光电复合海缆温度场建模分析及在在线监测中的应用

Analysis of temperature field model in optic-electric composite submarine cable and its applications in online monitoring

为了有效监测光电复合海缆的绝缘状况,基于迭代法改进了IEC60287电缆载流量和温度场计算标准,在有限元数值分析软件包COMSOL中基于热电耦合模块建立了110 k V YJQ41×300 mm^2海缆温度场模型,与改进IEC60287标准比较验证了建模方法的准确性,在此基础上确定了不同载流量下海缆模型最佳的分析范围。建模研究了海缆正常运行和绝缘性能下降情况下载流量和环境温度对光纤温升的影响;采用介质损耗表征绝缘状况,分析获得了典型介损值下光纤相对温升的变化规律。结果表明:正常情况下光纤温升随载流量的增加近似成平方增大,随环境温度的增加近似线性增大,增速较慢;海缆绝缘性能下降时光纤相对温升随tanδ的增加成正比增大,相对而言,受环境温度的影响很小。根据上述研究,提出了基于光纤相对温升和海缆载流量的介损计算公式和基于光纤相对温升的海缆绝缘状态监测方法。较之现有基于电气量的绝缘监测方法,该方法不易遭受电磁干扰的影响。在光电复合海缆在线监测方面具有参考应用价值。

To effectively monitor the insulation state of the optic-electric composite submarine cable, the IEC60287 cable′ ampacity and temperature calculation standard were improved by iteration algorithm and the temperature field model of 110 k V YJQ41 ×300 mm^2 submarine cable was established with the finite element analysis, solver and simulation software package COMSOL based on the thermoelectric coupling model. The results were validated by the improved IEC60287 and the optimal model size of the submarine cable at different values of ampacity was obtained. The effects of ampacity and ambient temperature on the optical fiber′ s temperature rise were investigated in normal insulation state and at different levels of insulation degradation of the submarine cable. Dielectric loss factor was used to characterize the insulation states, the change of optical fiber′ s relative temperature rise under the typical value of dielectric loss factor was investigated. The results reveal that, under normal circumstances, the temperature rise of fiber is approximately proportional to the square of ampacity and it increases approximately linearly with increasing ambient temperature with a slow velocity. When the cable′ s insulation degraded, the relative temperature rise of the optical fiber is proportional to the tanδ.Comparatively, the ambient temperature has little influence on it. According to above research, a formula for estimation of dielectric loss factor based on relative temperature rise and ampacity of cable is presented and a method for insulation degradation evaluation of the submarine cable based on relative temperature rise of optical fiber is proposed. Compared with the existing insulation monitoring methods based on electrical measurands, the error caused by electromagnetic interference can be avoided in proposed method, which can be applied in the online monitoring of the optic-electric composite submarine cable.