Optical properties and decomposition mechanisms of SF6 at different partial discharge determined by infrared spectroscopy

Probing the decomposition products of Sulfur hexafluoride (SF6) under partial discharge provides important information for fault diagnosis of Gas Insulated Switchgear (GIS). Here, the effects of discharging time, gas pressure, and discharging voltage on SF6 decomposition products have been investigated by Fourier transform infrared (FTIR) spectroscopy. The infrared spectra of decomposition products such as CF4, SOF2, and SO2F2 have been obtained. It can be found that the CF4, SOF2, and SO2F2 concentrations increase over increased discharging time up to 96 hours. The SO2F2 concentration increases while the discharging voltage is raised from 20 kV to 46 kV, due to the rapid deceleration to the lower energy of electron capture and dissociative attachment. The SO2F2 concentration is reduced while the gas pressure is increased from 0.3 MPa to 0.4 MPa. The present results about the SF6 decomposition can be useful for electrical fault diagnosis.