INFLUENCE OF GAP LENGTH ON DISCHARGE CHANNEL PROPAGATION AND BREAKDOWN MECHANISM IN AIR

Abstract: In order to clarify the discharge propagation mechanism, ultra-high speed electrical and optical measurement was performed in a needle (1 mm) -plane electrode system with gap length g=15 mm and 100 mm in 0.1 MPa dry air under applying a positive impulse voltage. Discharge current and optical images from initiation to breakdown (BD) were synchronously measured. In gap length g=15 mm, we found that the secondary streamer propagated and reached the grounded plane electrode, and the secondary streamer channel made the high-conductive channel, resulted in BD. In the case of g=100 mm, because the secondary streamer could not reach the grounded plane electrode due to the long gap, the high-conductive path was not made by the secondary streamer. However, BD occurred by a leader-like discharge propagated from the needle electrode. From these results, we found that secondary streamer propagation dominates the formation process of the discharge channel and the mechanism leading to BD.