Impulse breakdown delay in liquid dielectrics

Theoretical images of streamers, revealing the mechanisms behind impulse breakdown in liquid dielectrics, are presented. Streamers lead to electrical breakdown by forming paths, capable of carrying large current amplitudes between electrodes. Breakdown delays and terminal currents are calculated for various electrode geometries (40 μm needle and 6.35 mm sphere) and gap distances (up to 10 mm). Modeling results indicate that the breakdown in needle-needle electrodes requires higher impulse voltage amplitudes than in needle-sphere electrodes for the same gap distances. Streamers in needle-sphere geometries are about 50% thicker than streamers propagating in needle-needle geometries under similar impulse voltage amplitudes.ABB Corporate Research Center (Vasteras, Sweden)IEEE Dielectrics and Electrical Insulation Society (Fellowship