Railway DC circuit breaker based on the superconducting fault current limiter

The object of this paper is to design a new type railway DC circuit breaker based on the superconducting fault current limiter and artificial current zero method. The DC circuit breaker has a significant advantage in good compactness and high reliability. An experimental prototype was designed which includes a superconducting fault current limiter (SFCL) and a vacuum interrupter. The DC current switching characteristic was investigated experimentally. The current limiting characteristics of the SFCL were tested first. When a short-circuit current is encountered, the SFCL limited short-circuit current to 8%~15%. Then the vacuum interrupter in parallel with countercurrent circuit were tested together with SFCL. The main experimental current was supplied by a LC circuit. The overvoltage generated between two contacts of vacuum interrupter was suppressed by metal oxide arrester. The source voltage was charged from 100 V to 700 V and fault current ranged from 2.4kA to 15kA. All interruptions were successful. The experiment result shows that the prototype of the railway DC circuit breaker can interrupt the DC short-circuit current in a range from 4ms to 5ms. And the size of the capacitor in countercurrent branch can be reduced to 8%~15%. This is important to the compaction of railway substation station.