Abstract: The application of high-voltage vacuum circuit breakers in China's power supply system began in 1978. Their advantages, such as light weight, simple structure, and long service life, were quickly recognized by power sector operators, maintenance personnel, and technicians. Early domestically produced high-voltage vacuum circuit breakers were of unstable quality, exhibiting high overvoltage during operation, and some vacuum interrupters even showed leakage. Keywords: High-voltage vacuum circuit breaker, application technology discussion 1. Current Status of High-Voltage Vacuum Circuit Breakers in China The application of high-voltage vacuum circuit breakers in China's power supply system began in 1978. Their advantages, such as light weight, simple structure, and long service life, were quickly recognized by power sector operators, maintenance personnel, and technicians. Early domestically produced high-voltage vacuum circuit breakers were of unstable quality, exhibiting high overvoltage during operation, and some vacuum interrupters even showed leakage. By the time of the Tianjin Vacuum Switch Application Promotion Conference in 1992, China's vacuum circuit breaker manufacturing technology had entered the forefront of international counterparts, marking a new historical turning point in the application and manufacturing technology of high-voltage vacuum circuit breakers in China. 2. Leakage Problems in Vacuum Interruptors New generation high-voltage vacuum circuit breakers generally use the longitudinal magnetic field arc-extinguishing principle and copper-chromium contact materials to reduce contact burn-out and improve electrical service life. Improper adjustment of the concentricity of the conductive rod will lead to insufficient stability of the longitudinal gas wire, ceramic, and Kovar-metal sealing strength, resulting in leakage in the vacuum interruptor. The bellows of most vacuum interruptors are made of 0.15mm thick stainless steel through hydraulic pressing. Inappropriate selection of the pollution level, humidity, and salt spray conditions in the application environment of the high-voltage vacuum circuit breaker can cause pitting corrosion of the bellows due to harmful gases and condensation, leading to leakage in the bellows, cover plate, and sealing surfaces. Ensuring the concentricity adjustment of the high-voltage vacuum circuit breaker and appropriately selecting the usage and storage environment are important measures to solve the leakage problem of vacuum interruptors. 3. Appropriate Selection of Electrical Life of High-Voltage Vacuum Circuit Breakers The electrical life of a high-voltage vacuum circuit breaker refers to the number of full-capacity breaking operations specified in the equipment's technical conditions and actually performed in type tests. In applications, the contacts of high-voltage vacuum circuit breakers cannot be repaired or replaced, making a sufficiently long electrical life essential. The new generation of vacuum interrupters utilizes longitudinal magnetic field electrodes and copper-chromium contact materials. The longitudinal magnetic field electrodes significantly reduce the arc voltage (arc energy) under short-circuit breaking current and ensure uniform arc distribution on the contact surface; the copper-chromium contact material reduces contact burn-out per unit arc energy. This combination results in a breakthrough improvement in the electrical life of high-voltage vacuum circuit breakers. Currently, the performance of high-voltage vacuum circuit breakers in my country, including their re-breaking and making capabilities, is relatively high and stable. Early high-voltage vacuum circuit breakers in my country had an electrical life of only 30 cycles, with the longest-operating having been in service for over 20 years. To date, no high-voltage vacuum circuit breakers in the power system have been decommissioned due to electrical life issues related to short-circuit breaking current, nor have any accidents occurred due to short electrical life of short-circuit breaking current. This fully demonstrates that these high-voltage vacuum circuit breakers basically meet the power system's requirements for electrical life of short-circuit breaking current. Therefore, a higher short-circuit breaking current electrical life for high-voltage vacuum circuit breakers is not always better. 4. Emphasis on Adjusting the Mechanical Parameters of High-Voltage Vacuum Circuit Breakers High-voltage vacuum circuit breakers have many mechanical parameters, such as closing speed, opening speed, contact travel, contact closing bounce time, and contact opening rebound amplitude. These mechanical parameters are set to ensure the technical performance of the high-voltage vacuum circuit breaker. In China, the mechanical life of high-voltage vacuum circuit breakers is generally 10,000–20,000 cycles. Research is underway to increase the mechanical life to 30,000–40,000 cycles. Electromagnetic operating mechanisms are widely used due to their simple structure, reliable performance, convenient adjustment and maintenance, and familiarity with operation and maintenance by operators. In some areas, electric spring operating mechanisms are also commonly used. The operating mechanism is the most complex and precision-required part of the high-voltage vacuum circuit breaker's mechanical structure, and most manufacturers' production conditions are insufficient to meet the required machining precision. To ensure the reliability of high-voltage vacuum circuit breakers, China adopts a separate assembly structure, where the operating mechanism and the circuit breaker body are separated. The operating mechanism is centrally produced in factories with better production conditions, and then the output shaft of the mechanism is integrated with the circuit breaker. Therefore, the reasonable configuration of mechanical parameters directly affects the technical performance and mechanical life of the high-voltage vacuum circuit breaker. Ideal mechanical parameter adjustment is crucial for the mechanical performance of the high-voltage vacuum circuit breaker. A satisfactory buffering characteristic should be that the buffer provides a small reaction force at the moment of contact between the moving parts, and the buffering characteristic becomes steeper rapidly as the buffering distance increases, maximizing the absorption of separation energy and achieving the purpose of limiting tripping rebound and tripping stroke. 5. Improving the Reliability of High-Voltage Vacuum Circuit Breaker Operation Due to quality issues with domestically produced materials, components, and standard parts, as well as traditional product design concepts, the mechanical reliability and mechanical life of China's high-voltage vacuum circuit breakers are not yet ideal. (1) Master the basic structure of vacuum circuit breakers, be familiar with their technical performance indicators, rationally select usage conditions, maintain close communication with the manufacturer, and accurately apply the advanced technical functions of high-voltage vacuum circuit breakers; (2) Carefully perform the mechanical parameter debugging work of high-voltage vacuum circuit breakers, strictly adhere to the mechanical parameter requirements, and ensure their basic functions; (3) Standardize the management and storage of spare parts, and ensure the consistency, universality, and reliability of the technical performance indicators and quality of spare parts; (4) Keep good records of the operation of high-voltage vacuum circuit breakers and conduct accident analysis, summarize experience, and work closely with the manufacturing department to continuously improve the advancement, reliability, and economy of vacuum circuit breakers. 6 Temperature Rise of High-Voltage Vacuum Circuit Breakers The circuit resistance of high-voltage vacuum circuit breakers is the main heat source affecting temperature rise, and the circuit resistance of the arc-extinguishing chamber usually accounts for more than 50% of the circuit resistance of high-voltage vacuum circuit breakers. The contact resistance of the contact gap is the main component of the circuit resistance of the vacuum arc-extinguishing chamber, because the contact system is sealed in the vacuum arc-extinguishing chamber, and the heat generated can only be dissipated to the outside through the moving and stationary conductive rods. The stationary end of the vacuum interrupter is directly connected to the stationary support, while the moving end is connected to the moving support via a conductive clamp and a flexible connection. Although the upward movement of the moving end facilitates heat dissipation, the numerous connection points and long heat conduction path mean that the highest temperature rise in the high-voltage vacuum circuit breaker is concentrated at the junction of the moving conductive rod and the conductive clamp. In practical applications, effectively utilizing the heat dissipation-friendly components at the stationary end to force a greater amount of heat from the contact gap to be dissipated from the moving end is an effective measure to address the high temperature rise of high-voltage vacuum circuit breakers. The superior technical application characteristics of high-voltage vacuum circuit breakers have been widely recognized by the power sector. The issues mentioned above are provided for reference in practical work, aiming to fully utilize and better leverage the technical advantages of high-voltage vacuum circuit breakers, which is highly beneficial to improving the overall equipment level of my country's rural power grid.