The structure of the protective gap is simple, but the air gap can not quickly extinguish the arc, so the trip rate of the line is high. In order to solve this problem, this paper puts forward a method of installing an air cannon beside the protection gap, which can take away the heat of the arc and make the arc be drawn thin by ejecting high-speed air, so as to speed up the extinction of the arc. And the air gun can automatically inflate after arc-extinguishing for the next action. Based on magnetohydrodynamics (MHD) theory, the new protection gap model and arc simulation model are established by COMSOL software. According to the simulation calculation, the arc can be pulled down to 25% of the original thickness by the protection gap of self-charging air gun, which is easier to extinguish. Because the air flow takes away the heat, the temperature at the arc center is only 1/3 of the traditional protection gap, and the arc is easier to be extinguished. Field experiments show that the arc in the protection gap with self-charging air cannon can be extinguished in 13.3 ms, which is much less than the arc extinguishing time of the traditional protection gap, and the arc extinguishing time is only 31.8% of the traditional protection gap at most.