Analysis Of Overall Mechanical Performance Of Independent Lightning Rod Structure Under Strong Wind Based On Fluid Structure Coupling Theory

As an important part of substation,the safety performance of independent lightning rod structure directly affects the normal power transmission and transformation of substation.The common lightning rod structure is usually high and the section size is small,which belongs to the typical high flexible structure.Under the action of wind load,it is easy to have large displacement at the top of the structure.The weak position of the connecting flange of each section of the lightning rod structure is easy to cause damage,or even collapse.Under the joint support of the National Natural Science Foundation of China(51808374)and the science and technology activities of overseas students in Shanxi Province(dc1900000602),this paper takes the lightning rod structure replacement project of a 220 k V substation in Southeast China as the background,and uses ANSYS Workbench finite element analysis software to analyze the wind flow around the independent lightning rod structure and the overall mechanical performance.The main contents of this paper are as follows.(1)According to the actual project,the finite element model is established by Solid Works and imported into ANSYS The flow field around different sections of the independent lightning rod structure under different return period wind speed was simulated by FLUENT software,and the lift coefficient curves of different sections of the independent lightning rod structure were obtained.The frequency spectrum of the lift coefficient curve was analyzed by origin,and the distribution of wind pressure field and velocity field around the structure was compared.The results show that: the lift coefficient is similar to the sinusoidal function,and has a positive correlation with the height of the independent lightning rod and the wind speed;under different wind speeds,the lift coefficient CL oscillates up and down near zero,indicating that the cylinder is subjected to the symmetrical force along the crosswind direction.The windward side of the structure is the stagnation point of the wind speed,and the corresponding wind pressure is the largest and positive;the leeward side of the structure has vortex shedding due to the obstruction of the incoming flow encountering the round steel pipe,which produces a certain wind suction,and the wind pressure decreases to a negative value,and the backflow phenomenon on the leeward side of the structure is observed from the velocity vector diagram.(2)By using the modal module in workbench,the first 10 modes of the independent lightning rod structure are numerically simulated,and the first 10 natural frequencies of the structure and the corresponding vibration modes of each frequency are obtained.Through comparative analysis,the dynamic response of the structure under different conditions is obtained;and the importance of deformation checking calculation for the maximum displacement of the top of the structure is also obtained.(3)In the workbench finite element analysis software,the quasi-static analysis,one-way fluid structure coupling analysis and two-way fluid structure coupling analysis are carried out for five kinds of independent lightning rod structures with different heights.By comparing the maximum displacement and maximum stress of the structure under three different analysis methods.The results show that: the maximum displacement of the structure obtained by the three analysis methods is positively correlated with the wind speed,and the results obtained by the one-way fluid solid coupling analysis are 1.04 ～ 1.4 times of the results obtained by the quasi-static analysis;through the stress analysis of the independent lightning rod structure,it is known that the larger stress is at the connection between the bottom of the structure and the support;when the wind speed is 35 m / s,the 45 meter high independent lightning rod structure uses the one-way fluid solid coupling analysis Therefore,it is suggested that the fluid structure coupling theory should be used in the calculation of similar high flexible structures such as independent lightning rod to ensure the reliability of the structure.