Fault isolation characteristics of the hybrid DC circuit breaker

The topologies and operation principles of the hybrid Direct Current Circuit Breaker (DCCB) are present in this paper. The equivalent circuits of the hybrid DCCB in different period of the current breaking process are obtained. Then the fault current path of DC double pole short-circuit fault, monopole grounding fault, single phase to ground fault and the fault isolation characteristics of the hybrid DCCB during these fault are analyzed. The hybrid DCCB can isolate the fault lines from the converter stations, and can isolate the converter station if fault occurs in the AC side or in the converter, avoiding influences on another converter station. During current interrupting, the transient breaking voltage of the hybrid DCCB is added to the DC line voltage, then the insulation requirements of the DC line and DC equipment increase. Finally, simulations about hybrid DCCB isolating fault effect are carried to verify the analytical results.