The working principles of arc suppression and harmonic elimination are different. Arc suppression means that when the single-phase metal grounding of the bus occurs, the arc suppression device operates to make the metal ground directly ground through the vacuum contactor operated by the arc suppression device, which is beneficial to the bus protection action and avoids the generation of harmonics. Harmonic elimination is mainly to eliminate the second harmonic and higher harmonic, which is conducive to the safe operation of the power grid. During normal operation, no current flows through the arc suppression coil. When the power grid is struck by lightning or a single-phase arc is grounded, the neutral point potential will rise to the phase voltage. After being compensated, the residual current after compensation becomes very small, which is not enough to maintain the arc, thus extinguishing itself. In this way, the grounding can be eliminated quickly without causing overvoltage.
The arc suppression coil is mainly composed of an iron core with an air gap and a winding on the iron core, which are placed in an oil tank filled with transformer oil. The resistance of the winding is small and the reactance is large. The inductance of the arc suppression coil can be adjusted by changing the number of turns connected to the winding. Under normal operating conditions, since the voltage at the neutral point of the system is a three-phase asymmetrical voltage with a very small value, the current passing through the arc suppression coil is also very small, and the arc may be automatically extinguished.
Generally, overcompensation is adopted, that is, the inductor current is slightly larger than the capacitor current. The arc suppression coil is an inductance coil with an iron core. It is connected between the neutral point of the transformer (or generator) and the earth to form an arc suppression coil grounding system. During normal operation, no current flows through the arc suppression coil. When the power grid is struck by lightning or a single-phase arc is grounded, the neutral point potential will rise to the phase voltage. After being compensated, the residual current after compensation becomes very small, which is not enough to maintain the arc, thus extinguishing itself. In this way, the grounding can be eliminated quickly without causing overvoltage.