Wavelets: a new tool for the resonant grounded power distribution systems relaying

This paper introduces wavelets and shows that they may be efficient and useful for power distribution relaying. The wavelet transform of a signal consists in measuring the “similarity”between the signal and a set of translated and scaled versions of a “mother wavelet”. The “mother wavelet” is a chosen fast decaying oscillation function. Wavelets are used to analyse transient earth faults in a 20 kV resonant grounded network as generated by EMTP. It is shown that wavelets may be employed for analysing records to study efficiently the faulted network. Moreover, this new technique can actually be implemented in real time for protection devices. Thus, it is suitable for application to protective relays