Positive streamer inception in cyclohexane: evidence of formative time and cavitation process

This paper deals with physical processes involved during streamer inception in liquid cyclohexane under impulse voltage. In point-plane geometry, the inception of streamers is detected with a high temporal resolution (about 1 ns) by measurement of charge, visualization, and detection of phase change by scattered laser light. These techniques allow us to obtain precise measurements of the inception delay time, versus applied voltage and hydrostatic pressure. Measurements carried out in positive and negative polarity with a fast impulse voltage (20 ns risetime) show a large difference. In positive polarity, a minimum "formative time" close to 45 ns is observed, while negative streamers can appear almost immediately at high voltage. The hypothesis of cavitation induced by the EHD motion is considered to explain positive streamer inception.