Application and simulation of the active fault current limiter This paper presents the operating principle and application of an active fault current limiter (FCL) to a single phase distribution system. It employs an AC voltage source in phase with system voltage and an air core ideal transformer. The primary winding of the transformer is in series with AC main circuit and the secondary winding is connected to the homophase AC voltage source. In normal operating state (prefault condition), the secondary current of the transformer is adjusted so that FCL has no influence on the main circuit. During fault, by controlling the magnitude and phase of the secondary current, the fault current can be reduced to some extent. The model of system implementing FCL is created and simulated in MATLAB SIMULINK. The simulation results show that FCL can limit fault current effectively.