Observation of the Streamer–Leader Propagation Processes of Long Air-Gap Positive Discharges

A novel observation method is proposed to study the streamer-leader propagation processes of long air-gap positive discharges. Experiments of 3-12 m air-gap discharges have been conducted in this paper. The observed images could clearly and particularly describe the characteristics of the positive streamer-leader propagation processes. Some important phenomena of the propagation processes are indicated and discussed, such as the leader´s velocity that varied with the time, the different lengths of inception leaders, the leader´s branching phenomena, the continuous streamer-leader propagation processes simultaneously with the voltage´s descent, and the upward leader´s propagation processes.