Experimental Study on Commutation Parameter of HVDC Vacuum Circuit Breaker

For HVDC vacuum circuit breaker based on commutation principle, the commutation parameter is the key factor influencing the interrupting performance. In this paper, the DC breaking process is simulated by PSCAD/EMTDC and the result shows that the higher the commutation frequency and the breaking current amplitude, the higher the arc current decline rate is. The commutation parameter and interrupting performance of a DC vacuum breaker prototype are tested through a synthetic DC test circuit. The initial moment of commutation time and the safe stroke of the system are determined. The experimental result shows that when the commutation frequency and the amplitude ratio of breaking current to commutation current are constant, the commutation time is not affected by the breaking current amplitude, but the arc current decline rate increases with the increase of breaking current amplitude. High commutation frequency will make it difficult to break even reignite the arc. What’s more, a high commutation current will result in the higher TRV to the gap, when the breaking current is 5 kA and the commutation current is 8 kA, there will generate a 6 kV recovery voltage at the break, leading to arc reigniting.