impact of pollution location on time and frequency characteristics of leakage current of porcelain insulator string under different humidity and contamination severity

one of the important factors influencing outdoor insulators performance is pollution phenomenon. the pollution, especially during humidity condition, reduces superficial resistance of insulator and lead to a flow of leakage currents (lc) on the insulator surface, which may result in total flashover. the lc characteristics are affected by parameters such as nature and severity of pollution. location of pollution is another parameter that can be effective. this paper presents the analysis of lc waveforms of insulator strings under different pollution location and equivalent salt deposit density (esdd). the tests was performed on the hv porcelain suspension insulator string in which three adjacent discs of insulator string were contaminated and location of them changes along the insulator string. besides, the effect of humidity and operating voltage on lc waveforms were investigated. experimental data were analyzed in both time and frequency domain. obtained results indicate that there is strong correlation between the location of pollution and lc parameters such as peak value ( ), harmonic components and total harmonic distortion (thd). also, the ratio of fifth to third harmonic component ( ) is presented as an important index that has strong relationship to the pollution location.