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The Vacuum Interrupter: Theory, Design, and Application

Vacuum Interrupter Theory and DesignHigh Voltage Vacuum Interrupter Design Introduction The External Design Electrical Breakdown in Gas Creepage Distance Insulating Ambients and Encapsulation Electrical Breakdown in Vacuum Introduction The Electric Field The Microscopic Enhancement Factor (βm)The Geometric Enhancement Factor (βg)Pre-Breakdown Effects Field Emission Current Anode Phenomena Microparticles Microdischarges Vacuum Breakdown and the Transition to the Vacuum Arc The Transition to a Self-Sustaining Vacuum Arc Time to Breakdown Conditioning Spark Conditioning Using a High Voltage ac Power Supply Spark Conditioning Using a High Voltage Pulse Current Conditioning Other Conditioning Processes Puncture Deconditioninc INTERNAL VACUUM INTERRUPTER DESIGN The Control of the Geometric Enhancement Factor, βg Breakdown of Multiple Vacuum Interrupters in Series for Contact Gaps Greater Than 2mm Voltage Wave Shapes and Vacuum Breakdown in a Vacuum Interrupter Impulse Testing of Vacuum Interrupters Testing for High Altitude X-Ray Emission Arc Initiation When Closing a Vacuum Interrupter References The Vacuum Arc The Closed Contact Making Contact, Contact Area, and Contact Resistance Calculation of Contact Resistance The Real Area of Contact a Small Disk of Radius “a”Contact Resistance and Contact Temperature The Calculation of Contact Temperature Blow-Off Force Butt Contacts Contact Interface Melting During Blow-Off The Formation of the Vacuum Arc during Contact Opening The Diffuse Vacuum Arc Cathode Spots The Plasma between the Cathode Spot and the Anode Current Chop The Formation of the Low-Current and High-Current Anode Spot The Columnar Vacuum Arc The Transition Vacuum Arc The Interaction of the Vacuum Arc and a Transverse Magnetic Field The Diffuse Vacuum Arc and a Transverse Magnetic Field The Columnar Vacuum Arc and a Transverse Magnetic Field The Vacuum Arc and an Axial Magnetic Field The Low-Current Vacuum Arc in an Axial Magnetic Field The High-Current Vacuum Arc in an Axial Magnetic Field Overview and Review of the Three Forms of Anode Spot References The Materials, Design, and Manufacture of the Vacuum Interrupter Introduction Vacuum Interrupter Contact Materials Introduction Copper and Copper-Based Contact Materials That Have Been Developed Following the Initial Experiments on High Current Vacuum Arcs Using Copper Contacts Refractory Metals Plus a Good Conductor Semi-Refractory Metals Plus a Good Conductor Copper Chromium Materials Plus an Additive Chopping Current Summary The Contact Structures for the Vacuum Interrupter Introduction Disc- or Butt-Shaped Contacts Contacts to Force the Motion of the High Current, Columnar Vacuum Arc Contacts to Force the High Current, Columnar Arc into the Diffuse Mode Summary Other Vacuum Interrupter Design Features The Insulating Body The Shield The Bellows Vacuum Interrupter Manufacture Аssembly Testing and Conditioning Summary References Vacuum Interrupter ApplicationGeneral Aspects of Vacuum Interrupter Application Introduction The Interruption of ac Circuits The Interruption of the Diffuse Vacuum Arc for ac Currents Less Than 2 kA (rms.) with a Fully Open Contact Gap The Interruption of the Vacuum Arc for AC Currents Greater than 2 kA (rms.)The Interruption of High Current Vacuum Arcs Interruption of ac Circuits When the Contacts Open Just Before Current Zero Low Current Vacuum Arcs Low Current Interruption of Inductive Circuits Low Current Interruption of Capacitive Circuits High Current Interruption Contact Welding Introduction Welding of Closed Contacts Cold Welding and Diffusion Welding Welding Caused by the Passage of High Current A Comparison of the Calculated “iw" with Experimental Values Simple Butt Contacts with One Region of Contact and a Short Current Pulse Simple Butt Contacts with More Than One Region of Contact and a Short Current Pulse Axial Magnetic, Large Area, Vacuum Interrupter Contacts 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 Closed Large Area Vacuum Interrupter Contacts Passing Fault Currents from 1 to 4 Seconds Welding of Contacts That Slide Welding when Contacts Close an Electrical Circuit REFERENCES Application of the Vacuum Interrupter for Switching Load Currents Introduction Load Current Switching Switches Used at Distribution Voltages Switches Used at Transmission Voltages Switching Inductive Circuits Voltage Surges When Closing an Inductive Circuit Voltage Surges When Opening an Inductive Circuit Surge Protection Switching Three-Phase Inductive Circuits: Virtual Current Chopping Transformer Switching Tap Changers Switching Off Unloaded Transformers Switching Off an Unloaded Transformer’s In-Rush Current Switching Off Loaded Transformers Vacuum Contactors Introduction Solenoid Operation Sizing the Contact The Shield The Contact Material Switching Capacitor Circuits Inserting a Capacitor Bank Disconnecting a Capacitor Bank Switching Three-Phase Capacitor Banks The Capacitor Switch Recovery Voltage, Late Restrikes, and NSDDs Switching Cables and Overhead Lines Vacuum Interrupters for Circuit Switching, Circuit Isolation, and Circuit Grounding Background Vacuum Interrupter Design Concepts for Load Switching and for Isolation Vacuum Interrupter Design for Switching and Grounding Vacuum Interrupter Design for Fault Protection, Isolation, and Grounding Summary References Circuit Protection, Vacuum Circuit Breakers, and Reclosers Introduction Load Currents Short Circuit Currents Introduction The Short Circuit Current and Asymmetry The Transient Recovery Voltage (TRV), for a Terminal Fault First Pole-to-Clear Factor The Terminal Fault Interruption Performance of Vacuum Interrupters The Transient Recovery Voltage for Short Line Faults (SLF)TRV from Transformer Secondary Faults Late Breakdowns and Non-Sustained Disruptive Discharges (NSDDs)Vacuum Circuit Breaker Design Introduction Closed Contacts Mechanism Design The Vacuum Interrupter Mounting and Insulation The Vacuum Circuit Breaker’s Electrical Life Vacuum Circuit Breaker Testing and Certification Developmental Testing of the Vacuum Interrupter Certification Testing at an Independent High-Power Testing Laboratory Fault Current Endurance Testing Vacuum Circuit Breakers for Capacitor Switching, Cable and Line Switching, and Motor Switching Introduction Capacitor Switching Capacitor Switching and NSDDs Cable Switching and Line Dropping Motor Switching Application of Vacuum Circuit Breakers for Distribution Circuits (4.76 kV to 40.5 kV)Indoor Switchgear Outdoor Circuit Breakers Vacuum Reclosers The Ring Main Unit (RMU) for Secondary Distribution Pad-Mount Secondary Distribution Systems The Generator Vacuum Circuit Breaker High Continuous Currents Transformer/System Fed Faults Generator Fed Faults Out-of-Phase Switching Transportation Circuit Breakers Interrupting Fault Currents at Frequencies Less Than and Greater Than 50/60 Hz Switching Electric Arc Furnaces (EAF)Vacuum Interrupters in Series Vacuum Interrupters for Subtransmission and Transmission Systems Switching dc Circuits Using Vacuum Interrupters DC Interruption Using the Natural Vacuum Arc Instability DC Current Interruption Using an External Magnetic Field Pulse Switching High Voltage DC Transmission Circuits Using a Current Counter Pulse Development of Vacuum Interrupters for Low Voltage (< 1000V) Circuit Breakers Concluding Summary References

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