State of water vapour in SF/sub 6/ and several kinds of gases and its effect on partial discharge

State of water vapor in SF/sub 6/ is same as that in vacuum, but state of water vapor in CO/sub 2/ is quite different from in vacuum. State of water vapour in SF/sub 6/ does not change even though negative DC, positive DC and AC partial discharge occurs. Water cluster which disturbs partial discharge phenomena is not formed. Comparing the relation between area intensity and partial discharge inception voltage in all cases, partial discharge inception voltage is influenced by the amount of water vapour. However, these tendencies are different from the kinds of discharge and gases.