Abstract
In this study, the inception probability of negative streamers in technical air with 7.5 %vol C5-fluoroketone (C5-FK+air) at 1.0 bar absolute pressure is studied. Similar tests were done for both polarities in technical air (80% N 2 , 20% O 2 ) for comparison with the C5-FK+air results and to investigate polarity dependencies in air. The streamers emerged from a grounded needle electrode placed 48 mm below a planar electrode. The electrode setup was stressed by a fast rise time impulse voltage. The streamers in air showed a significant polarity dependence, with substantially higher voltages required for negative streamer inception. This is speculated to be due to either differences in source of first electron or the critical volume, or both. The negative streamers in C5-FK+air required a stronger field than both polarities in air. This is believed to be due to C5-FK being more electronegative than pure air. Differences in critical volume and source of first electron might also contribute to this difference.