Study On Mechanical Characteristics And Wind Loading Of Transmission Line

With the rapid development of China’s economy,the demand of the rational allocation and utilization of power resources is increasing dramatically.Ultra high voltage direct current(UHVDC)transmission line is an important part of China’s backbone state power grid,which has the characteristics of large transmission capacity,small transmission energy loss and long transmission distance.The large wind load exerted on the transmission line will cause the significant deformation and fracture of the transmission tower,which will not only cause the collapse of the tower-line system,but also cause serious life safety accidents and major economic losses.The study of UHVDC transmission lines can not only improve the level of power security in China,but also help China to carry out international energy cooperation and seize the new commanding heights in the field of power transmission in the worldThree methods,namely theoretical analysis,finite element analysis and field measurement,are usually used to study the sag and tension of strain section.The theoretical calculation method of single span is develped.Besides,the finite element analysis method based on the mutual transfer of MATLAB and ANSYS is put forward,and three possible working conditions based on different crimping positions are introduced and analyzed according to the line stringing construction process.Then,the sag of a certain straight and resistant section line is measured and analyzed by GPS and total station in the field.Finally the results of the three methods are compared.The results of the proposed finite element method are very close to the results of the proposed single span theoretical calculation method,both of which have good accuracy and can be applied to the shape finding of strain section in engineering.Also the measured sag and tension of strain section in the field can be fitted.Through wind tunnel test of multi-bundled conductors,the overall drag coefficients of multi-bundled conductors under different wind attack angles are obtained.A new wind tunnel test device of arc-shaped transmission line is developed,and the drag coefficient and wind distribution factor of arc-shaped conductor under yawed wind load are obtained.The overal drag coefficients of single conductor,two-bundled conductor,four-bundled conductor,six-bundled conductor,eight-bundled conductor are 1.02,1.02,1.00,0.97,0.93,respectively.The recommended values of wind distribution factor nX and nY under different yawed wind are given.Methods of wind tunnel force measurement and wind deviation displacement measurement are used to obtain the variation of the drag coefficients of insulators with wind speed and turbulence.Meanwhile,a wind tunnel testing method for the dynamic windage of suspension insulators is proposed.The characteristics of dynamic windage of composite insulators under free swinging condition are studied.Finally,the recommended values of the drag coefficients of disc and composite insulators are given.This paper recommend that the drag coefficient of disc insulators is 0.89(vertical),and the drag coefficient of composite insulators is 0.93(vertical)and 1(inclined)Based on the proposed calculation method and wind tunnel test results,the wind-induced response of transmission line under complex wind conditions is calculated.Firstly,wind loads in the direction of cross line and along line are discussed,where three different wind load distribution modes are proposed in the calculation of wind load in the along-line direction Secondly,the wind-induced responses of transmission lines with or without insulator string are calculated under yawed wind loads.The displacement and line tension of transmission line under 0° wind loads are the largest.The existence of insulator string causes the reduction of displacement and line tension.Finally,the wind deflections of transmission lines with or without insulator string and junmper wire are calculated under the wind load at different attack angles The transmission line displacement and line tension reduce in attack angles that shielding effect occurred.The wind deflection of jumper wire on windward slope is smaller than that on the ground,the wind deflection on the mountain top is larger than that on the ground,and the wind deflection on the leeward side is smaller.