Current Limiting Characteristics of a Novel Flux-Coupling Type Superconducting Fault Current Limiter

A novel flux-coupling type superconducting fault current limiter (SFCL) is proposed in this paper. This type SFCL is composed of two superconducting coupling coils, a controlled switch and two metal oxide arresters (MOAs). The primary coil and the secondary coil, which are wound in the reverse direction and are respectively in parallel with the two MOAs, are connected in parallel through the controlled switch and a main circuit breaker. Under normal condition, due to the non-inductive coupling characteristics between the two superconducting coils, the impedance of the proposed SFCL will be too small to affect the main circuit. After the fault happens, the controlled switch will be opened from its initial closed state, and meanwhile the MOAs will prevent the two coils from being damaged by the overvoltage caused by the switching operation. Since the flux between the coils cannot cancel out each other, the non-inductive coupling will disappear, and then the limiting impedance will be triggered for current-limitation. In order to evaluate the current-limiting performance of the novel flux-coupling type SFCL, a laboratory scale prototype was made. The two superconducting coils were fabricated with Bi2223/Ag, and an anti-parallel IGBT pair was chosen as the controlled switch. According to the test results, it was found that, the fault current could be limited quickly and effectively, and there was no overvoltage during the operation process of the controlled switch.