Abstract:Technology based on decomposed components analysis using for SF6 insulation equipment fault diagnosis is widely used in the fault diagnosis of power equipment for its advantage in anti-electromagnetic interference. Recently, some theoretical research focused on the formation of main SF6 derivatives have been carried out through chemical kinetics models, but the basic data (chemical reactions and their rate constants) adopted in the model are only appropriate for 300 K and not valid for the decomposition under partial over-thermal fault, as well as arc discharge. In this paper, the formation mechanism of SO2F2、SOF2 and SO2 have been investigated. The DFT-B3LYP method with 6-311G* basis set was used to calculate the optimized molecular geometries, as well as the transition states of hydrolysis reactions of SF4, SOF4 and SOF2. Those chemical reactions involve the main byproducts of SF6 decomposition. Energy of molecular geometries and transition states were calculated, using the sophisticated CCSD(T) ab-initio method with a large aug-cc-pVTZ basis set to obtain more accurate energies and barrier heights. Rate constants are estimated by TST based on the results obtained from DFT-B3LYP method mentioned above. The rate constants in this paper consider the influence of temperature and derived for a large temperature. This work is expected to lay a theoretical foundation for further study on SF6 decomposition mechanism under partial over-thermal fault and arc discharge.