Relevance of quantization in PDs activity measurements in presence of environmental noise

In order to maintain reasonable costs and high measure speed, the PRPDA (Phase Resolved Partial Discharges Acquisition) acquisition systems usually employ 8 bits A/D converters. Normally the PDs activity shows signals having different amplitudes (few high amplitudes PD signals with many low amplitudes). Avoiding the A/D converter saturation that lead to measurements information loss, it has been necessary to set the reference voltage on the expected maximum PD signal magnitude. Due to the presence of high amplitude PD signals in real cases it could be difficult recognize bad quantized PD signals (low amplitude) from the noise. In fact, the LSB (Least Significant Bit) of the noise results similar to the ones of PDs signal. In this study, the main issues relevant to this identification problem have been analyzed and discussed. The main purpose is to recognize PD signals from noise. PDs measurements have been performed maximizing the resolution of the maximum acquired discharge and, with the same resolution, noise measurements have been collected. This way the comparison among the noise and the PD signals have been performed. The applied method to distinguish the PD signal is the Equivalent Time — Equivalent Bandwidth (TW). The amplitude of each PD has been varied, keeping the same LSB resolution, in order to study the algorithm behavior.