微机消谐装置的主要缺点是难以正确区分基波谐振和单相接地。目前，对基波谐振和单相接地故障判据的主要区别在于零序电压 U0 的高低。通常，基频谐振定为当 U０≥150V 时；当 30V≤U０＜145V时定为单相接地故障。为了防止在单相接地时由于装置误动使 PT 长时间过负荷而烧毁的情况发生，通常将该装置基频谐振的判据电压定得比较高。这样，在工频位移电压不是很高的情况下（如空母线合闸）装置将无法动作，就可能使某些励磁特性欠佳、铁心易饱和 PT 的熔丝熔断。
The main disadvantage of microcomputer harmonic elimination device is that it is difficult to distinguish the fundamental resonance and single-phase grounding correctly. At present, the main difference between fundamental resonance and single-phase ground fault criterion is the level of zero sequence voltage U0. Generally, the fundamental frequency resonance is determined as single-phase ground fault when U0 ≥ 150V and when 30V ≤ U0 < 145v. In order to prevent the Pt from burning out due to the device misoperation during the single-phase grounding, the criterion voltage of the fundamental frequency resonance of the device is usually set high. In this way, when the power frequency displacement voltage is not very high (for example, the air bus is closed), the device will not be able to operate, which may cause some fuses with poor excitation characteristics and easily saturated Pt core to fuse.
而且这种装置当电网对地电容较大时，它对防止间歇性接地或接地消失瞬间互感器因瞬时饱和涌流而造成熔丝熔断的事故无能为力。此外，在持续时间较长的间歇电弧过电压激发下，流过PT高压绕组的电流将显著增大，仍可能会烧坏PT。
Moreover, when the capacitance of the power grid to the ground is large, this device is powerless to prevent the fuse fusing accident caused by the instantaneous saturation inrush current of the transformer when the intermittent grounding or the grounding disappears. In addition, under the excitation of intermittent arc over-voltage for a long time, the current flowing through the PT high-voltage winding will increase significantly, and the PT may still burn out.