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.
In this study, a finite element, fully three-dimensional solid modeling method was used to study the mechanical response of a steel-cored aluminum strand (ACSR) with a mid-phase jumper under wind load. A whole model (simplifying an ACSR into a solid cylinder) and a local model (modeling according to the actual structure of an ACSR) of the mid-phase jumper were established. First, the movement of the mid-phase jumper of the tension tower under wind load was studied based on the whole finite element model, and the equivalent Young’s modulus of the whole model was adjusted based on the local model. The results of the whole model were then imported into the local model and the stress distribution of each strand of the ACSR was analyzed in detail to provide guidance for the treatment measures. Therefore, the whole model and the local model complemented each other, which could reduce the number of model operations and ensure the accuracy of the results. Through the follow-up test to verify the results of the finite element simulation and the comparison of the simulation and fatigue test results, the causes of the broken strand of the ACSR were discussed. Although this modeling method was applied to the stress and deformation analysis of a mid-phase jumper in this study, it can be used to study the bending deformation of rope structures with a complex geometry and the main bending deformation. In addition, the effect of the friction coefficient on the bending of the mid-phase jumper was studied.
The design intensities of four parts, i.e. ground conductor, hardware fittings, pole tower and foundation are greatly different, so it is difficult to evaluate the reliability of the whole power distribution circuit exactly. In this thesis, the intensity distribution functions of ground conductor, hardware fittings, pole tower and foundation have been calculated respectively, and then based on the system reliability theory, the reasonable failure sequence of power distribution circuit conforming to economic optimization principle is recommended. Under the assumed failure sequence, the calculation about intensity matching coefficient at the target confidence level is implemented, and finally, the intensity matching coefficients of ground conductor, hardwire fittings, pole tower and foundation of power distribution circuit are given., 0 Web of Conferences https://doi.org/10.
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