Study on SF6 decomposition characteristics under thermal fault and its representation method

SF₆ electrical equipments always occur thermal fault developed from local overheating by poor contact. To find out SF₆ decomposition characteristics under thermal fault temperature and improve the method of using the decomposed components of SF₆ to indentify electrical fault, this paper exploited SF₆ thermal decomposition model to conduct serials of experiments. This paper firstly revealed the SF₆ thermal decomposition initial temperature. Then it found out the types of decomposed components, analyzed their formation regularity and identified the most stable characteristic components in SF₆ thermal decomposition. Finally, a representation method was established by using characteristic component to represent the thermal fault information. The results show that: SF₆ begins to decompose at 300°C and it contains CO₂, SO₂F₂, SOF₂, SOF₄, SO₂ and H₂S, but no CF₄; the improvement of fault temperature will promote the formation of decomposed components, but the influence regularity of each component is different; the established correlation picture and diagnosis table can effectively represent SF₆ fault temperature information.