Analysis of the feasibility of CF3I/CO2 used in C-GIS by partial discharge inception voltages in positive half cycle and breakdown voltages

SF₆ is widely used in C-GIS as an insulating medium. However, SF₆ and its decomposition products can pollute environment and harm human health and equipment. Firstly, this paper verifies the high-energy discharge promotes CF3I to produce C2F6 and I2 by simulation. Therefore the paper puts forward the significance of using mixture gas to reduce the use of CF3I and control the produce of I2. Secondly, the partial discharge inception voltages in the positive half cycle of power frequency (PDIV+) of CF₃I/CO₂ under different pressures, mixing ratios (k) and interelectrode distances were measured and compared with SF₆/CO₂. The results show that: when k is more than 10%, the PDIV+ of CF₃I/CO₂ is close to or higher than SF₆/CO₂ in the same experimental conditions; The PDIV+ of CF₃I/CO₂ (30%-40%) at 0.15-0.2MPa can reach the level of pure SF₆ in 0.1MPa. The breakdown experiments under different electric fields shows that the breakdown characteristic of CF₃I/CO₂ (30%-40%) at 0.15-0.2MPa can exceed the level of pure SF₆ at 0.1MPa. Considering the boiling point, producing of I₂ and insulating property, CF₃I/CO₂ (30%-40%) is likely to replace SF₆ used in C-GIS.