Application of Wavelet Transform to Obtain the Frequency Response of a Transformer From Transient Signals—Part 1: Theoretical Analysis

This paper introduces a new theoretical method to obtain the frequency-response curve with the transformer in service (online) from the transient signals analysis by applying the continuous wavelet transform. To validate the method, the transient signals were simulated in the Alternative Transient Program for two cases: 1) under injection of pulses over the 60-Hz wave and 2) under switching operations, respectively. To simulate the transformer, a suitable wide-bandwidth model was employed. This study proposes a new setup of the Morlet wavelet, denominated Morlet-Modified, which showed the best results obtained for our application purpose (FRA On-line). This paper is a contribution for signal processing for the online frequency-response analysis technique on transformers.