Numerical investigation of DC arc voltage-breaking capacity in an H₂-N₂ mixture using a self-initiation methodology

The limited research on kilovolt switches utilizing sealed gas has impeded the advance of medium-voltage direct current power grids, particularly in aeronautic and astronautic applications. A self-initiation methodology was introduced in the magnetohydrodynamic model, which defines a negative correlation between the minimum conductivity of the gas medium and time. This methodology enables spontaneous initiation of the arc in the contact gap, eliminating the need to specify the arc’s location and temperature. The proposed methodology was validated experimentally via a multicontact contactor, and two related characteristic parameters were simulated to be independent of the gas-phase arcing voltage, current and time. Furthermore, the primary characteristics and mechanisms of arc extinction, restrike-extinction and restrike-sustained arcing were comprehensively analyzed, with the voltage-breaking capacity at 450 A determined to be 1050 V at an opening distance of 1.5 mm in a 4 atm H₂-N₂ mixture (molar ratio 7:3). The mechanisms of motion and deformation during gas-phase arcing were interpreted based on characteristic times. Finally, the temperature of the conductive branch wake at time t ₅ under the condition of restrike-sustained arcing was analyzed, and its variation with gas composition and pressure was determined.