Neutral conductor matching IT (information technology) system single-phase earth fault phase selection method

The invention discloses a ship-to-shore power system single-phase fault phase selection method. The method includes acquiring a setting value of feature quantity in each fault resistance section of the ship-to-shore power system through experiments; detecting an insulation value of the ship-to-shore power system by an insulation measurement device IMD; when detecting that the insulation value of the ship-to-shore power system decreases by the insulation measurement device IMD, entering a phase selection process by the system; collecting earth voltage values of phase lines and neutral lines after the ship-to-shore power system faults; acquiring three feature quantities by calculation, namely a sum sigma (Ui-Ei) of A,B,C three-phase earth voltage Ui (i=1,2,3) and an absolute value of phase voltage Ei differential value, a maximum value of a specific value of lagging phase earth voltage changing quantities of an arbitrary phase line before faults and after faults and a biquadrate value D4 of the A, the B, and the C three-phase earth voltage changing quantities; and comparing the three feature quantities with the setting value of feature quantity in each fault resistance section acquired through the experiments, and acquiring fault phase line. The ship-to-shore power system single-phase fault phase selection method overcomes defects that fault signals of traditional IMD neutral lines are not clear.