Influence of water content and temperature on conduction and field on an Alumina/epoxy insulator

The influence of water inside an insulating material (epoxy resin with Alumina filler) on volume resistivity, is investigated. This parameter is measured versus temperature. The water content within samples is adjusted using a climatic chamber, and monitored by weighing. Measurements show a large enhancement of volume conductivity versus water concentration and temperature. The impact of a temperature gradient, and of the presence of water on the field distribution and current through a high voltage insulator under HVDC is calculated. This is done by numerical simulation with simplified insulator geometry. The simulation includes the coupling between temperature distribution, resistivity versus temperature, and field distribution.