| Energy is an important part of national development.It is also an important cornerstone of national security and social stability.However,due to the asymmetry of consumption demand and energy supply in China,the increase of energy transportation cost and the decrease of energy utilization efficiency are not conducive to the long-term and sustainable development of energy utilization.The rapid development of UHV power grid is beneficial to the realization of large-capacity energy cross-regional allocation,which has the advantages of large transmission capacity,long transmission distance,low energy consumption,small footprint and so on.In the process of erection and operation of EHV and UHV lines,the main cause of the line fault is the lightning stroke under severe weather,and the higher the voltage level,the higher the possibility of lightning fault.This paper mainly analyzes the influence of lightning trip fault on UHV transmission line,starting from the background,and illustrates the importance of lightning shielding problems for UHV transmission lines.And the electrical geometric model method for calculating the transmission rate of transmission lines is analyzed to verify the feasibility and the accuracy of the results.The improved method of electrical geometric model is put forward.The correction coefficient of the strike distance is taken into account while considering the tilt angle of the ground,and the accuracy of the model is improved.In addition,an electrical geometric model suitable for multi tower towers of the same tower is proposed.The following parts are mainly included in this article:(1)Three methods for calculating the line failure ratio:exposure arc projection method,exposure distance method and exposed arc ratio method are analyzed.By analyzing and comparing the results,a suitable method for calculating the failure ratio is chosen.(2)The influence of various factors on the shielding failure ratio of transmission line is analyzed,such as the height of lightning conductor,the height of transmission line,the protection angle of tower and pole,the angle of ground tilt and the coefficient of strike distance.(3)The methods of derivation and calculation of coordinate method and zero arc method are mainly introduced,and the effectiveness of the two methods is proved.(4)The software based on VC6.0 is written to analyze the influence degree of transmission lines and other factors on the transmission rate of transmission lines.The shielding failure rate in different towers has been calculated on ths basis of analysis and research.Through the adjustment of suspension point of lightning conductor and height of towers and other factors,the form of poles and towers is improved to satisfy the safety requirements of construction and transmission reliability.Besides,shielding failure rate is also reduced. |
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