Breakdown Characteristics of C₄F₇N/CO₂/O₂ Gas Mixtures with Low Content of C₄F₇N

Perfluoroisobutyronitrile (C₄F₇N) gas mixture is a promising SF₆ alternative characterized by its low global warming potential (GWP), high insulation strength, and short atmospheric lifetime. Considering the persistent environmental pollution and bioaccumulation risks associated with per- and polyfluoroalkyl substances (PFAS), regulatory measures have been implemented across regions to control PFAS and F-gases. Therefore, investigating the insulating performance of C₄F₇N gas mixtures with low concentration is essential. In this study, the influence of oxygen content and gas pressure on the insulation performance of C₄F₇N/CO₂/O₂ gas mixtures with low content of C₄F₇N were investigated. The results show that, compared with C₄F₇N mixture without O₂, increasing oxygen content at 0.1 MPa reduced the insulating strength of the gas mixture, with the smallest reduction of 0.33% observed at an O₂ concent of 4%. At 0.2 MPa, adding 4%-8% oxygen decreased the insulation strength, while an O₂ content of 12% enhances it by 7.36%. At pressures between 0.3 and 0.4 MPa, higher oxygen concentrations were found to enhance the insulation performance., with the maximum increases of 9.35% and 8.20% occurring at 8% O₂(0.3 MPa) and 12% O₂(0.4 MPa), respectively.