Influence of grounded back electrode on AC creepage breakdown

Solid insulation using back electrodes has been adopted in various types of electrical equipment. This paper investigates the impact of back electrode on solid insulation AC creepage discharge characteristics. Breakdown voltages at different gap distances are obtained via experiments, and electric field distribution is calculated using computer software. We compare the results between ´with´ and ´without´ use of back electrodes, and investigate the internal relationship between breakdown properties and electric field distribution. It is observed that back electrodes result in concentration of the electric field near the high voltage electrode. A larger gap distance results in an increase in the maximum tangential electric field strength. When tangential electric field strength exceeds a certain critical value, partial discharge streamers are generated. Such streamers help to lower the breakdown voltage and make the maximum electric field strength less than expected value.