The Research Of The Nonlinear Characteristics Of Transmission Conductor Under Service Load

As an important part of the power system,the safety of transmission line is related to the normal operation of the power system,Its importance is self-evident.At the same time,as a typical suspension structure,the transmission line long-term services on open-air,easily caused damage accumulation and even lead to the overall failure of the transmission line system in strong winds,ice and other strong environmental load.Therefore,the internal force response and structural response of the transmission line under the service load is very important.This paper first briefly introduces the research background and significance of the subject,the development and research status of computational theory of cable structure.The calculation method of the cable structure is usually divided into analytical method and finite element method.With the popularization of computer technology,the finite element method is adopted.Then,this paper summarizes the commonly used finite element model of cable structure,analyzes and compares the advantages and disadvantages of different units models.On the basis of previous research,a two-node cable element model based on exact analytic solution of catenary’s equation is proposed and the concrete expression of the shape function is deduced.The geometric relation of element based on Lagrangian strain and the physical equation of element by Kirchhoff stress are established.Nextly,on the basis of description of UL coordinate,according to virtual work principle,deducing the equilibrium equation of the element in the incremental form and the expression of tangent stiffness matrix of element.Then combining the Newton-Raphson method and the incremental method to solve the nonlinear equations.Based on the theory of dynamic characteristics and the basic theory of finite element,the mass matrix of two-node cable element is deduced.In this paper,MATLAB language is used to compose the finite element program based on the above theories to solve the static response and dynamic characteristics of the cable structure.Through several examples,the applicable conditions and advantages of two-node cable element model are obtained from the comparison of the calculation results between two-node cable element model with other cable element models.The expression of element stiffness matrix and element mass matrix is simple when used two-node cable element model,with high computing accuracy and fast convergent rate and less computation time consuming.According to the structural characteristics and geometric parameters of the actual conductor,the layered model of the conductor is established.Combining the strain relation between the layers of the conductor deduced by the displacement coordination equation with the physical equation of conductor to solve the tension of single-strand conductor.And the layerd mechanical properties of the conductor under static load and dynamic load are solved,at the same time,the general rule of tension distribution of each layer according to different layerd models of conductors is obtained.At the end of the paper,a brief summary and conclusions are done and given,and a proper prospect for a number of deficiencies in this article has done.