Numerical analysis of bubble behavior and pressure rise phenomena due to arc under insulating oil in closed vessel

When a fault arc occurs in oil-filled electric power equipment, it generates a flammable pyrolysis bubble. A dynamic pressure rise with the generation of the bubble, may lead to blowout of the oil and a high-temperature flammable gas. This paper presents a numerical model for the analysis of bubble behavior and pressure rise due to the arc in a closed vessel containing air and oil. The model is based on the Rayleigh-Plesset equation which expresses single bubble behavior in liquid to a driving pressure field with consideration of the evaporation/condensation phenomena of the bubble surface and the oil flux. Furthermore, the authors append physical properties of gas and effects of arc energy into the bubble based on measurement and calculation results. The calculated pressure magnitude and frequency of oscillation are similar to the experimental results. The results suggest that the numerical model covered important factors of the bubble behavior and pressure rise phenomena. © 2020 The Institute of Electrical Engineers of Japan.