Study on Temperature Distribution and Insulation Performance of Epoxy Resin Impregnated Paper Bushing Model

Abstract

In order to study the relationship between current carrying heat and insulation performance of epoxy resin impregnated paper (RIP) bushing, the RIP bushing model is researched in this paper, the internal temperature and insulation characteristics of the bushing model are measured under the same conditions. The internal heating and heat transfer laws under different current are studied. The change rule of dielectric loss factor (tan$\delta$), capacitance and frequency domain spectroscopy are analyzed at the same time. In order to obtain the insulation information carried by the frequency domain spectroscopy in the limited measurement frequency band, the frequency domain dielectric characteristic $S_{tan\delta}$ which can quantify the maximum operating temperature of the RIP bushing is extracted in this paper, and gives the fitting relationship between the characteristic parameters and the maximum temperature. The results show that greater current causes more heat release from the resistance and greater temperature gradient inside and outside the bushing; When the current is 1000A, Tmax = 55°C for 4 hours, and when the current is 1200A, Tmax = 58°C for 2 hours, reaching the “critical point” temperature of the tan$\delta$ value of the bushing model, the tan$\delta$ value will decrease first and then increase with the increase of the current loading time; The tan$\delta$ frequency spectroscopy curve shifts to high frequency region with the increase of current; The extracted characteristic parameters are sensitive to temperature in 5mHz~50Hz, $S_{tan\delta}$(50) has the high goodness of fitting function relationship with the maximum operating temperature, which can be applied to evaluate the maximum operating temperature of RIP bushing. The test results can provide reference for the non-destructive monitoring of the RIP bushing.