地下电缆群稳态温度场和载流量计算新方法

根据地表对流和深层土壤温度不变的原则,将地下电缆群开域温度场等效为闭域温度场,应用有限元分析了给定电缆负荷电流的地下电缆群闭域温度场分布.采用热路法将电缆金属套损耗归算到电缆导体,应用调和平均法对电缆导体外的薄层进行处理,最终将电缆等效为导体和外护两层结构,减少了剖分节点数,提高了计算精度和收敛速度.采用弦截法计算了地下电缆群载流量.试验和计算结果表明,利用有限元计算地下电缆群温度场和载流量满足工程实际需求.

A New Method to Calculate the Steady-State Temperature Field and Ampacity of Underground Cable System

Based on convection of ground surface and temperature of soil deep under the surface unchanged, open domain temperature field of underground cable system is equivalent to close domain temperature field. Finite element method (FEM) is used to calculate the temperature field of underground cable system given load current. Loss in cable sheath is attributed to cable conductor based on thermal circuit method. The thin layer of cable is handled by harmonic mean method, and the cable is equivalent to two layers, conductor and outer layer. Number of FEM nodes is reduced. Accuracy and rate of calculation is improved. Ampacity of underground cable system is calculated by subtense truncation approach. The results of test and calculation show that FEM is effective to calculate the temperature field and ampacity of underground cable system in engineering.