Ineffective grounding power distribution network single-phase grounding fault phase selection method based on grey correlation analysis

The invention provides an ineffective grounding power distribution network single-phase grounding fault phase selection method based on grey correlation analysis. The method includes steps: performinghigh-speed sampling on each phase current 20 ms after and before a fault generation moment, and obtaining sampling data of each phase current; subtracting the current sampling data 20 ms before the fault moment from the current sampling data 20 ms after the fault moment of each phase, obtaining a fault transient-state quantity of each phase current, and performing normalized and standardized processing on the fault transient-state quantities of the phase currents; calculating the association degrees of the fault transient-state quantities between A-phase and B-phase, A-phase and C-phase, andB-phase and C-phase currents, and calculating the average association degrees of the fault transient-state quantities of the phase currents, specifically the averages of the association degrees between each phase and other two phases; finally calculating a fault evaluation index of each phase, specifically the sum of absolute values of differences between the average association degree of the phase and the average association degrees of the other two phases; and fifthly, determining a fault phase determination threshold, and determining the phase is the fault phase if the fault evaluation index is higher than the fault phase determination threshold.