Current2Touch(Leakage)CurrentTopicsDefinitions(UL101,IEC60990)TouchcurrentpathsPhysiologicaleffectsoftouchcurrent(electricshock)Bodyimpedancemodelsand“safe”voltagelimitsTouch(Leakage)CurrentTestTouchcurrentinstruments(meters)MeasurementcircuitsandproceduresLimits3DEFINITIONSLEAKAGECURRENT(UL101-2023):Electriccurrentwhichflowsthroughapersonuponcontact,betweenaccessiblepartsofanapplianceand(1)ground,or(2)otheraccessiblepartsoftheapplianceTOUCHCURRENT(IEC60990):Electriccurrentthroughahumanbodyorananimalbodywhenittouchesoneormoreaccessiblepartsofaninstallationorofequipment.4Touch(Leakage)CurrentPathsAccessiblemetalLoadLoadElectricalinsulationSystemLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)Conductor?TouchcurrentReturnPath5TouchCurrentPathsLoadLoadExample:Ungrounded2wireCordandPlug-ConnectedAppliancestouchablemetalElectricalInsulationSystemToElectricalSupply6CanopenerToasterovenTVradioCoffeemakerironblenderExamplesof2-wireNon-GroundedAppliances7TouchCurrentPathsGroundedapplianceTouchablemetalLoadLoadUngrounded2wireapplianceTouchableMetalofGroundedAppliancesElectricalinsulationSystemEquipmentGroundingConductor(protectiveearthingconductor)GLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorTouchCurrentTouchablemetal

ReturnPaths-18dishwasherrangemicrowaverefrigeratorExamplesof3-wireGroundedAppliancesCanopenerToasterovenTVradioCoffeemakerironblenderExamplesof2-wireNon-GroundedAppliances9PlumbingFixturesConstructionGroundsMetallicPipingSystemBondingconnectiontowaterpipeTouchCurrentTouchablemetalTouchablemetalLoadLoadUngrounded2wireapplianceElectricalinsulationSystemGLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)Conductor

ReturnPaths-2TouchCurrentPaths10SinkExamplesofConstructionGroundsBaseboardheatingExamplesof3-wireGroundedAppliancesExamplesof2-wireNon-GroundedAppliancesdishwasherrangemicrowaverefrigeratorCanopenerToasterovenTVradioCoffeemakerironblender11TouchCurrentPathsUngrounded2wireapplianceLoadLoadPathwaythroughearthTouchablemetalElectricalinsulationSystemSoilLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorTouchCurrentReturnPaths-312TouchCurrentPathsTouchablemetalLoadLoadElectricalinsulationSystemLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorExample:Three-WireGroundedCordandPlugConnectedproductPotentialTouchCurrent13TouchCurrentPathsTouchablemetalLoadLoadElectricalinsulationSystemLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorExample:Three-WireGroundedCordandPlugConnectedproduct14Groundedmetal2-wirereceptacle(normal-oldconstruction)OR3to2adapterConnectiontoUngroundedReceptacleTouchCurrentTouchablemetalLoadElectricalinsulationSystemLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorExample:Three-WireGroundedCordandPlugConnectedproductOpencircuitorhighimpedance(fault)15TouchCurrentPaths-4touchablemetalLoadLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorTouchCurrentFromSimultaneouslyTouchablePartsofsameproductLoadZTouchCurrent16Touch(Leakage)CurrentTopicsDefinitions(UL101,IEC60990)Touchcurrentpaths

Physiologicaleffectsoftouchcurrent(electricshock)17PhysiologicalEffectsofTouchCurrent(sinusoidal,rms,60Hz)

Perception(microamperesto0.5mA)

Startlereaction(>0.5mA)

Muscletetanization(inabilitytoletgo)

(>5mA)

Ventricularfibrillation(>50mA)

Electricalburns(>70mA)V10-0011851061010-10.51510102035102103102103104Ventricular

FibrillationLet-GoStartleReaction1I=0.954f0.716f>70HzI~0.0007ff>1kHzIECThreshold

ULLimitEffectsofFrequencyonElectricShockThresholdsandLimitsforContinuousACcurrentBodyCurrent(rmsmA)Frequency(Hz)22.Inthecaseoflet-go,IECcurverepresentsaveragevalue1.threshold/limit

=2mAat0Hz(dc)(seenote3)3.respiratoryarrestobserved

indogsat20,30,and40mA19

CurrentDensity

Duration*

PathwaythroughbodyV10-015

(skincontactlocation)OtherTouchCurrentVariables*SeeSpecialSituationsforTouchCurrentMeasurements

Waveshape*20Touch(Leakage)CurrentTopicsDefinitions(UL101,IEC60990)TouchcurrentpathsPhysiologicaleffectsoftouchcurrent(electricshock)

Bodyimpedancemodelsand“safe”voltagelimits21+_ZBVsZSIBZB=bodyimpedanceVs=sourceopencircuitvoltageZS=sourceimpedanceIB=bodycurrentVSZS(ZB=f

,

,.....)ZBZS+VsIB=DeterminingTouchCurrentVoltageSource22R3C1C2R2R1FiveComponentBodyImpedanceModelImpedancerepresenting

oneskin-electrode

contactInternalbodyimpedance

(lesstheskin)Impedancerepresenting

otherskin-electrode

contact23EffectofCurrentPathwayonInternalBodyImpedanceInternalBody

Impedance(R3)(typicaladult)Elbow-200ohmsElbow-200ohmsTorso-

100ohmsWrist-

300ohmsWrist-

300ohmsKnee-

150ohmsKnee-

150ohmsAnkle-

350ohmsAnkle-

350ohmsWhatistheinternalbodyimpedance:Handtohand?_________ohmsOnehandtobothfeet?________ohmsBothhandstobothfeet?______ohmsCLASSEXERCISE:24SimplifiedBodyImpedanceModels3-componentmodelfor

dry-moistcontactand

lowtouchvoltageConservativemodelfor

lowskinimpedance(e.g.,

wetcontact,highvoltages,

and/orhighfrequency)0.22

Microfarad1500ohms500ohms500ohmsCombinationtwolargeareaskincontactsInternalbodyimpedance25E=IxZFrequencyinHertz10101010010010010001000100010,00010,00010,000BodyCurrentThresholdforLet-GoAppliedVoltageThreshold

ForLet-GoBodyImpedanceZICombinedEffectsofFrequencyonBody

ImpedanceandElectricShockThresholdsFrequencyinHertzFrequencyinHertz26Examplesof"Safe"VoltageCriteria(Checkthespecificend-productstandard)

15VACrms(<100Hz)

30VDC

30VACrms(<100Hz)

60VDC

42.4Vpeak(<100Hz)

(includingdc)

42.4Vpeak(<100Hz)

60VDC

71Vpeak(<100Hz)

120VDCDrylocationswhere

startlereaction

cannotbetolerated(UL)IECSELVcircuits:normalconditionsand

singlefaultconditions

fortime>0.2secsinglefaultconditions

fortime<0.2secLet-goandfibrillation,

drylocations(UL,NEC)Let-goandfibrillation,

wetlocations,notincluding

immersion(UL,NEC)ImmersionconditionsGenerallyno“safe”voltages27ElectricalInsulation:

BasicEquipmentSafeguard

AgainstElectricShock+_VsZsZBZIITVs=sourcevoltageZI=insulationimpedanceZB=bodyimpedanceIT=TouchcurrentZs=sourceimpedanceHazardousvoltageandcurrentsource:VSexceeds“safe”voltageANDIS=VS/Zs

exceeds“safe”availablecurrentISIS=availablesourcecurrent28Electrical

insulation

modelInsulation

Resistance

TestTouch(Leakage)

CurrentTestDielectric

Withstand

Test(Hi-pot)BasicTestsonElectricalInsulation29Touch(Leakage)CurrentTopicsDefinitions(UL101,IEC60990)TouchcurrentpathsPhysiologicaleffectsoftouchcurrent(electricshock)Bodyimpedancemodelsand“safe”voltagelimits

Touch(Leakage)CurrentTestTouchcurrentinstruments(meters)30Touch(Leakage)CurrentTestAccessiblemetalLoadLoadElectricalinsulationSystemLNG+_VSUngroundedConductorGroundedConductorGrounding(protectiveearthing)ConductorMEASUREMENTINSTRUMENT

applieswhensourceexceeds“safe”voltagelevels

representbodyimpedanceasfunctionoffrequency

representphysiologicaleffectasafunctionoffrequency31SelectionofMeasurementInstrumentInstrumentSpecificationsANSIC101-1986-AverageRespondingSystem(ARS)(StillspecifiedinmostULstandards)UL101-2023(ReplacedANSIC101)(SpecifiedinsomeULendproductstandardsandmostharmonizedULstandards)IEC60990-1999SPECIFICATIONSFORREACTION:SPECIFICATIONSFORLET-GO:IEC60990–1999SPECIFICATIONSFORELECTRICALBURNS:IEC60990-1999UL101-2023(0.5mArmslimit@60Hz)(3.5mArms,5mArmslimits@60Hz)(70mArms)32Ammeter(averageresponding)0.15

uFC1

MeasurementInstrumentSpecificationsforReaction1500ΩR1(ANSIC101-1986)(a)Inputimpedance(Z)(b)Metertypeandlocation(intendedtocombineeffectoffrequencyonbodyimpedanceandphysiologicalresponse)

AverageRespondingSystem(ARS)M33MVoltmeter(averageresponding)(d)Circuitfrequencyresponse(0to100kHz)IAIA=actualcurrenttonetworkI1=indicatedcurrenttonetwork(=V1/R1rmsforsinusoid)IAII/Z/R1=Z=R1parC1(0-100kHz)Indication(current)=1.11xVM(ave)/1500VMI1=I1=V1/R1(

rmsforsinusoid)(c)MeterindicationMax5%error@indicationof0.75mA0.15uFC1

MeasurementInstrumentSpecificationsforReaction1500ΩR1(ANSIC101-1986)(a)Inputimpedance(Z)(b)Metertypeandlocation(combineseffectoffrequencyonbodyimpedanceandphysiologicalresponse)

AverageRespondingSystem(ARS)V134SimpsonModel229(ANSIC101-1986)351500ΩR1C1Revisedbodyimpedancemodel500ΩR2Voltmeter0.22uFM10KΩ0.022uFR3C2Frequencysensitivenetworkforreaction(a)Inputimpedance

(UL101):V1I1RevisedMeasurementInstrumentforReactionUL101-1992,IEC60990-1999Z=V1/I1(20Hz-1MHz)

Rmsreading(UL101)Peakreading(IEC60990)

205060100200500100020235000 1000020230500001000002023005000001000000Freq(Hz)

19981990 1986 1961 1857 1433 973 661 512 485 479 477 476 476 476 476 V1/I1

500499498495480405284162.968.3 34.417.216.893.451.7220.6800.345V3/I1(b)Transferimpedance

(UL101):Z=V3/I1

(c)Meterindication(IIndicated):=V3/R2=V3/500(weightedmA-IEC60990;MIU-ANSIC101)(d)InputvoltagepermAindication

(IEC60990):

2.002.001.991.981.931.771.712.033.75 7.0613.934.669.1138346691

V1/IIndicatedV1/IIndicated(mA)

V336Frequencysensitivenetworkforreaction10KΩR31500ΩR1C1Bodyimpedancemodel500ΩR20.22uFIEC60990-1999MeasurementInstrumentforLet-GoFrequencysensitivenetworkforLet-GoM0.0062uF0.0091uF20KΩR4C2C3

205060100200500100020235000 1000020230500001000002023005000001000000Freq(Hz)

0.2500.251 0.251 0.253 0.261 0.298 0.348 0.377 0.280 0.164 0.0860 0.0349 0.0175 0.00874 0.00350 0.00175 V3/V1

2.001.991.991.981.921.681.441.331.79 3.045.8114.328.657.2143286

V1/IIndicatedV3V1VoltmeterPeakreading(IEC60990)(a)Outputvoltagetoinputvoltageratio:V3/V1(20Hz-1MHz)(c)Inputvoltagepermilliampereindication:(b)Meterindication(scale):IIndicated=V3

(peak)/500WeightedmAV1/Iindicated(mA)

3738Touch(Leakage)CurrentTopicsDefinitions(UL101,IEC60990)TouchcurrentpathsPhysiologicaleffectsoftouchcurrent(electricshock)Bodyimpedancemodelsand“safe”voltagelimitsTouch(Leakage)CurrentTestTouchcurrentinstruments(meters)Measurementcircuitsandprocedures39MeasurementInstrumentEUT(EquipmentUnderTest)PowerconnectionsTouch(Leakage)CurrentTestMeasurementCircuitComponentsPowersupplySwitchingnetworkMeasurementEquipmentConnections40120VGNDOPENAABBS2S12-pole,2-wire15ampnon-polarizedN15amppolarizedApplicableEUTPlugConfigurations2-pole,3-wireEQUIPMENTUNDERTEST(EUT)LoadPowerSupply20ampGN15ampGNLNPolarityreversingswitchGroundedconductorswitchMEASUREMENTINSTRUMENTConnectiontogroundedsupplyconductorMeasurementCircuitfor120VoltEquipmentINSULATINGTABLEUL101SwitchingNetwork41120VAABBS2S12-pole,2-wire15ampnon-polarized20ampG15ampGN15amppolarizedApplicableEUTPlugConfigurations2-pole,3-wireEQUIPMENTUNDERTEST(EUT)LoadS3Optionaltransformer<1%linevoltageFor3-wireapplications120VsupplyLNGIEC60990MeasurementCircuitfor120VoltEquipmentMEASUREMENTINSTRUMENT42GNDOPENAABBS2S1EQUIPMENTUNDERTEST(EUT)LoadPowerSupplyPolarityreversingswitchLineSwitchConnectiontogroundedsupplyconductorMeasurementcircuitfor2-pole208or230-240Voltequipmentsuitableforuseon230-240volttogroundcircuit208or230-240VLNLApplicableU.S.EUTPlugConfigurations15amp20amp

20ampG15ampG2-pole,2-wire2-pole,3-wireINSULATINGTABLE(U.S.Commercial/Industrial)(European230/400vresidential)MEASUREMENTINSTRUMENT43S1GNDOPENAABBS2Measurementcircuitfor2-pole208and240voltequipmentforconnectiononlyto120voltstogroundcircuits(120/208,120/240)ApplicableU.S.EUTPlugConfigurations15amp20amp

20ampG15ampG2-pole,2-wire208or240V120V120V2-pole,3-wireEQUIPMENTUNDERTEST(EUT)LoadLLNPolarityreversingswitchLine