Ageing Behavior of Epoxy Resin Impregnated Paper under Electrical and Thermal Stress for Wall Bushing

Epoxy resin-impregnated insulating paper is an important insulating material for dry-type Resin-Impregnated Paper (RIP) bushings of converter transformers, and it has been subjected to the combined action of heat and electricity for a long time. In order to study the effect of electrothermal aging on resin-impregnated paper, the main insulating material in dry bushings, Resin-Impregnated Paper samples were subjected to electro-thermal aging tests, and the electrical conductivity and dielectric properties of the aged samples were tested regularly. The results show that with the increase of electrothermal aging time, its volume resistivity shows a decreasing trend and its dielectric constant and dielectric loss value increase. Compared with the single factor effect of electricity and heat, the combined effect of electricity and heat on the volume resistivity and dielectric properties of the material is more significant, and it is greater than the superposition effect of electricity and heat. Electricity and heat mutually enhance the aging effect and have a synergistic effect. As the aging progresses, the volume resistivity decreases, the dielectric constant and dielectric dielectric loss increases which is of great engineering significance for grasping the aging law and evaluating the insulation state of the bushings.