Analysis of Ultrawide-band Detected Partial Discharges by Means of a Multiresolution Digital Signal-processing Method

Ultrawide-band detection of partial discharges (PDs) mainly aims at recording the true shape of a PD current signal. It is thus possible to achieve more useful information than that provided by other detection techniques about sources and causes of both PD current signals and the physical processes taking place. However, external interference, reflections, oscillations and stray elements in the measuring circuit may distort the signal being recorded; hence, the information extracted from it might sometimes be meaningless. In the paper, a digital signal-processing method for reliable analysis of ultrawide-band detected PD current signals is proposed. The method, exploiting the multiresolution approach peculiar to the Wavelet Transform, is capable of setting the detected signal free from most disturbances affecting its true shape, thus ensuring the significance of the measurements carried out on the signal itself. After a brief remark about the main features of the Wavelet Transform and its multiresolution approach, the proposed method is described in detail. Experimental results obtained on actual PD current signals are then given in order to highlight the method's reliability and effectiveness