Experimental Research on V–t Characteristics of C5F10O/CO2 Gas Mixture Under Lighting Impulse Voltage

C5F10O has excellent insulation and environmental performance. It has the potential to replace SF6 in low- and medium-voltage gas-insulated equipment. For gas-insulating medium, its breakdown law under the impulse voltage is an important basis for the design and calibration of equipment insulation. The research on the insulation performance of C5F10O mixed gas under the impulse voltage is still incomplete. In this article, the empirical formula of the
${V}$
–
${t}$
characteristic curve of C5F10O/CO2 mixed gas is obtained through the lightning impulse withstand voltage test under extremely nonuniform electric field, and compared with the SF6 under the same conditions. The results showed that the breakdown voltage of C5F10O/CO2 and SF6 decreases with the increase of breakdown time and stabilizes at around
$U_{{50}\%}$
with the extension of breakdown time. The breakdown point of C5F10O/CO2 mixed gas shows a significant “peak accumulation” effect. As the pressure increases, the
${V}$
–
${t}$
curve will rise accordingly, the distribution of breakdown points will become more compact, and the steepness of the curve will be steeper. In addition, the increase of C5F10O content and the change of the gap distance will also shorten the discharge time delay, so that the distribution of the breakdown point is more concentrated, and the steepness of the
${V}$
–
${t}$
characteristic curve becomes larger. In particular, the
${V}$
–
${t}$
characteristic curve of C5F10O/CO2 gas mixture appears to increase with the increases of breakdown time when the gas distance is small due to the influence of space charge layer, and this phenomenon changes when the distance increases. The results provide an important basis for the insulation design and calibration of C5F10O mixed-gas-insulated equipment.