Research On Improving The Security And Reliability Of Large Span Sections Of Overhead Lines In Mountainous Areas

Shanxi is a typical mountainous plateau widely covered by loess,with high terrain in the northeast and low terrain in the southwest.The plateau has undulating interior,horizontal and horizontal valleys,complex and diverse landforms,many mountains and few rivers,and mountainous and hilly areas account for 80.1% of the province’s total area.Main mountain ranges in Shanxi:Taihang Mountain,Luliang Mountain,Hengshan Mountain,Wutai Mountain,Zhongtiao Mountain,Taiyue Mountain,etc.At present,land resources are precious in the plain area of Shanxi,and line corridors are tight.A large number of ultra-high voltage and ULTRA-high voltage lines are located in deep mountains and valleys,and large distances of more than 1000 m can be seen everywhere.Therefore,in this topic,the main use and summarizes the ultra-high pressure and ultra-high voltage lines in the province has been made at this stage of experience and design principles,aiming Shanghaimiao ～shandong±800k V High Voltage DC Line Engineering,basic conditions(micro terrain conditions,weather conditions,conditions of power system,etc.)as the basis of this thesis research conditions,based on uneven ground static distance,lead to take off the ice,wire jump off ice,the longitudinal uneven tension,conductor ice dance move,wire shock situation analysis and demonstrate these thoughts.How to design and study the overhead line with large distance in mountain area safely and reliably is an urgent problem to be solved.Based on the analysis and research of Shanxi section of Shanghai Miao ～Shandong ±800k V UHVDC transmission line project,according to the aerial data provided by Rosta Company,after the pole tower positioning optimization,about 20 stations within Shanxi section of Shanghai Miao ～ Shandong ±800k V UHVDC line have a range of more than 1000 m,with a maximum range of1500 m.With the increase of the spacing,the influence of meteorological factors,such as wind,ice and thunder,on the large spacing is more serious than that of the ordinary spacing,which causes the clearance distance of the conductor to decrease,the probability of starting vibration to increase and the vibration to intensify.This topic is aimed at the research on the large distance of more than1000 m,and the following conclusions are drawn.1)economy and operation of the large span particularity: large span of this project is mainly across the canyon,a deep ditch,terrain available,the aim is not high,and ground model and meteorological conditions and all the same,while the big span average over navigable rivers,large span,high ground guide suspension point,should be considered high wind speed increases,and choice of wire,wire vibration control and so on all need special consideration.Large distance in mountainous area,as long as the line selection can make full use of the terrain conditions,avoid landslide,gully,collapse,debris flow and other unfavorable geological zone,can reduce the base of tower,reduce steel consumption,has a relatively superior economy;However,from the perspective of construction operation,the large distance is generally located in the high mountain areas with steep slopes and deep valleys and difficult traffic,so the construction is quite difficult.In case of accidents during operation,it will take time to repair and restore.Therefore,in the choice of mountain route path,the choice of the crossing point of large distance should be investigated and studied carefully,and the scheme is compared,so as to achieve technical and economic reasonability.For the general meteorological conditions of the large distance should not be avoided,but also the need for comprehensive balance,careful choice of spanning point;Large spacing for heavy ice should be avoided as far as possible.2)Selection of meteorological conditions with large distance: "canyon deep gully type" with large distance,generally with low poles and towers,and most of the ground guide lines fall in deep gullies,which are located in the low depression of the mountain,and the wind speed and ice thickness are not larger than the adjacent mountains.However,for special "micro-terrain and micro-meteorological points",such as those across the valley and tuyles,designers should investigate and study together with meteorological personnel,fully consider the influence of narrow tube effect,terrain uplift,valley direction and other adverse terrain factors on the increase of wind speed and ice cover,and appropriately increase the design meteorological conditions to check the calculation of the tower foundation.According to the principle of large distance selection of route path recommended in this paper,it is applied to the Shanghai Miao ～ Shandong ±800k V UHVDC transmission line project.The project started in August 2015,was completed and put into operation in November 2017,and has been running well so far.