Książki

The book is written for students as well as for teachers and researchers in the field of High Voltage and Insulation Engineering. It is based on the advance level courses conducted at TU Dresden, Germany and Indian Institute of Technology Kanpur, India. The book has a novel approach describing the fundamental concept of field dependent behavior of dielectrics subjected to high voltage. There is no other book in the field of high voltage engineering following this new approach in describing the behavior of dielectrics. The contents begin with the description of fundamental terminology in the subject of high voltage engineering. It is followed by the classification of electric fields and the techniques of field estimation. Performance of gaseous, liquid and solid dielectrics under different field conditions is described in the subsequent chapters. Separate chapters on vacuum as insulation and the lightning phenomenon are included.

High Voltage and Electrical Insulation Engineering

PREFACE xi

ACKNOWLEDGMENTS xv

CHAPTER 1 INTRODUCTION 1

1.1 Electric Charge and Discharge 2

1.2 Electric and Magnetic Fields and Electromagnetics 3

1.3 Dielectric and Electrical Insulation 5

1.4 Electrical Breakdown 5

1.4.1 Global Breakdown 6

1.4.2 Local Breakdown 6

1.5 Corona, Streamer and Aurora 6

1.6 Capacitance and Capacitor 8

1.6.1 Stray Capacitance 9

References 10

CHAPTER 2 ELECTRIC FIELDS, THEIR CONTROL AND ESTIMATION 11

2.1 Electric Field Intensity, "E" 11

2.2 Breakdown and Electric Strength of Dielectrics, "Eb" 13

2.2.1 Partial Breakdown in Dielectrics 14

2.3 Classifi cation of Electric Fields 15

2.3.1 Degree of Uniformity of Electric Fields 17

2.4 Control of Electric Field Intensity (Stress Control) 20

2.5 Estimation of Electric Field Intensity 25

2.5.1 Basic Equations for Potential and Field Intensity in Electrostatic Fields 26

2.5.2 Analytical Methods for the Estimation of Electric Field Intensity in Homogeneous Isotropic Single Dielectric 29

2.5.3 Analysis of Electric Field Intensity in Isotropic Multidielectric System 38

2.5.4 Numerical Methods for the Estimation of Electric Field Intensity 48

2.5.5 Numerical Optimization of Electric Fields 61

2.6 Conclusion 66

References 67

CHAPTER 3 FIELD DEPENDENT BEHAVIOR OF AIR AND OTHER GASEOUS DIELECTRICS 69

3.1. Fundamentals of Field Assisted Generation of Charge Carriers 71

3.1.1 Impact Ionization 74

3.1.2 Thermal Ionization 75

3.1.3 Photoionization and Interaction of Metastables with Molecules 76

3.2 Breakdown of Atmospheric Air in Uniform and Weakly Nonuniform Fields 77

3.2.1 Uniform Field with Space Charge 78

3.2.2 Development of Electron Avalanche 80

3.2.3 Development of Streamer or "Kanal Discharge" 86

3.2.4 Breakdown Mechanisms 87

3.2.5 Breakdown Voltage Characteristics in Uniform Fields (Paschen's Law) 99

3.2.6 Breakdown Voltage Characteristics in Weakly Nonuniform Fields 108

3.3 Breakdown in Extremely Nonuniform Fields and Corona 109

3.3.1 Development of Avalanche Discharge 110

3.3.2 Development of Streamer or Kanal Discharge 114

3.3.3 Development of Stem and Leader Corona 122

3.3.4 Summary of the Development of Breakdown in Extremely Nonuniform Fields 132

3.3.5 Breakdown Voltage Characteristics of Air in Extremely Nonuniform Fields 134

3.3.6 Effects of Partial Breakdown or Corona in Atmospheric Air 159

3.4 Electric Arcs and Their Characteristics 168

3.4.1 Static Voltage-Current, U-I, Characteristics of Arcs in Air 169

3.4.2 Dynamic U-I Characteristics of Arcs 171

3.4.3 Extinction of Arcs 173

3.5 Properties of Sulphurhexafl uoride, SF6 Gas and Its Application in Electrical Installations 174

3.5.1 Properties of Sulphurhexafl uoride, SF6 Gas 176

3.5.2 Breakdown in Uniform and Weakly Nonuniform Fields with SF6 Insulation 180

3.5.3 External Factors Affecting Breakdown Characteristics in Compressed Gases 187

3.5.4 Breakdown in Extremely Nonuniform and Distorted Weakly Nonuniform Fields with Stable PB in SF6 Gas Insulation 199

3.5.5 Electrical Strength of Mixtures of SF6 with Other Gases 202

3.5.6 Decomposition of SF6 and Its Mixtures in Gas Insulated Equipment 206

3.5.7 SF6 Gas and Environment 209

References 211

CHAPTER 4 LIGHTNING AND BALL LIGHTNING, DEVELOPMENT MECHANISMS, DELETERIOUS EFFECTS, PROTECTION 217

4.1 The Globe, A Capacitor 218

4.1.1 The Earth's Atmosphere and the Clouds 219

4.1.2 Clouds and Their Important Role 221

4.1.3 Static Electric Charge in the Atmosphere 223

4.2 Mechanisms of Lightning Strike 227

4.2.1 Mechanisms of Breakdown in Long Air Gap 228

4.2.2 Mechanisms of Lightning Strike on the Ground 229

4.2.3 Preference of Locations for the Lightning to Strike 231

4.3 Deleterious Effects of Lightning 232

4.3.1 Loss of Life of the Living Beings 233

4.3.2 Fire Hazards Due to Lightning 233

4.3.3 Blast Created by Lightning 233

4.3.4 Development of Transient Over-Voltage Due to Lightning Strike on the Electric Power System Network and Its Protection 234

4.4 Protection from Lightning 236

4.4.1 Protection of Lives 237

4.4.2 Protection of Buildings and Structures 238

4.4.3 The Protected Area 240

4.5 Ball Lightning 242

4.5.1 The Phenomenon of Ball Lightning 243

4.5.2 Injurious Effects of Ball Lightning 243

4.5.3 Models and Physics of Ball Lightning 244

4.5.4 Ball Lightning without Lightning Strike 245

References 247

CHAPTER 5 ELECTRICAL PROPERTIES OF VACUUM AS HIGH VOLTAGE INSULATION 249

5.1 Pre-breakdown Electron Emission in Vacuum 250

5.1.1 Mechanism of Electron Emission from Metallic Surfaces 250

5.1.2 Non-Metallic Electron Emission Mechanisms 253

5.2 Pre-Breakdown Conduction and Spark Breakdown in Vacuum 258

5.2.1 Electrical Breakdown in Vacuum Interrupters 265

5.2.2 Effect of Conditioning of Electrodes on Breakdown Voltage 267

5.2.3 Effect of Area of Electrodes on Breakdown in Vacuum 268

5.3 Vacuum as Insulation in Space Applications 269

5.3.1 Vacuum-Insulated Power Supplies for Space 270

5.3.2 Vacuum Related Problems in Low Earth Orbit Plasma Environment 270

5.4 Conclusion 271

References 272

CHAPTER 6 LIQUID DIELECTRICS, THEIR CLASSIFICATION, PROPERTIES, AND BREAKDOWN STRENGTH 275

6.1 Classifi cation of Liquid Dielectrics 276

6.1.1 Mineral Insulating Oils 277

6.1.2 Vegetable Oils 278

6.1.3 Synthetic Liquid Dielectrics, the Chlorinated Diphenyles 280

6.1.4 Inorganic Liquids as Insulation 282

6.1.5 Polar and Nonpolar Dielectrics 282

6.2 Dielectric Properties of Insulating Materials 283

6.2.1 Insulation Resistance Offered by Dielectrics 283

6.2.2 Permittivity of Insulating Materials 285

6.2.3 Polarization in Insulating Materials 286

6.2.4 Dielectric Power Losses in Insulating Materials 293

6.3 Breakdown in Liquid Dielectrics 296

6.3.1 Electric Conduction in Insulating Liquids 297

6.3.2 Intrinsic Breakdown Strength 301

6.3.3 Practical Breakdown Strength Measurement at Near Uniform Fields 302

6.3.4 Breakdown in Extremely Nonuniform Fields and the Development of Streamer 307

6.4 Aging in Mineral Insulating Oils 313

References 316

CHAPTER 7 SOLID DIELECTRICS, THEIR SOURCES, PROPERTIES, AND BEHAVIOR IN ELECTRIC FIELDS 319

7.1 Classifi cation of Solid Insulating Materials 320

7.1.1 Inorganic Insulating Materials 320

7.1.2 Polymeric Organic Materials 323

7.1.3 Composite Insulating System 333

7.2 Partial Breakdown in Solid Dielectrics 337

7.2.1 Internal Partial Breakdown 337

7.2.2 Surface Discharge (Tracking) 345

7.2.3 Degradation of Solid Dielectrics Caused by PB 347

7.2.4 Partial Breakdown Detection and Measurement 349

7.3 Breakdown and Pre-Breakdown Phenomena in Solid Dielectrics 351

7.3.1 Intrinsic Breakdown Strength of Solid Dielectrics 352

7.3.2 Thermal Breakdown 355

7.3.3 Mechanism of Breakdown in Extremely Nonuniform Fields 359

7.3.4 "Treeing" a Pre-Breakdown Phenomenon in Polymeric Dielectrics 360

7.3.5 Requirement of Time for Breakdown 363

7.3.6 Estimation of Life Expectancy Characteristics 366

7.3.7 Practical Breakdown Strength and Electric Stress in Service of Solid Dielectrics 368

References 369

INDEX 371