For the 10kV boundary switch controller reliability fault isolation boundary switch controller based on the high performance DSP processing and the quality of electric energy metering chip MCP3903 in the hardware sampling and calculation on CPU, combined with ARM9200 as upper management processing, software adopts a practical TDFT non synchronous sampling measurement method. The boundary switch controller adopts the first half wave method of small current grounding, and the ground fault is judged according to zero sequence voltage, zero sequence current and reactive power direction. The boundary switch controller and main station communicate with each boundary switch controller through the 4G network, and management and maintenance of the boundary switch controller is convenient for data management. The experimental results show that the design is accurate and reliable in judging and isolating user faults.