Improving Capacitive Load Breaking Performance of Circuit Breakers

When a circuit breaker interrupts a capacitive load, improving the dielectric recovery strength is an important measure to ensure the successful breaking process because of the competition between transient recovery voltage and dielectric recovery strength after current zero-crossing. The recovery strength of the medium is related to factors such as the gap and contact surface conditions. The contact surface condition directly affects and determines the withstand voltage capability of the circuit breaker's arc gap. The contact surface condition is also closely related to whether welding occurs during the contact closing process. Welding is determined by the current at closing and the duration of that current. This paper presents a 10 kV model of capacitor bank energization in PSCAD software, calculates the magnitude of the inrush current, and determines the inrush current duration. The product of the square of the current during the inrush period and the inrush time are used to represent the thermal heat on contacts of the circuit breaker during the closing process. The paper analyses the factors that affect the thermal heat generation, especially the relationship between the inrush current peak and duration. Therefore, as long as the inrush current is reduced, the occurrence of welding can be effectively prevented.