Neutral and ground lines wiring faults on the user side of low-voltage distribution systems（LVDS） lead to common yet highly concealed leakage current faults in practical engineering, posing significant challenges for operation and maintenance in LVDS. Existing methods for locating leakage faults struggle to address insufficient sample sizes and multicollinearity problems among users currents, making it difficult to rapidly and accurately identify leakage fault users in large-scale low-voltage power substation area. Firstly, the impacts and hazards of user-side wiring faults and leakage faults in the context of current graded residual current protection（RCD） and grounding system protection configurations in LVDS are analyzed. Further, the differences in the impact of load current on residual current in the substation area when there are faults in the neutral and ground wire connections for individual and multiple users are investigated. To address the limitations of insufficient samples due to restricted measurement capabilities in substation area and the multicollinearity among user load current curves, a ridge regression-based method is proposed for identifying leakage user caused by wiring fault in LVDS. This method can accurately identify leakage fault user in small sample sizes. Further considering the number of faults and the differences in their phases, simulation experiments of different wiring fault leakage cenarios are carried out to verify the effectiveness of the proposed method, and comparative tests against multiple linear regression method demonstrate its superiority.