A crest factor-based technique for the analysis of polluted insulator leakage current under harmonically distorted supply voltage

High-voltage insulators are one of the essential components of a power network, and regular monitoring of them ensures the reliable operation of the network. Therefore, several research groups have proposed different condition assessment indices by analyzing the measured leakage current of the polluted insulator at different environmental conditions. At laboratory conditions, those indices are developed under pure or nearly sinusoidal voltage waveforms. However, a considerable amount of harmonic distortion is prevalent in the supply voltage in real life owing to the ever-increasing trend in the use of power electronic devices in the power network; as a result, insulators in the power network are immediately subject to this distortion. Therefore, in the presence of distorted supply voltage, the efficacy of these current indicators developed for pollution severity assessment under purely sinusoidal voltage will become dubious. In this work, authors have investigated the impact of distorted supply voltage waveforms on the leakage current of an artificially polluted silicone rubber insulator. The result of this work indicates that in combination with contaminant severity and relative humidity, supply voltage distortion causes significant changes in the measured leakage current. Based on these findings, the authors further proposed a new crest factor-based index to predict the pollution level of a silicone rubber insulator.