| Electricity is an indispensable energy source for our production and life.The rapid economic development in China has brought about the increasing demand for electricity,and it also results in the kilometers increase of the high-voltage transmission lines have also increased at a high rate.The long distances,large spans,and large-scaled spatial distribution,as well as the complex and changeable weather in some specific regions,make the high-voltage transmission lines are more susceptible to lightning strikes.The resultant lightning accident is regarded as a major accident in modern power systems.According to statistics,lightning accidents account for more than half of the current grid accidents,which seriously threaten the safe and stable operation of the power grid.Therefore,it is necessary to study the line trip accidents caused by lightning strikes,which could optimize the design and reduce trip accidents caused by lightning strikes,and improve the reliability of power supply.This study takes the 220 k V transmission line in Suining County in Xuzhou as an example to study the theory of lightning protection,influence factors,and improvement measures.Suining County of Xuzhou is a low mountain and hilly area.Generally,the landform can be divided into two types: yellow flooded alluvial plains and scattered low mountain remnants.Its high-voltage transmission lines are very complex and vulnerable to lightning strikes.The above reasons also reduce the lightning shielding effect of the line.Under the influence of severe weather,such as thunderstorms,transmission lines located in mountainous,valleys,and hilly areas are prone to be affected by large-scale lightning accidents and cannot operate reliably.Therefore,key protection for transmission lines is needed,and additional lightning protection measures must be taken.Firstly,this paper summarizes and deeply analyzes the research status of transmission line lightning protection technology at home and abroad,and briefly introduces the lightning protection measures at present.Then,this paper explores the principle of lightning discharge and relevant parameters of transmission line.Furthermore,we investigate the main factors affecting the level of lightning protection,such as geological conditions,climate,meteorology,and geographical location.Based on the electromagnetic transient simulation software,lightning counterattack and lightning circling strike models are developed.Taking 220 k V transmission line in Suining County as the research object,the lightning intensity,geographical characteristics,and soil resistivity of Suining County were analyzed,and the lightning hazard risk of transmission line was qualitatively evaluated.Finally,the lightning risk of transmission line is evaluated through simulation modeling,which provides a theoretical basis for lightning protection design,and the lightning protection improvement measures of 220 kV transmission line are proposed. |
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