APPLIED PHYSICS LETTERS 100, 192910 (2012) 1 Impulse breakdown delay in liquid dielectrics

Theoretical images of streamers, revealing the mechanisms behind impulse breakdown in liquid dielectrics, are presented. Streamers form paths that are capable of carrying large current amplitudes through the electrode gap, leading to electrical breakdown. Breakdown delays are calculated for different electrode geometries (40 µm needle and 6.35 mm sphere) and gap distances (up to 10 mm) as well as time dependent currents through the gap. Modeling results indicate that the breakdown within needle-needle electrodes requires higher impulse voltage magnitudes than within needle-sphere electrodes for the same gap distances. Streamers in needle-sphere geometries are about 50 percent thicker than streamers propagating in needle-needle geometries under similar impulse voltage amplitudes