Switching Impulse Characteristics of C 5 F 10 O Gas Mixtures Under Extremely Nonuniform Field.

$\text{C}_{{5}}\text{F}_{{10}}\text{O}$ gas mixture is one of the most promising SF6 replacement gases with outstanding electrical performance and excellent environmental characteristics. Its switching impulse (SI) breakdown characteristics are important for future insulation design and insulation coordination. In this article, factors that can influence SI withstand voltage and the synergy of the gas mixture such as gas pressure, and the type and content of the buffer gas, are experimentally studied. According to the experimental results, $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ gas mixtures under nonuniform electric field show significant polarity effects under SI voltage. When the polarity of the applied voltage is negative, its $U_{\mathrm {50\%}}$ tends to increase linearly with the increase in gas pressure, while the “hump phenomenon” is observed under positive SIs as the gas pressure increases, which can be explained by the enhanced electric field distortion by the space charge. The insulation strength of the two gas mixtures increases more obviously with the increase in $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ content at lower mixing ratios and shows a saturation trend at higher mixing ratios. Based on the calculation, CO2 in discharge processes is likely to produce more low-energy electrons than that can be produced by N2 under the same conditions, so that SI withstand voltage of $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ /CO2 is higher than that of $\text{C}_{{5}}\text{F}_{{10}}\text{O} / \text{N}_{2}$ according to the attachment of low-energy electrons by $\text{C}_{{5}}\text{F}_{{10}}\text{O}$. On this basis, the synergistic effects between different gas components are calculated. The synergy between the components of a gas mixture is related to the gas pressure and $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ content, and the synergistic effects are more significant in $\text{C}_{{5}}\text{F}_{{10}}\text{O} / \text{N}_{{2}}$ mixture than in $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ /CO2 mixture. The results show that SI withstand voltage of $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ gas mixtures under a nonuniform electric field can be improved by increasing the gas pressure or $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ content. $\text{C}_{{5}}\text{F}_{{10}}\text{O}$ gas mixture has the potential to replace SF6 in certain mixing ratio and under certain gas pressure. [ABSTRACT FROM AUTHOR]