Objective Accurate calculation of the ampacity for export cables from offshore wind farms is crucial for their economical and reliable operation. However, the existing IEC 60287 standard lacks a calculation method for the J-tube laying configuration, and the calculation error for the shallow cable trough laying configuration is significant.

Method The heat transfer mechanism of submarine cables in the J-tube section was analyzed, and the corresponding equivalent thermal circuit model was established. An analytical ampacity calculation method for cables in the J-tube was proposed, considering solar radiation, external air flow and other conditions. The heat dissipation characteristics and ampacity influencing factors of cables in the unfilled cable trough were analyzed. The causes of inaccurate calculation results for the shallow cable trough under varying ambient temperatures were identified, and a modified calculation method for air temperature rise in the unfilled cable trough specified in the standard was put forward.

Result The proposed calculation methods are compared with the finite element analysis (FEA) results. The results show that under actual operating conditions, the error between the analytical algorithm and FEA results for the ampacity of cables in the J-tube is 0.8%. After using the modified calculation method for air temperature rise in the trough, the error between analytical calculation and FEA results decreases from 4.8% to 0.8% within the ambient temperature range of 10 ℃ to 40 ℃.

Conclusion This study remedies the insufficient coverage of the IEC 60287 standard and improves the accuracy of analytical calculations. It provides a comprehensive and precise calculation method for the ampacity calculation of export submarine cables for offshore wind farms.