Variable window filtered power system signals for electric power system monitoring and protection operations of an electric power system are provided herein. Upon detection of a power system disturbance, the filter window is decreased after a predetermined resize delay such that pre-disturbance samples are not included in the new window. As additional samples are obtained, the filter window grows to include new samples until the window reaches an initial filter window length. Gain and group delay correction factors accounting for window size and signal frequency are approximated.