| With the development of "West-East power transmission project" and "North-South power transmission project " development strategies,China’s ± 800 kV UHV DC transmission lines are developing rapidly.However,as a lifeline to ensure the safe operation of power systems,transmission lines are affected by various geological disasters such as typhoons,earthquakes,and low temperatures.Among them,earthquake disasters seriously threaten the safe operation of power systems.In recent years,damage to domestic and foreign power facilities due to earthquakes has frequently occurred.Therefore,ensuring the reliability of the ± 800 kV UHVDC transmission tower is of great significance to the safe operation of the entire transmission system.Aiming at the problem of seismic reliability of the structure of ± 800 kV UHV DC transmission towers,this paper carried out the following work:Firstly,this paper establishes the finite element model of the transmission tower based on the ± 800 kV UHV DC transmission project in northwestern Yunnan.The model includes a straight tower with a nominal height of 69 m and 78 m and a strain tower with a nominal height of 48 m.According to four types of site soil types,this paper selects the representative seismic waves,and then loads the ± 800 kV UHV DC transmission pole tower with three-dimensional ground motion to obtain the dynamic seismic response of the three transmission towers and analyze it in order to explore the dynamics of different pole tower structures.The conclusions show that when the three-dimensional seismic excitation,as the site soil type becomes softer,the axial force of the main material of the transmission tower and the displacement of the top of the tower both increase;when the site soil type is the same,the straight tower with a taller tower body is more vulnerable to ground motion.Compared with the straight tower,the strain tower is less susceptible to the impact of ground motion;Secondly,this paper introduces the basic theory and calculation method of the reliability of structural seismic extreme response,reliability and reliability index,Monte Carlo sampling method,and first-order second moment method.In this paper,the statistical parameters of the main material resistance of the transmission tower and the seismic load are counted.According to the dynamic response results of the transmission tower in Chapter 2,the reliability of the transmission tower component strength and tower top displacement are checked.Combining the two failure control modes,the conclusions show that: the seismic performance of the transmission tower under the hard ground is better;the seismic performance of the strain tower is better than that of the straight tower;the overhead site is not suitable for transmission under the soft site;Finally,this paper introduces the basic theory of power reliability,including for the first time beyond the failure criterion and Edgeworth series expansion.According to the dynamic response of the transmission tower in Chapter 2,the reliability of the transmission tower component strength and the top displacement are checked respectively.Combining the two failure control modes,the conclusion shows that as the soil type on the site continues to soften,the seismic resistance of the transmission tower gradually decreases,and the seismic resistance of the strain tower is higher than that of the straight tower. |
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