320kV交联聚乙烯绝缘直流电缆电气特性研究

Electrical Properties of 320 kV XLPE Insulation DC Cable

在进行直流电缆的绝缘结构设计和优化时,其电场分布特性是重要的参考依据。通过COMSOL仿真软件建立了320 kV直流电缆的简化模型,并研究其稳态和暂态电气特性规律,然后通过试验对仿真模型的可靠性进行验证。结果表明:以导体最高温度和绝缘层内外表面最大温差为约束条件,当环境温度低于12℃时,直流电缆载流量的决定性因素为绝缘层的内外温差(20℃),当环境温度高于12℃时,直流电缆载流量的决定性因素为导体最高工作温度(70℃);在仿真操作冲击试验、雷电冲击试验及绝缘温差30℃下负荷循环试验过程中,分别得出暂态和稳态最大击穿场强为58 kV/mm、25 kV/mm,对比直流绝缘材料性能参数可知直流电缆结构满足设计要求。试验表明COMSOL多物理场仿真模拟对于直流电缆的结构设计具有重要的指导意义。

When we design and optimize the insulation structure of a DC cable,its electric field distribution characteristics is an important reference basis.A simplified model of 320 kV DC cable was established by COMSOL simulation software,and its steady-state and transient electrical characteristics were studied.Then the reliability of the simulation model was verified by experiments.The result shows that the maximum temperature of conductor and the maximum temperature difference between inner and outer surfaces of insulating layer were used as the constraint conditions,when the ambient temperature is lower than 12℃,the decisive factor of DC cable ampacity is the tem-perature difference between inner and outer surface of the insulating layer(20℃).When the ambient temperature is higher than 12℃,the decisive factor of DC cable ampacity is the maximum operating temperature of conductor(70℃).In the process of simulated switching impulse test,lightning impulse test,and load cycle test under 30℃of insulation temperature difference,the maximum transi-ent and steady-state breakdown field strength are 58 kV/mm and 25 kV/mm,respectively.According to the performance parameters of DC insulating material,the DC cable structure can meet the design requirements.The test results indicate that the COMSOL multi-physical field simulation has important guiding significance for the structure design of DC cable.