Power transformer protection based on transient detection using discrete wavelet transform (DWT)

This paper addresses a new relaying scheme for power transformer protection. In principle, the new technique implements the wavelet transform to extract the transient components from the captured transform currents. The powerful function of a discrete wavelet transform (DWT) in analysing nonstatic signals is capable of extracting those predominant transient signals energised by transformer internal fault. With the aid of spectrum analysis of extracted transients, the high selectivity of the proposed relay can be achieved. The new relay possesses the advantages of high speed response, immunity to the CT saturation, ability of detecting low level internal faults and inrush current, etc. The study in this paper evaluates the performance of the proposed relaying scheme and proves its feasibility.