HIGH VOLTAGE CIRCUIT BREAKERS

Transcription

1 HIGH VOLTAGE CIRCUIT BREAKERS Design and Applications Second Edition, Revised and Expanded RUBEN D. GARZON Square D Co. Smyrna, Tennessee MARCEL Ш D E К К E R MARCEL DEKKER, INC. NEW YORK BASEL

2 CONTENTS Preface to the Second Edition Preface to the First Edition v vii 1 Electric Arc Fundamentals Introduction Basic Theory of Electrical Discharges Non-Self-Sustaining Discharges Self-Sustaining Discharges The Electric Arc High-Pressure Arcs Low-Pressure (Vacuum) Arcs The Alternating Current Arc The Current Interruption Process Interruption of Direct Current Interruption of Alternating Currents Review of Main Theories of AC Interruption Slepian's Theory Prince's Theory Cassie's Theory Mayr's Theory Browne's Combined Theory Modern Theories 24 References 25 2 Short Circuit Currents Introduction Characteristics of the Short Circuit Current Transient Direct Current Component The Volt-Time Area Concept Transient Alternating Current Components Asymmetry of Three-Phase Short Circuit Currents Measuring Asymmetrical Currents Calculation of Short Circuit Currents 40 xi

3 xii Contents The Per Unit Method The MVA Method Unbalanced Faults Introduction to Symmetrical Components Forces Produced by the Short Circuit Currents Direction of the Forces Between Current Carrying Conductors Calculation of Electrodynamic Forces Between Conductors Forces on Conductors Produced by Three-Phase Currents 69 References 72 3 Transient Recovery Voltage Introduction Transient Recovery Voltage: General Concepts Basic Assumptions for TRV Calculations Current Injection Technique Traveling Waves and the Lattice Diagram Calculation of Transient Recovery Voltages Single Frequency Recovery Voltage Double Frequency Recovery Voltage: General Case Particular Case of Double Frequency Recovery Voltage Short-Line Fault Recovery Voltage Initial Transient Recovery Voltage 104 References Switching Overvoltages Introduction Contacts Closing Closing of a Line Reclosingof a Line Energizing Unloaded Transformers Contact Opening Interruption of Small Capacitive Currents Interruption of Inductive Load Currents Current Chopping Virtual Current Chopping Temporary Overvoltages Controlling Overvoltages 125 References Types of Circuit Breakers Introduction Circuit Breaker Classifications Circuit Breaker Types by Voltage Class Circuit Breaker Types by Installations 130

4 Contents xiii Circuit Breaker Types by External Design Circuit Breaker Types by Interrupting Mediums Air Magnetic Circuit Breakers Arc Chute Type Circuit Breakers Air Magnetic Circuit Breaker Typical Applications Air Blast Circuit Breakers Blast Direction and Nozzle Types Series Connection of Interrupters Basic Interrupter Arrangements Parameters Influencing Air Blast Circuit Breaker Performance Oil Circuit Breakers Properties of Insulating Oil Current Interruption in Oil Types of Oil Circuit Breakers Bulk Oil Circuit Breakers Minimum Oil Circuit Breakers Sulfurhexafluoride Properties of SF Arc Decomposed By-Products SF 6 Environmental Considerations Recycling of SF Current Interruption in SF Two Pressure SF 6 Circuit Breakers Single Pressure SF 6 Circuit Breakers Pressure Increase of SF 6 Produced by an Electric Arc Parameters Influencing SF 6 Circuit Breaker Performance SF 6 -Nitrogen Gas Mixture Vacuum Circuit Breakers Current Interruption in Vacuum Circuit Breakers Vacuum Interrupter Construction Vacuum Interrupter Contact Materials Interrupting Capability of Vacuum Interrupters 193 References Mechanical Design Introduction Contact Theory Contact Resistance Insulating Film Coatings on Contacts Contact Fretting Temperature at the Point of Contact Short Time Heating of Copper Electromagnetic Forces on Contacts Contact Erosion 210

5 XIV Contents 6.2 Mechanical Operating Characteristics Circuit Breaker Opening Requirements Closing Speed Requirements Operating Mechanisms Cam Versus Linkage Weld Break and Contact Bounce Spring Mechanisms Pneumatic Mechanisms Hydraulic Mechanisms Magnetic Mechanism 226 References Dielectric Design Introduction Fundamentals of Dielectric Theory Electric Fields Types of Insulation Gaseous Insulation General Principles Paschen'sLaw Factors Influencing Dielectric Strength Air Insulation SF 6 Insulation Simplified Design Approach Vacuum Insulation Solid Insulation Solid Insulation: Basic Concepts Dielectric Loss Layered Insulation Partial Discharges Insulating Materials Solid Insulation Design Guidelines 256 References A Comparison of High Voltage Circuit Breaker Standards Introduction Recognized Standards Organizations ANSHEEE/NEMA International Electrotechnical Commission (IEC) Circuit Breaker Standards and Ratings Comparisons Normal Operating Conditions Rated Power Frequency Voltage Related Ratings Maximum Operating Voltage Rated Voltage Range Factor К 269

6 Contents xv Rated Dielectric Strength Rated Transient Recovery Voltage 8.4 Current Related Ratings and Requirements Preferred Number Series Rated Continuous Current Rated Short Circuit Current 8.5 Additional Switching Duties Capacitance Switching 8.6 Mechanical Requirements Mechanical Operating Life References 9 Short Circuit Testing 9.0 Introduction 9.1 Test Methodology Direct Tests Indirect Tests Single Phase Tests Unit Tests Two Part Tests Synthetic Tests 9.2 Test Measurements and Procedures Measured Parameters and Test Set-Up Test Sequences References 10 Circuit Breaker Applications 10.0 Introduction 10.1 Overload Currents and Temperature Rise Effects of Solar Radiation Continuous Overload Capability Short Time Overloads Maximum Continuous Current at High Altitude Applications 10.2 Interruption of Current from High X/R Circuits 10.3 Generator Circuit Breaker Applications Short Circuit Current Ratings Generator Asymmetrical Short Circuit Current Calculation Transient Recovery Voltage 10.4 Application Frequencies Other Than 50 or 60 Hertz 10.5 Capacitance Switching Applications Open Line Isolated Cable Back-to-Back Cables Isolated Shunt Capacitor Bank

7 xvi Contents Back-to-Back Capacitor Banks General Application Guidelines Circuit Breaker Characteristics Reactor Current Switching, High TRV Applications Ferroresonance High Altitude Dielectric Considerations Reclosing Duty Derating Factors Vacuum Circuit Breaker Applications Transformer Circuits Applications in Motor Circuits Review of Surge Protection Methods Choosing Between Vacuum or SF References Synchronous Switching and Condition Monitoring Introduction Synchronous Switching Mechanical Performance Considerations Contact Gap Voltage Withstand Synchronous Capacitance Switching Synchronous Reactor Switching Synchronous Transformer Switching Synchronous Short Circuit Current Switching Condition Monitoring of Circuit Breakers Choice of Monitored Parameters Mechanical Parameters Electrical Parameters Monitored Parameters Selection Analysis Monitored Signals Management Cost-Benefit Analysis 414 References 417 Appendix: Conversion Tables 419 Index 425