Simulation and Analysis on Surface Discharge Development in Composite Dielectrics

The discharge of solid insulation in gas or liquid insulation is regarded as the surface discharge. The theory of discharge in liquid and composite dielectric is not as comprehensive as that in gas at present. In this paper, the surface discharge of composite insulated rod surface electrode under ac voltage was analyzed theoretically and simulated. Moreover, an assumption was proposed based on liquid streamer theory and gas surface discharge process. Surface discharge is triggered by electron emission in local high electric field intensity area in high purity oil. The electric field distortion caused by bubbles was regarded as the evolution process of excited surface discharge. When the channel between the electrodes is closed by the bubble, Flashover may happen in the oil-impregnated paper insulation. Then, by the method of establishing physical model, COMSOL multi-physical software was used as the numerical simulation tool to calculate the distribution of electric field and analyze the factors influencing the electric field distribution. The simulation results showed that the concentration of electric field intensity and the insulation of oil-impregnated paper would lead to the field emission of the initial electron. In addition, bubbles may be a major contributor to surface discharge development in such insulated systems.