Calculation of Overhead Insulated Cable Ampacity Considering Compacted Conductor Structure

The radial heat transfer mechanism of compacted conductors in overhead insulated cables is unclear, and the insulation layer complicates the thermal boundary conditions, limiting the direct applicability of existing ampacity calculation methods. Based on the Morgan model framework, this paper proposes an ampacity calculation method that accounts for the “plastic-then-elastic” deformation characteristics of compacted conductors. Material plastic flow and elastic deformation of the substrate are incorporated to refine the formulations for interlayer thermal contact conductance and thin-layer air gap thickness, while the equivalent distance of air voids is corrected using the fill factor. An iterative convergence procedure for the insulation outer surface temperature is established to accurately evaluate conductor Joule losses. Validated by wind tunnel tests on JKLGYJ 240/30 cables, the proposed method yields a radial temperature difference of 2.41 °C, closely matching the measured 2.6 °C, with an error of 7.4% compared to 13.5% for the conventional Morgan model. Parametric analysis reveals that equivalent radial thermal conductivity is independent of external environmental factors. Conductor stress has a negligible effect on the ampacity (variation < 0.1%). Under low wind speeds (0–5 m/s), the ampacity increases substantially with wind speed.