DC current interruption by a combination of electric fuse and vacuum switch

The objective of this paper is to experimentally investigate the DC current switching characteristic of a combined DC circuit breaker. The DC circuit breaker, which is a combination of a DC switch and a fuse, has a significant advantage in full-range DC current switching. When a load current or an over-load current emerges, the DC load switch has the ability to clear the current. However, when a short-circuit current is encountered, which would have been exceeded the ability of the DC switch, the fuse is used to decrease the fault current to a lower value, then the DC switch is used to clear the tail current. In this case, it is easier for the combined DC circuit breaker to withstand a transient recovery voltage (TRV) after current zero, because the TRV of power lines stresses on both terminals of fuse and DC switch. In a current making operation of DC circuit breaker, the DC switch makes the current individually. A diode is connected in series with the LC discharging circuit to generate a test DC current of 3kA. Another LC discharging circuit is used to generate a high-frequency counter current of 3.1 kA, which is injected into the DC current to generate an artificial current-zero. Experimental results showed that the combined DC circuit breaker can interrupt the test DC current under 1 kA in a range from 3ms to 4ms. Fuse can interrupt the short circuit current of 3 kA in 20ms.