Calculation of Charge and Current Characteristics of Partial Discharges in Helium Bubble in Dielectric Liquid from First Principles

The electrical characteristics of partial discharge in a spherical bubble filled with helium in dielectric liquid (transformer oil) were studied using kinetic equations. The diffusion-drift approximation was used for the description of the dynamics of the electron and ion concentrations. The non-linear dependencies of the ionization by electron impact, the electron drift and diffusion coefficients on the local electric field were used. Three dimensional calculations of streamers in gas bubble were performed for different locations of initial ionized spot (seed) of gas in the bubble. The parallel algorithm for the calculation of the electric field potential in the electrode gap was developed and realized on graphical processing unit. The dependence of the electric charge accumulated on the bubble surface (true charge) was calculated for tree positions of the seed. The dynamics of apparent charge, the electric current of partial discharge were calculated for the time periods of several nanoseconds. The evolution of the distribution of the electric charge surface density on the electrodes was obtained.