Investigation on the formation reactions of SOF₄ and SO₂F₂ under electric discharges

The analysis technique of main SF₆ decomposition products (etc. SOF₄ and SO₂F₂) is expected to compensate for the ultra-high frequency (UHF) method in partial discharge (PD) diagnosis and insulation condition monitoring of power equipment. SOF₄ and SO₂F₂ as well as other corrosive byproducts derived from the reactions of SF₆ dissociation species (e.g., SF₂, SF₃ and SF₄) with the trace impurities of H₂O and O₂ under electric discharges. But the formation processes of SOF₄ and SO₂F₂ are still not clear, which are closely related to the evaluation of PD type and energy, making the analysis method of SF₆ decomposition products in PD diagnosis a lack of theoretical supports. For this reason, this paper is devoted to investigating the formation reactions of SOF₄ and SO₂F₂ under electric discharges. The possible formation reactions of SOF₄ and SO₂F₂ are studied by quantum chemistry calculations with density functional theory (DFT). Then the rate constants of these chemical reactions are calculated in a large temperature range 300-12 000 K by transition state theory (TST) with Wigner's tunneling effect correction. This work lays a basis for better understanding of the analysis approach of key SF₆ decomposition products in electric discharge diagnosis and insulation condition monitoring of power equipment.