Experimental Method for Determining the Recovery of Superconducting Fault Current Limiter Using Coated Conductor in a Power System

Research on resistive superconducting fault current limiters (SFCLs) using coated conductor(CC) has now been advanced from development to commercialization stage. It is necessary to investigate the recovery characteristics of SFCL for effective application to power system. In Korea, if the SFCL is directly inserted to distribution power grid, it must be recovered in 0.5 s after fault. Since temperature sensor is not accurate in liquid nitrogen bathe and temperature of CC, after falling down below 92 K, is impossible to be measured by electrical method, it is difficult to measure the temperature of SFCL during the recovery of YBCO CC. In this paper, an experimental method was proposed to determine the recovery of resistive SFCLs. Under over-current for 0.1 s, maximum temperature of high temperature superconductor (HTS) wire increased to 300 K; after a few seconds, recovery time was measured by increasing DC current. With these experiments, thermal relaxation time required for the temperature of CC to decrease to 77 K was analyzed.