考虑轴向传热的单芯电缆线芯温度实时计算模型研究

为了研究轴向传热对电缆线芯温度的影响,首先以单芯电缆的三维微元热路模型为基础,建立了考虑单芯电缆轴向与径向传热的三维热路模型,且根据该三维热路模型实现了单芯电缆线芯温度实时计算的理论推导。其次,通过不同敷设环境下分别加载恒定与阶跃电流的实验,讨论了电流、电缆敷设环境与外界环境温度等因素对轴向、径向温度分布的影响。实验结果表明,电流是决定轴向温度梯度变化趋势的主要因素,空气中电缆的线芯温度上升速度最快,土壤中电缆次之,水中电缆最慢。最后通过有限元仿真工具,对比了空气中电缆中间接头三维有限元模型与二维有限元模型计算的线芯温度。研究结果表明,只考虑电缆径向传热的二维热路模型会造成线芯温度计算的误差,而考虑电缆轴向与径向传热的三维热路模型能够提高计算的精度。

Model Research of Real-time Calculation for Single-core Cable Temperature Considering Axial Heat Transfer

In order to study the influence of axial heat transfer on conductor temperature,firstly,on the basis of three-dimensional micro-element thermal circuit model,we established a three-dimensional thermal circuit model considering axial and radial heat transfer,by which we realized theoretical derivation of calculation for single-core cable temperature in real-time.Secondly,by experimentally investigating single-core cable loaded with constant and step current,respectively,in different laying circumstances,we discussed the influences of current and external laying condition on axial and radial temperatures of cable.The experimental results show that current is a predominate factor to determine the axial temperature gradient trend.The temperature of cable core surrounded by air rises in the fastest rate,that of the straight buried cable follows,and that of cable surrounded by water rises in the slowest rate.Finally,we compared the temperature of cable core of cable joints which was calculated by threedimensional model and two-dimensional model through finite element simulation tool.The results show that,if only the cable radial heat transfer is taken into consideration,the two-dimensional thermal circuit model will cause errors in the wire core temperature calculation,and three-dimensional thermal circuit model can improve the calculation accuracy.