Insulation Characteristics of Spacer Filled with Different Gas insulating mediums Under Superimposed Voltage of DC and Impulse

The analysis of the influence of different dielectric gases on the flashover characteristics of insulators under DC voltage superimposed impulse voltage is mainly performed in this paper. In the experiment, the spacer surface charge is saturated by applying DC voltage under working temperature in advance. The flashover experiments were conducted with and without linear metal particle in pure SF6, C4F7N/CO2 (4%/96%) and SF6/N-2 (20%/80%) gas mixtures. At the same time, the surface potential distribution was measured and analyzed. The results show that the type of the gas medium is not the dominant factor of potential distribution without particle, and there is little difference in different gas environments. When metal particle defects appear on spacer surface, it will cause severe potential distortion and these regions are located around the tip of the particle and coincide with the flashover path. It also has proved that the gas insulating medium has influence on the surface charge accumulation in this circumstance. In C3F7CN/CO2 mixture, the minimum potential value is -9954.86V, which is lower than that of others, and the decline percentage of flashover voltage is 16.82%. These indicate that C3F7CN/CO2 is better than SF6 and its mixed gas in some respects.