Study On Collapse Mechanism Of High-Voltage Transmission Tower-Line System Under Tornado

As an important power lifeline project,transmission lines are mostly established in the wild,invaded and threatened by various natural disasters frequently,among which the tornado’s attack on transmission lines is particularly serious.But at present,there is still a lack of research on transmission lines attacked by extreme strong winds such as tornadoes,and the relevant design regulations of transmission towers against extreme weather loads such as tornadoes,the design code of pole towers in China has not been involved at present.Tornadoes will be the biggest potential threat to the collapse of transmission towers in China.Therefore,it is very important to study the collapse mechanism of transmission tower under the action of tornado.This article simulates a tornado wind field based on Wen’s semi-empirical formula of tornado to obtain a three-dimensional wind speed field of a tornado wind field.Taking the universal straight line 5A-ZB2 500k V wine glass tower single circuit line as the research object,using the component-by-component method to calculate the tornado load of each angle steel component,and the whole process of dynamic collapse of single tower and tower line system under the action of mobile tornado was studied.The main work is divided into the following parts:(1)The advantages and disadvantages of the most widely used Rankine vortex model and Wen model are compared and analyzed.A more comprehensive Wen model is selected to simulate the wind speed of three dimensional tornado wind field.(2)Aiming at the particularity of tornado,the calculation formula of component wind pressure in the specification was improved,and the component-by-component method in the literature was improved.The improved component wind pressure calculation formula was used in combination with the improved component-by-component method to calculate tornado loads on angle steel components and transmission lines(3)The finite element model of A-ZB2 transmission tower and transmission tower-line system is established,and the modal analysis of the two systems is carried out to verify the accuracy of the single tower limited model,and to compare the difference between the dynamic characteristics of the single tower and the tower line system(4)Taking single tower as the research background,the envelope damage range of single tower damage caused by tornado is determined by calculating a large number of tornado action conditions,and the most unfavorable response of a single tower under various attacks,that is,the most unfavorable working condition,is determined based on the most unfavorable response of the structure.(5)On the basis of the most unfavorable working conditions,a tornado moving path with attack angles of 0~0,45~0 and 90~0is set up to analyze the collapse process of single tower and tower line system under the action of moving tornado,to study the yield path of the rod,the weakest position,and to analyze the influence mechanism of transmission line on the tower body.