Influence regularity of O2 on dielectric and decomposition properties of C4F7N–CO2–O2 gas mixture for medium-voltage equipment

摘要

Fluorinated nitrile (C₄F₇N) gas mixture has been introduced as the most promising candidate to replace sulfur hexafluoride using in gas-insulated equipment. In this study, the authors explored the influence of oxygen on the dielectric and decomposition properties of C₄F₇N–CO₂–O₂ gas mixture. The authors found that the dielectric strength of the C₄F₇N–CO₂–O₂ gas mixture with 2, 4, 6, 8 and 10% O₂ was increased by 4.85%, 6.49%, 7.70%, 3.21% and 2.74% compared with C₄F₇N–CO₂. The addition of 2–6% O₂ to the C₄F₇N–CO₂ gas mixture could effectively reduce the content of most of the decomposition by-products such as CF₄, CO, C₂F₆, C₃F₆, C₃F₈, CF₃CN, C₂F₅CN, (CN)₂. While high content of oxygen (>6%) results in higher decomposition of C₄F₇N, which has a negative effect on the stability of C₄F₇N gas mixture. Generally, it is recommended to add 2–6% O₂ in the C₄F₇N–CO₂ gas mixture to improve its insulation properties as well as inhibit the decomposition of C₄F₇N in the discharge