Simulation and Experimental Analysis of DC Arc Characteristics in Different Gas Conditions

The structures of high-voltage direct current (HVDC) relays are compact. In order to extinguish the arc, the external magnetic field is applied near the contact. HVDC relays with a large capacity are also filled with gas medium to enhance the ability of arc extinguishing. The research on the characteristics of the arc in different gases under different pressures is of great significance to improve the reliability and the lifetime of the HVDC relays. The characteristics of the arc in nitrogen, hydrogen, and nitrogen-hydrogen mixtures and that of the arc root motion in the magnetic field are simulated by means of magnetohydrodynamics (MHD). The arcing processes in N₂ and air are tested by a high-speed camera, and the arc root coordinates are calculated by the image processing method, and the simulation models are verified. The result shows that under the same condition, the hydrogen arc voltage is the highest, and the moving speed of the arc root is the fastest, so that the arc extinguishing performance of the hydrogen is the best. Nitrogen-hydrogen mixture is also a superior arc extinguishing gas, and the higher the proportions of H₂, the better the performance. With the increase of the pressure, arc voltage increases. Except H₂, increasing the pressure of the gas is beneficial for arc motion.