Electrical Tree Performance of Epoxy Resin Used in Power Electronic Transformer under Bipolar Square Wave Voltage

The electrical tree characteristics of epoxy resin used in power electronic transformer under bipolar square wave voltage are investigated. The results show that the number of electrical tree branches increases with voltage amplitude while decreases with voltage frequency. The increase of voltage amplitude and frequency accelerates the growth of electrical tree and reduces the withstanding time of the epoxy resin exposed to electrical tree. In addition, it is found that electric breakdown lead to great release of CO, CO 2 and hydrocarbon gases in epoxy resin.