When the proportion of non-linear power load in distribution system is large and the shunt capacitor bank is put into operation, on the one hand, the harmonic impedance of the capacitor bank is small and the harmonic current injected into the capacitor bank is large, which makes the capacitor overload and seriously affects its service life. On the other hand, when the harmonic capacitance of the capacitor bank is equal to the equivalent harmonic inductance of the system, the harmonic current of the capacitor bank is serious The discharge capacitor is damaged due to overheating. Therefore, if the voltage harmonic and current harmonic exceed the limit, the working current of the capacitor will increase and appear abnormal. For example, for the common self-healing shunt capacitor, the allowable over-current multiple is 1.3 times of the rated current. When the current of the capacitor exceeds this limit, the loss of the capacitor will increase, the heating will be abnormal, the insulation will accelerate aging, and the service life of the capacitor will be reduced To cause damage accident. At the same time, harmonics make the power frequency sinusoidal waveform distorted and produce serrated peak wave, which is easy to cause partial discharge in the insulating medium. Long time partial discharge will also accelerate the aging of the insulating medium, reduce the self-healing performance, and easily lead to the damage of the capacitor.