The effect of contaminant in breakdown time lag of uniform electric field using impulse breakdown in mineral oil

A breakdown time lag of uniform electric field using sphere-sphere electrodes was measured in pure mineral oil and in contaminated oil. The electrodes were steel spheres of diameter 12.5 mm. The effect for breakdown time lag wielded by differences of the distance between electrodes, applied impulse voltage and contaminant was measured, The breakdown time lag increased proportionally to applied voltage and the breakdown time lag of contaminated oil was shorter than the one of no contaminated oil. It was found that the breakdown phenomenon in this experiment was a streamer type breakdown structure