Analysis Of Transmission Line Stiffness Parameters And Galloping Influence

Under certain conditions,iced transmission line will galloping under the action of wind load,which will cause strand abrasion,conductor fracture and even collapse of transmission tower,which will have a great impact on social production and life.In the study of transmission line galloping,the cable element model or beam element model is often used for numerical simulation analysis,but the cable element does not consider the bending stiffness,which is inconsistent with the actual transmission line bending stiffness.At the same time,as the main material of transmission line,AC SR has many theories of mechanical properties and different effects.However,as a spiral structure,the research on the unique tension torsion coupling effect of ACSR is less.Therefore,it is necessary to establish accurate simulation models and research methods.In this paper,a variety of wire stiffness theories are compared and analyzed through simulation,and the change rule and reason of the bending stiffness of the wire are explored.The calculation formula related to the curvature of the axial force is put forward.In this paper,the galloping finite element analysis of transmission line is carried out by using the straight beam model which considers the tensile stiffness,bending stiffness and torsional stiffness.The research contents include:1)Based on the lanteigne model,the stiffness matrix theory under the action of tension,torsion and bending is derived based on the discrete model of each independent strand,which can accurately predict the mechanical behavior of the spiral structure under the condition of small deformation,so it can be used to calculate the bending stiffness of the guide wire itself;for the coupling phenomenon of tension and torsion,the boundary condition proposed by utting is used to test the specimen Through the simulation of tension and torsion,it is found that ACSR has a strong coupling effect of tension and torsion,and the tension of conductor has a strong strengthening effect on torsion,while the torsion of conductor has little effect on tension.M-Z method,M-D method and K-C method,including H-L method,all have good accuracy for the stiffness coefficient related to tension and torsion except for torsional stiffness.However,the prediction of torsional stiffness by H-L method is quite different from that by ANSYS simulation,which is lower than that by ANSYS and other theories.2)Based on the experimental bending model of ACSR designed by McConnell,a finite element model is established to simulate and analyze the change rule and reason of the equivalent bending stiffness of Conductor:when the axial load is fixed,the equivalent bending stiffness of conductor decreases with the increase of vertical load;when the vertical load is the same,the equivalent bending stiffness of conductor increases with the increase of axial load.Further analysis shows that the direct cause of the reduction of the equivalent bending stiffness of the multi-layer conductor is the slippage of the strands,and the fundamental cause is the imbalance of the internal forces of the strands.The increase of the curvature of the conductor leads to the increase of the axial force difference in the outer strand,which exceeds the increase of the friction force caused by the radial force,thus destroying the equilibrium state of the strand and causing slip.Once the slip occurs,the integrity of the conductor will be weakened,and the slip strand will no longer provide bending stiffness,which leads to the reduction of the equivalent bending stiffness.The friction coefficient has a great influence on the multi-layer conductor.The larger the friction coefficient is,the greater the friction between the strands of the multi-layer ACSR is,the less likely it is to slip,and the more stable the change trend of the equivalent bending stiffness is.According to the simulation data,the curve of bending stiffness is fitted,and the relationship between equivalent bending stiffness and axial tension and curvature is proposed.3)In this paper,a straight beam model with two nodes and six degrees of freedom is used to simulate the galloping of a single conductor by MATLAB.The coupling effect of tension and torsion and the attenuation of bending stiffness are introduced to explore the influencing factors of the galloping amplitude and the wind speed of dancing.It is found that the coupling effect of tension and torsion will increase the galloping amplitude and the wind speed of dancing,while the bending stiffness will increase the galloping amplitude,but it will affect the dancing Wind speed has no effect.At the same time,the effects of span and initial stress are compared.