Time-scale analysis of the applied voltage waveform in uniform pollution conditions as a new monitoring technique of the insulator flashover

In this report, we have examined the impact of pollution severity on the dielectric performance of an insulating plane model which reproduces the 1512 L outdoor insulator. This insulator is largely used by the Algerian company of Gas and Electric power (SONELGAZ). These investigations were carried out using different conductivities composed of distilled water and NaCl for the insulator surface contamination. The aim of this study is to control the pollution severity in order to predict the imminent moment of insulator flashover. In order to monitor performance of the outdoor insulator, the continuous wavelet transform (CWT) is proposed as a new technique by using the scalogram analysis. The CWT is applied only on voltage waveforms during electric discharges occurrence on the polluted insulator surface. This technique examines the fractal nature of the applied voltage waveform which is distorted by electric discharges. These discharges cause important voltage drops. Obtained results with this method establish clearly the pollution severity deposited on the insulating surface and show the critical situation by which the insulator flashover can occur for low applied voltage levels. The red color appearing in the scalogram shows that electric discharges occur on the polluted surface. This color reaches low scales indicating that the frequency occurrence of electric discharges increases when the pollution level is critical.