Interruption capability of CF/sub 3/I Gas as a substitution candidate for SF/sub 6/ gas

We studied the interruption performance of CF
₃
I gas because its environmental effect is smaller than that of SF
₆
gas with a model arc-extinguishing chamber. First, we measured the arc time constant and arc power loss coefficient using Mayr's equation. Comparing CF
₃
I with other gases, the arc time constants are SF
_6
3
I₂
< H
_2
2
. The arc power loss coefficient is H
₂
>SF
₆
>CO
₂
>Air>N
₂
>CF
₃
I. Next, we evaluated the short line fault (SLF) interruption capability by measuring the di/dt-dv/dt characteristic. Consequently, the SLF interruption performance of pure CF
₃
I was about 0.9 times that of SF
₆
. However, CF
₃
I application to gas insulated switchgear (GIS) and gas circuit breakers (GCB) is difficult because the liquefying temperature of the gas is high. Therefore, we adopted a countermeasure to obtain a lower liquefying temperature mixing CF
₃
I with CO
₂
. The result showed that the SLF interruption performance of the mixture approximated that of pure CF
₃
I when the ratio of CF
₃
I exceeds 20%