Estimation of Overcurrent Performance in YBCO Superconducting Thin Films for Fault-Current Limiter

Superconducting fault-current limiters (SFCLs) are expected to be useful for preventing increases in the fault currents caused by the expansion of power systems with dispersed generators. In this study, we focus on resistance-type SFCLs with YBCO superconducting thin films fabricated by the metal-organic deposition (MOD) method and propose a computational approach to calculate the resistance generated in YBCO elements in response to overcurrents. An approximate method for calculating the overcurrent performance of an SFCL, which consists of parallel-connected YBCO elements with an Au-Ag protective metal coating, is developed on the basis of the voltage and current waveforms measured in overcurrent-carrying experiments performed on each YBCO element. It is confirmed that the current distributions for the parallel-connected elements can be approximately calculated by this method. In addition, a trial numerical analysis of the heat conduction phenomena is performed to estimate the transient response of the resistance and temperature profiles of YBCO thin film elements to overcurrent injection.