Effect of space charges on the corona onset in the short-gap insulated SF6 under non-uniform fields

Though the environment impact made SF₆ a greenhouse gas and be used strict limitation, it still used as a kind of excellent insulation dielectrics is applied to the high voltage engineering fields. So it is very essential to undertake research of the SF₆ insulated characteristic in a particular situation or extreme conditions. Based on the Raether-Meek criterion of the avalanche transferring the streamer, the effects of space charges on the corona onset in short-gap insulated SF₆ under non-uniform fields are researched carefully, which the mathematical model is set up and the calculation method described in details. The results obtained for non-uniform field as well as geometries in SF₆ for a wide range of geometrical parameters and pressures are significant technical support for logical utilizing gas dielectric, design electrode geometries and insulating system coordination. Space charges of the negative point-plane system effect on the corona onset at the short gap insulated SF₆ is much heavier than that of the positive point-plane system, and with the pressure increasing, the effects are gradually decreased. Furthermore, the results show that the electrons promote the growth of the avalanche, and the positive ions retard the growth of the avalanche, but it is not prominent, another important fact that the space charge field effect is negligible at higher pressures.