Demonstration of a Superconducting Fault Current Limiter in a Real Grid

A 22.9 kV superconducting fault current limiter (SFCL) has been in operation in a real grid in Korea. The SFCL is of hybrid type, in which the fault current is detected by a superconductor and bypassed by a high-speed switch to a reactor in a parallel circuit for current limitation. It has a current rating of 630 A, and has been operated in a distribution line in Icheon Substation, which is located in a suburban area with moderate loads. The SFCL has been operated very stably with no degradation in performance. Temperatures and level of the liquid nitrogen cooling the superconductors have been maintained within 0.1 K and 0.3 cm, respectively, under large daily load variation of about 100 A. Performance of the SFCL was tested by measuring minimum limitation current and impedance of the SFCL, and was proved to maintain the initial level of performance. There was a single line-to-ground fault event in the distribution line where the SFCL has been operated, and the SFCL limited the fault current successfully. Data analysis showed that the SFCL limited the current as designed. These results proved reliability and performance of the SFCL.