Discrimination between faults and magnetising inrush currents in transformers based on wavelet transforms

This paper presents the development of a wavelet-based scheme, for distinguishing between transformer inrush currents and power system fault currents, which proved to provide a reliable, fast and computationally efficient tool. The operating time of the scheme is less than half power frequency cycle (based on 5 kHz sampling rate). In this work wavelet transform concept is presented. Feature extraction and method of discrimination between transformer inrush and fault currents is derived. A 132/11 M transformer connected to a 132 kV power system were simulated using the EMTP. The generated data were used by the MATALB to test the performance of the technique as to its speed of response, computational burden and reliability. The proposed scheme proved to be reliable, accurate and fast. (C) 2002 Published by Elsevier Science B.V.