Continuous monitoring of SF6 degradation in high voltage switchgear using Raman scattering

In high voltage SF₆ insulated switchgear, the level of SF₆ concentration needs to be monitored regularly because of its degradation by switching arcs and on-going partial discharges or coronas. In the work reported here, measurements of SF₆ dissociation rate following 75 μA positive and negative coronas have been made using a mass spectrometer and Raman spectroscopy. The two sets of data correlate well, the rates of degradation of SF₆ and production of gaseous by-products being shown to be proportional to the charge transported by the corona. SF₆ provides a particularly strong Raman signal at 773.5 cm^-1, and the results demonstrate the feasibility of using Raman scattering to monitor SF₆ degradation in high-voltage switchgear.