Most high voltage circuit breakers in operation use SF6 as the arc interruption medium because of its high dielectric strength and good arc interruption properties. However SF6 also displays a high global warming potential which motivates the investigation of possible alternatives such as CO2–Novec™4710 and N2–Novec™5110 mixtures proposed by different HVCB manufacturers. CB power test comparison between pure CO2 and CO2–Novec™4710 mixture shows that the latter created a large amount of graphite and reduced CB performances after several current breaking shots. Using Gibbs free energy method, a theoretical study has been conducted on SF6 replacement candidates listed above. Aiming to understand graphite formation, several parameters impact were discussed: carrier gas such as CO2 and N2, pressure and O2 initial mixture proportions. The study focuses on graphite condensation temperature and graphite production amount evolutions in respect to the study parameters as well as in respect to CB inter-contacts space condition in terms of pressure and temperature at current-zero. It has been shown that a high percentage of CO2 in the mixture reduces graphite condensation temperature by 2600 K while adding N2 do not make such an impact. Pressure increases graphite condensation temperature and O2 reduces it. The amount of graphite produced is pressure independent but decreases with the increase of O2 proportion in the initial mixture. It has been shown that adding a sufficient O2 amount can prevent graphite production at all.

中文翻译：

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用新型 SF6 替代气体在灭弧过程中生产石墨

大多数运行中的高压断路器使用SF6作为电弧中断介质，因为它具有高介电强度和良好的电弧中断性能。然而，SF6 也显示出较高的全球变暖潜势，这促使研究可能的替代品，例如不同 HVCB 制造商提出的 CO2–Novec™4710 和 N2–Novec™5110 混合物。纯 CO2 和 CO2–Novec™4710 混合物之间的 CB 功率测试比较表明，后者产生大量石墨并在几次电流断流后降低 CB 性能。使用吉布斯自由能方法，对上面列出的 SF6 替代候选物进行了理论研究。为了了解石墨的形成，讨论了几个参数的影响：载气如 CO2 和 N2、压力和 O2 初始混合比例。研究的重点是石墨冷凝温度和石墨产量在研究参数方面的演变，以及在零电流时的压力和温度方面的 CB 接触间空间条件。已经表明，混合物中高百分比的 CO2 将石墨冷凝温度降低了 2600 K，而添加 N2 不会产生这种影响。压力会增加石墨的冷凝温度，而 O2 会降低它。产生的石墨量与压力无关，但随着初始混合物中 O2 比例的增加而减少。已经表明，添加足够的 O2 量可以完全阻止石墨的产生。