Analysis on Current Limiting and Bus-voltage Sag Suppressing Characteristics of a Flux-lock type SFCL using an Isolated Transformer

Abstract

In this paper, the current limiting and bus-voltage sag suppressing characteristics of a flux-lock type superconducting fault current limiter (SFCL) with an isolated transformer were analyzed through short-circuit tests for a simulated power system with the SFCL. The isolated transformer, which was connected to the superconducting (SC) element of the flux-lock type SFCL, was designed to improve the current limiting and the bus-voltage sag suppressing characteristics of the flux-lock type SFCL by preventing the fault current from directly passing through the SC element. An analysis of the experimental results considering the winding ratio of the isolated transformer confirmed that the flux-lock type SFCL, which was planned with a lower winding ratio, performed the limiting operation more effectively, while the flux-lock type SFCL with a higher winding ratio of the isolated transformer, was more effective from the point of view of the suppression of the bus-voltage sag.