Influence Mechanisms of Trace H2O on the Generating Process of SF6 Spark Discharge Decomposition Components

Trace H2O directly participates in the SF6 decomposition generating process under spark discharge, but its mechanism remains ambiguous. Thus , determining the influence rules of trace H2O on the decomposition characteristics of SF6 spark discharge is necessary . Moreover, the foundation of the effective spark discharge fault diagnosis methods should be established for SF6 gas-insulated apparatus. In this paper, a series of spark decomposition experiments of different proportions of SF6/H2O mixtures were conducted with a trace H2O injector accurately controlling H2O content. Influence mechanisms of trace H2O on the effective generation rates and the characteristic ratio of spark decomposition components were determined. Results show that trace H2O remarkably influences the effective generation rates of SF6 spark decomposition components, including SOF2, SOF4, SO2F2, SO2 and CF4. The characteristic ratio varies because of the distinct mechanisms of H2O on the components. Mathematical expression between the ratio and H2O contents was also derived. In addition, the X-ray photoelectron spectra show that the solid materials contain Al2O3 and AlF3, and the existing forms of S are sulfite and sulfate.