特高压输电用换位导线铜的热效应-中国材料进展

文章信息/Info

Title:: Thermal Effect in Copper Used for Continuously Transposed Cables of Ultra-High Voltage Transmission System

作者:: 杨岳清1; 王章洁1; 王悦存1; 陆焕焕1; 杜君莉2; 马云瑞2; 王朝华2; 单智伟1; （1.西安交通大学金属材料强度国家重点实验室，陕西西安 710049）（2.国网河南省电力公司电力科学研究院，河南郑州 450052）

Author(s):: YANG Yueqing1; WANG Zhangjie1; WANG Yuecun1; LU Huanhuan1; DU Junli2; MA Yunrui2; WANG Chaohua2; SHAN Zhiwei1; (1. State Key Laboratory for Mechanical Behaviors of Materials, Xi’an Jiaotong University, Xi’an 710049, China) (2. State Grid Henan Electric Power Research Institute, Zhengzhou 450052, China)

Keywords:: ultra-high voltage transmission(UHVT); continuously transposed cables; copper; temperature; hardness

摘要:: 冷变形强化铜材广泛应用于特高压输电换位导线等关键部件。服役过程中，电流的焦耳热效应会不可避免地造成铜材力学性能劣化，引发安全隐患甚至灾难性事故，但目前鲜有关于铜材力学性能随服役时间变化规律的研究。以显微硬度计为主要工具，研究了正常和短路两种工况下，特高压输电用换位导线铜材硬度随时间的变化规律，结果表明：换位导线铜材在正常工况温度范围保温168 h（约设计寿命的0.04%），其硬度下降2%～5%；在估算的短路工况温度范围加热1 h，换位导线铜材硬度损失最高达～50%。基于透射电子显微镜和电子背散射衍射技术的微观结构分析表明，正常工况温度范围最长保温168 h的铜材晶粒尺寸及形态无明显变化，位错密度小幅下降；短路工况下，400 ℃加热1 h后铜材缠结位错解体但无明显晶粒长大，而600 ℃加热1 h则观察到铜材内显著的晶粒生长与位错湮灭。上述研究表明，对特高压输电用铜材在近服役条件下的力学性能演化规律开展系统全面的研究，进而科学评估其使役寿命，明晰其安全使用范围，对特高压输电线网的安全运行不仅是必要的，也是迫切的。

Abstract:: Cold-working strengthened copper material has been widely used as conductive components in the ultra-high voltage transmission (UHVT). However, little attention has been paid to the inevitable Joule heat induced softening of the copper, which may cause catastrophic accidents. Here, we quantitatively investigated the hardness change of copper specimens from continuously transposed cables of UHVT system under two typical working temperature ranges. We demonstrate that the microhardness decreases 2%~5% under normal working temperature range for only 168 h (~0.04% of the target lifetime). In addition, the hardness reduction can reach up to ~50% under the estimated short-circuit temperature range for only 1 h. Microstructural characterizations based on EBSD and TEM reveal that there is no obvious change in grain morphology and only slight decrease of dislocation density in specimens heated at normal working temperatures even for 168 h. Under short-circuit condition, heating at 400 ℃ for 1 h brings destruction of tangled dislocations but no grain growth, while substantial grain coarsening and dislocation annihilation are observed in samples heated at 600 ℃ for 1 h. Our work suggests that it’s necessary and urgent to perform studies on mechanical properties evolution and lifetime evaluation of key component materials of UHVT under service conditions.