双向间接耦合有限元法预估电力电缆载流量

Bidirectional Indirect Coupled Finite Element Method for Estimating Ampacity of Power Cable

建立了多导体电力电缆置于具有散热孔的托架上时3D有限元时谐磁场模型,在计及各金属涡流效应的条件下,得到所有导体单元的功率损耗密度。以此功率体密度损耗为载荷,建立了电缆系统的"热-流体"直接耦合场模型,求解了电缆系统各导体的温升,由此完成一次完整的"磁场"与"热-流体"场间接耦合的求解。由于电缆导体电阻率与温度密切相关,形成"磁场"与"热-流体"场间接耦合的双向耦合。反复迭代,可求解得到当热点为90°C时导体的电流,即为电缆的载流量。以无铠装单载流和有铠装三并联载流电缆为例,采用间接耦合法计算和测量了系统的总功率、电流分布、导体热点温度。计算和测量一致性说明了双向间接耦合有限元模型建立的正确性和计算结果的准确性,为进一步分析电力电缆系统的磁、热特性奠定了基础。

A 3-D finite element harmonic field model of multi-conductor power cables placed on a perforated metal tray is established. Power loss densities of all metallic elements with the skin effect are obtained. By taking the power densities as a load, the direct thermal-fluid coupled model of the cable system is set up and temperature rises are calculated. Therefore, the magnetic field and the thermal-fluid field indirect coupled solution for the cable system is achieved. Because the conductor resistivity is af- fected by its temperature, the coupled model of the cable system becomes a bi-indirect coupled model between the magnetic field and the thermal-fluid field. Using an iterative procedure, the ampacity of the cable system can be solved with a high temperature 90 ℃. Using the examples of a non-armored cable with the single current and an armored cable with the mode of three-parallel cable, the total power losses, the hottest point temperature of conductors and the current distributions are calculated and tested by the indirect coupled method. The match of calculated and tested results illustrates that the bidirectional indirect coupled model is valid and accurate. And it can be used for analyzing magnetic and thermal properties of power cable systems.