Investigation of the performance of CF3I Gas as a Possible Substitute for SF6

Our research has investigated the use of CF3I, which has lower Global Warming Potential (GWP), as a substitute gas for SF6. The use of pure CF3I in gas insulated switchgear (GIS) and gas circuit breakers (GCB) is difficult because liquid CF3I has a high boiling point. We have therefore mixed CF3I with CO2or N2. By investigating the decomposed gas after a current interruption, we have shown that the iodine density from CF3I-CO2(30%-70%) is about 1/3 of that of pure CF3I. In addition, no fluorine was detected from the gas mixture. Our investigation of the breakdown voltage characteristics has shown that the dielectric strength of CF3I-CO2(30%-70%) is about 0.75 to 0.80 times that of SF6. In breaker terminal fault (BTF) and short line fault (SLF) interruption, CF3I-CO2is superior to CF3I-N2. Because of the high boiling point of CF3I, the proportion of CF3I should be small. In BTF interruption, the performance approximates to that of pure CF3I when the proportion of CF3I exceeds 30%. Similarly, the SLF interruption performance approximates to that of pure CF3I when the proportion of CF3I exceeds 20%.