Fault current limitation characteristics of Bi-2212 bulk coil with different types of shunt coils

We investigated fault current limitation characteristics of a resistive superconducting fault current limiter (SFCL) which consists of a Bi-2212 bulk coil and a shunt coil. For the experiments, different types of shunt-coils which had the same impedance were prepared. One group had high resistance, and the others were designed to have high inductance. The effects of the impedance component variation on current limitation characteristics of the SFCL were compared with each other. The test results showed that the SFCLs of both groups successfully limited the fault current of 7 kA(rms) to below 5 kA(P) right after the fault occurred. The SFCLs with a shunt coil of higher inductance quenched more uniformly, but had a high voltage spike by Ldi/dt at the first half cycle after fault. On the other hand, the ones with higher resistance quenched comparatively less uniformly, but the voltage spike was much smaller. The impedance of the shunt coil is being optimized, taking into consideration stability, insulation, its effect on the circuit and other factors.