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In order to study the generation mechanism and dynamic physical properties of the secondary arc, the combination of low-voltage simulation experiment and simulation modeling is used to analyze the movement characteristics of the secondary arc and the plasma state before the start of secondary arc. Based on high-speed camera shooting pictures in low-voltage simulation experiments, the arc movement characteristics were analyzed, and the effects of different secondary currents on the characteristics of the secondary arc are compared. The results show that due to the large current, the short-circuit arc discharge channel is bright and rapidly developing. The secondary arc has a strong ionization at the arc root, and is prone to mutual short circuit. The part of the arc column is obviously affected by external electromagnetic force and thermal buoyancy, and obvious elongation and floating motion occur. The magnitude of the secondary current will significantly affect the combustion characteristics of the arc. Based on the combination of the general form of the coefficient partial differential equations and the classical drift diffusion model, the secondary arc theoretical model of the numerical simulation is obtained, and then the realization method based on the finite element software COMSOL is given. Transient analysis was used to simulate the discharge, diffusion and dissipation process of the arc in the short-circuit arc discharges. The simulation results show that the electron and positive ion concentrations are concentrated near the arcing copper wire during the rising phase and peak phase of the short-circuit current and produce a luminescent effect. When the copper wire is melted, the new electrons and positive ions generated gradually diffuse into the surrounding space under the action of electric field migration and convection diffusion of ions, and finally reach a spatial distribution of electron and positive ion concentration tending to a stable state.