Analysis of the Unbalanced Fault in Three-Phase Flux-Coupling Type SFCL Using the Symmetrical Coordinate Method

Abstract

The power demand is rapidly increasing in Korea, especially in the urban areas that include the metropolitan area. In addition, the transmission system in Korea is a network structure that ensures the high reliability and stability of power supply. Accordingly, the fault current rapidly increases in the case of a power system fault, due to the decrease in the line impedance. The superconducting fault current limiter (SFCL) was devised to address these existing problems [1]-[4]. This paper analyses the sizes of fault currents limited by flux- coupling type SFCL using the symmetrical coordinate method in the case of unbalanced faults such as a single and double line-to- ground faults in the power system. An unbalanced current of three- phase was indicated by three balanced symmetrical components using the symmetrical coordinate method comparing the component sizes. This study examines the operating characteristics of the SFCL that are required by the system, considering the expected coordination with the protective devices in the actual system.