Small-current grounding line selection assisting increment device and method

The invention relates to the technical field of small-current grounding line selection, and provides a small-current grounding line selection assisting increment device and method, and a grounding transformer module, which are used for providing a neutral point for a target power system. The target power system is a neutral point ungrounded system; the neutral point voltage detection module is used for detecting the voltage of a neutral point when a grounding fault occurs; the selection assisting increment module is used for selecting a corresponding input resistor according to the magnitude of the voltage of the neutral point when a grounding fault occurs, and obtaining an increment current matched with the voltage of the neutral point; the input resistor is connected with a neutral point; and the zero-sequence current detection module is used for judging a ground fault according to the incremental current matched with the voltage of the neutral point. According to the technical scheme, the problem that grou