Study On Torsional And Turnover Characteristics Of Large Span Multi-bundle Conductor

The large span multi-bundle conductor will twist tempestuously and result in torsion failure due to the ice accretion eccentric and uplift flow,which poses a great threat to the power system safety.Thus,it is important to study the effects of various parameters on the torsion and turnover characteristics of large span multi-bundle conductor,and it is also of great significance to the anti-turnover optimization design of overhead transmission line.After summarizing the domestic and foreign up-to-date researches,this study established a refined finite element model of large span multi-bundle conductor and conducted the numerical simulation analysis.Further,the corresponding scale model was designed for twist test,as well as the study of torsion and turnover characteristics for various parameters.The main contents are as follows:1.Finite element model analysis of the bundle conductors’ torsional stiffness:A refined finite element model of large span multi-bundle conductor was built by LINK and BEAM element,simulating the conductors and spacers,respectively.The relationship between the torque and rotation angle of bundle conductors was established,which was used to infer the global torsional stiffness.The effects of varied span length and conductor initial tension on the torsional stiffness were studied.Further,the derivation of Nigol’s model as well as its causes was analyzed.According to the generalized Hamilton principle,a 3-D galloping model for the iced conductor was set up,and the numerical solution of the galloping response was obtained by the 4-order Runge-Kuta method.Based on that,the effect of the torsional stiffness error on the galloping response was discussed.2.Theoretical calculation of the relationship between the torque and rotation angle of bundle conductors:according to the essential mechanical theories and geometric relations of overhead transmission line,a semi-analytic multi-parameter model of the bundle conductor was developed by means of the numerical calculation.Take a single span 4-bundle conductor for example,the torsional mechanism was analyzed deeply based on the comparison of the torque-rotation angle curves from different models.3.Scaled model test and simulation studies on the torsion process of bundle conductor:Based on the dual-scale similarity criterions,a reduced scale test device was designed,which could be used to study the torsion and turnover characteristics of multi-bundle conductor.Based on explicit finite element analysis of LS-DYNA,the quasi-static simulation for the turnover process of bundle conductor subjected to concentrated torque was carried out with the dynamic relaxation method.Take a real 680m-span transmission line for example,the torsion and turnover characteristics of multi-bundle conductor were studied by scaled model test,explicit and implicit finite element analysis,respectively.4.Study on the torque loads causing the turnover of bundle conductor:Based on the implicit finite element analysis,the torsion and turnover characteristics of multi-bundle conductor which was built by BEAM element and subjected to different distributed torque loads were studied.The corresponding relationship was established between the torsional state of bundle conductors and the general parameters of load(i.e.,wind speed,ice thickness,etc.),which was used to prejudge the onset of turnover.In this paper,some more perfect and effective methods were proposed.Based on those methods,the discussion on the torsion and turnover characteristics of multi-bundle conductor and the analysis of the torque loads could be used as reference for designing the overhead transmission lines.