Investigation on the Surface Flashover Characteristics of Epoxy Composites in C4F7N/CO2 Mixture

Although SF
6
is widely used in electrical apparatus, it has a strong greenhouse effect, so it is necessary to find alternative gases. C
4
F
7
N/CO
2
mixture, as a potential substitute, has been widely concerned by researchers. The long-term working insulation performance of C
4
F
7
N, especially the surface insulation, still needs more research. In this paper, two types of spacers are used to study the surface flashover characteristics in C
4
F
7
N/CO
2
mixture. It is found that the flashover voltage of the plate spacer in 10% C
4
F
7
N /90%CO
2
mixture is lower than SF
6
. When the C
4
F
7
N content increases from 5% to 20%, the surface flashover voltage of the downsized GIL basin spacer increases and C
4
F
7
N/CO
2
mixture has obvious synergistic and polar effect. If the voltage is applied for ten minutes in advance, the homo-charges increase the surface flashover voltage, while the hetero-charges reduce the surface flashover voltage to a certain extent.