Short-Line Fault Interruption Performance Comparison of SF₆ Alternatives

Measurements of the interruption performance of SF<tex-math notation="LaTeX">₆</tex-math> and its alternatives including air, CO<tex-math notation="LaTeX">₂</tex-math>, and its mixtures with O<tex-math notation="LaTeX">₂</tex-math>, C<tex-math notation="LaTeX">₄</tex-math>F<tex-math notation="LaTeX">₇</tex-math>N, and C<tex-math notation="LaTeX">₅</tex-math>F<tex-math notation="LaTeX">₁₀</tex-math>O were performed under short-line fault like conditions. The measurements were conducted with an experimental puffer-type circuit breaker in which the same upstream pressure and the same contact separation at the current zero instant were ensured for every gas. At <tex-math notation="LaTeX">Δ p = 5.8 bar</tex-math>, the interruption limit of SF<tex-math notation="LaTeX">₆</tex-math> was found to be <tex-math notation="LaTeX">12.39 A/ μ s</tex-math>. In the CO<tex-math notation="LaTeX">₂</tex-math>-based alternatives at the same pressure, the thermal interruption limit was found to range from <tex-math notation="LaTeX">9.01 A/ μ s\,to\, 9.46 A/ μ s</tex-math>, while in air an interruption limit of <tex-math notation="LaTeX">4.17 A/ μ s</tex-math> was identified. Despite the similar thermal performance among CO<tex-math notation="LaTeX">₂</tex-math> based mixtures, it was found that in those mixtures without fluorinated additives, the overall interruption limit is lowered by the occurrence of hot dielectric failures. Limit values of the arc conductance decay, G200 and G500, were found to be <tex-math notation="LaTeX">1.44 mS</tex-math> and <tex-math notation="LaTeX">3.83 mS</tex-math> respectively in SF<tex-math notation="LaTeX">₆</tex-math>, while in the alternatives these limit values ranged from two to six times lower. Arc voltage extinction peak was also evaluated, with SF<tex-math notation="LaTeX">₆</tex-math> found to have the lowest limit value at <tex-math notation="LaTeX">628 V</tex-math>, and air found to have the highest at <tex-math notation="LaTeX">1535 V</tex-math>. Post-arc current was also measured, and found to not exceed <tex-math notation="LaTeX">350 mA</tex-math> in any gas, with a duration limited to <tex-math notation="LaTeX">9\; μ s</tex-math> or less. Gas analysis of two fluorinated CO<tex-math notation="LaTeX">₂</tex-math> mixtures (CO<tex-math notation="LaTeX">₂</tex-math>/C<tex-math notation="LaTeX">₄</tex-math>F<tex-math notation="LaTeX">₇</tex-math>N and CO<tex-math notation="LaTeX">₂</tex-math>/O<tex-math notation="LaTeX">₂</tex-math>/C<tex-math notation="LaTeX">₄</tex-math>F<tex-math notation="LaTeX">₇</tex-math>N) showed no significant influence of oxygen on the creation of byproducts.