Abstract: Gap arc overvoltages can not be completely suppressed by the traditional arc suppression coil, and serious phase-to-phase grounding short-circuit overcurrent can be caused by the fault phase transfer device in the case of developmental fault.Therefore, an active step-down arc suppression method of ground fault phase based on power supply potential feedback is proposed. When a single-phase grounding fault occurs, the line voltage vector opposite to the phase potential of the fault phase is extracted from the secondary side of the grounding transformer and fed to the neutral point of the distribution network by injecting transformer boost, so that the voltage of the fault point is forced to be below the arc reignition voltage, the arc extinguishing and preventing arc reignition can be realizied, the intermittent arc grounding overvoltage can be effectively suppressed, and recoverable insulation faults can be handled in the live working conditions. An active step-down arc extinguishing device is developed, which consists of grounding transformer, single-phase injection transformer, and other related equipment. The feasibility and reliability of the proposed method and device is verified through a large number of experiments and tests in the 10 kV distribution network true laboratory and on-site operation of the substation. Compared with the existing similar technology, the device has the advantages of good performance, strong compatibility, low cost and low risk of short-circuit current.