C₄F₇N/CO₂ mixture has been widely studied as an environmental-friendly insulating gas expected to replace sulfur hexafluoride (SF₆) in high-voltage equipment. In high-voltage power systems, the medium dielectric characteristics under switching impulse (SI) voltage are an important factor in insulation coordination. Nevertheless, few studies on this aspect of C₄F₇N/CO₂ mixture have been reported. This article investigates the surface flashover of a cylindrical insulator in a C₄F₇N/CO₂ mixture under switching voltage. The effects of molar fraction, gas pressure, creepage distance, and insulator materials on surface flashover voltage are studied in a uniform field. The result shows that the increase of flashover voltage indicates a saturation trend with the increase of C₄F₇N molar fraction and pressure, respectively. The dielectric strength of 13% C₄F₇N/87% CO₂ relative to SF₆ can reach at least 84%. The limiting factors of the flashover voltage increase under high pressure are preliminarily discussed. Additionally, the empirical formula on the critical flashover electrical field has been obtained, which can provide a reference for insulation design for environment-friendly gas insulation equipment.

中文翻译：

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C4F7N/CO2混合物中圆柱绝缘子在开关脉冲电压下的表面闪络特性

C ₄ F ₇ N/CO ₂混合物作为一种环保绝缘气体已被广泛研究，有望替代高压设备中的六氟化硫（SF _{6 ）。}在高压电力系统中，开关脉冲（SI）电压下的介质介电特性是绝缘协调的重要因素。然而，很少有关于C ₄ F ₇ N/CO ₂混合物这方面的研究报道。本文研究了圆柱形绝缘子在 C ₄ F ₇ N/CO _{2中的表面闪络}开关电压下的混合物。在均匀场中研究了摩尔分数、气体压力、爬电距离和绝缘体材料对表面闪络电压的影响。结果表明，随着C ₄ F ₇ N摩尔分数和压力的增加，闪络电压的增加呈饱和趋势。_{13% C 4} F ₇ N/87% CO ₂相对于SF ₆的介电强度至少可以达到84%。初步讨论了高压下闪络电压升高的限制因素。此外，还得到了临界闪络电场的经验公式，可为环保型气体绝缘设备的绝缘设计提供参考。