Effective Strategy Of Improving Overhead Line Sag And Research On Transmission Capacity

With the development of economy and society,electricity plays a role of more importance in national daily life,science,technology,industry,economy,and many other fields.Since the 1990's,large-scale blackouts have occurred a great many times in China and other countries.Through the analysis if the blackout accident,people found that there were a lot of accident of vegetation-related failures in transmission lines.And the lowering of arc sag is the main factor of arcing fault tree.With the accelerating pace of the construction of power system,the problem of the lag and lack of power grid planning and construction is increasing obvious.Under this background,especially in the field of the prevention of vegetation-related failures,the improvement of lines transmission ability and economic efficiency,it is meaningful to study the transmission lines in order to search for the strategy of improving the sag and transportation capacity.This paper has proposed an improved strategy of the prevention of vegetation-related failures by improving the sag of overhead transmission lines.The steel core of aluminum stranded wires should be stripped out at the condition of given expense to reduce the original degree of sag and expansion due to thermal factor.Meanwhile each conductor within the span is divided into several small parts by interval rods or other fixed tools,in order to achieve the purpose of effectively reduce the archives line biggest sag.Through the discussion of the feasibility of improvement strategy,we get the calculation formula of the sag,and propose the economical model based on overhead transmission lines to improve sag.And through calculation and analysis,we get the following conclusions: overhead transmission lines improvement strategy can make the overhead transmission lines sag effectively improve,and about60% improvement in the sag of 300 meters' span of 220 kV transmission lines.With increasing of span,the improved rate of the sag will gradually decrease.Under the condition of the same span,as the temperature of conductor rise,the sag improved rate will increase;the higher temperature of the conductor,the better improvement people will get.From the above,the proposed strategy is very suited for heavy-loaded or large-span transmission lines,which could bring both obvious improving effects and fantastic economic benefit.In this paper,based on the analysis method of power system dynamic security probability index,and the study of the strategy of the method to improve the capacity of the transmission lines and the consideration of the influencing factors of transmission lines transmission capacity,we propose the probability security model of the transmission capacity.The proposed Probabilistic security model can help improve the transmission capacity of transmission lines,therefore it also can improve the transmission rate of transmission unit,which have a significance in the field of alleviating transmission congestion,reducing system operating losses and improving the economic benefit.