Observation of Prebreakdown and Breakdown Phenomena in Liquid Hydrocarbons II. Non-Uniform Field Conditions

The prebreakdown and breakdown processes have been recorded in n-hexane toluene and Marcol 70, both in a pure state and with selected impurities. The study was carried out using a point-plane geometry. A low ionization potential additive had only a small effect on the breakdown voltage or the streamer propagation speed but did significantly alter the shape of the prebreakdown streamer when the needle was positive, an anode. For a negative needle, a cathode, chemical impurities affected the breakdown voltage. The significance of these findings is discussed in detail.