Abstract
It is found that the mean time lags of the breakdowns of an aluminum sphere gap in SF6 gas enclosed in a test chamber are more decreased, when the chamber that has been exposed in a higher atmospheric humidity condition, prior to the gas filling, is used. The main purpose of the present paper is to investigate the cause of this phenomenon
It is confirmed in the present experiment that the water vapor content in the test chamber increases with the time elapsed after the gas filling. In the case that the time from a gas filling to a beginning of the time lag measurement is more increased, the increase in this water vapor causes the mean time lags to decrease markedly. This effect is considerable for the rough electrode, but a little for the smooth electrode. It is also found that the mean time lags is influenced by the condition of the cathode surface, not the anode. From these results, it is clear that the water vapor desorbed from the test chamber wall attaches to some microscopic protrusions on the cathode and accelerates the emission of the initiatory electrons, and then this results in the decrease in the mean time lags.
