Local Inter-foil Insulation Deterioration Diagnosis and Simulation of RIP Bushing Based on FDS Method

Resin-impregnated paper (RIP) bushings have been widely used in power system, however failure caused by local inter-foil insulation deterioration has occurred from time to time, which has seriously affected the safe and stable operation of substations. Due to the damaging effect of partial discharge, the resistance of local inter-foil insulation will gradually decrease, and breakdown may even occur. To study the phenomenon of local inter-foil insulation deterioration of RIP bushing, a test platform is established for 72.5kV RIP transformer bushings, and corresponding frequency-domain dielectric spectroscopy(FDS) test is conducted at room temperature. It is found that the FDS curve of bushing with inter-foil insulation deterioration and breakdown is significantly shifted compared to the normal one. In addition, due to the obvious development process of local inter-foil insulation deterioration of RIP bushings, a simulation model is established in this paper, and the method of changing the local electrical conductivity of local inter-foil insulation material is used to characterize the degree of insulation deterioration, and corresponding FDS response curves are obtained. The results show that with the development of the deterioration of local inter-foil insulation, the C-f and tant5-f curves have obvious transitional processes. In the initial and middle stage of insulation deterioration, the FDS method has higher diagnostic effectiveness than the traditional power frequency dielectric loss method. This article can provide a basic theoretical reference for the on-site diagnosis of local inter-foil insulation deterioration of RIP bushings.