The Research On Bearing Capacity Properties Of Multiple Bundle Transmission Conductor

Multiple bundle transmission lines,especially long-span transmission lines,play an important role in power system.Due to the long-term service of the wire in complex environment,it is difficult to ensure the safety of the transmission line system which is often subjected to wind loads,temperature loads and icing loads.Therefore,how to effectively predict the bearing capacity of the structure is very important.Based on this,the static characteristics of transmission conductors and multi-split transmission lines under various strong environmental load were actively investigated by selecting these structures as the main research object.Based on previous research,several calculation models of the cable structure commonly used in analytical method and finite element method were summarized.which serves as the fundamental basis for innovation and improvement.Firstly,a torsion three-node isoparametric element model was presented based on exact analytical solution of unequal-high catenary.Meanwhile,two-node space beam element was used to simulate spacer rod in multi-split transmission lines.Then,according to the basic modeling of finite element,the expression of element tangent stiffness matrixs of two models were separately developed.Finally,using the method of decreasing the torsional DOF(degree of freedom)of beam element to realize the connection between the beam element node and the cable element node.Thus,a global model of multi-split wires was established.In this paper,based on the above theory the finite element program of solving the static response of the cable structure was composed by using MATLAB language.In this paper,three numerical examples under icing loads temperature loads and lateral wind loads were designed to examine the geometry and internal force calculation results.The results indicated that the increase of wire span,icing thickness,temperature difference and lateral wind loads will induce the midspan displacement and bearing capacity to increase.At the same time,the increment significantly increased with the increase of external loads and structural span.Thus,the effects of three environment loads on the cable structures shouldn't be neglected.Taking ACSR(aluminium conductor steel reinforced)as the actual analysis object,the layered mechanical calculation model of the whole structure was established to research internal strained condition of cable under temperature loads.Firstly,the interlaminar extrusion pressure was obtained from the stress relationship between the strand and the whole conductor.Then according to the deformation of wire,the strain relation of displacement coordination equation was established.Finally,the tension distribution of single strand and each layer were obtained by solving the equations with several unknowns.Two real ACSR under temperature loads was taken as the basic examples to obtain the tension general distribution law between single stranded conductor and layers of the conductor.The analysis results indicated that under temperature loads,Outer aluminum stranded conductors broke firstly and internal steel stranded conductors were the main reinforcement part which consistent with that of actual engineering.Thus the conclusion has practical significance.