In order to ensure the safe operation of a system and not change the small current grounding mode of the original system neutral point, the DG neutral point is generally ungrounded. When a single-phase ground fault occurs in the main network, DG does not provide zero sequence current to the system, so it does not affect the fault characteristics of the transient zero sequence current. Further analysis of the waveform characteristics of the transient zero sequence current shows that the concave convex characteristics contain fault information that can be used for location. In this paper, the VMD algorithm is used to extract the effective components. These can represent the concave convex characteristics of the transient zero sequence current, and a wave peak valley algorithm is proposed to describe the concave convex characteristics of the effective frequency components. Given that the concave convex numbers on both sides of the fault point are quite different and the initial concave convex is opposite, while the concave convex numbers on the same side of the fault point are roughly the same and the initial concave convex are the same, a new algorithm based on the kurtosis and the initial concave convex is constructed. By comparing the kurtosis difference of each section with the set threshold and judging whether the initial bump is consistent, the fault section can be located. The simulation results show that the method can be applied to the fault location on an active distribution network, and has strong applicability in different fault situations. This work is supported by National Natural Science Foundation of China (No. U1766204).