Influence of Metal Particle Contaminnation on Surface Flashover Characteristics of GIL Spacer in C4F7N/CO2 Mixtures

C
4
F
7
N/CO
2
mixture is one of the most promising environmental-friendly SF
6
alternative gases, which is favored by scholars and manufacturers at home and abroad. Aiming at the problem of metal particle contamination in C
4
F
7
N/CO
2
mixture insulation equipment, a surface flashover test platform suitable for scaled spacers is built to study the DC surface flashover characteristics of C
4
F
7
N/CO
2
mixture. The effects of metal particle length and attachment position on the surface flashover characteristics of C
4
F
7
N/CO
2
mixture are studied. The results show that the surface flashover voltage decreases with the increase of the length of metal particles. When the metal particle ia in contact with the high-voltage electrode, the electric field distortion at the particle tips is serious, and the flashover voltage is lower than that when the particle is not in contact with the electrode. In C
4
F
7
N/CO
2
mixture, the flashover voltage of negative polarity under extremely uneven electric field is higher than that of positive polarity, showing polarity effect. With the increase of C4F7N content, the polarity effect becomes more and more significant.