Influence of micro-water on AC breakdown characteristics of C_(4)F_(7)N/CO_(2)gas mixture under non-uniform electric field

The application of eco-friendly C_(4)F_(7)N/CO_(2)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 C_(4)F_(7)N/CO_(2)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 C_(4)F_(7)N/CO_(2)gas mixture insulated equipment is formulated.