Abstract: With the advancement of new power system construction, a high proportion of distributed power sources (DGs) are connected to the distribution network, which leads to the risk of failure of traditional current protection due to the bidirectional flow of fault currents and the ambiguity of the characteristics of high-impedance ground faults. In this paper, to address the fault detection challenges of active distribution networks containing DGs, an active protection scheme based on characteristic harmonic injection is proposed to combine power electronic equipment and relay protection scheme, and a 10 kV active distribution network model is constructed through MATLAB, and the results show that the active protection scheme can achieve high-precision autonomous fault detection and rapid action.