High voltage insulator contamination level online monitoring with conventional and novel methods

Conventional online monitoring techniques used for monitoring the levels of contamination on high voltage insulators, such as leakage current and partial discharge, are not effective in dry conditions since they require the surface of the insulator to be wetted by fog, rain, condensation or snow. In order to address this problem, the authors have formerly reported two new techniques based on microwave radiometry and microwave reflectometry. This paper compares the performance of conventional pollution monitoring methods with the novel radiometry and reflectometry techniques under controlled environmental conditions. The results show that when the insulator surface is dry the conventional methods are unable to distinguish the pollution level while the novel methods are able to clearly identify varying levels of pollution. After the surface is wetted, the conventional methods become effective however the partial discharge activity may rapidly develop to a flashover prior to the preventative maintenance being implemented. Thus, the novel contamination monitoring methods will potentially facilitate advanced warning of the future failure of a wet insulator in climates where insulators experience dry conditions for extended periods.