Experimental study on the partial discharge and AC breakdown properties of C4F7N/CO2 mixture

Abstract

As an environmental friendly insulating medium, C4F7N has received extensive attention in the past two years. In this study, the partial discharge (PD) and breakdown characteristics of C4F7N/CO2 gas mixture were investigated using the gas insulation performance test platform. The influence of gas pressure and mixing ratio on the PD initial voltage (PDIV) and breakdown voltage of C4F7N/CO2 gas mixture in different electric fields was tested. It was found that the PDIV and breakdown voltage of gas mixture with 2-8% C4F7N in the highly non-uniform field showed a linear saturation increasing trend with the change of gas pressure and mixing ratio. The breakdown voltage of gas mixture increases linearly with gas pressure in the quasi-uniform electric field. The relative breakdown voltage of gas mixture in the highly non-uniform field under high-pressure conditions is inferior to those of low-pressure conditions. The C4F7N/CO2 gas mixture containing 2-8% C4F7N is sensitive to the non-uniformity of electric field. According to the PD and breakdown tests results, C4F7N/CO2 gas mixture with 2-8% C4F7N has the potential to replace SF6 using in gas-insulated equipment.