Principles of Electrical Safety: (IEEE Press Series on Power and Energy Systems)

Principles of Electrical Safety discusses current issues in electrical safety, which are accompanied by series’ of practical applications that can be used by practicing professionals, graduate students, and researchers. . • Provides extensive introductions to important topics in electrical safety • Comprehensive overview of inductance, resistance, and capacitance as applied to the human body • Serves as a preparatory guide for today’s practicing engineers

Table of Contents:
List of Figures xiii List of Tables xxv Preface xxix Acknowledgments xxxvii Chapter 1 Mathematics Used in Electromagnetism 1 1.1 Introduction 1 1.2 Numbers 2 1.3 Mathematical Operations with Vectors 17 1.4 Calculus with Vectors—The Gradient 18 1.5 Divergence, Curl, and Stokes’ Theorem 23 1.6 Maxwell’s Equations 25 Chapter 2 Electrical Safety Aspects of the Resistance Property of Materials 30 2.1 Introduction 30 2.2 Hazards Caused by Electrical Resistance 31 2.3 Resistance and Conductance 38 2.4 Example—Trunk of a Human Body 42 2.5 Example—Limb of a Human Body 43 2.6 Power and Energy Flow 44 2.7 Sheet Resistivity 47 2.8 Example—Square of Dry Skin 48 2.9 Spreading Resistance 48 2.10 Example—Circle of Dry Skin 49 2.11 Particle Conductivity 50 2.12 Examples—Potassium, Sodium, and Chlorine Ions 53 2.13 Cable Resistance 53 Chapter 3 Capacitance Phenomena 59 3.1 Fundamentals of Capacitance 59 3.2 Capacitance and Permittivity 62 3.3 Capacitance in Electrical Circuits 65 3.4 Capacitance of Body Parts 69 3.4.1 Example—Skin Capacitance 69 3.4.2 Example—Capacitance of Trunk and Limb 70 3.5 Electrical Hazards of Capacitance 71 3.6 Capacitance of Cables 72 Chapter 4 Inductance Phenomena 74 4.1 Inductance in Electrical Theory 74 4.2 Inductance of Wires 76 4.3 Example—Inductance of a Conductor 76 4.4 Example—Inductance of Trunk and Limb 77 4.5 Inductors or Reactors 77 4.6 Skin Effect 77 4.7 Cable Inductance 81 4.8 Surge Impedance 83 4.9 Bus Bar Impedance Calculations 84 Chapter 5 Circuit Model of the Human Body 90 5.1 Calculation of Electrical Shock Using the Circuit Model of the Body 90 5.2 Frequency Response of the Human Body 93 Chapter 6 Effect of Current on the Human Body 101 6.1 Introduction to Electrical Shock 101 6.2 Human and Animal Sensitivities to Electric Current 102 6.3 Human Body Impedance 104 6.4 Effects of Various Exposure Conditions 107 6.4.1 Bare Feet, Wet Conditions, and Other Variations 107 6.4.2 Shoes and Other Insulated Objects and the Earth 108 6.5 Current Paths Through the Body 108 6.6 Human Response to Electrical Shock Varies with Exposure Conditions, Current Magnitude, and Duration 113 6.7 Medical Imaging and Simulations 114 Chapter 7 Fundamentals of Ground Grid Design 118 7.1 Introduction to Ground Grid Design 118 7.2 Summary of Ground Grid Design Procedures 119 7.2.1 Site Survey 119 7.2.2 Conductor Sizing 119 7.2.3 Step and Touch Voltages 122 7.2.4 Ground Grid Layout 124 7.2.5 Ground Resistance Calculation 124 7.2.6 Calculation of Maximum Grid Current 125 7.2.7 Calculation of Ground Potential Rise (GPR) 125 7.2.8 Calculation of Mesh Voltage, Em 125 7.2.9 Calculation of Step Voltage, Es 127 7.2.10 Detailed Design 127 7.3 Example Design from IEEE Standard 80 128 Chapter 8 Safety Aspects of Ground Grid Operation and Maintenance 138 8.1 Introduction 138 8.2 Effects of High Fault Currents 138 8.3 Damage or Failure of Grounding Equipment 142 8.3.1 Thermal Damage to Conductors Due to Excessive Short-Circuit Currents 142 8.3.2 Connector Damage Due to Excessive Short-Circuit Stresses 143 8.3.3 Drying of the Soil Resulting in Increased Soil Resistivity 144 8.4 Recommendations 145 Chapter 9 Grounding of Distribution Systems 147 9.1 Stray Currents in Distribution Systems 147 9.2 Three-Phase Multigrounded Neutral Distribution Line 148 9.3 Secondary Systems: 120/240 V Single Phase 154 9.3.1 Example of Stray Currents—Touching a Grounded Conductor 158 9.3.2 Example of Stray Currents—With One Conductor Shorted to Neutral 159 9.4 Remediation of Stray-Current Problems 160 9.5 Grounding and Overvoltages in Distribution Systems 163 9.6 High-Resistance Grounding of Distribution Systems 167 9.6.1 Methods of Determining Charging Current 169 Chapter 10 Arc Flash Hazard Analysis 172 10.1 Introduction to Arc Flash Hazards 172 10.2 Factors Affecting the Severity of Arc Flash Hazards 176 10.3 Example Arc Flash Calculations 179 10.4 Remediation of Arc Flash Hazards 180 10.4.1 Example: Correcting an Arc Flash Problem When a Coordination Problem Requires Replacing Trip Units 180 10.4.2 Example: Correcting a Coordination Problem Without Introducing an Arc Flash Problem 182 10.5 Coordination of Low-Voltage Breaker Instantaneous Trips for Arc Flash Hazard Reduction 185 10.5.1 Hospital #1—Time–Current Curve Examples 189 10.5.2 Hospital #2—Time–Current Curve Examples 194 10.5.3 Hospital #3—Time−Current Curve Examples 200 10.6 Low-Voltage Transformer Secondary Arc Flash Protection using Fuses 205 Chapter 11 Effect of High Fault Currents on Protection and Metering 216 11.1 Introduction 216 11.2 Current Transformer Saturation 217 11.3 Saturation of Low-Ratio CTs 219 11.3.1 AC Saturation 219 11.3.2 DC Saturation 221 11.4 Testing of Current Transformer Saturation 224 11.5 Effect of High Fault Currents on Coordination 228 11.6 Protective Relay Ratings and Settings 230 11.7 Effects of Fault Currents on Protective Relays 232 11.7.1 Examples 233 11.8 Methods for Upgrading Protection Systems 233 11.8.1 Update Short-Circuit Study 233 11.8.2 Update Protective Device Coordination Study 233 Chapter 12 Effects of High Fault Currents on Circuit Breakers 235 12.1 Insufficient Interrupting Capability 236 12.2 High Voltage Air Circuit Breakers 236 12.3 Vacuum Circuit Breakers 237 12.4 SF6 Circuit Breakers 239 12.5 Loss of Interruption Medium 241 12.6 Interrupting Ratings of Switching Devices 242 12.7 Circuit Breakers 243 12.8 Fuses 244 12.9 Case Studies 245 12.9.1 Example: Diablo Canyon 245 12.9.2 Example: Dresden and Quad Cities 248 12.10 Low-Voltage Circuit Breakers 249 12.11 Testing of Low-Voltage Circuit Breakers 251 12.11.1 Testing of Low-Voltage Molded-Case Circuit Breakers According to UL Standard 489 252 12.11.2 Testing of Low-Voltage Molded-Case Circuit Breakers for Use With Uninterruptible Power Supplies According to UL Standard 489 259 12.11.3 Testing of Supplementary Protectors for Use in Electrical Equipment According to UL Standard 1077 261 12.11.4 Testing of Transfer Switch Equipment According to UL Standard 1008 272 12.11.5 Testing of Low-Voltage AC Power Circuit Breakers According to ANSI Standard C37.50-1989 276 12.11.6 Testing of Low-Voltage DC Power Circuit Breakers According to IEEE Standard C37.14-2002 280 12.11.7 Testing of Low-Voltage Switchgear and Controlgear According to IEC Standard 60947-1 284 12.11.8 Testing of Low-Voltage AC and DC Circuit Breakers According to IEC Standard 60947-2 285 12.11.9 Testing of Circuit Breakers Used for Across-the-Line Starters for Motors According to IEC Standard 60947-4-1 288 12.11.10 Testing of Circuit Breakers Used in Households and Similar Installations According to IEC Standard 60898-1 and -2 290 12.11.11 Testing of Circuit Breakers Used in Equipment such as Electrical Appliances According to IEC Standard 60934 293 12.12 Testing of High-Voltage Circuit Breakers 296 Chapter 13 Mechanical Forces and Thermal Effects in Substation Equipment Due To High Fault Currents 299 13.1 Introduction 299 13.2 Definitions 299 13.3 Short-Circuit Mechanical Forces on Rigid Bus Bars 300 13.3.1 Short-Circuit Mechanical Forces on Rigid Bus Bars—Circular Cross Section 300 13.3.2 Short-Circuit Mechanical Forces—Rectangular Cross Section 302 13.4 Dynamic Effects of Short Circuits 302 13.5 Short-Circuit Thermal Effects 304 13.6 Flexible Conductor Buses 305 13.6.1 Conductor Motion During a Fault 307 13.6.2 Pinch Forces on Bundled Conductors 311 13.7 Force Safety Devices 316 13.8 Substation Cable and Conductor Systems 318 13.8.1 Cable Thermal Limits 318 13.8.2 Cable Mechanical Limits 319 13.9 Distribution Line Conductor Motion 319 13.10 Effects of High Fault Currents on Substation Insulators 320 13.10.1 Station Post Insulators for Rigid Bus Bars 320 13.10.2 Suspension Insulators for Flexible Conductor Buses 322 13.11 Effects of High Fault Currents on Gas-Insulated Substations (GIS) 322 Chapter 14 Effect of High Fault Currents on Transmission Lines 325 14.1 Introduction 325 14.2 Effect of High Fault Current on Non-Ceramic Insulators (NCI) 325 14.3 Conductor Motion Due to Fault Currents 328 14.4 Calculation of Fault Current Motion for Horizontally Spaced Conductors 329 14.5 Effect of Conductor Shape 330 14.6 Conductor Equations of Motion 331 14.7 Effect of Conductor Stretch 332 14.8 Calculation of Fault Current Motion for Vertically Spaced Conductors 332 14.9 Calculation Procedure 333 14.10 Calculation of Tension Change with Motion 334 14.11 Calculation of Mechanical Loading on Phase-to-Phase Spacers 335 14.12 Effect of Bundle Pinch on Conductors and Spacers 336 Chapter 15 Lightning and Surge Protection 338 15.1 Surge Voltage Sources and Waveshapes 338 15.2 Surge Propagation, Refraction, and Reflection 343 15.3 Insulation Withstand Characteristics and Protection 346 15.4 Surge Arrester Characteristics 349 15.5 Surge Arrester Application 350 References 352 Index 361

About the Author :
Peter E. Sutherland serves as lead consultant at GE Energy Services, in Schenectady, New York. He has a PhD in Electric Power Engineering from Rensselaer Polytechnic Institute. He is a well-respected industry expert who has taught several courses on the topic. He is a fellow of IEEE.