The objective of this paper is to propose a dc current interruption technology for railway dc traction systems, consisting of a dc vacuum circuit breaker with a superconducting fault-current limiter (SFCL). To this end, a 1.5-kV dc circuit breaker prototype is designed, involving a dc vacuum circuit breaker and a resistive-type SFCL serially connected. The dc vacuum circuit breaker is developed with a commutation circuit to generate a reverse injection current, and the resistive-type SFCL is composed of yttrium barium copper oxide superconducting tape. An LC current source tested the 1.5-kV prototype, showing that, when the precharged capacitor voltage is 1.5 kV, the prospective current is 47 kA increasing at a rate of 9.4 A/μs. The SFCL limits this current to ∼3 kA (peak value), and then, decreases the current to 2 kA after 6 ms, followed by successful clearance via the dc vacuum circuit breaker. The proposed 1.5-kV circuit breaker will successfully clear short-circuit faults up to 47 kA by first limiting the prospective current and then interrupting it.

A DC circuit breaker based on the artificial current zero can interrupt a fault current fast and at low cost. However, its working reliability is greatly reduced by a charging device of the commutation capacitor which generates the current zero. Here, a new DC circuit breaker topology that solves the pre-charging problem is proposed. A resistive superconducting fault current limiter (SFCL) is used to limit the fault current. Meanwhile, the voltage of the quenched SFCL charges the commutation capacitor. The operation principle of the proposed topology is explained, and simulations are performed to select the proper charging parameters; also, the experiments are carried out to prove the feasibility of the proposed topology. The experimental results show that SFCL voltage can charge the commutation capacitor to the level enough to generate an artificial current zero within a few milliseconds, and then, the DC circuit breaker interrupts the fault current successfully.