Review of Novel Environmentally Friendly Insulating Gas Mixture Systems

Sulfur hexafluoride (SF6) has become an urgent target for substitution in the green transformation of the power industry due to its extremely high global warming potential (GWP ≈ 23,900) and long atmospheric lifetime. This review summarizes the research progress of novel eco-friendly insulating gas mixtures over the past five years, outlining three technological pathways: conventional gases (N?, CO?, etc.) with insufficient dielectric strength, SF?-containing mixtures as transitional solutions, and fluorinated compounds (C4F7N, C5F10O, etc.) as the core of complete alternatives. Among these, the C4F7N/CO2 system stands out due to its synergistic effect—achieving a band gap of 7.56 eV at a 1:9 mixing ratio, with synergy coefficients ranging from 0.25 to 0.45, and a 7% C4F7N formulation reducing GWP to 500–900, while exhibiting dielectric performance that can surpass SF? under specific conditions. However, current solutions still face the challenge of balancing dielectric strength, environmental friendliness, and low-temperature adaptability. Future research will focus on rational molecular design, fine-tuned formulation optimization, and long-term service performance evaluation, aiming to promote the tiered substitution of eco-friendly gases from medium to high voltage levels, thereby supporting the low-carbon transition of power equipment.