Molecular Dynamics of SF6/N2 Gas Mixtures under Superheated Defects by Electric Fields

Efforts are currently underway to explore the use of SF6/N2 gas mixtures as a potential alternative to SF6 as an insulating medium in the power industry. The application of a 30% SF6/70% N2 gas mixture has made some progress, and its safe operation is critical. However, local overheating faults are inevitable during the long-term operation of SF6/N2 gas-insulated equipment. Under such overheating conditions, the SF6/N2 mixed gas undergoes decomposition, generating various by-products. This study systematically investigates the decomposition mechanism of SF6/N2 mixed gas as an insulating medium using molecular dynamics simulations. The findings reveal that, under different electric field conditions, for a gas mixture ratio of 30% SF6/70% N2, as the electric field increases from 0.02 V/Å to 0.1 V/Å, the decomposition of SF5, SF4, and SF3 becomes significant, with nearly complete breakdown. The primary decomposition products are SF2 and SF, while N2 remains relatively stable across all five electric field conditions. High-fluoride compounds such as SF5, SF4, and SF3 are less abundant compared to low-fluoride compounds such as SF2 and SF. Moreover, as the temperature rises, the decomposition of SF6 becomes more pronounced, with both SF6 and its by-products showing a clear trend toward transitioning into lower-fluoride compounds. Across different electric field conditions, the products continuously decompose and recombine, forming new molecules. These results indicate that higher electric fields lead to more thorough decomposition of SF6/N2 mixtures, with an increasingly significant shift toward smaller molecules and higher proportions of SF3, SF2, and SF.