Impulse and DC breakdown tracks of air in point-plane gaps

Impulse and DC breakdown tracks of 4 and 30 cm point-plane air gaps were investigated. For smaller gap in both voltages types, the positive-voltage breakdown tracks were found to wander further away from the axis than for negative voltage. For 30 cm point-plane gap the results are inverted, the trajectories of the electrical discharges for negative polarities, as a general rule, may travel more outward from the axis than for positive polarities. This shows that the electrical breakdown trajectories depends of the various discharge modes, so that simple models like the proposed by Watson are unsuited for explaining breakdown tracks.