Recovery process of a transformer type superconducting fault current limiter

Recovery process of a transformer type superconducting fault current limiter (SCFCL) was investigated by experiments using three-phase test SCFCL designed and made. "Recovery time" decreases, as "fault time" is longer. It is pointed out that the FCL current at the limiting mode affects the cooling process of the secondary wire during the current limiting operation. A simple simulation of the SCFCL based on the heat equation was performed. The simulation results of the "recovery time" agree well with the experimental ones. The temperature of the normal zone was estimated by use of the simulation. It decreases even in the current limiting mode and its decreasing rate depends on the limiting current. After a long limiting operation (over 5 s), the temperature saturated at about 22 K, the secondary coil current is the minimum propagation current of the wire and the "recovery time" is quite short and independent of the limiting current.