运行中的户外架空输电线路断股缺陷将引发局部过余温升，温度极大值出现在缺陷处，并向无缺陷区域迅速衰减。基于温度分布的红外热成像技术能识别断股缺陷程度，但不同的风速会显著影响观测对象表面温度，为红外热像检测带来困难。为研究低风速下架空线路断股处轴向温度分布，以LGJ-240/30钢芯铝绞线为例，在重庆大学输配电装备及系统安全与新技术全国重点实验室的人工气候室对其进行热循环试验。通过人工破坏制造断股缺陷，利用自制集风装置调节风速，交流大电流发生装置提供稳定的焦耳热源，得到断股数对线路缺陷背侧最大温升与轴向无缺陷区域温差的影响规律，并基于此提出风速为1~3 m/s时，线路断股数红外识别方法，最后通过在雪峰山能源装备安全国家野外科学观测研究站进行自然实验对该方法进行验证。结果表明：架空输电线路发生断股后，缺陷温度极大值与非缺陷区域正常温度的轴向温差随风速增大迅速减小；轴向温差θ和风速u拟合关系式中，描述传热项的拟合系数b随载流量、断股数增加而增加；在低风速条件且线路载流量为360、480及600 A，断股数大于3时，通过提出的方法断股数识别准确率大于90.1%，断股缺陷识别率大于94%，解决了低风速下红外热巡检工程无法实施而错失最佳检修时间的难题，使线路检修效率大幅提高，从而保障电网安全稳定运行，对架空输电线路红外热巡检工程具有指导意义。

Defects in operating outdoor overhead transmission lines with broken strands will cause local excess temperature rise. The maximum temperature occurs at the defect and decays rapidly to a defect-free area. Infrared thermography based on temperature distribution can identify the degree of broken strands defects. However, the wind speed will significantly reduce the surface temperature of the observed object, making infrared detection difficult. To study the axial temperature distribution at the broken strand area of overhead lines under low wind speed, the paper took the LGJ-240/30 type steel-cored aluminum strand as an example, and conducted thermal cycling tests in the State Key Laboratory of Power Transmission Equipment & System Security and New Technology of Chongqing University. The broken strand defect was produced by manual destruction, the homemade wind speed was regulated by the air collecting device, and the AC large current generator provided a stable Joule heat source. The influence of the number of broken strands on the maximum temperature rise at the back of the defect and the temperature difference in the axial defect-free area was obtained. And based on this, the infrared identification method of broken strand number when the wind speed is 1~3 m/s was proposed. Finally, the method was verified by natural experiments in the National Field Science Observation and Research Station. The results show that after the occurrence of strand breaks in overhead transmission lines, the axial temperature difference between the extreme value of the defective temperature and the normal temperature in the non-defective area decreases rapidly with the increase of the wind speed; the fitting coefficient b, which describes the heat transfer term in the fitting equation of the axial temperature difference θ and the wind speed u, increases with the increase of current carrying capacity and the number of strand breaks. The proposed method has a recognition rate of more than 90.1% for the number of broken strands and more than 94% for defects under the condition of low wind speed, the load current is 360, 480, and 600 A, and the number of broken strands is more than 3. It solves the problem of infrared thermal inspection project under low wind speed without missing the best maintenance time, greatly improves the maintenance efficiency of line maintenance, guarantees the safe and stable operation of power grid, and has guiding significance for the infrared thermal inspection project of overhead transmission lines.