In power systems, ferromagnetic resonances frequently occur, and overvoltages are generated during resonance, which seriously threatens system safety. Ferromagnetic resonance overvoltage can occur in any system from 3 to 220 kV, especially in power grids of 35 kV and below. Almost all internal overvoltage accidents are caused by ferromagnetic resonance. The overvoltage caused by ferromagnetic resonance is long and may even exist for a long time. In the frequency division resonance, the overvoltage is generally not high, but the current of the PT is large, which will easily cause the PT to overheat and explode; when the fundamental wave and frequency doubling resonance, the general current is not large, but the overvoltage is high, which often damages the equipment insulation , Causing a vicious accident. The power microcomputer harmonic elimination device is a new type of intelligent power resonance elimination device developed by our company. It is simple and convenient to use, without maintenance, and can quickly eliminate ferromagnetic resonances of various frequencies.