When the proportion of non-linear power load in distribution system is large and parallel capacitor banks are put into operation, on the one hand, because the harmonic impedance of capacitor banks is small and the harmonic current injected into capacitor banks is large, the capacitor load will seriously affect its service life; on the other hand, when the harmonic reactance of capacitor banks is equal to the system equivalent harmonic inductance and resonance occurs, the harmonic current of capacitor banks will be serious The discharge capacitor is damaged by overheating. Therefore, voltage harmonics and current harmonics exceeding the standard will make the working current of the capacitor increase day by day and appear abnormal. For example, for common self-healing shunt capacitors, the allowable over-current multiple is 1.3 times of the constant frequency current. When the current of the capacitor exceeds this limit, it will cause damage accidents. 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.