计及材料温变特性与热机械应力的高压直流海缆温度与载流量计算优化模型

In recent years, offshore wind power systems have developed rapidly. Submarine cables serve as critical transmission components whose load capacities are significantly influenced by marine environments. It is crucial to calculate its temperature accurately to ensure their long-term stable operation. The object studied in the paper was the ±400 kV submarine cables at the Rudong offshore wind farm. First, the variations in thermal conductivity, thermal expansion coefficient, and elastic modulus with temperature were investigated. The temperature-dependent functional relationships of these material parameters are obtained through polynomial fitting. Moreover, based on the traditional electro-thermal models, material temperature-dependent properties and thermo-mechanical stress within the cable were considered. An electro-thermal-fluid-mechanical coupling model of the submarine cable was established in COMSOL Multiphysics. This model was capable of representing the impact of mechanical losses caused by the thermal expansion on the temperature distribution within the cable. To verify the accuracy of the model, a temperature-rise experiment was conducted on a ±400 kV submarine cable in the laboratory. Compared to the traditional electro-thermal coupling model, the proposed optimized model reduced the maximum temperature error of the cable in air from 3.2 K to 0.8 K, improving the calculation accuracy from 93.9% to 98.5%. Subsequently, based on the model, the research investigated the effects of sea temperature and velocity on the thermo-mechanical coupling characteristics of cables by using two typical conditions, namely, burying and laying conditions. It was found that, as the sea temperature increased from 15 ℃ to 25 ℃, the conductor temperature rose by approximately 9 ℃, the ampacity decreased by about 38%, and the accumulated deformation within the cable reduced by 49.9%. As the sea velocity increased in the low range (0~0.01 m/s), the ampacity increased by 12.3% and the accumulated deformation increased by 17.9%. The proposed optimization model provides a reference for the dynamic adjustment of ampacity and the long-term stable operation of cables.