Influence of H₂O and O₂ on the main discharge mechanism in 50 Hz ac point-plane corona discharge

It is common to identify the internal insulation conditions of Sulfur Hexafluoride (SF₆) insulated equipment by monitoring the concentrations of SF₆ decomposition products. Corona discharge can lead to the decomposition of SF₆, and thus, a lot of reactions occur in the mixture of SF₆ with the impurities H₂O and O₂. Even under the same strength of corona discharge, the reactions can cause the decomposition products to differ due to the different concentrations of H₂O and O₂. This paper systematically studies the effects of H₂O and O₂ on the formation mechanism of SF₆ decomposition products from a theoretical perspective. Two coupled zero-dimensional chemical kinetic models were built to investigate the discharge mechanism of 50 Hz ac point-plane corona discharge. By calculating the related contributions of the pathways at different moisture and oxygen contents (from 200 ppm to 5000 ppm), the main chemical process and the influence of the moisture and oxygen contents on the main discharge mechanism are analyzed.