Development of MV synchronous circuit breaker

High voltage synchronous circuit breakers (SCBs) have been widely accepted as a promising solution for reduction of switching surges. It is essential for SCBs to keep the operating times consistent or predictable over their service life. Extensive investigations have been made on the operating parameter dependency on operating times such as control voltage, stored energy of the drive (hydraulic pressure/spring load) and ambient temperature, etc. Although MV SCB has been developed based on the permanent magnetic actuators, studies on the operating time dependencies for MV SCBs driven by permanent magnetic actuators are still limited. A 40.5kV VCB with 3 independent poles driven by 3 individual permanent magnetic actuators has been developed. A synchronous control unit (SCU) has been developed as well based on a MCU system. A new MV SCB has then been developed by the combination of both. Temperature dependency of operating time for the newly developed SCB has been investigated, the measured result shows, for the permanent magnetic actuators the operating time is irrelevant with the ambient temperature. Tests have been carried out on the capacitor bank switching with the developed SCB, the testing results show the satisfied performance of the SCB in respect of the reduction in the inrush currents as well as the reduction of the over voltages.