Temperature effect in the electrical breakdown of SF6

Hickam(1) has shown that at extremely low pressures (10^-4-10^-5 mm) the electron capture curve of SF₆ is dependent on the temperature at which the experiment is conducted. Experiments were performed to see if there was a temperature effect on the breakdown of SF₆. In non-uniform fields, the positive direct voltage for breakdown in SF₆ as a function of pressure goes through a maximum. The reason for this maximum has previously been shown to be due to the positive corona which precedes breakdown(2). Changing the gas temperature from 25°C to 125°C shifts the maximum of the breakdown curve to higher pressures as might be expected from the pressure change on increasing the temperature. However, when the higher temperature data are plotted as a function of density the peak occurs at the same density as it does in the lower temperature case but the breakdown values are increased in the region where corona precedes breakdown. Thus, the breakdown voltage is not only a function of density but also of temperature.