Study On Fatigue Characteristics Of Overhead Transmission Lines In Extremely Cold Environment

China has a vast territory,and the unbalanced distribution of power resources and power load makes the long-distance transportation of power resources inevitable.However,so far,there have been few studies on the structural safety of overhead transmission lines in the low-temperature environment of extreme meteorological areas.The research on the mechanical properties of the wires under extremely cold conditions helps to ensure the safe operation of the power grid and reduce the huge economic losses caused by power outages.Fatigue strand breakage of transmission wires(especially at the exit position of the wire clamp)is one of the main failure modes in the operation of transmission lines,and wind-induced wire vibration is one of the main causes of fatigue breakage.Therefore,this paper mainly studies the fatigue problem caused by the breeze vibration of transmission lines under low temperature conditions.The overhead line is affected by the breeze vibration and may generate dynamic bending stress.However,it is very difficult to directly measure the dynamic bending stress for running overhead lines.Therefore,this paper first tries to find a better way to accurately reflect the actual vibration of the overhead line,and to measure and understand the level of the dynamic bending stress of the wire.Combined with the steel-cored aluminum stranded wire commonly used in UHV transmission lines,the corresponding low-temperature vibration testing device to the wire was designed and constructed.Considering the fact that the wire is fatigued and stranded at the outlet of the suspension clamp,combined with the experimental principle,the dynamic equation of the wire is established,and the relationship between the strain at the exit of the wire clamp and the amplitude of the antinode is derived.The simulation software ANSYS establishes a three-dimensional model of steel-cored aluminum stranded wire and simulates the vibration under harmonic excitation.The fatigue life of the wire is predicted according to the strain at the exit of the clamp combined with the Miner cumulative damage theory and the Wohler safety boundary curve.The mechanical analysis and simulation results of this paper were verified by conducting low temperature vibration test of the wire,and the influence of temperature on the fatigue characteristics of the wire was further discussed.