Abstract: In response to the problems of weakened transient characteristics, short duration, and complex harmonics caused by the integration of high proportion distributed power sources and power electronic devices in distribution networks, traditional relay protection methods have significantly reduced performance and are prone to misoperation or misjudgment. The application of active protection in distribution networks usually relies on transient zero sequence components or detection signal amplitude differences to achieve fault diagnosis, which is easily affected by transient factors such as harmonics. In response to the above issues, a fault section identification strategy for active distribution network active injection of detection signals is proposed to expand the fault difference. Signal energy analysis is used to study the principle of detection signal injection, the theory of detection signal parameter selection and its injection start control strategy are explored, and a protection action criterion is established for comparing the energy difference of detection signals based on the fault identification principle, multiple inverter distributed power sources are utilized to actively inject detection signals into the distribution network in case of faults, achieving rapid identification and localization of fault sections while also having island detection function. Finally, the effectiveness of the proposed strategy is verified through simulation.