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1、Hazard Based Safety Engineering - Touch (Leakage) Current1课件学习Overall Session Objectives:1. To understand the rationale for the Touch (leakage) Current Test, instrumentation, connections, test procedures and limits2. To understand limitations of test and alternative approaches Touch (Leakage) Curren
2、t2课件学习Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current TestTouch current instruments (meters)Measurement circuits and proceduresLimits3课件学
3、习DEFINITIONSLEAKAGE CURRENT (UL101-2002): Electric current which flows through a person upon contact, between accessible parts of an appliance and (1) ground, or (2) other accessible parts of the applianceTOUCH CURRENT (IEC 60990): Electric current through a human body or an animal body when it touc
4、hes one or more accessible parts of an installation or of equipment.4课件学习Touch (Leakage) Current PathsAccessible metalLoadLoadElectrical insulation SystemLNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) Conductor?Touch currentReturnPath5课件学习Touch Current PathsLoadLoadExamp
5、le: Ungrounded 2 wire Cord and Plug-Connected Appliancestouchable metalElectrical InsulationSystemTo Electrical Supply6课件学习Can openerToaster ovenTVradioCoffee makerironblenderExamples of 2-wire Non-Grounded Appliances7课件学习Touch Current PathsGrounded applianceTouchable metalLoadLoadUngrounded 2 wire
6、applianceTouchable Metalof Grounded AppliancesElectrical insulation SystemEquipment Grounding Conductor (protective earthing conductor)GLNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) ConductorTouch CurrentTouchable metal Return Paths-18课件学习dishwasherrangemicrowaverefrige
7、ratorExamples of 3-wire Grounded AppliancesCan openerToaster ovenTVradioCoffee makerironblenderExamples of 2-wire Non-Grounded Appliances9课件学习PlumbingFixturesConstruction GroundsMetallic Piping SystemBonding connectionto water pipeTouch CurrentTouchable metalTouchable metalLoadLoadUngrounded 2 wire
8、applianceElectrical insulation SystemGLNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) Conductor Return Paths-2Touch Current Paths10课件学习SinkExamples of Construction Grounds Baseboard heatingExamples of 3-wire Grounded AppliancesExamples of 2-wire Non-Grounded Appliancesdis
9、hwasherrangemicrowaverefrigeratorCan openerToaster ovenTVradioCoffee makerironblender11课件学习Touch Current PathsUngrounded 2 wire applianceLoadLoadPathway through earthTouchable metalElectrical insulation SystemSoilL LNGG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) Conducto
10、rTouch CurrentReturn Paths-312课件学习Touch Current PathsTouchable metalLoadLoadElectrical insulation SystemLNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) ConductorExample: Three - Wire Grounded Cord and Plug Connected productPotential Touch Current13课件学习Touch Current PathsT
11、ouchable metalLoadLoadElectrical insulation SystemLNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) ConductorExample: Three - Wire Grounded Cord and Plug Connected product14课件学习Grounded metal2-wirereceptacle(normal- old construction)OR3 to 2 adapterConnection to Ungrounded
12、ReceptacleTouch CurrentTouchable metalLoadElectrical insulation SystemLNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) ConductorExample: Three - Wire Grounded Cord and Plug Connected productOpen circuit or highimpedance (fault)15课件学习Touch Current Paths-4touchable metalLoad
13、LNG+_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) ConductorTouch Current From Simultaneously Touchable Parts of same productLoadZTouch Current16课件学习Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (ele
14、ctric shock)17课件学习Physiological Effects of Touch Current(sinusoidal, rms, 60 Hz) Perception (microamperes to 0.5 mA) Startle reaction ( 0.5 mA) Muscle tetanization (inability to let go) ( 5 mA) Ventricular fibrillation ( 50 mA) Electrical burns ( 70 mA)V10-00118课件学习51061010-10.5151010203510210310210
15、3104VentricularFibrillationLet-GoStartle Reaction1I = 0.954 f0.716f 70 HzI 0.0007 ff 1 kHzIEC ThresholdUL LimitEffects of Frequency on Electric Shock Thresholdsand Limits for Continuous AC currentBody Current (rms mA)Frequency (Hz)22. In the case of let-go, IECcurve represents average value1. thresh
16、old/limit = 2 mA at 0 Hz (dc)(see note 3)3. respiratory arrest observedin dogs at 20, 30, and 40 mA19课件学习 Current Density Duration* Pathway through bodyV10-015 (skin contact location) Other Touch Current Variables* See Special Situations for Touch Current Measurements Waveshape*20课件学习Touch (Leakage)
17、 Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits21课件学习+_ZBVsZSIBZB= body impedanceVs= source open circuit voltageZS= source impedanceIB= body currentVSZS(ZB= f , ,.)ZBZS+VsIB= D
18、etermining Touch CurrentVoltage Source22课件学习R3C1C2R2R1Five Component Body Impedance ModelImpedance representingone skin-electrodecontactInternal body impedance(less the skin)Impedance representingother skin-electrodecontact23课件学习Effect of Current Pathway on Internal Body ImpedanceInternal BodyImpeda
19、nce (R3)(typical adult)Elbow- 200 ohmsElbow- 200 ohmsTorso-100 ohmsWrist-300 ohmsWrist-300 ohmsKnee-150 ohmsKnee-150 ohmsAnkle-350 ohmsAnkle-350 ohmsWhat is the internal body impedance: Hand to hand? _ohms One hand to both feet? _ohms Both hands to both feet? _ ohmsCLASS EXERCISE:24课件学习Simplified Bo
20、dy Impedance Models3-component model fordry-moist contact andlow touch voltageConservative model forlow skin impedance (e.g.,wet contact, high voltages,and/or high frequency)0.22Microfarad1500 ohms500 ohms500 ohmsCombination two large area skin contactsInternalbodyimpedance25课件学习E = I x ZFrequency i
21、n Hertz10101010010010010001000100010,00010,00010,000Body Current Threshold for Let-GoApplied Voltage ThresholdFor Let-GoBody ImpedanceZICombined Effects of Frequency on BodyImpedance and Electric Shock ThresholdsFrequency in HertzFrequency in Hertz26课件学习Examples of Safe Voltage Criteria(Check the sp
22、ecific end-product standard) 15 V AC rms ( 100 Hz) 30 V DC 30 V AC rms ( 100 Hz) 60 V DC 42.4 V peak ( 100 Hz)(including dc) 42.4 V peak ( 100 Hz) 60 V DC 71 V peak ( 0.2 secsingle fault conditionsfor time 0.2 secLet-go and fibrillation,dry locations (UL, NEC)Let-go and fibrillation,wet locations, n
23、ot includingimmersion (UL, NEC)Immersion conditionsGenerally no “safe” voltages27课件学习Electrical Insulation:Basic Equipment SafeguardAgainst Electric Shock+_VsZsZBZIITVs= source voltageZI= insulation impedanceZB= body impedanceIT= Touch currentZs= source impedanceHazardous voltage and current source:
24、VS exceeds “safe” voltage ANDIS = VS / Zs exceeds “safe” available currentISIS = available source current28课件学习ElectricalinsulationmodelInsulationResistanceTestTouch (Leakage)Current TestDielectricWithstandTest (Hi-pot)Basic Tests on Electrical Insulation29课件学习Touch (Leakage) Current Topics Definiti
25、ons (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current TestTouch current instruments (meters)30课件学习Touch (Leakage) Current TestAccessible metalLoadLoadElectrical insulation SystemLNG+
26、_VSUngrounded ConductorGrounded ConductorGrounding(protective earthing) ConductorMEASUREMENTINSTRUMENT applies when source exceeds “safe” voltage levels represent body impedance as function of frequency represent physiological effect as a function of frequency31课件学习Selection of Measurement Instrumen
27、tInstrument SpecificationsANSI C101- 1986 - Average Responding System (ARS) (Still specified in most UL standards)UL 101- 2002 (Replaced ANSI C101)(Specified in some UL end product standards and most harmonized UL standards) IEC 60990 - 1999 SPECIFICATIONS FOR REACTION:SPECIFICATIONS FOR LET-GO:IEC
28、60990 1999 SPECIFICATIONS FOR ELECTRICAL BURNS:IEC 60990 - 1999 UL101- 2002(0.5 mA rms limit 60 Hz)(3.5 mA rms, 5 mA rms limits 60 Hz)(70 mA rms)32课件学习Ammeter(averageresponding)0.15 uFC1 Measurement Instrument Specifications for Reaction1500R1(ANSI C101- 1986)(a) Input impedance (Z) (b) Meter type a
29、nd location(intended to combine effect of frequency on body impedance and physiological response) Average Responding System (ARS)M33课件学习MVoltmeter(averageresponding)(d) Circuit frequency response ( 0 to 100 kHz)IAIA = actual current to networkI1 = indicated current to network ( = V1/R1 rms for sinus
30、oid)IAII/Z / R1=Z = R1par C1(0 - 100 kHz)Indication (current) = 1.11 x VM (ave)/1500 VMI1= I 1 = V1 / R1( rms for sinusoid) (c) Meter indicationMax 5% error indication of 0.75 mA 0.15uFC1 Measurement Instrument Specifications for Reaction1500R1(ANSI C101- 1986)(a) Input impedance (Z) (b) Meter type
31、and location(combines effect of frequency on body impedance and physiological response) Average Responding System (ARS)V134课件学习Simpson Model 229 (ANSI C101- 1986)35课件学习1500R1C1Revised body impedance model500R2Voltmeter0.22uFM10 K0.022uFR3C2Frequency sensitive network for reaction(a) Input impedance
32、(UL 101):V1I1Revised Measurement Instrument for ReactionUL 101-1992, IEC 60990- 1999Z= V1 / I1 (20 Hz - 1 MHz) Rms reading(UL101)Peak reading(IEC 60990) 20 50 60 100 200 500 1000 2000 5000 10000 20000 50000 100000 200000 5000001000000Freq (Hz) 1998 1990 1986 1961 1857 1433 973 661 512 485 479 477 47
33、6 476 476 476V1 / I1 500 499 498 495 480 405 284 162.9 68.3 34.4 17.21 6.89 3.45 1.722 0.680 0.345V3 / I1(b) Transfer impedance (UL101):Z= V3 / I1 (c) Meter indication (IIndicated):= V3 / R2 = V3 / 500 (weighted mA -IEC 60990; MIU- ANSI C101)(d) Input voltage per mA indication (IEC 60990): 2.00 2.00
34、 1.99 1.98 1.93 1.77 1.71 2.03 3.75 7.06 13.9 34.6 69.1 138 346 691 V1 / IIndicatedV1 / I Indicated (mA) V336课件学习Frequency sensitive network for reaction10 KR31500R1C1Body impedance model500R20.22uFIEC 60990- 1999Measurement Instrument for Let-GoFrequency sensitive network for Let-GoM0.0062uF0.0091u
35、F20 KR4C2C3 20 50 60 100 200 500 1000 2000 5000 10000 20000 50000 100000 200000 5000001000000Freq (Hz) 0.250 0.251 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 0.00175V3 / V1 2.00 1.99 1.99 1.98 1.92 1.68 1.44 1.33 1.79 3.04 5.81 14.3 28.6 57.2 143 286 V1 / II
36、ndicatedV3V1VoltmeterPeak reading(IEC 60990)(a) Output voltage to input voltage ratio:V3 / V1 (20 Hz - 1 MHz) (c) Input voltage per milliampere indication:(b) Meter indication (scale): IIndicated = V3 (peak) / 500Weighted mAV1 / Iindicated (mA) 37课件学习38课件学习Touch (Leakage) Current Topics Definitions
37、(UL101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current TestTouch current instruments (meters)Measurement circuits and procedures39课件学习MeasurementInstrumentEUT (Equipment Under Test)Powerco
38、nnectionsTouch (Leakage) Current Test Measurement Circuit ComponentsPower supplySwitchingnetworkMeasurement Equipment Connections40课件学习120 VGNDOPENAABBS2S12-pole, 2-wire15 ampnon-polarizedN15 amppolarizedApplicable EUT Plug Configurations2-pole, 3-wireEQUIPMENT UNDER TEST (EUT)LoadPowerSupply20 ampG
39、N15 ampGNLNPolarity reversing switchGrounded conductorswitchMEASUREMENTINSTRUMENTConnection to grounded supply conductorMeasurement Circuit for 120 Volt EquipmentINSULATING TABLEUL101Switching Network41课件学习120 VAABBS2S12-pole, 2-wire15 ampnon-polarized20 ampG15 ampGN15 amppolarizedApplicable EUT Plu
40、g Configurations2-pole, 3-wireEQUIPMENT UNDER TEST (EUT)LoadS3Optionaltransformer 1% linevoltageFor 3-wire applications120 VsupplyLNGIEC 60990Measurement Circuit for 120 Volt EquipmentMEASUREMENTINSTRUMENT42课件学习GNDOPENAABBS2S1EQUIPMENT UNDER TEST (EUT)LoadPowerSupplyPolarity reversing switchLine Swi
41、tchConnection to grounded supply conductorMeasurement circuit for 2- pole 208 or 230-240 Volt equipment suitable for use on 230-240 volt to ground circuit208 or 230-240 VLN LApplicable U.S. EUT Plug Configurations15 amp20 amp 20 ampG15 ampG2-pole, 2-wire2-pole, 3-wireINSULATING TABLE(U.S.Commercial
42、/ Industrial) (European 230/400 v residential)MEASUREMENTINSTRUMENT43课件学习S1GNDOPENAABBS2Measurement circuit for 2- pole 208 and 240 volt equipmentfor connection only to 120 volts to ground circuits (120/208, 120/240)Applicable U.S. EUT Plug Configurations15 amp20 amp 20 ampG15 ampG2-pole, 2-wire208
43、or240 V120 V120 V2-pole, 3-wireEQUIPMENT UNDER TEST (EUT)LoadLLNPolarity reversing switchLine SwitchConnection to grounded supply conductorINSULATING TABLEPowerSupplyMEASUREMENTINSTRUMENT(U.S.Residential)44课件学习EQUIPMENT UNDER TEST (EUT)LoadAABBS2 20 ampN15 ampNGNG20 amp3-pole, 3-wire3-pole, 4-wireMe
44、asurement circuit for single phase, 3- pole, 208 or 240 Volt Equipment Applicable U.S. EUT Plug Configurations208 or 240 V120 V120 VS1GNDOPENNG30 amp 30 ampNLLNLine and Neutral SwitchConnection to grounded supply conductorINSULATING TABLEPowerPowerSupplySupplyPolarity reversing switchMEASUREMENTINST
45、RUMENT(e.g., electric ranges, clothes dryers)45课件学习Touch (Leakage) Current Topics Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current TestTouch current instruments (meters)
46、Measurement circuits and proceduresLimits46课件学习LimitsTouch (Leakage) Current TestUL 101- 2002 RecommendationsUL 101- 2002 RecommendationsType of applianceTwo-wire cord- and plug-connected applianceIndication in MIU0.50 MIUThree-wire (includinggrounding conductor)cord- and plug- connectedportable app
47、liance0.50 MIUThree-wire (includinggrounding conductor)cord- and plug- connectedstationary or fixed appliance0.75 MIUAll70 mA rms (electric burn)47课件学习SUMMARY Definitions (UL 101, IEC 60990) Touch current paths Physiological effects of touch current (electric shock) Body impedance models and “safe” voltage limits Touch (Leakage) Current TestTouch current instruments (meters)Measurement circuits and proceduresLimits48课件学习Questions and Answers49课件学习- END -50课件学习
