Abstract: To address the limitations of perfluoroisobutyronitrile (C₄F₇N)/carbon dioxide (CO₂) binary gas mixtures in terms of low-temperature adaptability and global warming potential (GWP) optimization, 2,3,3,3-tetrafluoropropene (HFO-1234yf)-which features low GWP and low liquefaction temperature-is introduced as a third component to construct a C₄F₇N/HFO-1234yf/CO₂ ternary gas mixture. The liquefaction temperature of the mixture is calculated by combining the Antoine equation with Dalton’s law of partial pressures, and the relative global warming potential (R-GWP) index is introduced to comprehensively evaluate the greenhouse effect of the mixture. Experiments are conducted on the power-frequency insulation performance of the ternary gas mixture. The results show that the GWP of the ternary mixture decreases with increasing HFO-1234yf content; the GWP of 10% C₄F₇N/20% HFO-1234yf/70% CO₂ is approximately 0.8 times that of 10% C₄F₇N/90% CO₂, and its R-GWP at 0.5 MPa is only 1.2% that of SF₆. Under the constraints of a total filling pressure of 0.6 MPa and a minimum liquefaction temperature of -30 ℃, the maximum allowable molar fractions of C₄F₇N and HFO-1234yf are 6.61% and 20.79%, respectively, indicating that the addition of HFO-1234yf has little effect on the liquefaction temperature. At 0.6 MPa, the power-frequency breakdown voltage of 5% C₄F₇N/9% HFO-1234yf/86% CO₂ is 1.36 times that of the binary mixture with the same C₄F₇N proportion, and at 0.8 MPa it reaches the level of SF₆ at 0.6 MPa. These findings demonstrate that the proposed C₄F₇N/HFO-1234yf/CO₂ ternary gas mixture can effectively reduce GWP and improve power-frequency breakdown characteristics while maintaining liquefaction properties comparable to those of C₄F₇N/CO₂, thereby providing a theoretical basis and data support for the engineering application of environmentally friendly insulating gases in power equipment.

Key words: C₄F₇N/HFO-1234yf/CO₂, SF₆ alternative gas, GWP, liquefaction temperature, insulation characteristics