Effect Of Low Environment Temperature On Mechanical Properties Of Overhead Transmission Line

The central and western regions in China are mostly complicated terrains such as mountains and hills,where the climate is uncertain and the natural conditions are harsh.In such an environment,overhead conductors are often in a long-term vibration state,which is prone to major accidents such as fatigue broken strands,hardware damages,and even broken conductors.At present,the existing researches on the mechanical properties of conductors are mostly based on normal temperature environments,and insufficient attention is paid to the mechanical characteristics of conductors in low temperature environments,and the reliability of conductors is difficult to be guaranteed.In a low temperature environment,the elastic modulus and the running force of the conductor are different from the normal temperature owing to lower ambient temperature and higher wind speed.The effects of tension and bending stiffness on the self-damping characteristics of conductors are less studied,theoretical and calculated data of the mechanical properties of sags in low temperature environments are lack.Moreover,most studies of the temperature field of transmission lines used simplified models,in which the final calculation results are not accurate enough.Based on the above issues,the main research contents of this article are as follows:Firstly,based on the energy balance method,a calculation model of the self-damping characteristics of the conductor is established,the self-damping characteristics of the conductor under low temperature environment are calculated,the amplitude and self-damping characteristics of the conductor under low temperature environment and the effects of the running tension,terrain and bending stiffness on the self-damping power of the conductor are analyzed.It is found that the self-damping power and amplitude of the conductor based on the energy balance method increase with the rise of frequency.Secondly,based on the thermal equilibrium equation,a finite element model of the conductor was established,and the radial temperature and stress distribution of the conductor under different wind speeds in a low temperature environment were calculated.The effects of running tension,wind speed,and radial temperature difference on the stress distribution of the conductor conductors under low temperature environment were analyzed.With the ambient temperature dropping from 20℃ to-40℃,the average conductor temperature decreases from 50.34℃ to-9.31℃,and the outermost layer stress increases from 44.59MPa to 60.19MPa.At the same time,the outermost layer stress of the conductor under low temperature environment increases with the rise of the wind speed and the tension.Finally,a finite element model of the suspended overhead conductor was established,the sag and stress of the conductor under low temperature were calculated,the effects of ambient temperature,tension and wind speed on the sag and stress of the conductor under low temperature were analyzed.With the ambient temperature dropping from 20℃ to-40℃,the sag of the conductor decreases from 12.59m to 10.10m,and the stress rises from 53.82MPa to 68.56MPa.In low temperature environment,the sag of the conductor is directly proportional to the change of wind speed and inversely proportional to the change of tension;the stress of the conductor is inversely proportional to the change of wind speed and proportional to the change of tension.