On streamer inception in hydrocarbon liquids in point-plane gaps

Estimates for the discharge initiation voltage in hydrocarbon liquids in point-plane gaps are obtained, basing on evaluation of the ionization integral describing electron multiplication in avalanches in liquids. An approach for estimation of the voltage required to inception of filamentary streamers is presented. It assumes that, like in gases, a minimum radius of streamers propagating in liquids exist. It is shown, in agreement with published experimental data for cyclohexane and pentane, that at point radii smaller than some threshold value (of several micrometers) the discharge initiation voltage is lower than the voltage of inception of filamentary streamers. At point radii exceeding this threshold, filamentary streamers occur just at the discharge inception.