Diagnostic study of the surface condition of the insulation structure using wavelet transform and neural networks

S-Transform Based Time-Frequency Analysis of Leakage Current Signals of Transmission Line Insulators under Polluted Conditions

“…In the S-transform contour plot, a thick dark line is now formed corresponding to 50 Hz, showing that the magnitude of fundamental frequency component increases when compared with the higher order harmonic components. Compared with dry clean surface condition, it is clear that density of time-frequency contour in the high frequency region is considerably reduced now [10,12,17].…”

“…In addition, thermal stress, UV stress, water absorption stress and operating electrical stress acts on the surface of the polymeric insulating material and thereby the material slowly loses its hydrophobicity. Under wet conditions, formation of contamination layer allows the flow of LC and causes partial evaporation of the contaminant due to the heating effect, which leads to the formation of dry bands [10,12]. This causes voltage redistribution along the insulator surface and in turn leads to high electric field intensity across dry bands and formation of partial arcs over the dry band.…”

“…Also from the results, it is noticed that when the frequency of occurrence of short duration discharges increases, then the magnitude of fundamental component also increases along with third harmonic component. Therefore these short duration discharges and corresponding third harmonic component plays a major role in the increase in local surface temperature of the material, which in turn leads to the surface degradation and aging of the material [10,12].…”

“…Various approaches were used to predict the flashover and surface degradation of outdoor insulators [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. R.S.Gorur et al, [7] measured the surface resistance to identify the surface condition of non-ceramic insulators.…”

Investigation on Flashover Development Mechanism of Polymeric Insulators by Time Frequency Analysis

“…They suggested that both the fundamental and low frequency harmonics of leakage current can be used a tools to determine both the beginning of aging and end of life of silicone rubber in salt-fog. R. Sarathi et al, [9] have shown that application of moving average technique for the trend analysis of leakage current signal could be useful to predict the surface condition of outdoor polymeric insulators. Farhad Shahnia et al, [10] have studied the characteristics of polluted composite insulator and concluded that the densities of pollution and electrical field caused flashover for polluted insulators.…”