Partial Discharge and Decomposition Characteristics of C4F7N/CO2/O2 Under Metallic Protrusion Defects

C 4 F 7 N/CO 2 /O 2 gas mixtures have become the most promising gaseous insulating medium to replace SF 6 in the electric power industry due to their excellent environmental and insulating properties. Although the addition of O 2 can enhance the insulating performance and chemical stability of C 4 F 7 N/CO 2 gas mixture to a certain extent, the influence of O 2 addition and its content change on the gas by-product generation characteristics of the gas mixture under the action of PD is not clear. In this paper, experiments on C 4 F 7 N/CO 2 /O 2 96h PD and its decomposition characteristics were carried out through needle-plate electrodes simulating metal protrusion defects in the device, and it was found that the addition of 2-4% O 2 to the C 4 F 7 N/CO 2 mixture could significantly inhibit the generation of most of the by-products, and that the cumulative discharge per second and average discharge per second increased dramatically when the O 2 content was greater than 6%, resulting in the aggravation of the decomposition of the gas mixture.