Fundamental study on practical application of high-performing and environmentally-friendly CF3I gas insulation system

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CF3I gas is one of alternatives to SF6 gas, which are utilized for electric power equipment, and has some advantages as follows: the insulation performance of CF3I is equivalent or superior to SF6 in uniform field and its global warming potential, GWP, is quite low as same as CO2. It has, however, a low sparkover voltage in non-uniform field. The surface flashover voltage on a new and clean insulator in CF3I gas is 1-1.2 times higher than that in SF6 gas. As the saturated vapor pressure of CF3I gas is low, the reduction of partial pressure of CF3I gas is effectively reduced by mixing other gases in order to prevent CF3I from devolatilization. The insulation characteristics of CF3I/N2, CF3I/CO2 and CF3I/SF6 mixtures are systematically investigated. Through these discussions, it is proposed that the most optimum gas is CF3I/N2 mixture and that it can be practically applied to gas insulated transmission lines, GIL.