Influence of micro‐water on AC breakdown characteristics of C 4 F 7 N/CO 2 gas mixture under non‐uniform electric field

Abstract

The application of eco-friendly C4F7N/CO2 gas mixture has become a hot topic in the power industry. To obtain the influence law of micro-water on the AC insulation characteristics of C4F7N/CO2 gas mixture, breakdown tests were carried out under different non-uniform electric fields and micro-water volume fractions. With the gap distance of 1 mm and the electric field non-uniform coefficient less than 4.42, the breakdown voltage is positively correlated with gas pressure. With the gap distance of 6 mm and the electric field non-uniform coefficient of 9.28, the breakdown voltage shows a typical N-type change trend with the increase of gas pressure. With the gap distance of 9 mm and the electric field non-uniform coefficient up to 16.45, the breakdown voltage shows a typical N-type change trend with the increase of gas pressure. Micro-water has a negative effect on breakdown voltage under different electric fields, meanwhile the breakdown voltage of slightly non-uniform electric field is greatly affected by micro-water, and the influence of micro-water on breakdown voltage is different under different gas pressures. Therefore, the influence of operating gas pressure and slightly non-uniform electric field should be considered when the micro-water control index of C4F7N/CO2 gas mixture insulated equipment is formulated.