Abstract
Secondary arc is more severe in the ultra-high voltage (UHV) power grid. However, the mechanism for the generation process of secondary arc at the extinction moment of a short-circuit arc is not yet clear. It is of great theoretical significance and technological application value to study the generation mechanism and dynamic physical characteristics of secondary arc, and further to develop effective suppression technology. In this article, an arc numerical simulation model based on the coefficient partial differential equations combining with classical drift-diffusion model was established, and the implementation method based on the finite element software COMSOL (COMSOL Multiphysics 5.2a, COMSOL Inc., Stockholm, Sweden) was given. Then, the transient analysis method was applied to simulate the generation, diffusion and dissipation phenomena of the short-circuit arc strike, and further to explore the electric field, microscopic particle spatial distribution and reaction process during the arc discharge process. The simulation results show that the development of short-circuit arc mainly includes two processes: corona discharge and arc discharge, of which the former has a very short duration and the latter is caused by short-circuit. During the discharge process, the electron density first increases and then decreases, which is different from the general characteristics of streamer discharge. Although the concentration distribution curve of the positive ions and negative ions has the same trend, there are subtle differences. The diffusion effect of space ions in the initial discharge stage is almost zero, while radial diffusion direction in the peak discharge stage and axial direction in the late discharge stage. The electric field intensity in space has an S-shaped upward trend during discharge. The time relationship of the ion source generated by the neutralization reaction and by the short-circuit arc discharge are basically the same, and the rate of neutralization reaction is lowest near the electrode. When the ionic reaction is approaching the end of the simulation, the ionic concentration is higher than the initial level, which proves that the space ionic concentration is increased due to the short-circuit discharge, and providing the necessary environmental conditions for the subsequent generation of the secondary arc.
Highlights
Secondary arc is a kind of long-gap arc that can be freely burning in the air
In this article, an arc striking line was added into the simulation model, and the high charge density arc channel generated by the short-circuit arc combustion was simulated by setting the ion source on the arc striking line after the beginning of simulation
When the ion reaction approached the end of the simulation time, the ion concentration was higher than the initial level, which proves that the space ion concentration was increased due to the short-circuit arc discharge, providing the necessary environmental conditions for the subsequent secondary arc generation
Summary
Secondary arc is a kind of long-gap arc that can be freely burning in the air. If the secondary arc cannot be extinguished in time, it would lead to the single-phase reclosing failure. In the study of the hydrodynamic model based on the partial differential equations, Davie and Yoshida [13] established a two-dimensional hydrodynamic model of discharge between plate electrodes, which can accurately reveal the phenomenon of discharge process. This model continued to be improved by GE. A continuous numerical model based on partial differential equations is chosen to simulate arc process. A numerical model of arc discharge process based on the finite element simulation software (COMSOL) was established to study the influence of short-circuit arc on secondary arc. The generation, diffusion and adsorption processes of short-circuit arc discharge were simulated with transient analysis, and the spatial distribution of positive ions, negative ions and electrons in the discharge process were further explored
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