三芯海底电缆中复合光纤与导体温度关系建模

摘要

It is difficult to calculate the thermal resistant of filling layer within optical fiber in 3-core optical composite submarine power cable. The temperature relationship between optical fiber and conductor can not be established until the above problem is resolved. In this paper, the temperature at external diameter of filling layer was calculated using virtual thermal source and image method, based on the established thermal circuit of 3-core submarine power cable. Then the temperature at external diameter of armor layer was calculated. The thermal resistant between optical fiber and external diameter of armor layer was calculated according to Fourier heat transfer theory. The summation of thermal resistant between inner diameter of filling layer and external diameter of armor layer was acquired by shape factor method. Finally, the thermal resistant of filling layer within optical fiber was obtained, as the difference between the above summation and the thermal resistant. The temperature relationship equation between optical fiber and conductor was accordingly established based on thermal circuit. It is indicated the relationship between the temperatures of optical fiber and conductor in 3-core submarine power cable is linear. The temperature of optical fiber will rise 1℃ if the temperature of conductor rises 1.15℃. The temperature of optical fiber will rise 1℃ if the ambient temperature rises 7.7℃ with constant temperature of conductor. The temperature of conductor can be calculated according to temperatures of optical fiber and environment, which can be regarded as the theoretical basis for monitoring the temperature of conductor and calculating current-carrying capacity for 3-core submarine power cables.%三芯光纤复合海底电缆中光纤以内填充层热阻的准确计算是建立光纤与导体温度关系的关键和难点。本文在建立三芯海缆热路模型的基础上，根据虚拟热源和镜像法，利用光纤温度计算出填充层外径处温度，进而计算出铠装层外径处温度；根据傅氏传热学原理计算出光纤处等温面至铠装层外径处等温面的热阻；利用形状因子法计算出填充层内径至铠装层外径的总热阻，再减去光纤处等温面至铠装层外径处等温面的热阻，得到光纤以内填充层的热阻；根据热路模型建立了光纤与导体的温度关系方程，并用有限元求解结果验证了方程的正确性。结果表明，三芯海缆的光纤与导体温度呈线性关系，导体温度每上升1.15℃，光纤温度上升1℃；相同导体温度下，环境温度每上升7.7℃，光纤温度上升1℃。根据光纤温度和环境温度可计算出导体温度，作为三芯海缆导体温度监测和载流量计算的理论依据。