Influence of micro‐water on AC breakdown characteristics of C4F7N/CO2 gas mixture under non‐uniform electric field

Abstract

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.