Current and Light Emission Characteristics of Unstable Leader under Positive Voltage in Long Air Gap

Unstable positive leader propagation is of great interest for lightning and spark researchers. However, there are few detailed studies about this phenomenon. To research the current and light emission characteristics of the unstable leader, a digital time-resolved current measurement system and high-speed camera with high sensitivity are used to observe the process. Based on the analysis of the results, two types of the current waveform are classified, and the relationship between the restrike frequency and voltage rise rate is explained. The results and analysis in this paper could help to understand the discontinuous and unstable leader phenomenon.