What is the "electrostatic vacuum effect" of DC
Under DC voltage, the charged particles in the air are attracted to the surface of the insulator by the action of a constant direction electric field. This is the "electrostatic effect" of DC. Due to its function, the surface area of the DC insulator can be more than doubled under the AC voltage under the same environmental conditions. As the amount of contamination increases, the level of insulation decreases, and the smudging of the insulator easily occurs under certain weather conditions. Therefore, due to this technical characteristic of the DC transmission line, the external insulation characteristics are more complicated than those of the AC transmission line.