Principles of Electrical Safety

406 Pages·2014·4.16 MB·English

by  Peter E. Sutherland

PRINCIPLES OF
ELECTRICAL SAFETY
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PRINCIPLES OF
ELECTRICAL SAFETY
PETER E. SUTHERLAND
Copyright©2015byTheInstituteofElectricalandElectronicsEngineers,Inc.
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LibraryofCongressCataloging-in-PublicationData:
Sutherland,PeterE.
Principlesofelectricalsafety/PeterE.Sutherland.
pagescm
ISBN978-1-118-02194-1(cloth)
1. Electricalengineering–Safetymeasures.2. Electricity–Safetymeasures.3. Electricapparatus
andappliances–Safetymeasures. I.Title.
TK152.S81742015
621.3028′9–dc23
2015012677
PrintedintheUnitedStatesofAmerica
10987654321
Toallthevictims
CONTENTS
LISTOFFIGURES xiii
LISTOFTABLES xxv
PREFACE xxix
ACKNOWLEDGMENTS xxxvii
CHAPTER1 MATHEMATICSUSEDINELECTROMAGNETISM 1
1.1 Introduction 1
1.2 Numbers 2
1.3 MathematicalOperationswithVectors 17
1.4 CalculuswithVectors—TheGradient 18
1.5 Divergence,Curl,andStokes’Theorem 23
1.6 Maxwell’sEquations 25
CHAPTER2 ELECTRICALSAFETYASPECTSOFTHERESISTANCE
PROPERTYOFMATERIALS 30
2.1 Introduction 30
2.2 HazardsCausedbyElectricalResistance 31
2.3 ResistanceandConductance 38
2.4 Example—TrunkofaHumanBody 42
2.5 Example—LimbofaHumanBody 43
2.6 PowerandEnergyFlow 44
2.7 SheetResistivity 47
2.8 Example—SquareofDrySkin 48
2.9 SpreadingResistance 48
2.10 Example—CircleofDrySkin 49
2.11 ParticleConductivity 50
2.12 Examples—Potassium,Sodium,andChlorineIons 53
2.13 CableResistance 53
CHAPTER3 CAPACITANCEPHENOMENA 59
3.1 FundamentalsofCapacitance 59
3.2 CapacitanceandPermittivity 62
3.3 CapacitanceinElectricalCircuits 65
3.4 CapacitanceofBodyParts 69
3.4.1 Example—SkinCapacitance 69
3.4.2 Example—CapacitanceofTrunkandLimb 70
3.5 ElectricalHazardsofCapacitance 71
3.6 CapacitanceofCables 72
vii
viii CONTENTS
CHAPTER4 INDUCTANCEPHENOMENA 74
4.1 InductanceinElectricalTheory 74
4.2 InductanceofWires 76
4.3 Example—InductanceofaConductor 76
4.4 Example—InductanceofTrunkandLimb 77
4.5 InductorsorReactors 77
4.6 SkinEffect 77
4.7 CableInductance 81
4.8 SurgeImpedance 83
4.9 BusBarImpedanceCalculations 84
CHAPTER5 CIRCUITMODELOFTHEHUMANBODY 90
5.1 CalculationofElectricalShockUsingtheCircuitModeloftheBody 90
5.2 FrequencyResponseoftheHumanBody 93
CHAPTER6 EFFECTOFCURRENTONTHEHUMANBODY 101
6.1 IntroductiontoElectricalShock 101
6.2 HumanandAnimalSensitivitiestoElectricCurrent 102
6.3 HumanBodyImpedance 104
6.4 EffectsofVariousExposureConditions 107
6.4.1 BareFeet,WetConditions,andOtherVariations 107
6.4.2 ShoesandOtherInsulatedObjectsandtheEarth 108
6.5 CurrentPathsThroughtheBody 108
6.6 HumanResponsetoElectricalShockVarieswithExposureConditions,Current
Magnitude,andDuration 113
6.7 MedicalImagingandSimulations 114
CHAPTER7 FUNDAMENTALSOFGROUNDGRIDDESIGN 118
7.1 IntroductiontoGroundGridDesign 118
7.2 SummaryofGroundGridDesignProcedures 119
7.2.1 SiteSurvey 119
7.2.2 ConductorSizing 119
7.2.3 StepandTouchVoltages 122
7.2.4 GroundGridLayout 124
7.2.5 GroundResistanceCalculation 124
7.2.6 CalculationofMaximumGridCurrent 125
7.2.7 CalculationofGroundPotentialRise(GPR) 125
7.2.8 CalculationofMeshVoltage,Em 125
7.2.9 CalculationofStepVoltage,Es 127
7.2.10 DetailedDesign 127
7.3 ExampleDesignfromIEEEStandard80 128
CHAPTER8 SAFETYASPECTSOFGROUNDGRIDOPERATION
ANDMAINTENANCE 138
8.1 Introduction 138
8.2 EffectsofHighFaultCurrents 138
CONTENTS ix
8.3 DamageorFailureofGroundingEquipment 142
8.3.1 ThermalDamagetoConductorsDuetoExcessiveShort-Circuit
Currents 142
8.3.2 ConnectorDamageDuetoExcessiveShort-CircuitStresses 143
8.3.3 DryingoftheSoilResultinginIncreasedSoilResistivity 144
8.4 Recommendations 145
CHAPTER9 GROUNDINGOFDISTRIBUTIONSYSTEMS 147
9.1 StrayCurrentsinDistributionSystems 147
9.2 Three-PhaseMultigroundedNeutralDistributionLine 148
9.3 SecondarySystems:120/240VSinglePhase 154
9.3.1 ExampleofStrayCurrents—TouchingaGroundedConductor 158
9.3.2 ExampleofStrayCurrents—WithOneConductorShortedtoNeutral 159
9.4 RemediationofStray-CurrentProblems 160
9.5 GroundingandOvervoltagesinDistributionSystems 163
9.6 High-ResistanceGroundingofDistributionSystems 167
9.6.1 MethodsofDeterminingChargingCurrent 169
CHAPTER10 ARCFLASHHAZARDANALYSIS 172
10.1 IntroductiontoArcFlashHazards 172
10.2 FactorsAffectingtheSeverityofArcFlashHazards 176
10.3 ExampleArcFlashCalculations 179
10.4 RemediationofArcFlashHazards 180
10.4.1 Example:CorrectinganArcFlashProblemWhenaCoordinationProblem
RequiresReplacingTripUnits 180
10.4.2 Example:CorrectingaCoordinationProblemWithoutIntroducinganArc
FlashProblem 182
10.5 CoordinationofLow-VoltageBreakerInstantaneousTripsforArcFlashHazard
Reduction 185
10.5.1 Hospital#1—Time–CurrentCurveExamples 189
10.5.2 Hospital#2—Time–CurrentCurveExamples 194
10.5.3 Hospital#3—Time−CurrentCurveExamples 200
10.6 Low-VoltageTransformerSecondaryArcFlashProtectionusingFuses 205
CHAPTER11 EFFECTOFHIGHFAULTCURRENTSONPROTECTION
ANDMETERING 216
11.1 Introduction 216
11.2 CurrentTransformerSaturation 217
11.3 SaturationofLow-RatioCTs 219
11.3.1 ACSaturation 219
11.3.2 DCSaturation 221
11.4 TestingofCurrentTransformerSaturation 224
11.5 EffectofHighFaultCurrentsonCoordination 228
11.6 ProtectiveRelayRatingsandSettings 230
11.7 EffectsofFaultCurrentsonProtectiveRelays 232
11.7.1 Examples 233
11.8 MethodsforUpgradingProtectionSystems 233
11.8.1 UpdateShort-CircuitStudy 233
11.8.2 UpdateProtectiveDeviceCoordinationStudy 233
x CONTENTS
CHAPTER12 EFFECTSOFHIGHFAULTCURRENTSONCIRCUITBREAKERS 235
12.1 InsuficientInterruptingCapability 236
12.2 HighVoltageAirCircuitBreakers 236
12.3 VacuumCircuitBreakers 237
12.4 SF6CircuitBreakers 239
12.5 LossofInterruptionMedium 241
12.6 InterruptingRatingsofSwitchingDevices 242
12.7 CircuitBreakers 243
12.8 Fuses 244
12.9 CaseStudies 245
12.9.1 Example:DiabloCanyon 245
12.9.2 Example:DresdenandQuadCities 248
12.10 Low-VoltageCircuitBreakers 249
12.11 TestingofLow-VoltageCircuitBreakers 251
12.11.1 TestingofLow-VoltageMolded-CaseCircuitBreakersAccordingtoUL
Standard489 252
12.11.2 TestingofLow-VoltageMolded-CaseCircuitBreakersforUseWith
UninterruptiblePowerSuppliesAccordingtoULStandard489 259
12.11.3 TestingofSupplementaryProtectorsforUseinElectricalEquipment
AccordingtoULStandard1077 261
12.11.4 TestingofTransferSwitchEquipmentAccordingtoULStandard
1008 272
12.11.5 TestingofLow-VoltageACPowerCircuitBreakersAccordingtoANSI
StandardC37.50-1989 276
12.11.6 TestingofLow-VoltageDCPowerCircuitBreakersAccordingtoIEEE
StandardC37.14-2002 280
12.11.7 TestingofLow-VoltageSwitchgearandControlgearAccordingtoIEC
Standard60947-1 284
12.11.8 TestingofLow-VoltageACandDCCircuitBreakersAccordingtoIEC
Standard60947-2 285
12.11.9 TestingofCircuitBreakersUsedforAcross-the-LineStartersforMotors
AccordingtoIECStandard60947-4-1 288
12.11.10 TestingofCircuitBreakersUsedinHouseholdsandSimilarInstallations
AccordingtoIECStandard60898-1and-2 290
12.11.11 TestingofCircuitBreakersUsedinEquipmentsuchasElectrical
AppliancesAccordingtoIECStandard60934 293
12.12 TestingofHigh-VoltageCircuitBreakers 296
CHAPTER13 MECHANICALFORCESANDTHERMALEFFECTSIN
SUBSTATIONEQUIPMENTDUETOHIGHFAULTCURRENTS 299
13.1 Introduction 299
13.2 Deinitions 299
13.3 Short-CircuitMechanicalForcesonRigidBusBars 300
13.3.1 Short-CircuitMechanicalForcesonRigidBusBars—CircularCross
Section 300
13.3.2 Short-CircuitMechanicalForces—RectangularCrossSection 302
13.4 DynamicEffectsofShortCircuits 302
13.5 Short-CircuitThermalEffects 304
CONTENTS xi
13.6 FlexibleConductorBuses 305
13.6.1 ConductorMotionDuringaFault 307
13.6.2 PinchForcesonBundledConductors 311
13.7 ForceSafetyDevices 316
13.8 SubstationCableandConductorSystems 318
13.8.1 CableThermalLimits 318
13.8.2 CableMechanicalLimits 319
13.9 DistributionLineConductorMotion 319
13.10 EffectsofHighFaultCurrentsonSubstationInsulators 320
13.10.1 StationPostInsulatorsforRigidBusBars 320
13.10.2 SuspensionInsulatorsforFlexibleConductorBuses 322
13.11 EffectsofHighFaultCurrentsonGas-InsulatedSubstations(GIS) 322
CHAPTER14 EFFECTOFHIGHFAULTCURRENTSONTRANSMISSIONLINES 325
14.1 Introduction 325
14.2 EffectofHighFaultCurrentonNon-CeramicInsulators(NCI) 325
14.3 ConductorMotionDuetoFaultCurrents 328
14.4 CalculationofFaultCurrentMotionforHorizontallySpacedConductors 329
14.5 EffectofConductorShape 330
14.6 ConductorEquationsofMotion 331
14.7 EffectofConductorStretch 332
14.8 CalculationofFaultCurrentMotionforVerticallySpacedConductors 332
14.9 CalculationProcedure 333
14.10 CalculationofTensionChangewithMotion 334
14.11 CalculationofMechanicalLoadingonPhase-to-PhaseSpacers 335
14.12 EffectofBundlePinchonConductorsandSpacers 336
CHAPTER15 LIGHTNINGANDSURGEPROTECTION 338
15.1 SurgeVoltageSourcesandWaveshapes 338
15.2 SurgePropagation,Refraction,andReflection 343
15.3 InsulationWithstandCharacteristicsandProtection 346
15.4 SurgeArresterCharacteristics 349
15.5 SurgeArresterApplication 350
REFERENCES 352
INDEX 361