Influence of Micro-water on Insulation and Decomposition Characteristics of SF6/N2 Mixtures

Mixing N2 into SF6 can effectively reduce the amount of SF6 used in electrical equipment. Micro-water is a common operating condition in electrical equipment, so the effect of micro-water on SF6/N2 needs to be considered before it is put into use. In this paper, the AC voltage breakdown experiments were performed on 0.5 MPa 30% SF6/70% N2 gas mixture at different concentrations and the decomposition products and breakdown voltage were quantitative analyzed. The experimental results show that when the water content exceeds 331 ppm, the content and gas production rate of SOF2 and SO2F2 increase significantly, which can affect the safety of people and equipment. There is a linear relationship between the content of H2S and the content of water inside the equipment, which can be used as a characteristic quantity to monitor the water content inside the equipment. When the water content exceeds 549 ppm, the insulation strength of the gas mixture is significantly reduced. Overall, the micro water content inside the equipment should not exceed 300 ppm.