Experiment Study on Defect Development Process of Resin Impregnated Paper Bushing under Electro-thermal Effect

The epoxy resin impregnated paper bushing (RIP bushings) has the advantages of oil-free, small size and excellent electrical properties, it has been widely used in transformer bushings and wall bushings. However, it has the disadvantages of complicated manufacturing process and its defects are prone to occur in the production process. In order to obtain the insulation characteristic parameters corresponding to the defects, this paper has analyzed the causes of the defects, and simulated the defects in the actual RIP bushing, including the poor drying of the insulating paper inside of it and the core caused by the concentration of thermal stress during the curing process of the core. Through comparative measurement, the characteristics of partial discharge dielectric loss factor tan δ and capacitance number during the development of early insulation defects of RIP bushings are studied. The results show that the tanδ value and the capacitance value of the defective bushing show an overall increasing trend with the aging time. The research results can provide a reference for the bushing factory test and on-site insulation diagnosis.