Detection of decomposition products of SF6/air gas mixture by electron attachment mass spectrometry

Abstract

Sulphur hexafluoride (SF6) is widely used in gas insulation, and its decomposition products can be used to diagnose potential insulation failures. Quick and accurate detection of decomposition products can help to understand equipment-operating conditions in time. In this study, the decomposition products of SF6/air gas mixtures under different pulsed discharge voltages were studied. It was found that the main products were SOF2, SO2F2, SO2, CF4 and SOF4, and the yields of SOF2, SO2F2, SO2 and SOF4 increased with the number of discharge pulse. The productive rate of SOF2, SO2 and SOF4 were positively correlated with the discharge voltage, and when the discharge voltage increased from 5 to 15 kV, their yields after 50,000 discharges increased by 49%, 120% and 1100%, respectively. The productive rate of SOF2 and SO2 were positively correlated with the proportion of air in the gas mixtures while that of SOF4 was opposite. When the proportion of air increases from 0% to 90%, their yields after 50,000 discharges became 270%, 3169% and 10% of the originals, respectively. In addition, the productive rate of SO2F2 was not affected by discharge voltage and the proportion of air in the gas mixtures. SO2F2, SOF2, SOF4 and SO2 can be used as the basis for judging the discharge failures and the discharge degree of power equipment.