Tensile-torsional stress induced degradation in wind turbine output cables: electromechanical response and failure mechanism

• A coupled electromechanical-thermal model was established and validated via strain measurement. • Stress, temperature, and electric field distributions under tensile-torsional loads were revealed. • The outer sheath of the cable exhibited higher sustained stress than the insulation layer. • Cable strain exhibits a distinct directional dependence, significant at 0° and 90°. The degradation of feed cables due to prolonged exposure to tensile and torsional loads poses a serious threat to the safe and stable operation of wind turbines. To address the performance degradation of wind turbine feed cables under coupled tensile-torsional mechanical loads, a cylindrical multilayer composite model based on the cable structure was constructed. Stress, temperature field, and electric field equations were derived to establish an electromechanical-thermal sequential coupled simulation model for cables under tensile and torsional loading. Experimental validation was conducted using strain-voltage measurement. Simulation analysis revealed the stress distribution, temperature field, and electric field characteristics across each cable layer under combined tensile-torsional loading, along with the interaction mechanisms between these factors. Results indicate that at an ambient temperature of 25°C, increasing the torsion angle significantly exacerbates the non-uniformity of stress distribution in the cable, leading to a two-order-of-magnitude increase in stress levels. Temperature rise induced by current flow partially mitigates stress non-uniformity caused by material differences, yet simultaneously compounds thermal stress with mechanical stress, thereby amplifying the overall stress endured by the cable. Furthermore, the strain behavior of the cable under combined tensile and torsional loading exhibited pronounced directional and positional dependencies. The most significant circumferential and axial strain responses were observed at 0° and 90° orientations, revealing stress concentration and non-uniform deformation characteristics, with particularly pronounced strain peaks at high torsion angles. Through theoretical derivation, simulation modeling, and experimental validation, this study provides new research perspectives and support for evaluating cable performance degradation under complex stress conditions.