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

Our research has investigated the use of CF
₃
I, which has lower Global Warming Potential (GWP), as a substitute gas for SF
₆
. The use of pure CF
₃
I in gas insulated switchgear (GIS) and gas circuit breakers (GCB) is difficult because liquid CF3I has a high boiling point. We have therefore mixed CF
₃
I with CO
₂
or N
₂
. By investigating the decomposed gas after a current interruption, we have shown that the iodine density from CF
₃
I-CO
₂
(30%-70%) is about 1/3 of that of pure CF
₃
I. In addition, no fluorine was detected from the gas mixture. Our investigation of the breakdown voltage characteristics has shown that the dielectric strength of CF
₃
I-CO
₂
(30%-70%) is about 0.75 to 0.80 times that of SF
₆
. In breaker terminal fault (BTF) and short line fault (SLF) interruption, CF
₃
I-CO
₂
is superior to CF
₃
I-N
₂
. Because of the high boiling point of CF
₃
I, the proportion of CF
₃
I should be small. In BTF interruption, the performance approximates to that of pure CF
₃
I when the proportion of CF
₃
I exceeds 30%. Similarly, the SLF interruption performance approximates to that of pure CF
₃
I when the proportion of CF
₃
I exceeds 20%.