Ravindra Arora, Dr.-Ing. from TU Dresden, Germany is a Senior Life Member of IEEE and a Life Member of the Institution of Engineers (India). He worked at the Indian Institute of Technology Kanpur (IITK) for 34 years, retiring in 2008. While at IITK, he established a unique high voltage laboratory where he conducted research activity and several industry-sponsored projects. Dr. Arora has over five decades of experience with industry, education, and research where he is still active. His special field of research interest has been "lightning".

Wolfgang Mosch, Dr.-Ing. habil. retired as Head and Chair Professor of the Institute of High Voltage Technology, Electrical Engineering (Power) Division of Technical University Dresden, Germany in 1993. He has been actively involved with practical research in high voltage and insulation engineering for five decades working with both industry and academia since 1960. He has authored a number of books on the subject in German and English languages.

Author Biographies xv

Preface xix

Acknowledgments xxiii

1 Introduction 1

1.1 Electric Charge, Discharge, Current, and Potential 2

1.2 Electric and Magnetic Fields 4

1.3 Electromagnetism 4

1.4 Dielectric and Electrical Insulation 6

1.5 Electrical Breakdown 6

1.5.1 Global Breakdown 7

1.5.2 Local Breakdown or Partial Breakdown 7

1.5.3 Breakdown Strength or Electric Strength 7

1.6 Corona, Streamer, Star, and Leader 7

1.6.1 Aurora 9

1.6.2 Electric Arc 10

1.7 Capacitance and Capacitor 10

1.7.1 Stray Capacitance 11

1.8 Forms of Voltages and Currents 12

1.8.1 TravelingWaves 13

1.8.2 Neutral and Ground 13

References 13

2 Electric Fields, Their Control and Estimation 15

2.1 Electric Field Intensity, "E" 15

2.2 Breakdown and Electric Strength of Dielectrics, "Eb" 18

2.2.1 Partial Breakdown in Dielectrics 18

2.3 Classification of Electric Fields 19

2.3.1 Degree of Uniformity of Electric Fields 21

2.3.1.1 Effect of Grounding on Field Configuration 23

2.4 Control of Electric Field Intensity (Stress Control) 25

2.5 Estimation of Electric Field Intensity 30

2.5.1 Basic Equations for Potential and Field Intensity in Electrostatic Fields 31

2.5.2 Analytical Methods for the Estimation of Electric Field Intensity in Homogeneous Isotropic Single Dielectric 34

2.5.2.1 Direct Solution of Laplace Equation 35

2.5.2.2 "Gaussian Surface" Enclosed Charge Techniques for the Estimation and Optimization of Field 39

2.5.3 Analysis of Electric Field Intensity in Isotropic Multidielectric System 46

2.5.3.1 Field with Longitudinal Interface 46

2.5.3.2 Field with Perpendicular Interface 48

2.5.3.3 Field with Diagonal Interface 53

2.5.4 Numerical Methods for the Estimation of Electric Field Intensity 54

2.5.4.1 Finite Element Method (FEM) 55

2.5.4.2 Charge Simulation Method (CSM) 62

2.5.5 Numerical Optimization of Electric Fields 69

2.5.5.1 Optimization by Displacement of Contour Points 70

2.5.5.2 Optimization by Changing the Positions of Optimization Charges and Contour Points 71

2.5.5.3 Optimization by Modification of "Contour Elements" 73

2.6 Conclusion 75

References 76

3 Field Dependent Behavior of Air and Other Gaseous Dielectrics 79

3.1 Fundamental Process of Field Assisted Generation of Charge Carriers 83

3.1.1 Impact Ionization 85

3.1.2 Thermal Ionization 86

3.1.3 Photoionization and Interaction of Metastables with Molecules 86

3.2 Breakdown of Atmospheric Air in Uniform andWeakly Nonuniform Fields 88

3.2.1 Uniform Field with Space Charge 89

3.2.2 Development of Electron Avalanche 91

3.2.3 Development of Streamer or "Kanal Discharge" 96

3.2.4 Breakdown Mechanisms 99

3.2.4.1 Breakdown in Uniform Fields with Small Gap Distances (Townsend Mechanism) 99

3.2.4.2 Breakdown with Streamer (Streamer or Kanal Mechanism) 106

3.2.5 Breakdown Voltage Characteristics in Uniform Fields (Paschen's Law) 111

3.2.6 Breakdown Voltage Characteristics inWeakly Nonuniform Fields 122

3.3 Breakdown in Extremely Nonuniform Fields and Corona 123

3.3.1 Development of Avalanche Discharge of Below Critical Amplification 124

3.3.1.1 Positive Needle-Plane Electrode Configuration (Positive or Anode Star Corona) 125

3.3.1.2 Negative Needle-Plane Electrode Configuration (Negative or Cathode Star Corona) 127

3.3.2 Development of Streamer or Kanal Discharge 129

3.3.2.1 Positive Rod-Plane Electrode (Positive Streamer Corona) 129

3.3.2.2 Negative Rod-Plane Electrode (Negative Streamer Corona) 134

3.3.2.3 Symmetrical Positive and Negative Electrode Configurations in Extremely Nonuniform Fields 136

3.3.3 Development of Stem and Leader Corona 137

3.3.3.1 Development and Propagation of Positive Leader Corona 141

3.3.3.2 Development and Propagation of Negative Leader Corona and the Phenomenon of Space Leader 144

3.3.3.3 Electromagnetic Interference (EMI) Produced by Corona 147

3.3.4 Summary of the Development of Breakdown in Extremely Nonuniform Fields 148

3.3.5 Breakdown Voltage Characteristics of Air in Extremely Nonuniform Fields 150

3.3.5.1 Breakdown Preceded with Stable Star Corona 152

3.3.5.2 Breakdown Preceded with Stable Streamer Corona 156

3.3.5.3 Breakdown Preceded with Stable Streamer and Leader Coronas (Long Air Gaps) 163

3.3.5.4 The Requirement of Time for the Formation of Spark Breakdown with Impulse Voltages 168

3.3.5.5 Effect of Wave Shape on Breakdown with Impulse Voltages 171

3.3.5.6 Conclusions from Measured Breakdown Characteristics in Extremely Nonuniform Fields 175

3.3.5.7 Estimation of Breakdown Voltage in Extremely Nonuniform Fields in Long Air Gaps 176

3.3.6 Effects of Partial Breakdown or Corona in Atmospheric Air 178

3.3.6.1 Chemical Decomposition of Air by Corona 179

3.3.6.2 Corona Power Loss in Transmission Lines 182

3.3.6.3 Electromagnetic Interference (EMI) and Audible Noise (AN) Produced by Power System Network 184

3.3.6.4 Other Effects of High Voltage Transmission Lines and Corona on the Environment 187

3.4 Electric Arcs and Their Characteristics 188

3.4.1 Static Voltage-Current, U-I, Characteristics of Arcs in Air 189

3.4.2 Dynamic U-I Characteristics of Arcs 192

3.4.3 Extinction of Arcs 194

3.5 Properties of Sulfurhexafluoride, SF6, Gas, and Its Application in Electrical Installations 194

3.5.1 Properties of Sulfurhexafluoride, SF6 Gas 197

3.5.1.1 Physical Properties 199

3.5.1.2 Property of Electron Attachment 199

3.5.2 Breakdown in Uniform and Weakly Nonuniform Fields with SF6 Insulation 201

3.5.3 External Factors Affecting Breakdown Characteristics in Compressed Gases 210

3.5.3.1 Effect of Electrode Materials and Their Surface Roughness on Breakdown 210

3.5.3.2 Effect of Particle Contaminants in Gas Insulated Systems (GIS) 212

3.5.3.3 Particle Initiated PB and Breakdown Measurements in GIS 219

3.5.3.4 Preventive Measures for the Effect of Particles in GIS 222

3.5.4 Breakdown in Extremely Nonuniform and Distorted Weakly Nonuniform Fields with Stable PB in SF6 Gas Insulation 222

3.5.5 Electrical Strength of Mixtures of SF6 with Other Gases 226

3.5.6 Decomposition of SF6 and Its Mixtures in Gas Insulated Equipment 230

3.5.7 SF6 Gas and Environment 234

3.5.8 Development in Gas Insulated Power Apparatus 236

3.5.9 Mineral Oils Versus SF6 Gas 236

3.5.10 Basic Electrical Insulation Requirements for GITs 238

3.5.11 SF6 Gas Insulation, a Replacement for Oils 239

3.5.12 Basic Cooling Requirements Met by Gas for GITs 240

3.5.13 Environment Concerns and Future Trends 241

3.6 Investigations for the Requirement of Optimum Clearance for 25 kV Electric Traction: A Case Study 242

3.6.1 Field Estimation for the Traction Overhead Conductor at 25 kV 243

3.6.2 Measurement of Breakdown/Withstand Voltage Characteristics 247

3.6.3 Measurements with ac Power Frequency Voltage 247

3.6.4 Measurements Under FairWeather, Natural Fog, and Natural Rain Conditions 248

3.6.5 Measurements Under Artificial Rain 249

3.6.6 Investigation of the Performance of Air-Gap Under System Overvoltages 250

3.6.7 Measurements with Impulse Voltages 252

3.6.8 Measurements with Insulating-Barrier in the Gap 253

3.6.9 Choice of Solid Insulating Barrier 253

3.6.10 Positioning and Fastening of the Solid Insulating Barrier in the Gap 254

3.6.11 Measurement Results with Teflon Sheet as a Barrier 254

3.7 Conclusions and Recommendations 255

References 257

4 Lightning and Ball Lightning, Development Mechanisms, Deleterious Effects, Protection 267

4.1 The Globe, a Capacitor 268

4.1.1 The Earth's Atmosphere and the Clouds 269

4.1.1.1 The Troposphere 270

4.1.1.2 The Stratosphere 270

4.1.1.3 The Ionosphere 271

4.1.2 Clouds and Their Important Role 271

4.1.2.1 Classification of Clouds 271

4.1.3 Static Electric Charge in the Atmosphere 273

4.1.3.1 External Source of Electric Charge 273

4.1.3.2 Charges Due to Ionization Within the Atmospheric Air 275

4.1.3.3 Charging Mechanisms and Thunderstorms 276

4.2 Mechanisms of Lightning Strike 278

4.2.1 Mechanism of Breakdown in Long Air Gap 278

4.2.2 Mechanisms of Lightning Strike on the Ground 280

4.2.3 Preference of Locations for the Lightning to Strike 282

4.3 Deleterious Effects of Lightning 284

4.3.1 Loss of Life of the Living Beings 284

4.3.2 Fire Hazards Due to Lightning 284

4.3.3 Blast Created by Lightning 285

4.3.4 Development of Transient Over-Voltage Due to Lightning Strike on the Electric Power System Network and Its Protection 286

4.4 Protection from Lightning 288

4.4.1 Protection of Lives 289

4.4.2 Protection of Buildings and Structures 290

4.4.2.1 Air Termination Network 291

4.4.2.2 Down Conductor 292

4.4.2.3 Earth Termination System 292

4.4.3 The Protected Area 292

4.4.3.1 Protected Volume Determined by a Cone 292

4.4.3.2 Protected Volume Evolved by Rolling a Sphere 293

4.5 Ball Lightning 295

4.5.1 The Phenomenon of Ball Lightning 295

4.5.2 Injurious Effects of Ball Lightning 296

4.5.3 Models and Physics of Ball Lightning 296

4.5.4 Ball Lightning Without...