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Searching... | 30000010338259 | TK152 E47 2014 | Open Access Book | Book | Searching... |
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Summary
Summary
Electric power engineering education traditionally covers safety of the power equipment and systems. Little attention, if any, is given to the safety of people. When they reach professional status, most power engineers are not familiar with electric safety issues such as practices governing site works or grounding techniques of dwellings, hospitals, and factories. Designed for both electrical engineering student and practicing power engineers, Electric Safety: Practice and Standards provides the knowledge and analysis they need to be well versed in electric safety.
Features:
Includes techniques to assess safety practices at worksites and provides remedies to correct safety problems Addresses the elusive stray voltage problem and provides techniques to mitigate its impact in dwellings as well as in sensitive installations such as hospitals and dairy farms Provides approximate, yet accurate, analyses and techniques that can be used to assess electric safety without the need for extensive computation or elaborate programs Includes several case studies from real events and examples demonstrating how variations in electric safety procedure implementation influence safety levelsBased on the authors' years of experience as an expert witness and electric safety training instructor, the book covers the analysis of electric safety practices as well as the interpretations of various safety codes. Including homework problems and a solutions manual, this book is a comprehensive guide to recognize and eliminate hazards of electric shocks for professionals working on electric power equipment, as well as people such as the general public in commonly used places, farms workers and animals, and hospital patients.
Table of Contents
Preface | p. xiii |
Author | p. xv |
List of Acronyms | p. xvii |
Disclaimer | p. xix |
1 Fundamentals of Electricity | p. 1 |
1.1 Electric Fields | p. 2 |
1.2 Magnetic Fields | p. 6 |
1.3 Alternating Current | p. 10 |
1.3.1 Root Mean Square | p. 11 |
1.3.2 Phase Shift | p. 12 |
1.3.3 Concept of Phasors | p. 12 |
1.3.4 Complex Numbers | p. 13 |
1.4 Three-Phase Systems | p. 13 |
1.4.1 Wye-Connected Balanced Circuit | p. 15 |
1.4.2 Delta-Connected Balanced Circuit | p. 18 |
Exercises | p. 19 |
2 Basic Components of an Electric Grid | p. 21 |
2.1 Power Lines | p. 21 |
2.1.1 Conductors | p. 22 |
2.1.1.1 Cables | p. 23 |
2.1.1.2 Bundled Conductors | p. 27 |
2.1.1.3 Static Wires | p. 29 |
2.1.2 Insulators | p. 30 |
2.2 Substations | p. 32 |
2.2.1 Transformers | p. 33 |
2.2.2 Circuit Breakers | p. 33 |
2.2.3 Circuit Reclosers | p. 35 |
2.2.4 Circuit Sectionalizers | p. 35 |
2.2.5 Isolators and Bypasses | p. 36 |
2.2.6 Load Switches | p. 37 |
2.2.7 Fuses | p. 37 |
2.2.8 Surge Protectors | p. 38 |
2.2.9 Measuring Equipment | p. 41 |
2.2.9.1 Voltage Sensors | p. 41 |
2.2.9.2 Current Transformers | p. 44 |
2.2.10 Reactive Power Control Equipment | p. 45 |
2.2.10.1 Fixed or Switched Capacitors | p. 45 |
2.2.10.2 Static Reactive Power Compensators | p. 45 |
Exercises | p. 46 |
3 Physiological Effects of Electricity | p. 49 |
3.1 Classifications of Electric Shocks | p. 49 |
3.2 Factors Determining the Severity of Electric Shocks | p. 52 |
3.2.1 Effect of Voltage | p. 52 |
3.2.2 Effect of Current | p. 53 |
3.2.3 Effect of Body Resistance | p. 54 |
3.2.4 Effect of Current Pathway | p. 56 |
3.2.5 Effect of Shock Duration | p. 57 |
3.2.6 Effect of Frequency | p. 60 |
3.2.7 Effect of Impulse versus Continuous Current | p. 61 |
3.3 Symptoms and Treatments of Electric Shock | p. 63 |
3.4 Microshocks | p. 64 |
Exercises | p. 64 |
4 Ground Resistance | p. 65 |
4.1 Ground Resistance of Objects | p. 66 |
4.1.1 Ground Resistance of Hemisphere | p. 67 |
4.1.2 Ground Resistance of Circular Plate | p. 71 |
4.1.3 Ground Resistance of People | p. 72 |
4.1.4 Ground Resistance of Rod | p. 76 |
4.1.4.1 Ground Resistance of Rods Inserted in Concrete | p. 78 |
4.1.4.2 Ground Resistance of a Cluster of Rods | p. 79 |
4.1.5 Ground Resistance of Buried Wires | p. 82 |
4.1.5.1 Ground Resistance of Buried Wires in Grid Arrangement | p. 83 |
4.1.5.2 Ground Resistance of Combined Grids and Rods 86 | |
4.2 Soil Resistivity | p. 89 |
4.2.1 Measuring Ground Resistance | p. 89 |
4.2.2 Measuring Soil Resistivity | p. 91 |
4.2.2.1 Wenner Four-Pin Method | p. 91 |
4.2.2.2 SchLumberger Four-Pin Method | p. 93 |
4.2.2.3 Driven-Rod Method | p. 94 |
4.2.2.4 Nonuniform Soils | p. 95 |
4.2.2.5 Comments on the Three Methods | p. 100 |
4.3 Soil Treatment | p. 100 |
4.4 Factors Affecting Ground Resistance | p. 101 |
4.4.1 Effect of Voltage Gradient | p. 101 |
4.4.2 Effect of Current | p. 102 |
4.4.3 Effect of Moisture, Temperature, and Chemical Content 102' | |
4.4.4 Surface Material | p. 103 |
Exercises | p. 103 |
5 General Hazards of Electricity | p. 105 |
5.1 Touch Potential | p. 105 |
5.1.1 Touch Potential of Energized Objects | p. 106 |
5.1.2 Touch Potential of Unintentionally Energized Objects | p. 108 |
5.1.3 Touch Potential of De-Energized Objects | p. 115 |
5.2 Step Potential | p. 118 |
Exercises | p. 123 |
6 Induced Voltage due to Electric Field | p. 125 |
6.1 Equipotential Surface | p. 126 |
6.2 Induced Voltage on a Conductor without Field Distortion | p. 128 |
6.2.1 Effect of Line Length on Induced Voltage | p. 132 |
6.2.2 Generalized Method for Short Lines | p. 134 |
6.2.3 Approximate Method for Long Lines | p. 136 |
6.3 Electric Field Distortion due to Earth | p. 140 |
6.3.1 Image Charge | p. 141 |
6.3.2 Error When Earth Effect Is Ignored | p. 146 |
6.3.3 Bundled Conductors | p. 147 |
6.4 Induced Voltage due to Multiple Energized Phases | p. 148 |
6.4.1 Computation of Conductor Charge | p. 151 |
6.4.2 Computational Steps for Induced Voltage on De-Energized Conductors | p. 155 |
6.5 Effect of Line Configuration on Induced Voltage | p. 158 |
6.6 Induced Voltage due to Energized Cables | p. 161 |
Exercises | p. 162 |
7 Induced Voltage due to Magnetic Field | p. 165 |
7.1 Flux and Flux Linkage | p. 165 |
7.2 Induced Voltage due to Single Energized Conductor | p. 168 |
7.3 Induced Voltage due to Multiple Energized Conductors | p. 172 |
7.3.1 Induced Voltage due to Steady-State Current | p. 173 |
7.3.2 Induced Voltage due to Transient Current | p. 177 |
7.4 Induced Voltage due to Electric and Magnetic Fields | p. 179 |
Exercises | p. 181 |
8 De-Energized Line Work | p. 183 |
8.1 Definition of a De-Energized Conductor | p. 183 |
8.2 Methods of Detecting Induced Voltage | p. 185 |
8.3 Main Protection Techniques | p. 186 |
8.3.1 Isolation | p. 186 |
8.3.2 Insulation | p. 187 |
8.3.3 Grounding | p. 188 |
8.4 Grounding System | p. 191 |
8.4.1 Protective Grounds | p. 191 |
8.4.2 Sizing of Temporary Ground Conductors | p. 195 |
8.5 Grounding Methods | p. 197 |
8.5.1 Equipotential Zone | p. 197 |
8.5.1.1 Single-Point Grounding | p. 199 |
8.5.1.2 Bonding to Best Ground at the Site | p. 203 |
8.5.1.3 Single versus Three-Phase Grounding | p. 205 |
8.5.2 Examples of Equipotential Zone Design | p. 206 |
8.5.2.1 Worksite 1: Aerial Work Away from Towers with Isolated Ground Equipment | p. 207 |
8.5.2.2 Worksite 2: Aerial Work near Towers with Isolated Ground Equipment | p. 211 |
8.5.2.3 Worksite 3: Aerial and Ground Work | p. 215 |
8.5.3 Bracketed Grounds | p. 219 |
8.5.4 Circulating Current | p. 223 |
8.6 Case Studies | p. 225 |
8.6.1 Case Study 1 | p. 225 |
8.6.2 Case Study 2 | p. 232 |
8.6.3 Case Study 3 | p. 234 |
8.6.4 Case Study 4 | p. 238 |
8.6.5 Case Study 5 | p. 239 |
8.6.6 Case Study 6 | p. 240 |
Exercises | p. 240 |
9 Live-Line Work | p. 243 |
9.1 Hot Stick Method | p. 243 |
9.2 Insulate and Isolate Method | p. 247 |
9.3 Bare-Hand Method | p. 248 |
9.4 Case Study | p. 253 |
Exercises | p. 255 |
10 Arc Flash | p. 257 |
10.1 Arc Fl ash Phases | p. 257 |
10.1.1 Arc Fault | p. 258 |
10.1.2 Arc Flash | p. 258 |
10.1.3 Arc Blast | p. 258 |
10.2 Assessment of Arc Flash | p. 259 |
10.2.1 Calculation of Arc Flash Current | p. 259 |
10.2.2 Calculation of Incident Energy | p. 261 |
10.3 Calculation of Arc Flash Protection Boundary | p. 263 |
10.4 Personal Protection Equipment | p. 264 |
10.5 Approach Boundaries | p. 266 |
Exercises | p. 268 |
11 Atmospheric Discharge | p. 269 |
11.1 Characteristics of Lightning Discharge | p. 269 |
11.2 Protection from Lightning Strikes | p. 274 |
11.2.1 Lightning Pole and Lightning Discharge Tower | p. 274 |
11.2.2 Overhead Ground Wire | p. 279 |
11.2.3 Surge Arresters | p. 282 |
11.2.4 Spark Gap | p. 284 |
11.3 Safe Distance from Lightning Protection Devices | p. 285 |
Exercises | p. 287 |
12 Stray and Contact Voltages | p. 289 |
12.1 Neutral versus Ground | p. 290 |
12.1.1 Grounding Chassis | p. 294 |
12.1.2 Bonding Chassis to Neutral | p. 296 |
12.1.3 Grounding Chassis and Bonding Ground to Neutral | p. 299 |
12.1.4 Receptacles and Plugs | p. 303 |
12.1.5 Ground Fault Circuit Interrupter | p. 306 |
12.2 Service Transformer | p. 308 |
12.3 Voltage on Neutral Conductor | p. 314 |
12.4 Stray Voltage | p. 315 |
12.4.1 Power Distribution of a Dwelling | p. 316 |
12.4.2 Stray Voltage in Farms | p. 320 |
12.4.3 Stray Voltage in Swimming Pools | p. 322 |
12.4.4 Stray Voltage in Outdoor Showers | p. 328 |
12.4.5 Stray Voltage in Hospitals | p. 331 |
12.4.5.1 Microshock due to Grounded System | p. 331 |
12.4.5.2 Microshock in Isolated System | p. 334 |
12.5 Detection of Stray Voltage | p. 339 |
12.6 Mitigation of Stray Voltage | p. 342 |
12.6.1 Double-Bushing Transformers | p. 342 |
12.6.2 Isolation Transformer | p. 344 |
12.6.3 Neutral Isolator | p. 346 |
12.6.4 Four-Wire System | p. 347 |
12.6.5 Cable Television, Phone Lines, and Metal Pipes | p. 348 |
12.6.6 Equipotential Area | p. 351 |
12.6.7 Reducing Grounding Resistance | p. 355 |
12.7 Mitigation of Stray Voltage in Hospitals | p. 357 |
12.7.1 Equipotential Grounding | p. 358 |
12.7.2 Neutral Isolation | p. 359 |
12.7.3 Protection against Microshock | p. 363 |
12.8 Contact and Structure Voltages | p. 364 |
12.8.1 Light Rail Systems | p. 365 |
12.8.2 Fences and Gates | p. 370 |
12.8.2.1 Effect of Ground Currents | p. 370 |
12.8.2.2 Effect of Electric Coupling | p. 374 |
12.8.3 Street Structures | p. 379 |
12.9 Neutral Deterioration | p. 382 |
12.10 World's Residential Grounding Practices | p. 386 |
12.10.1 Two-Wire System | p. 386 |
12.10.2 Two-Wire Bonded System | p. 387 |
12.10.3 Two-Wire EGC System | p. 387 |
12.10.4 Three-Wire EGC System | p. 388 |
Exercises | p. 389 |
13 Electric Safety under Power Lines | p. 393 |
13.1 Electric Field Calculation | p. 393 |
13.2 Electric Field near Objects | p. 397 |
13.3 Electric Field Profile under Power Lines | p. 403 |
13.4 Allowable Limits for Electric Fields | p. 405 |
13.4.1 Electric Safety Limits | p. 406 |
13.4.2 Health Limits | p. 407 |
13.5 Minimum Vertical Clearance Methods | p. 407 |
13.5.1 Method 1: MVC for Systems with Unknown Switching Surges | p. 408 |
13.5.2 Method 2: MVC for Systems with Voltage Exceeding 98 kV and with Known Switching Surges | p. 409 |
13.6 Measurement of Electric Field Strength | p. 411 |
13.6.1 Free-Body Meter | p. 413 |
13.6.1.1 Dipole Free-Body Meter | p. 413 |
13.6.1.2 Isotropic Free-Body Meter | p. 414 |
13.6.2 Ground-Reference Meter | p. 414 |
13.6.3 Electro-Optic Meter | p. 415 |
13.7 Mitigation of Electric Field | p. 416 |
Exercises | p. 416 |
14 Coupling between Power Lines and Pipelines, Railroads, and Telecommunication Cables | p. 419 |
14.1 Electric Field Coupling | p. 420 |
14.2 Magnetic Field Coupling | p. 423 |
14.2.1 Electrically Continuous Underground Pipeline | p. 426 |
14.2.2 Electrically Discontinuous Underground Pipeline | p. 428 |
14.3 Mitigation of Electromagnetic Coupling | p. 429 |
14.4 Ground Current | p. 430 |
Exercises | p. 434 |
Index | p. 437 |