Detection of electrical tree in epoxy resin under non-uniform DC electric field measured by current integrated charge method

Epoxy resin not only has excellent insulation properties, but also has properties such as heat resistance, water resistance and so on. For these reasons, epoxy resin is used in various applications. It is necessary to pay attention to the deterioration of partial discharge and electrical tree, when the epoxy resin is used as an insulating material for DC high-voltage equipment, because they are exposed to a high DC electric field. In addition, it is known that the insulation performance of the epoxy resin is significantly reduced, when a foreign matter or air void is mixed in them, because non-uniform electric field will be generated. The electrical tree generated by non-uniform electric field increases the risk of dielectric breakdown and reduces the reliability of equipment. Therefore, it is necessary to accurately diagnose the deterioration of the epoxy resin and to clarify the risk before dielectric breakdown. It is expected that the accurate degradation diagnosis for DC high-voltage equipment will be possible by using the current integrated charge method. The equipment can be operated safely by clarifying the correlation between the integrated charge and the electrical tree. In this study, the electrical tree in epoxy resin was diagnosed by the current integrated charge method under non-uniform DC electric field. As a result, several information on the electrical tree was obtained before dielectric breakdown. © 2020 The Institute of Electrical Engineers of Japan.