Transient Characteristics of a Flux-Coupling Type Superconducting Fault Current Limiter According to Winding Direction

The flux-coupling type superconducting fault current limiter (SFCL) is made by using the transformer. The flux-coupling type SFCL consists of the primary and the secondary coils connected in series, and the secondary coil has a superconducting unit connected in parallel. Before the fault occurrence in power system, the SFCL is operated without power loss ((IR)-R-2) because of the zero impedance behavior of the superconducting unit. When the fault occurs and the short-circuit current exceeds the critical current in the superconducting unit, the superconducting unit is quenched, and the short-circuit current is limited. The flux-coupling type SFCL could be divided into the additive and the subtractive polarity windings according to winding direction. The short-circuit current of the flux-coupling type SFCL with the additive polarity winding was limited more effectively than that of the subtractive polarity winding. It was because the direction of current according to the winding direction of a secondary coil was reversed. In the case of the voltage generated in the superconducting unit, the voltage in additive polarity winding was generated more than in the subtractive polarity winding. Consequently, we found that the additive polarity winding could reduce the power burden of the superconducting unit in the comparison with the subtractive polarity winding.