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.
Highlights
The investigation of the long air gap discharge mechanism is essential for the optimization design of the external insulation of power systems and lightning protection [1,2,3]
About 50% of breakdown voltage of long air gaps is closely related to the waveform of impulse voltages, which trends to a U-shaped curve
Results on onleader leaderdevelopment development a 10-m rod–plane work,the theexperimental experimental results in in a 10-m rod–plane configuration have been shown under positiveimpulse impulsewith with aa rise rise time of 250 configuration have been shown under positive
Summary
The investigation of the long air gap discharge mechanism is essential for the optimization design of the external insulation of power systems and lightning protection [1,2,3]. Researchers carried out several experiments to obtain the breakdown voltage of long air gaps under different configurations and impulse waveforms to fulfill the demands of external insulation design of power transmission systems [7,8]. Some studies have focused on positive polarity S.I tower window models having different breakdown voltages and sizes [9] The purpose of these tests was to evaluate the double exponential switching impulses of different front times, and the time to the crest of the wave. The long air gap discharge provided positive polarity in a three-meter rod–plane configuration, which was confirmed using double exponential switching impulses of different front times. The streamer to leader data under time voltage is lacking and it cannot support experimental setup is discussed in Section and the typical continuous discharge process and the theoretical results. The experimental apparatus consists of an upper electrode that is a hemisphere with a diameter
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