Dielectric simulation of capacitive switching behavior for vacuum circuit breaker

Abstract

Switching of capacitor banks or cables leads to small breaking currents in comparison with short-circuit currents. After current interruption the circuit-breaker must withstand twice the peak value of the system voltage. Furthermore, restrikes can lead to voltage multiplication. The conjunction of relatively small breaking currents with high voltage stress must be considered in detail. This leads to a reconsideration of an appropriate design of contact speed and gap distance for capacitive switching duties. In particular the dielectric strength (DS) of the contact gap plays a major role regarding restrike performance. To simulate the capacitive switching performance of a certain contact system, the DS of a contact gap is required. A former study with a notable number of restrikes allows the calculation of the rate of rise of dielectric strength (RRDS). Taking this into consideration restrike simulations for vacuum circuit breaker for distribution and transmission voltages are presented. The evaluation of the simulations yields necessary requirements for contact speed, stroke and dielectric strength.