Method for adjusting over-deviation of failure voltage signal

This invention relates to a method for regulating over-deviation of faulty voltage signals including: making point-M in the same potential with neutral point-N of the supply end with a circuit composed of equal impedance of ZA, ZB and ZC set on a phase line, setting sample impedance ZMN', ZMM' and ZMD taking fault voltage signals between M and N, M' and D, in which, ratio of the sample impedance of ZMN'(MM', MD) with the phase-line impedance ZA(B, C) is greater or equal to (1-delta)/3delta, and delta is a permit value of the deviation of fault voltage signal, the sampled impedance multiplies coefficient of ratio of the maximum value of the received voltage signal of a protector and the maximum value of the fault voltage signal to prepare output impedance Z'MN'(MN', MD), if it is less than (1-delta)/3delta, it should be modified according to Z'MN'(MM', MD)x(1+-delta)x(3k+1)/3k.