A new filter scheme for the filtering of fault currents

In protection relaying schemes, the digital filter unit plays the essential roles to calculate the accurate phasor. However, the decaying DC components in fault currents always cause false operations of relay systems. This paper presents a new filter scheme which can remove such components from fault currents. Using the proposed scheme, the full-cycle DFT (FCDFT) only needs one-cycle samples to obtain an accurate fundamental phasor. The decaying DC component is removed by an iterative computation. The proposed filter scheme can help digital filters achieve accurate results rapidly. Simulations results illustrate the effectiveness of this new algorithm for distance relaying applications.