A Method for Extracting Partial Discharge Signals in Transformer Winding with Wavelet Analysis

In this paper a method for extracting Partial Discharge (PD) signals is introduced, which is implemented for evaluating electrical measured partial discharges on a 66 kV / 25 MVA fully interleaved winding of a power transformer. Applying wavelet transform to a signal produces a wavelet detail coefficient distribution throughout the time-scale, which depends on the mother wavelet chosen. This method is based on the capability of the chosen mother wavelet for generating coefficients with maximum values. The paper demonstrates that the wavelet based de-noising method proposed in the paper can be employed in extracting the PD pulses from the measured signal successfully to provide enhanced information and further infer the original site of the PD pulse through capacitive ratio method. In fact, the basic idea of this method is described and applications to partial discharge studies are explored. Key-Words: Partial Discharge, Transformer, Transformer Winding, PD Location, Wavelet Transform, Signal Denoising, Signal Processing