The dynamic velocity of long positive streamers observed using a multi-frame ICCD camera in a 57 cm air gap

Abstract

The streamer propagation plays an important role in long air gap discharge. In this paper, a multi-frame intensified charge-coupled display (ICCD) camera was used to observe the long positive streamers in a 57 cm air gap. The propagation process of the 20–30 cm long streamers was captured, and the velocity variation in a single streamer was analysed. When applying a +210–290 kV lightning impulse voltage on a rod–plane gap with three different tips, the velocity of a streamer decreases from 8.3 ± 2.7 mm ns−1 at the ignition stage to 0.4 ± 0.1 mm ns−1 at the later stage. The influence of the applied voltage and the electrode size was obtained and analysed. Higher voltage amplitude and larger electrode size lead to a greater velocity. In addition, the relationship between the velocity and the background electric field is discussed here, and the experimental results are compared with an analytical model of different parameters.