Analytical Solution And Numerical Simulation Research On Breaking Tension Of Overhead Line

Overhead lines run under various complex load environments in the field for a long time,which is prone to cause various damages and safety accidents.After the overhead line is disconnected,the tower line system will be subject to unbalanced tension caused by instantaneous impact.The unbalanced tension will increase instantaneously the displacement and internal force of the transmission tower,which will easily cause the collapse of the tower or even the series collapsed of the transmission tower.Therefore,studying the disconnection effect of overhead lines is of great significance to the disaster prevention and mitigation of transmission lines,and it also provides a basis for the design of the strength of the transmission tower and the electrical gap between the tower and the conductor(ground)line.In this paper,the main research contents are as follows:(1)The theoretical formulas for the change in span of the k gear and the offset distance of the overhead line suspension point after the wire breaks are established;use the trial iterative method to program the two formulas until the iterative condition that the broken wire tension of the k+1 gear is constant to 0,Output the thread breaking tension of the k gear.Analytical solution and numerical simulation are used to calculate and compare the broken wire tension under the same working conditions.It is concluded that the broken wire tension calculated by the two methods increases with the increase of the pitch and the thickness of the icing,and the break tension decreases with the increase of insulator string length.The analytical solution shows that the broken wire tension is slightly larger than the numerical simulation result.The error results of the two methods are about 8%,which verifies the correctness of the numerical solution.(2)The analytic solution method and the nonlinear finite element method were used to find the conductor shape respectively,and the conductor elements obtained stress values by the two methods were compared.The error was within 2.5%,and the conductor shape finding was correct;The finite element model of eight towers and seven towers was established;modal analysis method is used to verify the transmission tower,and it is obtained that the first-order natural frequency of the transmission tower is 1.98325 Hz,which is within 1.637～3.04 Hz,which conforms to the structural specification.It is required to prove that the modeling of the transmission tower is reasonable.(3)In the LS/DYNA software,consider the presence or absence of the ground,respectively,to simulate the disconnection of the broken wire,the ground wire,and the broken ground wire at the same time,extract the time history diagram of the broken wire tension of each gear,and the suspension point displacement of the insulator string,unbalanced tension response.Studies have shown that the establishment of the ground will reduce the peak tension of the conductor,the residual static tension,and the dynamic and static unbalanced tension response of the suspension point of insulator string,and it has no effect on the displacement of the suspension point of insulator string.The greater the number of broken wires,the greater the peak tension and the smaller the residual static tension.The broken ground wire has little effect on the wire tension.The farther away from the wire break,the greater the peak tension and residual static tension,and the smaller the displacement and unbalanced tension of the suspension point of insulator string.The further away from the broken line,the closer the residual static tension is to the initial tension of the wire,the closer the static displacement response of the insulator string suspension point and the static unbalanced tension response are to zero.The peak tension increases with the increase of the span,the length of the insulator string,the thickness of icing,and the height difference.The residual static tension increases with the increase of the span,the thickness of the icing and the height difference,and the length of the insulator string decreases.