Numerical Simulation of Surface Dicharge in Oil-paper Insulation Under Various Temperatures

Power transformer is the key equipment for power transmission and transformation. However, the operating accidents caused by the insulation fault lead to huge economic loss. In order to reveal the mechanism of surface discharge in oil-paper insulation under various temperature, a numerical simulation model based on hydrodynamic equation for three kinds of charge carriers, coupled with current field equation, is proposed. The streamer inception and propagation along the oil-paper interface are simulated. According to the results, the effect of temperature on inception voltage, flashover voltage and streamer propagating velocity in oil-paper insulation are acquired and analyzed. According to the simulating results, the inception of streamer takes approximately 80 μs for charge carriers accumulation and only when the electric field intensity reaches a specific value can the streamer propagate along the oil-paper interface within about 3 μs. What's more, with the increase of temperature, the field ionization and the movement of charge carrier become more active, leading to the decrease of inception voltage and flashover voltage of surface discharge in oil-paper insulation. Last but not least, with the increase of temperature, the average velocity of surface discharge increases. When the temperature reaches 85 °C, the average velocity of streamer propagation increases sharply, with the value of 4790.1 m/s.