Prediction of Dielectric Breakdown Strength and Research on Synergistic Mechanisms of SF6 Gas Mixtures Based on First-Principles

To meet the dual requirements of low-temperature non-liquefaction and high dielectric strength for gas-insulated systems in extreme environments, this study establishes a prediction model for the dielectric breakdown strength of SF6 binary gas mixtures based on first-principles (DFT) methods, starting from microscopic molecular characteristics. First, key molecular parameters—including orbital energies, ionization energies, and polarizability—of SF6 and typical buffer gases (N2, $\mathrm{O}_{2}, \mathrm{CO}, \mathrm{CO}_{2}, \mathrm{C}_{2} \mathrm{H}_{4}, \mathrm{C}_{2} \mathrm{~F}_{6}$) were extracted to develop a multivariate regression model for the dielectric strength of single gases. Building on this, the bimolecular interaction energy between SF6 and each buffer gas was quantified, and a synergistic coefficient NN was proposed to characterize the discharge synergy between components in mixed systems. This coefficient was embedded into a modified weighted model to predict the dielectric strength of SF6 binary mixtures. Results demonstrate that the insulating performance of the $\mathbf{S F}_{\mathbf{6}} / \mathbf{C}_{\mathbf{2}} \mathbf{H}_{\mathbf{4}}$ system under specific ratios can reach $122.3 \%$ of pure SF6; systems such as $\mathrm{SF}_{6} / \mathrm{C}_{2} \mathrm{~F}_{6}$ and $\mathrm{SF}_{6} / \mathrm{CO}_{2}$ also exhibit significant synergistic effects. The proposed model integrates microscopic mechanism analysis with an engineering computational framework, providing theoretical support for the screening and ratio optimization of eco-friendly insulating gases.