Insulation Properties of Mixed Gases with CF3SO2F plus C3HF3 and Natural gases

SF
6
gas has high insulation strength, but SF
6
is a strong greenhouse gas. It is necessary to study environmental friendly insulation gas. $\mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F}$ binary gas mixture has before been studied to replace $\mathrm{SF}_{6}. \mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / \mathrm{N}_{2}$ is proposed as a potential substitute gas. However, $\mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / \mathrm{N}_{2}$ binary gas mixture at $\mathbf{0. 5 M P a}$ absolute pressure has a higher liquefaction temperature and cannot be directly applied to low temperature environment. At present, there are few reports on the research of $\mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F}$ ternary gas mixture. In order to study the feasibility of $\mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / \mathrm{C}_{3} \mathrm{HF}_{3} / \mathrm{N}_{2}\left(\mathrm{CO}_{2}\right)$ ternary gas mixture, the power frequency insulation strength of the ternary gas mixture was obtained by calculation and test. The results show that the power frequency breakdown voltage of $20 \% \mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / 15 \% \mathrm{C}_{3} \mathrm{HF}_{3} / 65 \% \mathrm{~N}_{2}$ reaches to about $95 \%$ of SF
6
when the absolute pressure is 0.5 MPa. And it can be used at lowest temperature at $-25^{\circ} \mathrm{C}$. The power frequency breakdown voltage of $20 \% \mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / 15 \% \mathrm{C}_{3} \mathrm{HF}_{3} / 65 \% \mathrm{CO}_{2}$ reaches about $\mathbf{9 4 \%}$ of SF
6
. According to the effective ionization coefficients of $\mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F}_{1} \mathrm{C}_{3} \mathrm{HF}_{3}, \mathrm{~N}_{2}, \mathrm{CO}_{2}$ and SF
6
pure gases measured by steady-state Townsend experiment (SST), The reduced critical electric field of $20 \% \mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / 15 \% \mathrm{C}_{3} \mathrm{HF}_{3} / 65 \% \mathrm{~N}_{2}$ and $20 \% \mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / 15 \% \mathrm{C}_{3} \mathrm{HF}_{3} / 65 \% \mathrm{CO}_{2}$ are similar to that of SF
6
. The study can verify the feasibility of $\mathrm{CF}_{3} \mathrm{SO}_{2} \mathrm{~F} / \mathrm{C}_{3} \mathrm{HF}_{3} / \mathrm{N}_{2}\left(\mathrm{CO}_{2}\right)$ ternary gas mixture, which has the potential to replace $\mathbf{S F}_{6}$.