Study on Power-Frequency Breakdown Characteristics of SF6-Based Ternary Gas Mixture

SF6 gas is widely utilized in gas-insulated equipment due to its exceptional dielectric strength and arc-quenching capability. However, its potent greenhouse effect and liquefaction risks in polar regions present significant drawbacks. To investigate the breakdown characteristics of ternary mixtures comprising SF6 blended with $\mathrm{N}_{2}, \mathrm{CO}_{2}$, and O2, this study established a dedicated gas mixture breakdown test platform. Experimental investigations were conducted on $\mathrm{SF}_{6} / \mathrm{N}_{2} / \mathrm{CO}_{2}$ and $\mathrm{SF}_{6} / \mathrm{N}_{2} / \mathrm{O}_{2}$ mixtures under varying gap distances and gas pressures, followed by comprehensive data analysis. Key findings reveal that breakdown voltage increases with both gap distance and gas pressure. In the $\mathrm{SF}_{6} / \mathrm{N}_{2} / \mathrm{CO}_{2}$ system, the breakdown voltage increases with higher CO2 content, and synergistic effects exist between CO2 and N2, though saturation characteristics emerge. Conversely, $\mathrm{SF}_{6} / \mathrm{N}_{2} / \mathrm{O}_{2}$ mixtures initially show enhanced breakdown voltage with elevated O2 concentration, but experience oversaturation effects at $15 \% \mathrm{O}_{2}$ content where breakdown voltage conversely diminishes. Optimal mixture ratios achieved $86.11 \%$ and $85.34 \%$ of pure SF6 performance at 2 mm gap distance and 0.5 MPa pressure, respectively. This research lays the groundwork for SF6 substitution studies and offers practical significance for enhancing the secure and stable operation of GIS equipment.