Switching in Electrical Transmission and Distribution Systems

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Switching in Electrical Transmission and Distribution Systems

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Switching in Electrical Transmission and Distribution Systems

    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.

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Key features:

• Summarizes 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.

Hydraulics of Pipelines

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TABLE OF CONTENTS

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

1.5 The Switching Arc 10

1.6 Transient Recovery Voltage (TRV) 14

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

2.3 Short-Circuit Current Impact on System and Components 35

2.4 Fault Statistics 43

References 46

3 Fault-Current Breaking and Making 48

3.1 Introduction 48

3.2 Fault-Current Interruption 48

3.3 Terminal Faults 49

3.4 Transformer-Limited Faults 58

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

3.8 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

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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

6.3 Oil as an Interrupting Medium 176

6.4 Sulfur Hexafluoride (SF6) as an Interrupting Medium 181

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

References 258

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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

11.4 Mitigation by Controlled Switching 320

11.5 Practical Values of Switching Overvoltages 341

References 344

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