Electrical Tree Growth in Fiber Reinforced Epoxy Composites for GIS Insulation Rod

Both high voltage (HV) and mechanical loads will be applied simultaneously to the insulation rod during operation, and their effects on the insulation degradation characteristics should be investigated. In this article, mechanical stresses with different magnitudes and types, parallel to the direction of the electric field, are applied to the samples, and electrical tree growth of two kinds of fiber-reinforced epoxy composites is explored. Obtained results show that the introduction of fibers makes electrical tree tend to grow along the fiber/epoxy interface, which results in a concentration of electrical tree growth angles at 0° and 90°. Compared with the neat epoxy resin (EP), the application of mechanical stress accelerates the deterioration and development of electrical trees in the composites to varying degrees, with lighter color, narrower channels, and enhanced amplitude and number of partial discharges. As the mechanical stress increases, the breakdown time of the composites decreases, which could be reduced by 17%–36%. This phenomenon can be attributed to the discrepancy in elastic moduli between the fiber and EP, resulting in stress concentration at the interface.