Analysis of Fault Current Limiting Characteristics According to the Fault Angle in an Integrated Three-Phase Flux-Lock Type Superconducting Fault Current Limiter

The integrated three-phase flux-lock type superconducting fault current limiter (SFCL) consists of three-phase flux- lock reactor wound on an iron core with the same turn's ratio between the primary coils and the secondary coils for each phase. When a SFCL is operating under normal condition, and assuming that the leakage flux is neglected, the magnetic flux generated between the primary and the secondary coils of each phase is canceled out perfectly. Therefore, the impedance of the SFCL is zero and the power system can operate normally without any loss. However, when a fault occurs, quench happens in high-TC superconducting (HTSC) elements and the magnetic flux generates in an iron core. Therefore, the impedance of the SFCL is large enough to limit fault currents. In this paper, we investigated the fault current limiting characteristics according to the fault angle in SFCL in fault types such as the single-line-to-ground fault, the double-line-to-ground fault and the triple-line-to-ground fault. Experiment results show that the fault current limiting characteristics of the SFCL are dependant on the quench characteristics of HTSC elements in each phase.