Research on Failure Mechanisms of Broken Strands of Jumper Wires for EHV Transmission Lines in Strong-Wind Areas

Abstract

The jumper wires of an extra-high voltage (EHV) transmission line in strong-wind areas in Northwest China frequently break down. We installed some acquisition devices to collect the data of the jumper wires and wind speed in the fault area of one 750-kV transmission line. We also developed a swing simulation machine based on the collected data. The machine could simulate the swing condition of the jumper wires under various wind speeds. We analyzed the broken aluminum wires obtained from the simulation experiment of jumper wires. Yield lines appeared on the surface of the broken aluminum wires in the simulation experiment. Proliferation of dislocation and grain deformation occurred in the broken aluminum wires using transmission electron microscopy observation. The results show that the aluminum wires in the experiment under a Level-6 wind and above were in a full yield state and demonstrated strain-fatigue failure condition. The fracture of the broken aluminum wires showed distinct strain-fatigue fracture characteristics using the scanning electron microscope fracture morphology analysis. From the combination of the abovementioned research, we conclude that the failure mechanism of the broken strands of the jumper wires of the EHV transmission line in the strong-wind area is mainly a strain-fatigue failure mechanism.