Electric field measurements on composite and ceramic insulators during pollution testing

High voltage insulators exposed to heavily polluted environments can flashover and cause undesired power interruptions. Power interruptions are very disturbing for the modern society, especially for the processing industry which will have cost and time consuming start-up problems. Today´s standard pollution test methods are, however, not representative of actual pollution conditions in service and are moreover not applicable to composite insulators. In order to distinguish which insulator design or material is better, new pollution test methods are needed which more closely simulate actual service conditions. The new pollution test used in this investigation is the so called DCM (dust cycle method), developed by Eklund et al. (1994) which imitates natural conditions with wind-borne pollution. To understand the behaviour and mechanism behind the flashover new diagnostic tools and analysis methods are needed. In order to investigate the possibilities of a pre-warning signal for flashover, electric field and current measurements have been performed during the pollution tests