Study on Gas Decomposition Characteristics of SF 6 with Moisture After Current Interruption

SF6 gas insulated switchgear is an important electrical equipment in the power system. However, moisture content in the gas chamber may lead to the decrease of insulation properties and cause operation failures, affecting the safety of the power system. In this paper, experimental test system was constructed to research the characteristics of SF6 decomposition component when micro amount of moisture exists, and series of current breaking test were carried out in a 40.5 kV SF6 circuit breaker with different concentration of moisture added. The gas decomposition products were detected by gas chromatograph and mass spectrometer. The curve of each decomposition products varies against time, breaking current and arcing energy was investigated. Comparing with the SF6 decomposition products generated in normal operation, the influence of moisture content to the decomposition products was analyzed and the mechanism of gas decomposition involved with moisture was investigated. The research can provide a theoretical basis for fault diagnosis of SF6 electrical equipment.