Table of Contents
Preface xv
1 Switching in Power Systems 1
1.1 Introduction 1
1.2 Organization of this Book 2
1.3 Power-System Analysis 5
1.4 Purpose of Switching 8
1.4.1 Isolation and Earthing 8
1.4.2 Busbar-Transfer Switching 8
1.4.3 Load Switching 8
1.4.4 Fault-Current Interruption 9
1.5 The Switching Arc 10
1.6 Transient Recovery Voltage (TRV) 14
1.6.1 TRV Description 14
1.6.2 TRV Composed of Load- and Source-Side Contributions 16
1.7 Switching Devices 19
1.8 Classification of Circuit-Breakers 22
References 27
2 Faults in Power Systems 28
2.1 Introduction 28
2.2 Asymmetrical Current 30
2.2.1 General Terms 30
2.2.2 DC Time Constant 33
2.2.3 Asymmetrical Current in Three-Phase Systems 34
2.3 Short-Circuit Current Impact on System and Components 35
2.4 Fault Statistics 43
2.4.1 Occurrence and Nature of Short-Circuits 43
2.4.2 Magnitude of Short-Circuit Current 45
References 46
3 Fault-Current Breaking and Making 48
3.1 Introduction 48
3.2 Fault-Current Interruption 48
3.3 Terminal Faults 49
3.3.1 Introduction 49
3.3.2 Three-Phase Current Interruption 51
3.4 Transformer-Limited Faults 58
3.4.1 Transformer Modelling for TRV Calculation 59
3.4.2 External Capacitances 61
3.5 Reactor-Limited Faults 62
3.6 Faults on Overhead Lines 64
3.6.1 Short-Line Faults 64
3.6.2 Long-Line Faults 81
3.7 Out-of-Phase Switching 81
3.7.1 Introduction 81
3.7.2 Switching between Generator and System 83
3.7.3 Switching between Two Systems 85
3.8 Fault-Current Making 86
3.8.1 Impact of Making a Short-Circuit Current on the Circuit-Breaker 86
3.8.2 Switching-Voltage Transients at Making in Three-Phase Systems 88
References 93
4 Load Switching 96
4.1 Normal-Load Switching 96
4.2 Capacitive-Load Switching 97
4.2.1 Introduction 97
4.2.2 Single-Phase Capacitive-Load Switching 98
4.2.3 Three-Phase Capacitive-Load Switching 104
4.2.4 Late Breakdown Phenomena 104
4.2.5 Overhead-Line Switching 114
4.2.6 Capacitor-Bank Energization 118
4.3 Inductive-Load Switching 122
4.3.1 Current Chopping 124
4.3.2 Implication of Current Chopping 125
4.3.3 Inductive-Load Switching Duties 127
References 138
5 Calculation of Switching Transients 141
5.1 Analytical Calculation 141
5.1.1 Introduction 141
5.1.2 Switching LR Circuits 142
5.1.3 Switching RLC Circuits 147
5.2 Numerical Simulation of Transients 153
5.2.1 Historical Overview 153
5.2.2 The Electromagnetic Transients Program 154
5.2.3 Overview of Electrical Programs for Transient Simulation 159
5.3 Representation of Network Elements when Calculating Transients 160
References 162
6 Current Interruption in Gaseous Media 164
6.1 Introduction 164
6.2 Air as an Interrupting Medium 166
6.2.1 General 166
6.2.2 Fault-Current Interruption by Arc Elongation 167
6.2.3 Arc Chutes 171
6.2.4 Arcs in Open Air 174
6.2.5 Current Interruption by Compressed Air 175
6.3 Oil as an Interrupting Medium 176
6.3.1 Introduction 176
6.3.2 Current Interruption in Bulk-Oil Circuit-Breakers 177
6.3.3 Current Interruption in Minimum-Oil Circuit-Breakers 180
6.4 Sulfur Hexafluoride (SF6) as an Interrupting Medium 181
6.4.1 Introduction 181
6.4.2 Physical Properties 182
6.4.3 SF6 Decomposition Products 186
6.4.4 Environmental Effects of SF6 189
6.4.5 SF6 Substitutes 195
6.5 SF6 – N2 Mixtures 197
References 198
7 Gas Circuit-Breakers 202
7.1 Oil Circuit-Breakers 202
7.2 Air Circuit-Breakers 205
7.3 SF6 Circuit-Breakers 207
7.3.1 Introduction 207
7.3.2 Double-Pressure SF6 Circuit-Breakers 210
7.3.3 Puffer-Type SF6 Circuit-Breakers 210
7.3.4 Self-Blast SF6 Circuit-Breakers 215
7.3.5 Double-Motion Principle 218
7.3.6 Double-Speed Principle 220
7.3.7 SF6 Circuit-Breakers with Magnetic Arc Rotation 221
References 222
8 Current Interruption in Vacuum 223
8.1 Introduction 223
8.2 Vacuum as an Interruption Environment 223
8.3 Vacuum Arcs 227
8.3.1 Introduction 227
8.3.2 Cathode- and Anode Sheath 229
8.3.3 The Diffuse Vacuum Arc 230
8.3.4 The Constricted Vacuum Arc 234
8.3.5 Vacuum-Arc Control by Magnetic Field 235
References 241
9 Vacuum Circuit-Breakers 243
9.1 General Features of Vacuum Interrupters 243
9.2 Contact Material for Vacuum Switchgear 246
9.2.1 Pure Metals 247
9.2.2 Alloys 247
9.3 Reliability of Vacuum Switchgear 248
9.4 Electrical Lifetime 249
9.5 Mechanical Lifetime 249
9.6 Breaking Capacity 251
9.7 Dielectric Withstand Capability 251
9.8 Current Conduction 252
9.9 Vacuum Quality 252
9.10 Vacuum Switchgear for HV Systems 253
9.10.1 Introduction 253
9.10.2 Development of HV Vacuum Circuit-Breakers 254
9.10.3 Actual Application of HV Vacuum Circuit-Breakers 255
9.10.4 X-ray Emission 256
9.10.5 Comparison of HV Vacuum- and HV SF6 Circuit-Breakers 257
References 258
10 Special Switching Situations 261
10.1 Generator-Current Breaking 261
10.1.1 Introduction 261
10.1.2 Generator Circuit-Breakers 266
10.2 Delayed Current Zero in Transmission Systems 267
10.3 Disconnector Switching 267
10.3.1 Introduction 267
10.3.2 No-Load-Current Switching 268
10.3.3 Bus-Transfer Switching 278
10.4 Earthing 279
10.4.1 Earthing Switches 279
10.4.2 High-Speed Earthing Switches 280
10.5 Switching Related to Series Capacitor Banks 282
10.5.1 Series Capacitor-Bank Protection 282
10.5.2 By-Pass Switch 283
10.6 Switching Leading to Ferroresonance 285
10.7 Fault-Current Interruption Near Shunt Capacitor Banks 286
10.8 Switching in Ultra-High-Voltage (UHV) Systems 288
10.8.1 Insulation Levels 289
10.8.2 UHV System Characteristics Related to Switching 289
10.9 High-Voltage AC Cable System Characteristics 291
10.9.1 Background 291
10.9.2 Current Situation 291
10.10 Switching in DC Systems 295
10.10.1 Introduction 295
10.10.2 Low- and Medium Voltage DC Interruption 295
10.10.3 High-Voltage DC Interruption 297
10.11 Distributed Generation and Switching Transients 298
10.11.1 General Considerations 298
10.11.2 Out-of-Phase Conditions 300
10.12 Switching with Non-Mechanical Devices 301
10.12.1 Fault-Current Limitation 301
10.12.2 Fuses 301
10.12.3 IS Limiters 303
References 304
11 Switching Overvoltages and Their Mitigation 310
11.1 Overvoltages 310
11.2 Switching Overvoltages 312
11.3 Switching-Voltage Mitigation 313
11.3.1 Principles of Mitigation 313
11.3.2 Mitigation by Closing Resistors 314
11.3.3 Mitigation by Surge Arresters 316
11.3.4 Fast Insertion of Shunt Reactors 319
11.4 Mitigation by Controlled Switching 320
11.4.1 Principles of Controlled Switching 320
11.4.2 Controlled Opening 321
11.4.3 Controlled Closing 323
11.4.4 Staggered Pole Closing 324
11.4.5 Applications of Controlled Switching 324
11.4.6 Comparison of Various Measures 334
11.4.7 Influence of Metal-Oxide Surge Arresters on Circuit-Breaker TRVs 336
11.4.8 Functional Requirements for Circuit-Breakers 337
11.4.9 Reliability Aspects 340
11.5 Practical Values of Switching Overvoltages 341
11.5.1 Overhead Lines 341
11.5.2 Shunt Capacitor Banks and Shunt Reactors 342
References 344
12 Reliability Studies of Switchgear 347
12.1 CIGRE Studies on Reliability of Switchgear 347
12.1.1 Reliability 347
12.1.2 Worldwide Surveys 348
12.1.3 Population and Failure Statistics 349
12.2 Electrical and Mechanical Endurance 354
12.2.1 Degradation Due to Arcing 354
12.2.2 Electrical-Endurance Verification 356
12.2.3 Mechanical Endurance 358
12.3 CIGRE Studies on Life Management of Circuit-Breakers 359
12.3.1 Maintenance 359
12.3.2 Monitoring and Diagnostics 360
12.3.3 Life Management of Circuit-Breakers for Frequent Load-Switching 362
12.4 Substation and System Reliability Studies 362
References 363
13 Standards, Specification, and Commissioning 365
13.1 Standards for Fault-Current Breaking Tests 365
13.1.1 Background and History of the Standardized IEC TRV Description 366
13.1.2 IEC TRV Description 368
13.1.3 IEC Test-Duties 370
13.1.4 IEC TRV Parameters Selection and Application 373
13.2 IEC Standardized Tests for Capacitive-Current Switching 373
13.3 IEC Standardized Tests for Inductive-Load Switching 377
13.3.1 Shunt-Reactor Switching 378
13.3.2 Medium-Voltage Motor Switching 381
13.4 Specification and Commissioning 381
13.4.1 General Specifications 381
13.4.2 Circuit-Breaker Specification 383
13.4.3 Information to be given with Requests for Offers 384
13.4.4 Information to be provided with Submitted Offers 384
13.4.5 Circuit-Breaker Selection 384
13.4.6 Circuit-Breaker Commissioning 384
References 385
14 Testing 386
14.1 Introduction 386
14.2 High-Power Tests 387
14.2.1 Introduction 387
14.2.2 Direct Tests 391
14.2.3 Synthetic Tests 395
References 411
List of Abbreviations 413
Index 417
