送电区段内典型敷设方式下海缆载流量模型分析

Analysis on ampacity model of submarine cable under typical laying mode in transmission section

海上送电线路中不同段敷设方式的差异性会对海缆载流量造成较大影响,因此从送电区段角度出发研究段内典型敷设方式下的载流量具有重要意义。本文建立了±160 kV直流输电工程送出海缆线路中登陆段、海底段的海缆电-热-流耦合模型,基于有限元用控制变量法研究了登陆段中海缆敷设于电缆沟底部和角钢支架、海底段中铺设和直埋4种典型敷设方式下的空气域尺寸、角钢支架放置位置、海水温度和流速及土壤温度对海缆稳态载流量的影响。结果表明:海缆敷设于电缆沟底部时受空气域尺寸的影响较大,增大对流散热面积可有效提高海缆稳态载流量;计算敷设于角钢支架上的海缆载流量要考虑到支架与沟内壁形成的半封闭区域,埋设于深度浅的支架时海缆的温度更低,载流量更大;在海底段,铺设时海缆温度跟随海水温度的升降发生同向变化,与海水流速增减趋势相反;土壤温度的升高造成埋设海缆载流量降低;登陆段为载流量计算的瓶颈段,电缆沟底部敷设可采用充水电缆沟有效提升载流量;敷设在支架上时加装冷却水管可使其载流量达到工程要求。

The difference of laying methods in different sections of marine transmission line has a great impact on the ampacity of submarine cable,so it is of great significance to study the ampacity under typical laying methods in transmission section.In this paper,an electric-heat-current coupling model of submarine cable in landing section and submarine section of submarine cable line in ±160 kV DC transmission project was established.On the basis of finite element method,the influence of air domain size,position of angle steel support,seawater and soil factor on the steady ampacity of submarine cable were studied under four typical laying methods,which is the submarine cable laid at the bottom of cable trench and laid on the angle steel support in landing section and the submarine cable laid and directly buried in submarine section.The results show that the submarine cable laid at the bottom of cable trench is greatly affected by the air domain size,and increasing the convection area can effectively improve the steady ampacity of submarine cable.The semiclosed area between the support and the inner wall of trench should be taken into account in calculating the ampacity of cable laid on the angle steel support.The temperature of submarine cable laid at the shallow depth of support is lower and its ampacity is larger.In the submarine section,the submarine cable temperature changes in the same direction with the rise and fall of sea water temperature,which is opposite to the increase and decrease trend of sea water velocity.The increase of soil temperature results in the decrease of buried submarine cable ampacity.The landing section is the bottleneck section of ampacity calculation,and the ampacity can be improved effectively by using the water filling cable trench when the submarine cable is laid at the bottom of cable trench.When the submarine cable is laid on the support,the ampacity can meet the engineering requirements by installing cooling water pipe.