Influence of trace water and oxygen on characteristic decomposed components of SF6 under partial discharge

Monitoring the contents of decomposed components of SF₆ in order to identify the internal insulation faults of electrical equipment with SF₆ dielectric is a common practice. Partial discharges (PDs) can lead to the decomposition of the SF₆ dielectric. The new reactions also cause the final decomposed components to differ due to the different concentrations of H₂O and O₂ even under the same strength of PD. Thus, the accuracy of assessing inner insulation faults is affected when using the concentration and corresponding change of decomposed components. In this work, two main characteristic components SO₂F₂ and SOF₂ was researched. The purpose is to perform influence analysis of trace H₂O and O₂ on the characteristic components. Research findings indicated that the amount of SOF₂ strongly correlates to the amount of trace H₂O, whereas the amount of SO₂F₂ is weakly related to trace H₂O. Furthermore, the dilution effect of trace O₂ on SOF₂ obviously exceeds that on SO₂F₂.