Abstract: An investigation into the winding ground fault in a ±800 kV converter station"s generator-motor rotor lead caused by lead breakage was conducted through test data analysis, disassembly inspection, finite element simulation, and experimental verification, systematically studying the failure mechanism and proposing improvement solutions. The results indicate that cracks in the rotor lead"s Ω-bend originate from insufficient design margin for concentrated stresses, leading to metal fatigue in the brazed joints under long-term alternating stress. Additionally, the brazed structure connecting the 36-layer thin copper strips of the lead terminal to the busbar poses a risk of stress concentration. By establishing a fault evolution model, an optimized Ω-bend structure and improved lead connection process were proposed. Theoretical calculations and multi-condition simulations confirmed that the modified design meets operational requirements. Field operation tracking over two years shows that the rotor lead"s Ω-bend and joints remain in good condition, verifying the effectiveness of the proposed solution.