Insulation Performance and Application of Enviroment-friendly Gases Mixtures of C₄F₇N and C₅F₁₀O with CO₂

Recently, fluoroketone and fluoronitrile gases attract great attention as potential SF₆ substitutes. We studied the insulation performances of the mixtures of C₄F₇N and C₅F₁₀O with CO₂. First, the Antoine constants were fitted by the reported liquefaction temperature data of C₄F₇N and C₅F₁₀O. The saturated vapor pressure characteristics of C₄F₇N-CO₂ and C₅F₁₀O-CO₂ mixtures were analyzed. Secondly, by combining the Antoine equation and the basic law of vapor liquid equilibrium, the application conditions at limits of environment temperature were discussed. Finally, the critical electric field strengths were determined from the experimental data in literatures, and the insulation performances and potentials of C₄F₇N-CO₂ and C₅F₁₀O-CO₂ mixtures were discussed. It is found that the electrical strengths of the C₄F₇N-CO₂ mixture under the limits of three environment temperatures (-5℃, -15℃, and -25℃) are all much higher than those of the C₅F₁₀O-CO₂ mixture, and the proper choice of mixed ratio and pressure for C₄F₇N-CO₂ can provide relatively high electrical strength, low GWP, and liquefaction temperature. Taking the environment temperature limit of -25℃ for example, the electrical strength of the 5%C₄F₇N-95%CO₂ mixture at 0.65 MPa can approximate pure SF₆ gas at 0.5 MPa. In addition, the GWPs of C₄F₇N-CO₂ mixtures are below 850 when C₄F₇N concentration is less than 20%.