SF 6 is widely used in the high-voltage field as its excellent insulation performance. but now, the application of SF 6 is limited to use more and more because it makes the greenhouse effect. So how to find out some gas to instead of it and how to reduce its using has become a hot issue. In this paper, the characteristics of SF 6 /N 2 gas mixtures are investigated. considering C-GIS structural features, the experiment platform with cubicle structure was set up. The experiment electrode is a kind of rot-plane. The experiment gas pressures were set in the range 0.1-0.2 MPa. According to the results, critical breakdown voltage curves, referring to C-GIS products voltage classes, were suggested.

Dynamic characteristics of discharge particles are described within the framework of a two-dimensional photoionization-hydrodynamic numerical model for the discharge process of SF6-N2-CO2 gas mixtures at atmospheric pressure, under a uniform DC applied field. The finite difference-flux corrected transport (FD-FCT) algorithm is used in the numerical implementation for improving the accuracy and efficiency. Then the tempo-spatial distributions of the gap-space electric field and electron velocity are calculated from the microscopic mechanism, and the dynamic behaviors of charged particles are obtained in detail. Meanwhile, the tempo-spatial critical point of the avalanche-to-streamer in this model is discovered, and several microscopic parameters are also investigated. The results showed that the entire gap discharge process can be divided into two phases of avalanche and streamer according to Raether-Meek criterion; the electron density within the discharge channel is lower compared to that of positive and negative ions; space charge effect is a dominant factor for the distortion of spatial electric field, making the discharge channel expand toward both electrodes faster; photoionization provides seed electrons for a secondary electron avalanche, promoting the formation and development speed of the streamer.

The two-dimensional and self-consistent fluid model of the SF 6 discharge was established based on the electron and ions continuity transfer equations coupled to Poisson's equation, and also simultaneously considered the photoionization event, and then the flux corrected transport technique (FCT) was employed to numerically solve the particle flux-continuity equations, and some significant microphenomena were achieved that the dynamic behaviors of the charged particles, the spatio-temporal evolution of the discharge channel and the transformation law of the avalanche-streamer for the SF 6 narrow-gap were revealed in this paper.