Analysis of the Operation Characteristics of the Flux Offset-Type Fault Current Limiter for Reinforcing the Safety of an Electric System

In this paper, a flux offset-type fault current limiter was proposed as a new means of reducing fault currents. The flux offset-type fault current limiter is a device that is integrated into the fault current technology, to which the flux offset principle of a transformer is applied, and is combined with a transformer and a fast switch. To secure the operation reliability of a flux offset-type fault current limiter, a simulation system was constructed to analyze its operation characteristics by generating a single line-to-ground fault and a triple line-to-line fault. According to the test results, the system performed stably without any impedance, because the primary and secondary winding fluxes of the transformer offset each other at normal times. However, when a fault current event occurred, because the fast switch was activated to limit the fault current by opening the secondary windings of the transfer within an average of 9.5 ms, which is shorter than the operation time of the existing electric circuit breakers by 3–5 cycles, the system is likely to perform protective coordination with circuit breakers in the future. In addition, the application of this current limiter could keep the fault current limit ratio to about 96 %.