Unstable Leader Inception Criteria of Atmospheric Discharges

Abstract

In the literature, there are different criteria to represent the formation of a leader channel in short and long gap discharges. Due to the complexity of the physics of the heating phenomena, and the limitations of the computational resources, a simplified criterion for the minimum amount of electrical charge required to incept an unstable leader has recently been used for modeling long gap discharges and lightning attachments. The criterion is based on the assumption that the total energy of the streamer is used to heat up the gas, among other principles. However, from a physics point of view, energy can also be transferred to other molecular processes, such as rotation, translation, and vibrational excitation. In this paper, the leader inception mechanism was studied based on fundamental particle physics and the energy balance of the gas media. The heating process of the plasma is evaluated with a detailed two-dimensional self-consistent model. The model is able to represent the streamer propagation, dark period, and unsuccessful leaders that may occur prior to the heating of the channel. The main processes that participate in heating the gas are identified within the model, indicating that impact ionization and detachment are the leading sources of energy injection, and that recombination is responsible for loss of electrons and limiting the energy. The model was applied to a well-known experiment for long air gaps under positive switching impulses reported in the literature, and used to validate models for lightning attachments and long gap discharges. Results indicate that the streamer-leader transition depends on the amount of energy transferred to the heating process. The minimum electric charge required for leader inception varies with the gap geometry, the background electric field, the reduction of electric field due to the space charge, the energy expended on the vibrational relation, and the environmental conditions, among others.

Optical Signatures Associated With Streamers and Leaders of Laboratory Discharges

“…Note that our group criterium is different than the concept of streamer‐to‐leader transition. The minimum amount of charge for a single or successive corona burst required for the thermal transition is estimated in the range of 0.2–1.0 μC (e.g., Arevalo & Cooray, 2017; Gallimberti, 1979; Wu et al., 2013). From our analysis, stems and leaders are incepted prior to the peak of blue irradiance, such as the cases shown in Figures 1b and 1c.…”

On the critical charge required for positive leader inception in long air gaps

“…The model of Gallimberti has also been used to describe the streamer-to-leader transition after one or several dark periods [6,16,17]. The gas temperature estimated with the model always increases with time during the dark period as energy stored in the vibrational reservoir relaxes [5].…”

Simulation of breakdown voltage associated with phase-to-phase air gap for ultra high voltage transmission lines under switching impulse voltage

“…The numerical simulation method based on SLIM model proposed in [20], was adopted to simulate the development and breakdown characteristics. The flow chart of the streamer inception and leader development in this model is shown in Figure 1.…”

“…Cooray replaced the "geometric secant method" with a simulated charge method or provided equivalent capacitance coefficients, further developing the Bondiou-Gallimberti model to establish the Self-Consistent Leader Inception and Propagation mode (SLIM) [15][16][17][18] . Currently, SLIM has gained widespread recognition in academia and industry and has been widely used for simulating rod-plane and sphere-plane gap discharge processes in laboratory settings, although no instances of its application in real engineering calculations for transmission line gap intervals have been identified [19][20] .…”