Torsional Parameters And Galloping Detuning Control Of Transmission Lines

Because the UHV transmission lines are often found in areas with abominable natural conditions,and the widely use of large-diameter conductors as well as bundled conductors,making icing transmission lines easy to gallop under wind loads.Therefore,galloping and related research have been paid more and more attention by scholars at domestic and overseas.However,the research on the galloping of UHV transmission lines is mainly concentrated on torsional parameters of the conductor and the determination of its accurate value remains deficient.The coupling effect of tension,bending and torsion of conductors is also discussed little.However,it is noted that the current research on the galloping of transmission lines and the galloping response control is less based on the measured parameters,especially the highly bundled transmission lines.Herein,it is significant to establish an accurate simulation model and research method.This article accurately determines the equivalent shear modulus of the single conductor with experiemental work and simulation model.And it is mainly based on the aerodynamic data of the Jianshan prototype eight-bundled transmission lines in Henan Province with the material and geometrical physical parameters of the structure.The actual galloping is simulated by finite element simulation software ANSYS with prestressed beam element.Finally,the anti-galloping effect of the detuning technique on the galloping of transmission lines is studied according to the mechanism of the detuning spacer.The specific research work is as follows:(1)A method for calculating the equivalent shear modulus of single conductor and the simulation model considering the contact between wires,friction and Poisson’s effect are presented in this article,which is based on the numerical method of helical structure response under loads,the torsion test and the simulation.The torque-torsion angle diagram is obtained towards the torsion test of 7-wire ACSR conductor LGJ/JL/G1A-70/10.The numerical simulation of the structure is carried out by using the finite element simulation software ANSYS.The analysis results show that the simulation model is consistent with the experimental results and better than the traditional numerical methods,whose error is only 3.79%.And as the lay angle increases,the equivalent shear modulus increases.As the Poisson’s ratio of the aluminum strand increases,the equivalent shear modulus decreases.As the number of stranded layers increases,the equivalent shear modulus tends to decrease.(2)The form funding of attack angle of conductor under static wind is accurately carried by using the Internal and External Double Iteration Search Method.And the finite element model is established in ANSYS to accurately simulate the galloping of eightbundled transmission lines.Based on the form funding and galloping theory of conductors,the article takes the prototype eight-bundled transmission lines as example,the corresponding finite element model is established and compared with the field measured data.The results show that the the vertical galloping amplitude and the natural frequency simulated are in good agreement with the field measured results of State Grid Henan Electric Power Company Electric Power Research Institute.And by using this galloping model for further research,the results show that the galloping amplitude of the O.Nigol mechanism decreases as the equivalent shear modulus of single conductor increases.(3)Based on the technology of detuning control,the different layouts of detuning spacers are studied.And the optimal detuning offset’s distance and the layout with the best anti-galloping effect are determined.By setting six different layouts,the detuning spacer is believed to perform well in anti-galloping effect compared with traditional integral spacer.And the relationship between the offset’s distance and galloping amplitude is hyperbolic.That is,as the offset’s distance increases,the galloping amplitude first increases and then weakens.In vertical direction,the layouts with six and eight spacers’ offset have the best anti-galloping effect in the case where the offset’s distance is 0.35 m.While in horizontal and torsional direction,the layout with five spacers’ offset performs the best where the offset’s distance is 0.6m.However,the direction of offset doesn’t bring any significant change to the effect.While the layouts with two-way-offset will always perform well on anti-galloping.When controlling the horizontal and torsional galloping,the layout with five spacers’ offset and two-way detuned performs the best,and the anti-galloping degree are 63.6% and 52.7% respectively.And the layout with eight spacers’ offset which is completely detuned performs the best and its anti-galloping degree is 68.7% in vertical direction.The results above show that the anti-galloping degree is positively correlated with the detuning degree.The detuning spacer can reduce the amplitude of galloping by increasing the natural frequency,at the same time,increasing the difference between the transverse frequency and torsional frequency to prevent the galloping by separating them.