Research And Design On Automatic Controller Of Magnetic Valve Arc Extinguishing Coil

In distributions, because of its low-level voltage, its neutral point used to disconnect to the ground in order to improve its reliability. However, in recent years the distributions are becoming larger and larger and the enormous use of cables in city power system, which increases the current through the grounded capacitor. These make the single-phase faulty current get greater, which lead to more and more instantaneously grounding faults unable to eliminate naturally. To solve these problems, the compensating method of neutral point grounding through arc extinguishing coil is commonly used in our country.There exists some defects to the present resonant regulation methods, a new method of resonant regulation based on injecting currant is presented in this paper. Various frequency constant current is injected to second side of PT (potential transformer) which the magnetic valve arc extinguishing coil is the first side. Arc extinguishing coil tuning system is implemented, which is based on measuring the system resonance frequency. This principle is not affected by system operation, and only need to choose one arc extinguishing coil to measure and not need communication. It has high precision and high reliability.This dissertation explains in detail the structure and tenet of working of the controllable magnetic valve arc extinguishing reactor and analyses the small current neutral grounding system and the special feature of the single-phase grounding happening, based on above all, by a new control method which organically combines line selection based on zero order current changing and automatic control of the controllable magnetic valve arc extinguishing coil, we can realize synthetically optimal control of line selection and compensation to capacitive current in single-phase earth fault.