Interruption characteristics of vacuum circuit breaker and the application to DCCB

Future, large, multi-terminal HVDC networks are likely to require fast operating circuit breakers to allow stable operation. Several circuit breaker topologies have been developed for fill this purpose [1][2][3]. In this paper, a mechanical active resonant current zero topology DC breaker, capable of interrupting fault current within several milliseconds after tripping, is analysed. In this topology, it is critical that the mechanical interrupter unit is capable of withstanding both high di/dt prior to current zero and high dv/dt post current zero. The high frequency interruption capabilities of gas circuit breaker (GCB) and vacuum circuit breaker (VCB) are examined to assess their use for mechanical DC breaker applications. Comparison of the maximum di/dt capabilities demonstrated that vacuum interrupters are more appropriate for the task. The concept of residual plasma density at current zero was evaluated to explain the relationship between breaking current and di/dt capability.