Assessment of current carrying capacity for shore power cable via multi-physical field coupling model under various ambient conditions

Shore power cables are directly laid in the air, in a humid port, and are directly exposed to sunlight. It will be affected by the sea breeze and tide. The special working conditions of shore power cables expedite the aging process of the insulation and lead to a decrease in the ampacity of these cables. Moreover, shore power cables are significantly influenced by factors such as ambient temperature, wind speed, water flow velocity, and solar radiation. The IEC 60287 standard does not elaborate the calculation method of ampacity under the influence of wind, water and solar radiation. There is no unified national or enterprise standard has been proposed. Based on the current situation and existing problems of shore power cable, firstly, an electromagnetic-thermal-flow-force multi-physics coupling model of shore power cables CEU94 - 8.7/10 kV - 3×120 mm2 is established suitable for ports, and the coupling form between each field is analysed, and the multi-physical field is solved by ANSYS software. Also, the correctness of the simulation model is verified by comparison with analytical calculation and experimental measurement. The following conclusion can be drawn that the average errors between the simulation results and the experimental data were 5.85% and 7.2%, respectively, which were relatively small. Secondly, the influence law of environmental temperature, wind speed, water flow velocity, and solar radiation on the temperature distribution of multi-circuit shore power cables were studied, and it comes to the result that when the ambient temperature increases by 10°C, the average temperature of the cable conductor increases by about 11.66°C; when the wind speed rises to 10 m/s from still, the maximum conductor temperature decreases by 13.84°C; under extremely high temperature and radiation conditions, the shore power cable's maximum temperature can reach 117.6°C. Finally, based on the Heat Balance Equation of the cable, an analytical calculation method of current carrying capacity of shore power cable based on Newton iteration was proposed and implemented by MATLAB programming. The analytical calculation method and finite element calculation method were used to compare and analyse the law of current carrying capacity affected by ambient temperature, wind speed, water flow velocity and solar radiation during the laying of air and water. The result obtained is that compared to the still state, the wind speed and water flow velocity significantly increase the current carrying capacity of the shore power cable: the current carrying capacity of the shore power cable increases with higher wind or water flow speed, showing a greater improvement when laid in water (23.4%) compared to air (22.5%). Additionally, higher ambient temperature and solar radiation significantly reduce the capacity, with the largest decrease (171.1 A) observed at high temperature and radiation levels. When laying in water, water has a certain absorption effect on solar radiation, and the increase in cable current carrying capacity is better; When laid in the air, solar radiation greatly reduces the current carrying capacity of shore power cables. And measures to improve the current carrying capacity of shore power cables were proposed, providing reference for the revision of the standard for calculating the current carrying capacity of shore power cables.