Low current neutral grounding malfunction detection and positioning device and method

The invention relates to a device and a method for detecting and positioning small current earthing fault. The device comprises a slave computer and a host computer composed of a CPU module, a DSP, a pre-loop unit module, a A/D conversion module, a memory module, a display and keyboard operation module as well as a communication module; wherein, the pre-loop unit module, the A/D conversion module, the CPU module and the DSP are connected in sequence; the memory module, the display and keyboard operation unit module and the communication module are respectively connected with the CPU; the host computer is connected with the communication module. The CPU module collects the analog signal of the zero-sequence voltage of the bus and the zero-sequence current of each line, and adjusts the value in proportion to the amplitude range so that the device can deal with. The analog signal is turned into digital signal recognized by the computer module, and analyzed by the DSP to judge whether the fault occurs or not. If the fault occurs, then the DSP gives the line selection result, saves the fault information and transfers the line selection result to the host computer for fault alarm.