Gas Discharge and Gas Insulation (eBook)

Preface 6
Contents 8
Chapter 1: Introduction 13
1.1 Definition and Content of Gas Discharge 13
1.2 History of Electrical Discharge Research 14
1.3 Classification of the Discharge 16
1.4 Application of the Discharge 18
1.5 Definition and Content of Gas Insulation 20
1.6 History and Application of Sulfur Hexafluoride 21
1.7 Situation and Development of Environmentally Friendly Insulating Gas 24
References 29
Chapter 2: Fundamentals of Gas Discharge 30
2.1 Charged Particles in the Process of Gas Discharge 30
2.1.1 Photons 31
2.1.2 Electrons 32
2.1.3 Ground State Atoms (or Molecules) and Excited Atoms (or Molecules) 33
2.1.4 Positive and Negative Ions 36
2.2 Movement of Charged Particles 37
2.2.1 Thermal Motion of Charged Particles 37
2.2.2 Diffusion Motion of Charged Particles 39
2.2.3 Drift Motion of Charged Particles 40
2.3 Collision Interactions of Charged Particles 45
2.3.1 Classification of Collision Between Particles 45
2.3.2 Collision Energy Transfer 46
2.3.2.1 Energy Transfer in Elastic Collision 46
2.3.2.2 Energy Transfer in Inelastic Collision 47
2.3.3 Collision Characteristic Parameters 47
2.3.3.1 Collision Cross Section 47
2.3.3.2 Probability of Collision and Collision Frequency 49
2.3.4 Elastic Collisions of Electrons, Ions and Atoms 49
2.3.5 Excitation and Ionization of Gas Atoms 50
2.3.6 Gas Particle Excitation Transferring 52
2.3.7 Disappearance of Charged Particles 53
2.3.7.1 Charged Particles´ Recombination 53
2.3.7.2 Charged Particles´ Diffusion 54
2.3.7.3 Charge Transferring of Charged Particles 55
2.3.7.4 Anion Formation and Attachment Process 55
References 56
Chapter 3: Fundamental Theory of Townsend Discharge 57
3.1 Formation and Development of Electronic Avalanche 57
3.1.1 Formation of Electronic Avalanche 57
3.1.2 ? Process 60
3.1.3 gamma Process 63
3.2 Self-Sustaining Discharge Criterion 64
3.2.1 Gas Discharge Volt-Ampere Characteristics 64
3.2.2 From Non-Self-Sustaining to Self-Sustaining Discharge 67
3.2.3 The Condition of Self-Sustained Discharge 68
3.3 Paschen´s Law 69
3.3.1 Paschen´s Law 69
3.3.2 The Impact of Impurity Gases on the Breakdown Potential 72
3.3.3 The Impact of Electrodes on Breakdown Voltage 77
3.3.4 The Impact of Electric Field Distribution on Breakdown Voltage 78
3.3.5 The Impact of External Ionization Source on Breakdown Potential 79
3.4 Townsend Discharge Experiments 79
3.4.1 The Steady-State Townsend Experiment (SST) 80
3.4.1.1 SST Experimental Principles and Measuring Circuit [3] 81
3.4.1.2 The Establishment of SST Mathematical Model and Solving Method of Discharging Parameters 83
3.4.1.3 SST Experimental Apparatus 85
3.4.2 Pulse Townsend Method (PT) 87
3.4.2.1 Principle Law and Basic Circuit of PT Method 88
3.4.2.2 The Establishment of PT Mathematical Model [3, 4] 90
3.4.2.3 The Calculation of Initial Electrons Distribution 94
3.4.2.4 Solution Method of Electrons Avalanche Parameters 94
3.4.2.5 Experimental Apparatus of PT Method [3] 95
References 98
Chapter 4: Fundamental Theory of Streamer and Leader Discharge 99
4.1 Streamer Discharge Mechanism 99
4.1.1 Basic Properties of Spark Discharge 100
4.1.1.1 Characteristics of Spark Discharge 100
4.1.1.2 Types of Spark Discharge 100
4.1.1.3 Streamer 101
4.1.1.4 Common Circuits for Spark Discharge 101
4.1.2 Streamer Discharge 103
4.1.2.1 Limitation of Townsend Discharge Theory 103
4.1.2.2 Introduction of Streamer Theory 105
4.1.2.3 Criterions of Streamer 106
4.1.2.4 Qualitative Description of Streamer Theory 110
4.1.2.5 Mechanism of Streamer Formation 115
4.1.2.6 Explanations for Different Phenomena by Streamer Theory 119
4.1.2.7 The Effect of Water Molecules on the Streamer Development 120
4.1.2.8 Transition Between Townsend Discharge and Streamer Discharge 121
4.2 Long Gap and Leader Discharge 123
4.2.1 Experimental Study on the Long Gap Discharge in Air 123
4.2.2 Discharge Process in Non-uniform Electric Field 124
References 131
Chapter 5: Theoretic Analysis Methods for Modeling Gas Discharge 132
5.1 Monte Carlo Simulation 132
5.1.1 Introduction of General Monte Carlo Simulation 132
5.1.1.1 Monte Carlo Simulation Model for Electron Avalanche in a Single Gas 132
5.1.1.2 Monte Carlo Simulation Model for Electron Avalanche in Gas Mixtures 136
5.1.2 Monte Carlo Simulation of Electron Avalanche Development 137
5.1.2.1 Initializing of the Simulated Electron 137
5.1.2.2 The Null-Collision Technique 137
5.1.2.3 Determining the Probability and the Type of Collision 138
5.1.2.4 The Scattering Parameters After Collision 138
5.1.2.5 Sampling the Electron Swarm Parameters 139
5.1.3 Electron Swarm Parameters from Monte Carlo Simulation 140
5.1.3.1 Simulation of Avalanche Discharge in SF6 140
5.1.3.2 Simulation of Avalanche Discharge in c-C4F8 Gas Mixtures 142
5.2 Boltzmann Equation Method 149
5.2.1 Introduction to Boltzmann Equation Method 149
5.2.2 Electron Swarm Parameters Calculated by Boltzmann Equation Method 151
5.2.2.1 Collision Cross Sections of CO2 and SF6 152
5.2.2.2 Comparison Between the Calculated and Experimental Results of Electron Swarm Parameters in Pure SF6 Gas and SF6/CO2 Ga... 153
References 155
Chapter 6: Dielectric Strength of Atmosphere Air 157
6.1 Breakdown Voltage Characteristics in Uniform and Quasi-uniform Electric Fields 158
6.1.1 Breakdown Characteristics Under Continuous Voltages 158
6.1.2 Breakdown Characteristics Under Lightning Impulse Voltages 162
6.1.2.1 Basic Conceptions of Lightning Discharge 162
6.1.2.2 Lightning Impulse Voltage Standard Waveform 165
6.1.2.3 Discharge Time Lag 166
6.1.2.4 Fifty Percent Breakdown Voltage 168
6.1.2.5 Breakdown Characteristics in Uniform and Weakly Nonuniform Electric Fields 169
6.1.3 Breakdown Characteristics Under Operating Impulse Voltage 169
6.1.3.1 Formation of the Operating Impulse Voltage 169
6.1.3.2 Operating Impulse Voltage Standard Waveform 170
6.1.3.3 Breakdown Characteristics in Uniform and Weakly Nonuniform Electric Fields 171
6.2 Breakdown Characteristics in Extremely Nonuniform Electric Fields 172
6.2.1 Breakdown Characteristics Under Continuous Voltage 172
6.2.1.1 Breakdown Voltage Under DC Voltage 172
6.2.1.2 Breakdown Voltage Under Power Frequency AC Voltage 174
6.2.2 Breakdown Characteristics Under Lightning Impulse Voltage 176
6.2.2.1 Breakdown Voltage in Extremely Nonuniform Electric Fields 176
6.2.2.2 Volt-Second Characteristics 178
6.2.3 Breakdown Voltage Under Operating Impulse Voltage 184
6.2.3.1 Polarity Effect 184
6.2.3.2 Influence of the Electric Field Distribution 185
6.2.3.3 Influence of the Waveform and U-Shaped Curve 185
6.2.3.4 Large Dispersion 187
6.2.3.5 Saturation 187
6.2.3.6 Empirical Formula for the Minimum Breakdown Voltage 187
6.3 Methods to Improve Insulation Strength in Air 188
6.3.1 Improve the Shape of Electrodes 188
6.3.2 Use of Electric Field Distortion by Space Charges 190
6.3.3 Use of Barrier in Extremely Nonuniform Electric Fields 193
6.3.4 Solid Insulating Coating Layer 197
6.3.5 Use of High Pressure 197
6.3.6 Use of High Vacuum 199
6.3.7 Use of High-Dielectric-Strength Gases 200
6.3.7.1 High-Dielectric-Strength Gases 200
6.3.7.2 Reasons for the High Dielectric Strength of Halide Gas 201
References 202
Chapter 7: Insulation Characteristics of Sulfur Hexafluoride (SF6) 203
7.1 Basic Physical and Chemical Properties of SF6 203
7.1.1 Molecular Structure 203
7.1.2 Gas State Parameters 204
7.1.3 Electronegativity and Thermal Performance 207
7.1.4 Decomposition of SF6 209
7.2 Breakdown Characteristics of SF6 212
7.2.1 Breakdown Characteristics in Uniform Electric Fields 212
7.2.2 Breakdown Characteristics in Quasi-uniform Fields 213
7.2.3 Breakdown Characteristics in Extremely Non-uniform Fields 214
7.3 Surface Discharge Characteristics of Solid Insulators in SF6 217
7.3.1 Effects of Electric Field Distribution 218
7.3.2 Other Factors Affecting Solid Surface Discharge Characteristics 220
7.4 Factors Affecting Insulation Properties of SF6 226
7.4.1 Effects of Gas Pressure on Breakdown Voltage of SF6 226
7.4.2 Effect of Electric Field Uniformity on Breakdown Voltage of SF6 [4] 228
7.4.3 Effect of Polarity on Breakdown Voltage of SF6 230
7.4.4 Effect of Surface Roughness on Breakdown Voltage of SF6 234
References 237
Chapter 8: Insulating Characteristics of SF6 Gas Mixtures 238
8.1 Improvements of Gas Mixtures on Defects of SF6 238
8.1.1 Liquefaction Temperature 238
8.1.2 Insulating Properties 240
8.1.2.1 Relative Electric Strength 240
8.1.2.2 Influence of Electric Field Uniformity 243
8.1.2.3 Very Fast Transient Overvoltage Problems of GIS 244
8.1.3 Cost of Gas 244
8.1.4 Environmental Protection 245
8.2 Mixing Characteristics of SF6 Gas Mixtures 245
8.2.1 Mixing Ratio 245
8.2.2 Changes of Mixing Ratio with Height 246
8.2.3 Mixing Process 248
8.2.4 Recovery of Gas Mixtures 248
8.2.4.1 Liquefaction Method 248
8.2.4.2 PSA Method 249
8.2.4.3 Polymer Film Method 249
8.3 Insulation Properties of Binary Mixtures of SF6 with Other Gases [2] 250
8.3.1 Electrical Strength of SF6/N2 Gas Mixtures 250
8.3.1.1 Uniform Electric Field 250
8.3.1.2 Non-Uniform Electric Field 255
8.3.1.3 Practical Application 257
8.3.2 Electrical Strength of SF6/CO2 Gas Mixtures 257
8.3.2.1 Uniform Electric Field 257
8.3.2.2 Non-Uniform Electric Field 262
8.3.3 Contrast Between SF6/N2 and SF6/CO2 263
8.4 Other Multivariate SF6 Gas Mixtures 264
8.4.1 SF6/He and SF6/Ne Gas Mixtures 264
8.4.2 SF6/Ar, SF6/Kr and SF6/Xe Gas Mixtures 267
8.4.3 Gas Mixtures Consisting of SF6 and Gases Containing Halogen Elements 272
8.4.3.1 Perfluorocarbon (CF4) 272
8.4.3.2 Octafluorocyclobutane (c-C4F8) 275
References 277
Chapter 9: Insulating Characteristics of Potential Alternatives to Pure SF6 278
9.1 Research Advances on Substitutes for SF6 278
9.1.1 Significance of Research 278
9.1.2 Current Research on Alternatives to SF6 Gas 281
9.1.2.1 Current Research Around the World 281
9.1.2.2 Research in China 283
9.2 Insulation Properties of c-C4F8 and Its Gas Mixtures 284
9.2.1 c-C4F8/CO2 Discharge Characteristics and Analysis 285
9.2.2 c-C4F8/CF4 Discharge Characteristics and Analysis 288
9.2.3 c-C4F8/N2 Discharge Characteristics and Analysis 290
9.2.4 c-C4F8/N2O Discharge Characteristics and Analysis 292
9.2.5 The Influence of CO2, CF4, N2 and N2O on the (E/N)lim of c-C4F8 295
9.3 Insulation Performance of CF3I and Its Gas Mixtures 296
9.3.1 Insulation Performance Analysis of CF3I 297
9.3.2 Feasibility Analysis of CF3I and Its Gas Mixtures Used in C-GIS 301
9.4 Insulation Performance of Other Potential Alternative Gas 304
9.4.1 Perfluoropropane (C3F8) 304
9.4.1.1 C3F8/N2 Gas Mixture 307
9.4.1.2 Pay Attention To Problems in Practical Application 309
9.4.2 Nitrous Oxide (N2O) 310
9.4.3 Trifluoromethane (CHF3) 311
9.4.4 Fluorinated Carbon (CF4) 313
Reference 316
Chapter 10: Development Prospects of Gas Insulation 317
10.1 Three Stages of Development of Gas Insulation 317
10.1.1 Application and Development of Pure SF6 Gas 320
10.1.2 Application and Development of SF6 Gas Mixtures 322
10.1.3 Development of Research on Environmentally Friendly Insulation Gas 324
10.2 Research and Development of c-C4F8 and Its Gas Mixtures 330
10.2.1 Properties of c-C4F8 330
10.2.2 Further Research on c-C4F8 and Its Mixtures Discharge Mechanism 333
10.2.2.1 Electrical Breakdown Model of Gas Mixtures 334
10.2.2.2 Improved Electrical Breakdown Model of Gas Mixtures 336
10.2.2.3 Proof of Gas Mixtures Breakdown Voltage Model 341
10.2.2.4 Boiling Point of c-C4F8 Mixture 343
10.2.2.5 Calculation of GWP Value in Gas Mixtures 343
10.2.2.6 AC Breakdown Voltage as a Function of Gas Pressure in c-C4F8 and N2 Gas Mixtures 344
10.2.2.7 AC Breakdown Voltage as a Function of Gas Pressure in c-C4F8/CO2 Gas Mixtures 348
10.2.2.8 Comparison of Dielectric Strength as a Function of Pressure in c-C4F8 Gas Mixtures and SF6/N2 Gas Mixtures 351
10.2.2.9 Comparison of Dielectric Strength in c-C4F8 Gas Mixtures and SF6/N2 at Different Mixing Ratios 353
10.2.3 The Application and Development of c-C4F8 and Its Gas Mixtures 355
10.3 Study and Development of CF3I and Its Gas Mixtures 357
10.3.1 Physical Properties of CF3I Gas 357
10.3.2 Further Study on Insulation Properties of CF3I Gas 358
10.3.3 Research Tendency and Application of CF3I and Its Gas Mixtures 363
References 365
Index 366