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Switching in Electrical Transmission and Distribution Systems

Switching in Electrical Transmission and Distribution Systems

René Smeets, Lou van der Sluis, Mirsad Kapetanovic, David F. Peelo, Anton Janssen

ISBN: 978-1-118-70361-8

Nov 2014

440 pages

Description

Switching in Electrical Transmission and Distribution Systems presents the issues and technological solutions associated with switching in power systems, from medium to ultra-high voltage.

The book systematically discusses the electrical aspects of switching, details the way load and fault currents are interrupted, the impact of fault currents, and compares switching equipment in particular circuit-breakers. The authors also explain all examples of practical switching phenomena by examining real measurements from switching tests.

Other highlights include: up to date commentary on new developments in transmission and distribution technology such as ultra-high voltage systems, vacuum switchgear for high-voltage, generator circuit-breakers, distributed generation, DC-interruption, aspects of cable systems, disconnector switching, very fast transients, and circuit-breaker reliability studies.

Key features:

  • Summarises the issues and technological solutions associated with the switching of currents in   transmission and distribution systems.
  • Introduces and explains recent developments such as vacuum switchgear for transmission systems, SF6 environmental consequences and alternatives,  and circuit-breaker testing.
  • Provides practical guidance on how to deal with unacceptable switching transients.
  • Details the worldwide IEC (International Electrotechnical Commission) standards on switching equipment, illustrating current circuit-breaker applications.
  • Features many figures and tables originating from full-power tests and established training courses, or from measurements in real networks.
  • Focuses on practical and application issues relevant to practicing engineers.
  • Essential reading for electrical engineers, utility engineers, power system application engineers, consultants and power systems asset managers, postgraduates and final year power system undergraduates.

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

“Engineers who design and perform testing of MV and HV circuit breakers, load break switches, or fuses as well as MV and HV test lab managers will find this book to be a very useful and handy reference.”  (IEEE Electrical Engineering magazine, 1 July 2015)