Influence of humidity on the decomposition products and insulating characteristics of CF3I

Recent studies show that CF
₃
I is possible to take the place of SF
₆
used in gas insulated switchgear (GIS) as insulating gas. H
₂
O is one of the key factors influencing the categories and quantities of decomposition products of SF6 in discharge. The process of decomposition of CF
₃
I and the influence from H
₂
O on the insulating property of CF
₃
I have not been studied. In this paper, we analyzed the process of decomposition of CF3I with micro-moisture at ambient temperature and pressure using simulation by density functional theory (DFT). The changes in energy of reactions were calculated and compared according to thermodynamic theories and the most likely reaction pathways and decomposition products were found. The results show that CF3I may break down after attaching electron in strong electric field, which is reversible. CF3I can react with H- and OH-coming from H
₂
O collided by high-energy electron and produce various and complex products, which breaks the dynamic balance of CF3I. Partial discharge experimental results show that the discharge in CF3I becomes more violent when the micro-moisture content increases. The result of simulation and experiment verifies H
₂
O can destroy the insulating property of CF3I.