Wind Disaster Vulnerability Analysis Of Ice-Covered Transmission Tower-Line System

Electric power is an important energy for a country’s economic development.The spatial distribution of energy in China is uneven,and the coal and gas used for thermal power generation are more in the West and less in the East,while the water energy used for hydropower generation needs rivers and mountains to form a topographic drop,so that the water energy has enough potential energy for power generation.The relatively developed southeast region is also the load center of power consumption.Due to the lack of these power generation energy,a large number of transmission lines are needed to transmit power from west to East.The transmission tower line system,an important part of overhead transmission line,is a long-span high-rise flexible structure,which has strong tower line coupling effect and is easy to be affected by wind load and icing load.Under the influence of strong wind and ice disaster,overhead transmission line accidents such as transmission tower damage,tower collapse and conductor and ground wire disconnection occur from time to time at home and abroad,and the consequences of the accidents are very serious.Therefore,the research on the vulnerability of transmission tower line system,an important part of overhead transmission line,under wind ice coupling has high engineering application value.Taking a 220 k V cathead transmission tower line coupling system as the research object,this paper adopts the coupling action of wind load and icing load,considers the randomness of the structure itself and the randomness of wind load,uses nonlinear buckling analysis and dynamic analysis,and draws the vulnerability curve of the structure under ice free and icing conditions based on the probabilistic reliability research method.The main work is as follows:(1)ABAQUS software is used to establish the structural model of transmission tower line system with different icing thickness,and MATLAB software is used to simulate the structural parameters by Monte Carlo,and the structural samples with multiple random parameters are obtained;Taking multiple uniformly distributed basic wind speeds as the main control factors of the simulation,i.e.independent variables,the fluctuating wind speed time history simulation is carried out by using MATLAB software,and multiple wind speed samples are generated by superposition with the average wind speed.The wind speed samples and structure samples are randomly combined to generate structure wind speed samples.(2)The nonlinear buckling analysis of single tower structure under the action of different structure wind speed samples is carried out,the damage limit of the structure is divided,the performance level of the structure is statistically analyzed,and the ultimate capacity of the structure is studied.(3)The dynamic time history analysis of wind load is carried out for all levels of iced transmission tower line system models under the action of different structure wind speed samples,and the dynamic response of models with different structural parameters under different load cases is studied.(4)The structural bearing capacity and dynamic response parameters are combined and analyzed.Based on the probabilistic reliability method,the vulnerability of the structure is studied by using conditional probability,that is,the probability that the dynamic response exceeds the structural bearing capacity is calculated as the failure probability of the structure.The failure probability of transmission tower line system structure with different icing thickness under different basic wind speeds is fitted as the wind disaster vulnerability of iced transmission tower line system.The analysis results show that the structure has good resistance to serious damage,but it is prone to slight damage under small wind speed,and the icing load increases the wind disaster vulnerability of the structure.The probability of serious damage or failure of the structure before the wind speed reaches the design condition is very low,indicating that the current design of transmission tower can ensure its safe operation.However,when dealing with the high wind speed exceeding the design condition and adding the icing load,the strength of the weak part is slightly insufficient and is prone to local damage.The results of vulnerability analysis can provide a reference for the performance evaluation of transmission tower line system against wind ice coupling load.