Abstract: In response to the issues of insufficient accuracy and reliability in the detection of single-phase grounding faults in the secondary circuit of substation relay protection equipment, this paper proposes an LSTM accurate positioning technology for grounding faults in the secondary circuit of relay protection equipment. This method utilizes an improved D-S evidence theory to effectively fuse multi-source signals such as current, voltage, transient waveforms, and equipment status, solving the problem of high conflict evidence fusion distortion and constructing a unified decision-making framework; Then, the Variational Mode Decomposition (VMD) technique is applied to adaptively decompose the zero sequence current signal, extracting the instantaneous parameters of the first four Intrinsic Mode Functions (IMF) as key features, and enhancing the comparability of the features through Z-score standardization processing; Finally, an improved LSTM classifier with auxiliary gating units is constructed to leverage the advantages of its gating mechanism, enhance the ability to extract weak fault temporal features, and achieve accurate modeling of temporal features and accurate fault discrimination. The application results show that the proposed method exhibits excellent performance on the test set, with a fault recognition rate of over 95% and a missed detection rate of less than 1%. The application effect is good.