Continuous and Discontinuous Streamer Leader Propagation Phenomena under Slow Front Impulse Voltages in a 10-meter Rod-Plane Air Gap

Abstract

Investigation of positive streamer-leader propagation under slow front impulse voltages can play an important role in the quantitative research of positive upward lightning. In this work, we performed a large-scale investigation into leader development in a 10-m rod–plane gap under a long front positive impulse. To describe the leader propagation under slow front impulse voltages, we recorded the leader propagation with a high-speed charge coupled device (CCD) camera. It is important to figure out this phenomenon to deepen our understanding of leader discharge. The observation results showed that the leader mechanism is a very complex physical phenomenon; it could be categorized into two types of leader process, namely, continuous and the discontinuous leader streamer-leader propagation. Furthermore, we studied the continuous leader development parameters, including two-dimensional (2-D) leader length, injected charge, and final jump stage, as well as leader velocity for rod–plane configuration. We observed that the discontinuous leader makes an important contribution to the appearance of channel re-illuminations of the positive leader. To clarify the above doubts under long front cases, we carried out extensive experiments in this study. The comparative study shows better results in terms of standard switch impulse and long front positive impulse. Finally, the results are presented with a view toward improving our understanding of propagation mechanisms related to restrike phenomena, which are rarely reported.

Observations of the Channel Illuminations During Dark Periods in Long Positive Sparks

“…Although the stable leader is not initiated in our experiments, current pulses (B, C), and (d) in Figure 2a and their corresponding direct images in Figure 2b shows similar characteristics to the abrupt elongation (or restrike/reillumination phenomenon) of positive leaders (Gallimberti, 1979; Huang et al., 2020; Kostinskiy et al., 2018; Shah et al., 2018). It is reasonable to infer that there is also capacitive current through the remaining channel during the so‐called dark period before these phenomena.…”

A Modified Model for Discharge Voltage of AC Transmission Line-Tower Air Gaps

“…Similarly, in the conductor-cylinder gap, substituting d with (d + b) in equation (10), the point charge -Q e in Fig. 2 can be expressed as:…”

“…In recent years, with the continuous investigation of discharge mechanism, more and more attention has been paid on the simulation of physical development process of air gap discharge, which includes first corona inception, streamer propagation, leader formation, leader propagation, and final jump. Based on the observation of discharge phenomena and measurement of the key physical parameters [10], [11], several physical models have been developed to describe each stage of air gap discharge [12]- [15] However, due to the influence of space charge, the spatial electric field distribution and the air dielectric properties will change continuously over time during the discharge process. Therefore, it is difficult to simulate the whole discharge processes accurately especially for the complicated structures such as conductor-tower electrode structures.…”

Non-Contact Measurement and Polarity Discrimination-Based Identification Method for Direct Lightning Strokes

“…Different protection methods should be used according to the type of the lightning stroke fault. These stroke faults should be identified to efficiently adopt targeted measures against lightning and improve lightning protection design [5][6][7][8][9][10].…”