Numerical Study on the Effect of Electric Field Non-uniformity on the Pulse Characteristics of Positive Corona Discharge in SF6/N2 Gas Mixtures

This paper establishes a two-dimensional axisymmetric needle-to-plane geometry model in SF6/N2 gas mixtures to simulate the effect of the electric field non-uniformity on the pulse characteristics of positive corona discharge. By changing the needle tip radii from 25 mu m to 300 mu m, the corona discharge process under different electric field non-uniformity is simulated. Meanwhile, the simulated results are verified by the experiments on a corona discharge experimental setup. The results show that the rising and falling edges of positive corona current pulses correspond to the development and termination of streamers, respectively. The sub-pulse will be generated during the formation of the first current pulse, and this phenomenon is closely related to the applied voltage. The generation of sub-pulse is expected to be a feature of positive corona discharge in SF6/N2 gas mixtures entering the brush-pulse stage. With increasing the electric field non-uniformity, the onset voltages of two characteristic pulse stages, including the streamer-pulse stage and brush-pulse stage, decrease. Moreover, the first current pulse amplitude increases, and the pulse-repetition rate presents an approximate exponential increasing trend.