DC Fault Current Limiting Characteristics of Flux-Lock Type SFCL With Parallel Connection of Two Coils Using Twice Quench

In this article, DC fault current limiting characteristics of DC flux-lock type superconducting fault current limiter (SFCL) with parallel connection between two coils were analyzed. DC flux-lock type SFCL with parallel connection between two coils was composed of two windings connected in parallel and two superconducting modules (SMs), which were connected in series with each secondary winding. DC flux-lock type SFCLs with a parallel connection between two coils and one SM with one secondary winding in series was thought to perform fault current limiting operation as in AC system. However, since the transient period after resistance generation in SM approaches into the constant value, unlike the AC system, there is a DC current limiting transient period. Therefore, the DC current limiting effect disappears in the DC system and the recovery characteristic after the fault is removed also disappears. To analyze the DC fault current limiting and recovery characteristics, a DC short-circuit test was per-formed, and the various behaviors of flux-lock type SFCLs in DC systems were investigated from the test results.