The air gap type belongs to the follow-up compensation system. The arc suppression coil belongs to the movable core structure, and the inductance can be continuously adjusted by changing the reluctance of the magnetic circuit by moving the iron core. However, it can only be adjusted at low or no voltage, and the ratio of upper and lower limits of inductance adjustment range is 2.5 times.
Under the normal operation of the control system, the arc suppression coil is adjusted to the vicinity of full compensation, and about 100 Euro resistance is connected in series to the arc suppression coil. It is used to limit the series resonance overvoltage so that the steady-state overvoltage value is within the allowable range (the neutral point potential increases less than 15% of the phase voltage). When single-phase grounding occurs, the resistance must be shortened within 0.2S to achieve the best compensation, otherwise the resistance will be in danger of explosion.