Abstract
Propagation process of an impulse creepage discharge on the surface of a solid insulator in transformer oil is investigated in detail by using a Schlieren method, a dust figure method, a current measuring system by LED, etc. simultaneously when an impulse voltage with various values of duration of wave front (Tf) is applied to a point-back electrode system. The main results may be summarized as follows:
(1) In case of the longer Tf for a constant peak value (Vm=±30kV),
(i) propagation of streamer-like density changes is alwayshalted before the voltage increases up to the crest point.
(ii) appearence of the plural groups of current pulses may be seen sometimes.
(2) As independently of the point polarity, the instantaneous value of the impulse voltage, which corresponds to a time lag to the inception of the discharge current, is larger,
(i) the discharge figure becomes larger in size and more branches appear.
(ii) the charge quantity of the discharge is larger.
(3) For the average propagation velocity υsd of streamer-like density changes, , υ+ sd>υ-sd, and the remarkable difference of the velocities can not be seen by the Tf for both point polarity.
