## 3 Results
### Gas Type  
Figure 9 displays the breakdown voltage and voltage dispersion of the corona-stabilized switch filled with various gas mediums at different frequencies. Figure 9: The effect of gas type on the repetitive breakdown voltage and its dispersion of the switches (electrode R1, 0.1 MPa, gap spacing of 5.0 mm): (**a**) Breakdown voltage of SF\({}_{6}\)–N\({}_{2}\); (**b**) voltage dispersion of SF\({}_{6}\)–N\({}_{2}\); (**c**) breakdown voltage of SF\({}_{6}\)–air; (**d**) voltage dispersion of SF\({}_{6}\)–air; (**e**) breakdown voltage of SF\({}_{6}\)–He; (**f**) voltage dispersion of SF\({}_{6}\)–He. Pure SF\({}_{6}\) exhibits the optimal electrical strength performance, but diluting it with other gases that have a lower electrical strength can significantly reduce the switch's withstand voltage level. In other words, adding SF\({}_{6}\) to other gases can significantly improve the withstand voltage level of the mixtures. The variation in breakdown voltage curves at different frequencies indicates the insulation recovery characteristics of the gas media. The variation trends and amplitudes of the breakdown voltage for SF\({}_{6}\)-air and SF\({}_{6}\)-N\({}_{2}\) mixtures at different repetition frequencies were similar to those of pure SF\({}_{6}\), indicating that their insulation recovery characteristics are comparable after 500 us of breakdown. The insulation recovery of air was slightly better than that of pure N\({}_{2}\), which may be due to the presence of weakly electronegative gas O\({}_{2}\). Considering its weak electronegativity, O\({}_{2}\) can absorb the free electrons generated by the previous breakdown to form a few negative residual charges. These negative charges can also produce electrons to enhance the corona stabilization effect on subsequent breakdowns. However, it is obvious that the improvement in the insulation recovery performance of N\({}_{2}\) by adding O\({}_{2}\) is very limited. In SF\({}_{6}\)-He gas mixtures, the influence of SF\({}_{6}\) content on the variation in the breakdown voltage at different repetition frequencies was greater than that of SF\({}_{6}\)-air and SF\({}_{6}\)-N\({}_{2}\), indicating that the insulation recovery performance of SF\({}_{6}\)-He gas mixtures are more sensitive to the content of SF\({}_{6}\). The breakdown voltage dispersion of pure SF\({}_{6}\) gas was generally lower than that of other gases (N\({}_{2}\), air, and He), the voltage dispersion of N\({}_{2}\) and air was similar, while helium had the maximum voltage dispersion. The difference in breakdown voltage dispersion of SF\({}_{6}\) was minimal at different repetition frequencies. The dispersion of SF\({}_{6}\)-N\({}_{2}\) and SF\({}_{6}\)-air was very similar, which may be attributed to the weak impact of O\({}_{2}\), a gas with low electronegativity, on the repetitive breakdown stability of the mixture. In these two mixtures, the voltage dispersion did not decrease monotonously with the content of SF\({}_{6}\). When the content of SF\({}_{6}\) reached about 50%, there was a sudden increase in voltage dispersion, especially noticeable in the SF\({}_{6}\)-air mixture. As the SF\({}_{6}\) content increased in the SF\({}_{6}\)-He mixture, there was initially a decrease and then an increase in the breakdown voltage dispersion. It is worth noting that during the breakdown with high-repetition frequencies (\(\geq\)1000 Hz), the dispersion of repetitive breakdown voltages in air and N\({}_{2}\) was slightly higher than that in SF\({}_{6}\). As the frequency decreased, the breakdown dispersion of N\({}_{2}\) and air increased, and the stability of breakdown at lower frequencies worsened. However, the addition of SF\({}_{6}\) to these two gases could improve their breakdown stability. The improvement effect became more obvious with an increase in the SF\({}_{6}\) content. The breakdown stability of helium was very good during high-repetition frequency (\(\geq\)1000 Hz) breakdown, comparable to that of pure SF\({}_{6}\).