210 / 2024-04-17 17:59:19

Study on electron swarm parameters and insulation properties of C4F7N-CO2-O2 mixture

C4F7N-CO2-O2,Electron swarm parameters,Insulation properties

In recent years, new environmentally friendly gases represented by perfluoronitrile (C₄F₇N) have attracted great attention with their extremely low GWP and high insulation strength, and have been applied in engineering. Manufacturers started to use mixtures of C₄F₇N with CO₂ and O₂, or with air, as insulating and switching media in medium and high voltage gas insulated substations. However, due to the lack of relevant electron swarm parameters, it is difficult to further study the microscopic discharge mechanism. In this study, the electron drift velocity, density-normalized effective ionization coefficient and density-normalized longitudinal diffusion coefficient of C₄F₇N-CO₂-O₂ mixtures at different mixing ratios were measured by pulsed Townsend technique. We discuss the effect of C₄F₇N-CO₂-O₂ rationing on electron swarm parameters and density-reduced critical electric field strength (E/N)cr, and evaluate the synergistic effects of the gas mixtures. The C₄F₇N content of the mixture varies between 5% ~ 20%. At a constant ratio of C₄F₇N, combined with the actual project needs, the ratio of CO₂:O₂ is set as: 1:0, 20:1, 15:1, 10:1, 5:1. Our measurements provide fundamental data for modelling the discharge of C₄F₇N-CO₂-O₂ mixtures.