Incomplete differential protection method and system based on load impedance

The invention discloses an incomplete differential protection method and system based on load impedance, and the method comprises the steps: recording the current and voltage of a main branch before and after a fault, calculating the equivalent load impedance before and after the fault based on the incomplete differential current, and taking the equivalent load impedance before the fault as a reference, comparing the equivalent load impedance calculated by the local side and the opposite side after the fault with the load impedance before the fault, if the error of the two groups of equivalent load impedance calculated after the fault does not exceed a threshold value, and the error of the two groups of equivalent load impedance and the equivalent load impedance calculated before the fault does not exceed the threshold value, judging that the fault point is outside the area, and if the error does not exceed the threshold value, judging that the fault point is outside the area. Executing a corresponding protec