The application of fault current limiter at Icheon substation in Korea

A 25.8 kV / 630 A hybrid superconducting fault current limiter (SFCL) has successfully designed, tested and finally installed in a real power grid at Icheon substation for the purpose of pre-commercial demonstrations. The hybrid SFCL is composed of high temperature superconductor (HTS), fast switch (FS), and current limiting reactor (CLR) module. In this hybrid SFCL, the HTS module plays a role in sensing fault current and letting the direction of an electric current turn to the FS path. A reduction in amplitude of fault current is done by CLR module. The combination of HTS and FS module made of conventional electrical equipment enables the volume and the cost of total system to be reduced significantly, and the operating reliability to be improved. A short circuit test (12.5 kA_rms) was conducted and we were able to verify reliable fault current limiting capability of hybrid SFCL. After passing all the required tests, including the impedance test and the electrical insulation test, the hybrid SFCL was installed at Icheon substation in 2010 and now it is waiting for connection to Jang-pyong distribution line (D/L). Recently, a stable operation of HTS cryocooling system was clearly proven through applying load current modeled on the worst fluctuating load among real daily load profiles of Jang-pyong D/L.