The "General Technical Conditions for 35 kV Indoor High-Voltage Vacuum Circuit Breakers" (ZBK97004-89) defines closing bounce as the time from the moment the contacts first touch during closing until the contacts reach stable contact. All switch characteristic testers with direct-reading data are designed and manufactured according to this definition. The electric arc affects the electrical life of the arc-extinguishing chamber, and the arc only occurs when the moving and stationary contacts are not in contact; it does not occur when the moving and stationary contacts are in contact. Extensive practical and theoretical analysis shows that the factor truly affecting the electrical life of the vacuum switch is the contact disconnection time during the closing process, from the moment the contacts first touch until the contacts reach stable contact. During installation, power supply departments generally accept equipment according to the "Standard for Acceptance Testing of Electrical Equipment in Electrical Installation Engineering" (GB50150-91). Clause 11.0.7 of GB50150-91 stipulates that the bounce time after contact during the closing process of a vacuum circuit breaker should not exceed 2 ms, which differs from actual operation. The opening and closing of a vacuum circuit breaker is accomplished by a vacuum interrupter. The switch parameters must meet the performance requirements of the interrupter. For example, if the interrupter requires a closing speed of 0.4–1.0 m/s, and the switch speed can be between 0.3–0.7 m/s, then the closing speed of a vacuum circuit breaker equipped with that type of interrupter must be adjusted to between 0.4–0.7 m/s. Similarly, if the closing bounce of the vacuum interrupter is required to be no greater than 5 ms, then the allowable range for the closing bounce of a circuit breaker equipped with that type of interrupter is also no greater than 5 ms. Whether the closing bounce should be uniformly set at no more than 2 ms is worth discussing. Technology is constantly being updated and developed, and standards should also be continuously improved. New contact materials have excellent resistance to welding. When welding occurs, the weld point is brittle, the weld layer has low mechanical strength, and the force required to break the weld is less than the opening force of the vacuum circuit breaker. Currently, many foreign products, such as Toshiba's 10 kV circuit breakers, only require a bounce time of less than 10 ms. The application of new contact materials has created conditions for breaking through the 2 ms barrier in closing bounce time. Currently, many vacuum interrupters specify a closing bounce time greater than 2 ms, requiring only less than 3 ms, or even 5 ms. Closing bounce is an important parameter of the mechanical characteristics of vacuum circuit breakers. During closing bounce, the contact disconnection distance is small, and the arc does not extinguish, leading to increased contact wear and affecting the electrical life of the interrupter. However, because its duration is short, much shorter than the arc burning time during closing, it is generally believed that within a certain range, the most significant harm of bounce is accelerated wear of the interrupter contacts, thus shortening the electrical life of the interrupter. During bounce, the current arc does not extinguish, and no operational overvoltage is generated. Type testing shows that the bounce of the circuit breaker improves significantly after aging or after breaking tests. Extensive operational experience has shown that after a period of operation, vacuum circuit breakers undergo subtle changes in the surface metal structure of the arc-extinguishing chamber contacts due to the switching of load currents. This significantly reduces or even eliminates the closing bounce time, while also improving vacuum level and power frequency withstand voltage. How significant is the impact of bounce on the electrical life of a vacuum arc-extinguishing chamber? One ZN23-35 vacuum circuit breaker, a capacitor switch, had been in operation for approximately one year, switching capacitors 524 times, before being scrapped due to damage to its external insulation. During the fault analysis, the arc-extinguishing chamber was opened, revealing that both the moving and stationary contacts were spotless, except for a melting point of approximately 3 mm² on the outer periphery of the moving contact's contact surface. Analysis suggested this melting point might have been left when the vacuum circuit breaker interrupted a fault current. Checking the circuit breaker's records, the bounce time for that phase before commissioning was 3 ms, with an oscillating waveform. Measuring this waveform revealed that the separation time between the moving and stationary contacts during the closing bounce was 1.5 ms. Unlike oil circuit breakers, vacuum circuit breakers do not have an insertion stroke in the closed state. Instead, two planes are joined together by a certain pressure. Therefore, during the closing process, the non-elastic collision of the moving and stationary contacts causes bouncing. The bouncing value is related to many factors, such as the elasticity of the contact spring, the closing speed, the opening distance, and the contact material of the vacuum switch. The quality of installation and commissioning, as well as the machining accuracy of components such as aluminum supports, arc-extinguishing chambers, shaft pins, and commutators, also affect the length of the vacuum circuit breaker's closing bouncing time. In order to reduce the closing bouncing time of the circuit breaker to the specified range, the following measures are usually taken: (1) Improve the machining accuracy of the accessories to ensure that the aluminum supports and shafts, commutators and steel pins, shafts, etc. are closely matched to reduce the clearance. (2) Strengthen the quality control of the assembly process and improve the quality of the assembly process. During the assembly of the vacuum circuit breaker, pay attention to reasonable installation and do not subject the vacuum arc-extinguishing chamber to additional force. Adjust the position of the guide tube so that the movement trajectory of the moving contact of the arc-extinguishing chamber passes through the axis of the arc-extinguishing chamber, and the moving contact of the vacuum arc-extinguishing chamber moves freely without any jamming. (3) Appropriately increase the preload of the contact overtravel spring. By taking the above measures, the closing bounce time of the vacuum circuit breaker can be effectively controlled. Due to the large contact area and long stroke of the ZN23-35 vacuum circuit breaker, the closing speed is fast and the impulse is large. Especially when equipped with the CT10 type spring operating mechanism, the bounce is large and it is not easy to stabilize. In order to reduce the bounce value, a butterfly spring can be added to the stationary end of the arc-extinguishing chamber of the vacuum circuit breaker to form a closing buffer and reduce the closing bounce time, but it brings about the problem of unreliable operation of the circuit breaker. In Yancheng, Jiangsu Province, power supply personnel reported that a ZN23-35 vacuum circuit breaker manufactured by a large switchgear factory exhibited very low bounce values ​​before installation, with all three phases showing only 1 ms. However, once connected to the busbar, the bounce became significantly larger, exceeding 10 ms. This was attributed to the use of a static support closing buffer. Before installation, the buffering effect was significant, resulting in minimal bounce. However, after connecting to the busbar, the static end was fixed, eliminating the buffering effect and exacerbating the bounce. Typically, the busbar is removed for mechanical characteristic tests, making this situation difficult to detect. With the addition of the closing buffer, the static contact is no longer rigid during closing, increasing the distance the static contact travels with the moving contact. This leads to increased jitter in the arc-extinguishing chamber, potentially causing it to crack. Furthermore, when interrupting fault current, the immense electrodynamic force generated by the fault current can cause the arc-extinguishing chamber to oscillate laterally, damaging it and potentially leading to a circuit breaker explosion. Relying on reducing the reliability of circuit breakers to ensure closing bounce parameters and extend the already sufficiently long electrical life of vacuum circuit breakers is counterproductive. my country has over 20 years of experience operating vacuum circuit breakers, and based on domestic operation, failures due to the end of their lifespan are rare. From operational experience, the biggest problem with domestically produced vacuum circuit breakers is poor reliability, especially a high rate of mechanical failure. Extensive data shows that various parameters of domestically produced vacuum circuit breakers, such as electrical life, have reached or even exceeded those of similar foreign products; only reliability and appearance still lag significantly behind. High reliability is the primary goal that domestic circuit breakers must strive to achieve. Before solving the reliability problem, an excessively long electrical life is an unnecessary waste. Therefore, while the bounce problem must be addressed, improving the reliability of domestically produced vacuum circuit breakers is paramount. Currently, domestically produced 10 kV series vacuum circuit breakers and 35 kV vacuum circuit breakers with electromagnetic mechanisms, through a series of technical measures and continuous improvement and development, have extremely high reliability, and all performance indicators, including closing bounce time, are very stable. The 35 kV vacuum circuit breaker equipped with the CT10 type spring operating mechanism suffers from high mechanical failure rate and low reliability due to design and manufacturing quality issues with the operating mechanism. In particular, it exhibits long closing bounce time, is difficult to adjust, and is unstable – a common problem encountered by all circuit breaker manufacturers producing this type of circuit breaker. The newly developed ZN23-35 vacuum circuit breaker with a spring operating mechanism achieves a better match between the operating mechanism and the reaction characteristics of the vacuum circuit breaker, eliminating the problems of large mechanism vibration, unstable bounce, and high mechanical failure rate inherent in the ZN23-35 vacuum circuit breaker with the CT10 type spring operating mechanism, effectively improving the reliability of the vacuum circuit breaker.