Abstract: This study systematically investigates the frequent insulation breakdown failures of 35 kV cable T-joints in wind farms, focusing on fault analysis and mitigation strategies. Taking the insulation breakdown failure of a 35 kV cable T-joint in a Hubei wind farm as a case study, statistical fault analysis reveals that the explosion-induced failure points predominantly occur at the interface between the cable main insulation cross-section and the joint insulation layer. A three-dimensional finite element simulation model was developed to analyze the electric field and temperature field distributions of the T-joint under three conditions: defect-free, metallic particle defect, and air gap defect. The results demonstrate that both metallic particle defects and air gap defects induce localized electric field distortion, with air gap defects exerting a more pronounced influence on the electric field, while metallic particle defects exhibit a more significant impact on the temperature field. This research elucidates the failure mechanism of cable T-joints, providing a theoretical foundation and technical support for optimizing joint design, improving installation processes, and developing online monitoring systems.