Interruption capability and decomposed gas density of CF3I as a substitute for SF6 gas

We investigated the fundamental characteristic of CF₃I as a substitute gas for SF₆. CF₃I has lower global warming potential. The use of pure CF₃I in gas-insulated switchgear and gas circuit breakers is difficult because liquid CF₃I has a high boiling point. We therefore mixed CF₃I with CO₂ or N₂. In short line fault (SLF, 1 kA_peak) and breaker terminal fault (BTF, 3 kA_peak) interruption, the performance of CF₃I¿CO₂ approximated that of pure CF₃I when the proportion of CF₃I exceeded 30%. However, for BTF (20 kA_peak) interruption, the performance of CF₃I¿CO₂ remarkably decreased. In loop current interruption for disconnecting switches, CF₃I¿CO₂ (30%/70%) was successfully used 200 times for 4000 A. We also measured CF₃I spectra. Investigation of the decomposed gas density after current interruption revealed that fluorine release from CF₃I was less than that from SF₆. Iodine density released from CF₃I-CO₂ (30%/70%) was approximately one-third of that released from pure CF₃I. In addition, iodine could be removed using an adsorbent.