Dynamic Response Of Transmission Line And Failure Analysis Of Fittings Under Random Wind Load

At present,people’s living standards are constantly improving,and the national economy is also developing rapidly.The power generation gradually highlights its pivotal position in the modern production power.With the increase of social demand,large-scale design and construction of overhead transmission lines will become inevitable.As an integral part of the power grid system,transmission lines have attracted the attention of a large number of scientific and technological workers.In addition to the connection function,the connection fittings are more important to bear external loads,and wind load is the most serious one.Based on the xin’an-xiaocheng line as the engineering background,this paper studies the dynamic response of transmission line and the failure of hardware under the random wind load,simulates the random wind field through the harmonic superposition method,carries out the numerical simulation of transmission line under the wind load,further finds out the vulnerable hardware in the overall connecting hardware,and finally completes the failure analysis of local vulnerable hardware.The main research work and achievements are as follows:(1)The basic principle and application characteristics of linear filtering method,harmonic superposition method,inverse Fourier transform method and wavelet analysis method are introduced.Through the MATLAB finite element software,based on the Kaimal wind speed spectrum and Davenport cross correlation spectrum,the fast Fourier transform harmonic superposition method is selected to simulate the random wind field of transmission line.By comparing the values of different spectrum partition number n,it is found that when the n value is large enough,the simulation spectrum and the target spectrum agree well.At the same time,the correlation functions of wind speed time history samples at different points are compared to prove the rationality of random wind field simulation.(2)Considering the spatial correlation of random wind,five wind speed intervals of200 m,150m,100 m,50m and 10 m are designed for the same wind speed,and the changes of stress and displacement of transmission line under different wind speed intervals are investigated.At the same time,compared with the stable wind load,it is found that the peak value of stress and displacement of transmission line under the random wind load is significantly greater than that under the stable wind load.The influence of random wind load on the stress and displacement response of transmission line can not be ignored;the smaller the wind speed spacing,the stronger the non-uniformity of random wind in the same range,resulting in the asynchronous wind speed along the line direction,the interaction between different wind speeds,resulting in the gradual reduction of the peak value and fluctuation range of the stress.(3)In order to investigate the influence of adjacent span and elevation difference angle on the stress and displacement response of transmission line,25 models of 100 m,150m,200 m,250m and 300 m spacing and 25 models of 0°,5°,10°,20° and 30° elevation difference angle are designed respectively for the two double split lines.The results show that the stress of transmission line under the action of random wind increases with the increase of adjacent span.When the span is 300 m,the maximum stress value increases0.5 times than when the span is 100 m.The displacement response of transmission line increases with the increase of its own span.At the same time,it is significantly affected by the self height difference angle and adjacent span height difference angle.In the actual project,the line with large span and height difference should be strengthened maintain.(4)In order to provide the theoretical guidance for the direction of the transmission line connecting hardware,the complex finite element model of the whole transmission line connecting hardware is established through ABAQUS platform,and the displacement and stress distribution of the connecting hardware under two typical working conditions of stable wind load and random wind load are compared and analyzed.The results show that the wind load has a significant effect on the stress of the fittings,and the effect of random wind is more prominent.In the overall connection hardware structure,the most likely failure fracture hardware is ball head hanging ring,followed by wire clamp and right angle hanging plate.Due to the change of the geometric structure of the connection between the ring and the rod of the ball head hanging ring,the local stress is concentrated,which is prone to failure and fracture damage.The stress at the connection position of the clamp and the bolt,the contact position at the lower end of the right angle hanging plate and the transition position of the rod of the composite insulator are large,which is easy to damage.For the fittings with ball and socket connection,it is easy to produce bending stress at the joint of ball and socket,and obvious strain at the stress concentration area,thus causing fracture and damage of the fittings.Therefore,inspection and maintenance should be strengthened for the fittings with this connection.(5)In this paper,the contact analysis of local vulnerable hardware is carried out,and the dynamic analysis of right angle hanging plate is carried out by using ABAQUS finite element software.It is found that the random wind load has a significant effect on the right angle hanging plate,and the phenomenon of stress concentration is obvious at the bend of right angle hanging plate.At the maximum bending position and the bending position,the right angle hanging plate is prone to failure and fracture.Combined with the analysis of the actual site situation,it is found that the joint fittings are easy to form fatigue cracks in the key parts due to their own quality defects,combined with environmental corrosion and wind load.In the long run,the cracks continue to expand and finally damage the fittings.It is suggested that the quality of the fittings should be strictly controlled.For the connecting fittings located at the tuyere or other special environment,the damage of the fittings can be avoided by improving the limit stress of the fittings and optimizing the geometry structure.Meanwhile,the key parts should be checked regularly to avoid affecting the safe operation of the transmission line.