The Vacuum Interrupter: Theory, Design, and Application

by Paul G. Slade

Overview

Title: The Vacuum Interrupter: Theory, Design, and Application
Shelving guide: Electrical Engineering

 

Dr. Paul Slade draws from his nearly six decades of active experience to develop this second edition of The Vacuum Interrupter: Theory, Design, and Application. This book begins by discussing the design requirements for high voltage vacuum interrupters and then the contact requirements to interrupt the vacuum arc. It then continues by describing the various applications in which the vacuum interrupter is generally utilized.

Part 1 of this book begins with a detailed review of the vacuum breakdown process. It continues by covering the steps necessary for the design and the manufacture of a successful vacuum interrupter. The vacuum arc is then discussed, including how it is affected as a function of current. An overview of the development and use of practical contact materials, along with their advantages and disadvantages, follows. Contact designs that are introduced to control the high current vacuum arc are also analyzed.

Part 2, on application, begins with a discussion of the arc interruption process for low current and high current vacuum arcs. It examines the voltage escalation phenomenon that can occur when interrupting inductive circuits. The occurrence of contact welding for closed contacts subjected to the passage of high currents, and for contacts when closing on high currents, is explored. The general requirements for the successful manufacture and testing of vacuum circuit breakers is then presented. The general application of vacuum interrupters to switch load currents, especially when applied to capacitor circuits, is also given. The interruption of high short circuit currents is presented along with the expected performance of the two major contact designs.

Owing to the ever-increasing need for environmentally friendly circuit protection devices, the development and application of the vacuum interrupter will only increase in the future. At present the vacuum circuit breaker is the technology of choice for distribution circuits (5kV to 40.5kV). It is increasingly being applied to transmission circuits (72.5kV to 242kV). In the future, its application for protecting high voltage DC networks is assured.

Audience

• This is a practical source book for engineers and scientists interested in studying the development and application of the vacuum interrupter
• Research scientists in industry and universities
• Graduate students beginning their study of vacuum interrupter phenomena
• Design engineers applying vacuum interrupters in vacuum switches, vacuum contactors, vacuum circuit breakers, and vacuum contactors
• It provides a unique and comprehensive review of all aspects of vacuum interrupter technology for those new to the subject and for those who wish to obtain a deeper understanding of its science and application
• Scientists and engineers, who are beginning their research into vacuum breakdown and aspects of the vacuum arc, will find the extensive bibliography and phenomenological descriptions to be a useful introduction

Product Details

ISBN-13:	9780367531720
Publisher:	CRC Press
Publication date:	08/01/2022
Edition description:	2nd ed.
Pages:	666
Product dimensions:	7.00(w) x 10.00(h) x (d)

About the Author

Paul G. Slade has been an independent consultant for vacuum interrupter technology, electrical contacts and circuit interruption, since his retirement. He is also the holder of 23 US patents. He is the major contributor and editor of the 2nd edition of the book “Electrical Contacts: Principles and Applications”. He is the recipient of the IEEE Ragnar Holm Scientific Achievement Award and of the German VDE Albert Keil Pries for his contributions to the science of electrical contacts. He is a fellow of the IEEE.

Table of Contents

Preface and Acknowledgments for the First Edition xiii

Preface and Acknowledgments for the Second Edition xv

Author xvii

Introduction xix

Part 1 Vacuum Interrupter Theory and Design

Chapter 1 High Voltage Vacuum Interrupter Design 3

1.1 Introduction 3

1.2 The External Design 6

1.2.1 Electrical Breakdown in Gas 6

1.2.2 Creepage Distance 17

1.2.3 Insulating Ambients and Encapsulation 21

1.3 Electrical Breakdown in Vacuum 23

1.3.1 Introduction 23

1.3.2 The Electric Field 31

1.3.2.1 The Micrpscopic Enhancement Factor (β_m) 31

1.3.2.2 The Geometric Enhancement Factor (β_g) 34

1.3.3 Pre-Breakdown Effects 38

1.3.3.1 Field Emission Current 38

1.3.3.2 Anode Phenomena 44

1.3.3.3 Microparticles 51

1.3.3.4 Microdischarges 56

1.3.4 Vacuum Breakdown and the Transition to the Vacuum Arc 62

1.3.5 The Transition to a Self-Sustaining Vacuum Arc 75

1.3.6 Time to Breakdown 84

1.3.7 Conditioning 86

1.3.7.1 Spark Conditioning Using a High Voltage AC Power Supply 87

1.3.7.2 Spark Conditioning Using a High Voltage Pulse 88

1.3.7.3 Current Conditioning 91

1.3.7.4 Other Conditioning Processes 92

1.3.8 Puncture 94

1.3.9 Deconditioning 95

1.4 Internal Vacuum Interrupter Design 96

1.4.1 The Control of the Geometric Enhancement Factor, β_g 96

1.4.2 Breakdown of Multiple Vacuum Interrupters in Series for Contact Gaps Greater Than 2mm 103

1.4.3 Voltage Wave Shapes and Vacuum Breakdown in a Vacuum Interrupter 104

1.4.4 Impulse Testing of Vacuum Interrupters 105

1.4.5 Testing for High Altitude 113

1.5 X-Ray Emission 114

1.6 Arc Initiation When Closing a Vacuum Interrupter 125

References 126

Chapter 2 The Vacuum Arc 137

2.1 The Closed Contact 137

2.1.1 Making Contact, Contact Area, and Contact Resistance 137

2.1.2 Calculation of Contact Resistance 139

2.1.2.1 The Real Area of Contact a Small Disk of Radius "a" 139

2.1.3 Contact Resistance and Contact Temperature 141

2.1.3.1 The Calculation of Contact Temperature 142

2.1.4 Blow-Off Force 143

2.1.4.1 Butt Contacts 145

2.1.4.2 Contact Interface Melting During Blow-Off 146

2.2 The Formation of the Vacuum Arc during Contact Opening 147

2.3 The Diffuse Vacuum Are 152

2.3.1 Cathode Spots 153

2.3.2 The Plasma between the Cathode Spot and the Anode 161

2.3.3 Current Chop 165

2.3.4 The Formation of the Low-Current and High-Current Anode Spot 169

2.4 The Columnar Vacuum Arc 173

2.5 The Transition Vacuum Arc 179

2.6 The Interaction of the Vacuum Arc and a Transverse Magnetic Field 181

2.6.1 The Diffuse Vacuum Arc and a Transverse Magnetic Field 181

2.6.2 The Columnar Vacuum Arc and a Transverse Magnetic Field 185

2.7 The Vacuum Arc and an Axial Magnetic Field 187

2.7.1 The Low-Current Vacuum Arc in an Axial Magnetic Field 188

2.7.2 The High-Current Vacuum Arc in an Axial Magnetic Field 193

2.8 Overview and Review of the Three Forms of Anode Spot 209

References 210

Chapter 3 The Materials, Design, and Manufacture of the Vacuum Interrupter 219

3.1 Introduction 219

3.2 Vacuum Interrupter Contact Materials 220

3.2.1 Introduction 220

3.2.2 Copper and Copper-Based Contact Materials That Have Been Developed Following the Initial Experiments on High Current Vacuum Arcs Using Copper Contacts 221

3.2.3 Refractory Metals Plus a Good Conductor 221

3.2.4 Semi-Refractory Metals Plus a Good Conductor 224

3.2.5 Copper Chromium Materials Plus an Additive 233

3.2.6 Chopping Current 233

3.2.7 Summary 242

3.3 The Contact Structures for the Vacuum Interrupter 245

3.3.1 Introduction 245

3.3.2 Disc- or Butt-Shaped Contacts 246

3.3.3 Contacts to Force the Motion of the High Current, Columnar Vacuum Arc 247

3.3.4 Contacts to Force the High Current, Columnar Arc into the Diffuse Mode 262

3.3.5 Summary 283

3.4 Other Vacuum Interrupter Design Features 283

3.4.1 The Insulating Body 283

3.4.2 The Shield 286

3.4.3 The Bellows 289

3.5 Vacuum Interrupter Manufacture 291

3.5.1 Assembly 291

3.5.2 Testing and Conditioning 298

3.5.3 Summary 304

References 306

Part 2 Vacuum Interrupter Application

Chapter 4 General Aspects of Vacuum Interrupter Application 321

4.1 Introduction 321

4.2 The Interruption of AC Circuits 323

4.2.1 The Interruption of the Diffuse Vacuum Arc for AC Currents Less Than 2 kA (rms.) with a Fully Open Contact Gap 323

4.2.2 The Interruption of the Vacuum Arc for AC Currents Greater than 2 kA (rms.) 337

4.2.3 The Interruption of High Current Vacuum Arcs 345

4.3 Interruption of AC Circuits When the Contacts Open Just Before Current Zero 361

4.3.1 Low Current Vacuum Arcs 361

4.3.1.1 Low Current Interruption of Inductive Circuits 362

4.3.1.2 Low Current Interruption of Capacitive Circuits 366

4.3.2 High Current Interruption 367

4.4 Contact Welding 369

4.4.1 Introduction 369

4.4.2 Welding of Closed Contacts 371

4.4.2.1 Cold Welding and Diffusion Welding 371

4.4.2.2 Welding Caused by the Passage of High Current 371

4.4.3 A Comparison of the Calculated "i_w" with Experimental Values 378

4.4.3.1 Simple Butt Contacts with One Region of Contact and a Short Current Pulse 378

4.4.3.2 Simple Butt Contacts with More Than One Region of Contact and a Short Current Pulse 379

4.4.3.3 Axial Magnetic, Large Area, Vacuum Interrupter Contacts 380

4.4.4 The Model to Determine the Threshold Welding Current for Closed Contacts with "n" Regions of Contact for Passage of Current of 1 to 4 Seconds 381

4.4.4.1 Closed Large Area Vacuum Interrupter Contacts Passing Fault Currents from 1 to 4 Seconds 383

4.4.5 Welding of Contacts That Slide 385

4.4.6 Welding when Contacts Close an Electrical Circuit 386

References 394

Chapter 5 Application of the Vacuum Interrupter for Switching Load Currents 401

5.1 Introduction 401

5.2 Load Current Switching 403

5.2.1 Switches Used at Distribution Voltages 403

5.2.2 Switches Used at Transmission Voltages 409

5.3 Switching Inductive Circuits 414

5.3.1 Voltage Surges When Closing an Inductive Circuit 414

5.3.2 Voltage Surges When Opening an Inductive Circuit 414

5.3.3 Surge Protection 415

5.3.4 Switching Three-Phase Inductive Circuits: Virtual Current Chopping 421

5.3.5 Transformer Switching 423

5.3.5.1 Tap Changers 424

5.3.5.2 Switching Off Unloaded Transformers 424

5.3.5.3 Switching Off an Unloaded Transformer's In-Rush Current 426

5.3.5.4 Switching Off Loaded Transformers 427

5.4 Vacuum Contactors 428

5.4.1 Introduction 428

5.4.2 Solenoid Operation 431

5.4.3 Sizing the Contact 433

5.4.4 The Shield 436

5.4.5 The Contact Material 436

5.5 Switching Capacitor Circuits 437

5.5.1 Inserting a Capacitor Bank 438

5.5.2 Disconnecting a Capacitor Bank 443

5.5.3 Switching Three-Phase Capacitor Banks 448

5.5.4 The Capacitor Switch Recovery Voltage, Late Restrikes, and NSDDs 450

5.5.5 Switching Cables and Overhead Lines 462

5.6 Vacuum Interrupters for Circuit Switching, Circuit Isolation, and Circuit Grounding 464

5.6.1 Background 464

5.6.2 Vacuum Interrupter Design Concepts for Load Switching and for Isolation 468

5.6.3 Vacuum Interrupter Design for Switching and Grounding 469

5.6.4 Vacuum Interrupter Design for Fault Protection, Isolation, and Grounding 473

5.7 Summary 474

References 475

Chapter 6 Circuit Protection, Vacuum Circuit Breakers, and Reclosers 481

6.1 Introduction 481

6.2 Load Currents 482

6.3 Short Circuit Currents 492

6.3.1 In traduction 492

6.3.2 The Short Circuit Current and Asymmetry 493

6.3.3 The Transient Recovery Voltage (TRV), for a Terminal Fault 496

6.3.3.1 First Pole-to-Clear Factor 499

6.3.4 The Terminal Fault Interruption Performance of Vacuum Interrupters 502

6.3.5 The Transient Recovery Voltage for Short Line Faults (SLF) 507

6.3.6 TRV from Transformer Secondary Faults 509

6.4 Late Breakdowns and Non-Sustained Disruptive Discharges (NSDDs) 509

6.5 Vacuum Circuit Breaker Design 515

6.5.1 Introduction 515

6.5.2 Closed Contacts 516

6.5.3 Mechanism Design 520

6.5.4 The Vacuum Interrupter Mounting and Insulation 532

6.5.5 The Vacuum Circuit Breaker's Electrical Life 540

6.6 Vacuum Circuit Breaker Testing and Certification 546

6.6.1 Developmental Testing of the Vacuum Interrupter 546

6.6.2 Certification Testing at an Independent High-Power Testing Laboratory 548

6.6.3 Fault Current Endurance Testing 549

6.7 Vacuum Circuit Breakers for Capacitor Switching, Cable and Line Switching, and Motor Switching 550

6.7.1 Introduction 550

6.7.2 Capacitor Switching 551

6.7.2.1 Capacitor Switching and NSDDs 554

6.7.3 Cable Switching and Line Dropping 555

6.7.4 Motor Switching 556

6.8 Application of Vacuum Circuit Breakers for Distribution Circuits (4.76 kV to 40.5 kV) 556

6.8.1 Indoor Switchgear 556

6.8.2 Outdoor Circuit Breakers 561

6.8.3 Vacuum Reclosers 561

6.8.4 The Ring Main Unit (RMU) for Secondary Distribution 564

6.8.5 Pad-Mount Secondary Distribution Systems 565

6.8.6 The Generator Vacuum Circuit Breaker 565

6.8.6.1 High Continuous Currents 568

6.8.6.2 Transformer/System Fed Faults 569

6.8.6.3 Generator Fed Faults 571

6.8.6.4 Out-of-Phase Switching 572

6.8.7 Transportation Circuit Breakers 572

6.8.7.1 Interrupting Fault Currents at Frequencies Less Than and Greater Than 50/60 Hz 573

6.8.8 Switching Electric Arc Furnaces (EAF) 575

6.9 Vacuum Interrupters in Series 576

6.10 Vacuum Interrupters for Subtransmission and Transmission Systems 582

6.11 Switching DC Circuits Using Vacuum Interrupters 589

6.11.1 DC Interruption Using the Natural Vacuum Arc Instability 589

6.11.2 DC Current Interruption Using an External Magnetic Field Pulse 590

6.11.3 Switching High Voltage DC Transmission Circuits Using a Current Counter Pulse 590

6.12 Development of Vacuum Interrupters for Low Voltage (< 1000V) Circuit Breakers 598

6.13 Concluding Summary 598

References 600

Author Index 613

Subject Index 627

Editorial Reviews

"The author has produced a classic book. It contains all the essential background needed for a reader to become well-versed in vacuum interrupter technology and it will be referenced for many years to come . . . Those working in the field of vacuum interrupter design would obviously be interested in this book, and those who perform or are interested in the vacuum arc switching technology would also find it an outstanding book that will be used for many years to come."

– In IEEE Electrical Insulation Magazine, January/ February 2009, Vol. 25, No. 1

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