Investigation on Internal Overvoltage Performance of EHV Multi-Break Circuit Breaker

The 500kV Extra High Voltage (EHV) grid plays a crucial role in China's west-to-east power transmission program. However, the insulation of the EHV system is significantly impacted by internal overvoltage resulting from operational factors. In recent years, there has been a notable increase in internal overvoltage within electrical equipment, emerging as a prominent factor that jeopardizes the safe operation of the entire system. It is imperative to address this issue in order to ensure the continued reliable and secure functioning of the EHV grid. This article discusses the occurrence of 500 kV circuit breaker failure caused by transient switching surges. It has been found that there is still a risk of breakdown even when the switch is opened. This breakdown occurs within the switch and poses a serious threat to the insulation of the extra high voltage system. This paper focuses on the development of faults and presents a comprehensive description of processes involved in their occurrence. By connecting a surge arrester in parallel with the grading capacitor inside the switch, the magnitude of the overvoltage can be effectively reduced, thereby preventing the failure of the grading capacitor.