Study on Relative Electrical Strength of SF6 Substitute Gas Based on Density Functional Theory

In order to achieve the goal of “double carbon” as soon as possible, SF₆ substitute gas is more environmentally friendly and applied in electrical equipment. Based on density functional theory (DFT), the ionization energy, polarizability and HOMO-LUMO energy level of the SF₆ substitute gas were calculated. First, some relevant electrical parameters representing the substitute gas were linearly fitted to their experimental values. Secondly, the prediction simulation equation of the relative electric strength of the substitute gas is obtained by multivariate nonlinear fitting, and then the prediction results are screened. Finally, the relationship between the electrical parameters of the surrogate gas molecule and the relationship between the relative molecular mass under the external electric field is further studied. The research results show that the ionization energy, average electron polarizability and HOMO-LUMO energy level of substitute gas molecules have a strong positive correlation with their relative electric strength, and HFO-type substitute gases can be used as SF₆ substitute gases. Under the external electric field, the ionization energy and HOMO-LUMO level of the surrogate gas molecules decrease with the increase of the gas molecular mass, and the average electron polarizability increases with the increase of the gas molecular mass. For the screening of alternative gases, the carbon chain should be selected to be shorter, the relative molecular mass is more significant, and the average molecular weight is higher. The fluoride of the electron polarizability functional group provides a more precise direction for screening SF₆ substitute gases and has a particular guiding significance.