Research Project on the Gas Insulation Using a Gas Mixture

SF_6广泛应用于气体绝缘开关设备（GIS）等重要电力系统中。然而，近年来，SF_6气体的高全球变暖潜能值（GWP）已成为一个非常严重的问题。本课题提出用PFC（全氟化碳）混合气体代替SF_6，实现“无SF_6（或少SF_6）气体绝热”。我们主要研究了应用由c-C_4F_8（全氟环丁烷）和N_2或CO_2组成的气体混合物的可能性。(1)我们导出了含有电负性气体的气体混合物在液化回收过程中的释放速率或损失率的表达式。应用这一推导可知，在相同的混合比例下，c-C_4F_8从c-C_4F_8 /N_2中释放的速率远低于SF_6从SF_6/N_2中释放的速率。(2)研究了不同条件下c-C_4F_8 /N_2（或CO_2）的绝缘特性，并与纯SF_6和SF_6/N_2的绝缘特性进行了比较。主要实验条件如下：气体压力：0.1 ~ 0.4 mpa，施加电压：直流，交流60Hz，雷电脉冲，半比重：0、5、10、20、100%（体积%）的电负性气体。结果表明，在准均匀电场条件下，与SF_6/N_2相比，含c-C_4F_8的混合气体具有较好的绝缘性能。对于含有c-C_4F_8的气体混合物，放电电压与混合比的非线性或协同效应随着Pd（气体压力x间隙长度）的增加而增加。(3) c-C_4F_8混合气体与SF_6/N_2混合气体相比，在模拟尖锐导电粒子的极端不均匀条件下，其绝缘特性几乎相同。在0.3MPa以上的压力下，c-C_4F_8 /N_2的交流火花电压比纯SF_6的更高。(4)我们估计，通过使用具有与纯SF_6相当的保温强度的c-C_4F_8混合气体，可以将全球变暖潜能值（GWP）降低到10%以下。在相同混合比下，SF_6/N_2的这个值大约是全球变暖潜能值的一半。少

SF_6 is widely used in important electric power systems such as gas-insulated switchgear (GIS). Recently, however, very high global warming potential (GWP) of SF_6 gas has become a very serious problem. This research project has proposed the "non-SF_6 (or SF_6-less) gas insulation" by substituting a gas mixture with PFC (perfluorocarbon) for SF_6. We have principally investigated the possibility of applying a gas mixture consisting of c-C_4F_8 (perfluorocyclobutan) and N_2 or CO_2.(1) We have derived the expression for the release rate or loss rate at the liquefaction recovery process of a gas mixture containing an electronegative gas. By applying this derivation, we have made clear that the release rate of c-C_4F_8 from c-C_4F_8 /N_2 is much lower than that of SF_6 from SF_6/N_2 at the same mixing ratio.(2) We have studied the insulation characteristics of c-C_4F_8 /N_2(or CO_2) in various conditions, and compared them with those of pure SF_6 and SF_6/N_2. Main experimental conditions … More are as follows :Gas pressure : 0.1〜0.4MPaApplied voltage : dc, 60Hz ac, lightning impulseMixingraito : 0, 5, 10, 20,100 %(vol %) of an electronegative gasIt has been shown that compared with SF_6/N_2, gas mixtures containing c-C_4F_8 have reasonably good insulation ability under quasi-homogeneous electric field conditions.Nonlinearity, or synergism, in discharge voltage relative to mixing ratio, increases with Pd (gas pressure x gap length) for gas mixtures containing c-C_4F_8.(3) Under extremely inhomogeneous conditions simulating sharp conducting particles in practice, the gas mixtures with c-C_4F_8 show almost equivalent insulation characteristics compared with SF_6/N_2. The ac sparkover voltage of c-C_4F_8 /N_2 is even higher at a pressure above 0.3MPa than that of pure SF_6.(4) We estimate that by applying a gas mixture with c-C_4F_8 having the insulation strength, comparable to pure SF_6, the GWP (global warming potential) can be reduced to less 10%. This value is about a half of the GWP in the case SF_6/N_2 is applied at the same mixing ratio. Less