A novel and fast moving window based technique for transformer differential protection

In this paper, a new technique is presented to discriminate between magnetizing inrush currents and internal fault currents in power transformers. The proposed technique uses two moving windows which both of them estimate magnitude of differential current of power transformer by different methods. The first moving window method is based on full-cycle Fourier algorithm (long window) and the second one is originated from least error square method that has five sample point input data (short window). The proposed technique presents a new criterion for discrimination between inrush currents and internal fault currents using the difference between output values of the two moving windows. Obtained results demonstrate precise operation of the proposed algorithm for different conditions such as CT saturation condition. PSCAD/EMTDC software is used for evaluating performance of the proposed algorithm.