Application of the wavelet transform to backup protection of MV networks-wavelet phase comparison method

Application of the wavelet transform (WT) to design of a single phase-to-ground protection that could be applied as a backup to standard medium voltage relays in (MV) overhead transmission lines is presented. The concept is based on the phase comparison between wavelet decomposition coefficients of zero sequence voltage and current signals. The idea was tested for signals generated in ATP/EMTP model of MV network. The results obtained are presented and the advantages as well as the drawbacks of the method are discussed.