| With the rapid development of economy and the improvement of productivity,the demand for electric power is increasing all over the country.In recent years,our electric power industry is developing continuously,and the scale of power grid has been further expanded.In order to ensure the safety and stable operation of the substation under the thunderstorm weather,the lightning current is introduced into the ground by installing the independent lightning rod in the engineering application to protect the substation equipment and its affiliated facilities from overvoltage damage.As a high-rise structure,the lightning rod has a large slenderness ratio and a low flexural stiffness,and is prone to occur frequent and strong vibration under wind load.Compared with the conventional quadrangle and triangular steel,the circular section of the steel rod is easier to cause the structure to form regular vortexes to fall off at low wind speed,and then the vortex-induced resonance of the transverse wind occurs.At the same time,the current code does not pay enough attention to the dynamic influence of wind load’s pulsating characteristics on the lightning rod structure.Under the long-term action of the reciprocating load of downwind and transverse wind,the mechanical strength of structural connections is easily reduced,which even cause the structure to crack or break at the weak position.In recent years,the lightning rod structure collapse accidents occur frequently,and the safety risks are serious.Therefore,it is of great theoretical and practical significance to study the characteristics of wind-induced vibration response of steel rod structure in substation frame.In this paper,the wind-induced vibration response characteristics of steel rod structure of substation frame are analyzed by means of wind tunnel test and field measurement.(1)To consider the Reynolds Number Effect and wind load characteristics of the circular section at the top of lightning rod,in this paper,a full-scale rigid force measuring model with a scale ratio of 1:5 corresponding to the top section is designed and made,which are installed end plates five times the diameter at both ends to eliminate end effects.The wind field was simulated in the high-speed test section of HD-2 wind tunnel of Hunan University wind engineering experimental research center.The wind speed was loaded from 0.5m/s to 20m/s,and the load response in thealong-wind direction and the cross-wind direction of the rigid model was measured under three wind fields: uniform flow field and turbulence flow filed with turbulence intensity of 3.5% and 6.5%.The influence of turbulence intensity and Reynolds number on wind load parameters such as Strouhal number,drag coefficient and lift coefficient of lightning rod are further studied and analyzed in detail.(2)The project background of this paper is a combined steel tube frame lightning rod of a 220 KV high-voltage substation in Aksu Weigan(southern suburb of Kuqa)of Xinjiang province,which is located in the northwest China with complex wind environment.In order to study the influence of different support conditions on the dynamic characteristics and wind load characteristics of lightning rod structure,ANSYS finite element software was used to establish the finite element model of typical combined steel tube frame lightning rod,fixed single cantilever steel lightning rod and type A bottom column steel lightning rod.The parameters of critical wind speed,the Reynolds number,vortex vibration amplitude of steel rods in different types of transformer substations are calculated and analyzed with reference to the European standard.(3)In order to simulate the influence of atmospheric boundary layer turbulence on the special structure of lightning rod more truly,based on the typical independent lightning rod in Aksu Weigan(southern suburb of Kuqa)of Xinjiang province,an aeroelastic model was designed and made.After the completion of dynamic calibration,the wind tunnel tests were carried out under three wind fields: uniform flow field and turbulence flow filed with turbulence intensity of 3.5% and 6.5% to obtain the acceleration and displacement response of the aeroelastic model at the bottom of the load response and the top of the load response in the along-wind direction and the cross-wind direction.The pulsating and spectral characteristics of the response are analyzed in detail,and the wind vibration coefficient of the lightning rod structure is calculated to provide corresponding evaluation and suggestions for the specification value.(4)Field investigation of Aksu Weigan(southern suburb of Kuqa)substation project site is carried out.Wind speed acquisition instrument is used to measure the wind environment data at the typical height of the substation.Acceleration sensors are installed at different heights in downwind direction and crossind direction of steel tube lightning rods of different types of substations.Dynamic characteristics were tested by using free vibration method and environmental excitation method,and parameters such as modal frequency modal damping ratio were analyzed in detail,andthe TMD scheme was designed by selecting a typical independent steel tube lightning rod for substation. |
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