An approach using wavelet transform for fault type identification in digital relaying

This paper proposes the use of wavelet transform (WT) in power transmission lines for identifying fault types. WT multiresolution properties are quite adequate for detection of fast changes contained in the disturbed signal. Wavelet decomposition associated with modal components have shown to be an excellent alternative for quick identification of faulted phases. Digitized phase voltage and/or current signals are fed to wavelet filters. The coefficients obtained are then transformed by a modified modal transformation matrix. From the resulting signals, the energy is measured with short time intervals. With an appropriately chosen threshold the fault type is identified. EMTP simulations are used to test and validate the proposed methodology. The obtained results are encouraging and the proposed technique requires a low computational complexity, allowing it to be used as part of a high speed protective relay.