某输电线路用铝包复合材料芯软铝型线绞线在架线后不久即发生断裂。通过宏观分析、力学性能试验、机电性能试验、断口分析、金相检验等方法对导线的断裂原因进行了分析。结果表明：该断裂导线的复合材料芯棒在包覆铝管前已多处受损及断裂，复合材料芯棒断裂的导线在架线后，所有张力都由软铝层和铝管承担。因夜间温度降低，且风载荷作用引发线路舞动，使得导线所受张力超过软铝层和铝管的强度极限，最终导致导线断裂。

The formed annealed aluminum conductors aluminum-clad composite core supported of a transmission line fractured soon after stringing. The causes of conductor fracture were analyzed by means of macroscopic analysis, mechanical property test, electrical property test, fracture analysis and metallographic examination. The results show that the composite core rod of the fractured conductor had been damaged and fractured in many places before the aluminum tube. After stringing, all the tension load of the conductor with fractured composite core rod was borne by annealed aluminum layer and aluminum tube. Due to the decreased temperature at night and the galloping of the line caused by wind load, the tension load on the conductor exceeded the strength limit of the annealed aluminum layer and aluminum tube, and finally led to the conductor fracture.