Thermal dynamics of leader decay and reactivation in long air gap discharges

Abstract

In this study, we present a comprehensive investigation of positive leader discharges, with the aim of enhancing our understanding of leader decay and reactivation. Our approach involved a detailed experimental and computational analysis of the phenomena. Specifically, we employed a time-resolved quantitative Schlieren platform, which provided us with a high spatial resolution (60.0 μm/pixel) and short exposure times (0.37 μs/frame), allowing us to capture the 2D spatial-temporal evolution of gas temperature in positive leaders with a gap length of up to three meters. In addition, we employed a detailed thermal-hydrodynamic model coupled with a comprehensive kinetic scheme, consisting of 28 chemical species and 125 chemical reactions. Our simulations showed good agreement with the measured mean gas temperature and expansion rate of thermal radius. We conducted experiments under the same applied conditions to obtain both stable and decaying leaders. Our results showed that once a positive leader starts to decay, the temperature drops below 3000 K. At the same time, both the electric field and conductivity decreased significantly compared to a stable leader. In addition, before the temperature drops below 2000 K and transforms into an aborted leader, a decaying leader might be reactivated.

Measurement of medium-voltage AC air arc temperature and particle number density based on dual-wavelength Moiré deflection technology

“…In the second zero-off stage shown in figure 8, no electron density drop was detected, which means that t x may be lower than t 2 . Other studies have observed that the initial ionization channel in the air gap can be formed within a few microseconds, well before t 2 [35,36]. • Arcing stage: the arc enters the arcing stage, and its electron density gradually decreases after a rapid decline.…”

Plasma characteristics of medium voltage AC air arc discharge and its application on arc electrical parameters calculation

“…Under the current amplitude of 1 A and the temperature of heavy particles at about 2000 K, the air gap can maintain enough electron number density to generate discharge. As an example, the electron number density of leader discharge with the current in the same low level is in the order of 10 20 ∼ 10 21 m −3 [38]. By analyzing the thermal radius expansion rate of the leader channel, it is shown that the main channel has not yet reached the LTE state [39].…”