Characterization of discharges on non-uniformly polluted glass surfaces using a wavelet transform approach

In this work, the electric discharges activity on non-uniformly polluted glass plane insulator model is investigated for increasing applied voltage levels up to flashover. The effect of pollution severity was simulated using pollution solution containing various kaolin concentrations. The polluted sample has a strip that is dry and clean which is parallel to the electrodes planes. Configurations with various widths (2 to 14 cm) and locations of this dry clean strip were tested, and both the leakage current and the accumulated charge were examined. Further in-depth examination of the leakage current waveforms was carried out using a wavelet analysis approach. The Discrete Wavelet Transform (DWT) is adopted for the leakage current decomposition in several time-frequency bands. The STD-MRA (Standard Deviation-Multi Resolution Analysis) representation is employed to specify the Detail components (frequency components). It is shown that these can be used to detect the presence or absence of partial arcs activity over the dry clean strips. The reported results show that the simultaneous increase in the standard deviation of the Details components D8 and D10 indicates the presence of the partial arcs. However, the increase only in the standard deviation of the Detail component D10 indicates no discharge activity. Such approach may have some useful application when analyzing the leakage current on its own to monitor discharge activity on polluted surface. Further work is on-going to apply this approach to full outdoor insulators.