摘要
接地体短路温升是校核接地材料短路耐受性能的重要指标,但目前的短路温升计算方法主要在无散流、无传热的空气环境中进行,校核结果未能充分反映接地导体在土壤中的温升特性。笔者采用电磁-温度耦合有限元计算方法模拟短路电流作用下接地导体的散流及地中温升过程。研究发现接地体轴向地中短路温升分布具有两端高中间低的特点,且由于土壤发热与本体发热共同作用,接地体两端温升显著高于空气环境短路温升。同时,土壤电阻率增大及趋肤效应会进一步加剧端部温升。随后结合侵蚀算法模拟了接地导体的过热失效,研究发现地中温升过高会导致接地体首端半径及末端长度减小,多次短路后可能会引起地网断裂失效,接地电阻增加。最后,给出了降低接地导体端部温升的方法。研究结果为接地网热稳定校核及设计提供参考。
The short-circuit temperature rise of grounding conductor is an important index for the short-circuit withstanding performance of grounding material. However,current estimation method for short-circuit temperature rise checking is mainly carried out in air environment in which heat dissipation and heat transfer between the soil and the conductor is ignored. So results fail to fully reflect the temperature rise characteristics of grounding conductor in the soil. The electromagnetic-thermal coupled finite element simulation is used to model the underground current dissipation and temperature rise process of conductors under short-circuit current. Results show that the temperature rise at the two ends is high while that at the middle is much lower. The temperature rise at both ends is significantly higher than that calculated in air environment due to the combined action of the soil heat source and bulk heat source. Besides,the temperature rise at the ends will be further aggravated by the increase of soil resistivity and skin effect. Then,the overheating failure phenomenon is also simulated in combination with the erosion algorithm. Results indicate that the excessive temperature rise will lead to reduction of the radius at the head and that of the length at the end,which may cause the increase of grounding resistance and the fracture of the grounding grid after several short circuit failures. Some suggestions on depressing the end-overheat phenomenon are proposed. The research results in this paper can provide reference for the thermal stability checking and design of grounding grids.
作者
吴泳聪
阮江军
WU Yongcong;RUAN Jiangjun(Electric Power Research Institute,China Southern Power Grid,Guangzhou 510080,China;School of Electrical Engineering and Automation,Wuhan University,Wuhan 430072,China)
出处
《电瓷避雷器》
CAS
北大核心
2020年第6期52-58,共7页
Insulators and Surge Arresters
关键词
地中短路温升
电磁-温度耦合有限元计算
侵蚀算法
过热失效
underground short-circuit temperature rise
electromagnetic-thermal coupled finite element simulation
erosion algorithm
overheating failure
