Study On Differentiated Grounding Method Of Transmission Line

The safe operation of transmission line is directly related to the stability of the power grid and the availability of power supply for users.Although the transmission line technology has been greatly improved,lightning accidents are still common,especially the lightning trip phenomenon.On the other hand,current studies on the grounding bodies of overhead transmission towers more often focus on the aspect of anti-drag effect,which are often from the perspective of the principle of reliability.However,there are few studies on the economic principles.This paper attempts to explore a new differential grounding method for towers to meet the requirements of lightning protection and to save manpower and material resources.This method is mainly based on the safe and stable operation of the power system and analyzes the transmission characteristics of lightning current in transmission towers.The method aims to put forward a more practical differential grounding designing scheme for towers,from the considerations of lightning protection,personal safety and the incoming line of substations.In this paper,the present situation of the tower grounding is analyzed and the typical"important line"-35kV HuangYeXian line in the power grid of Changsha Electric Power Company in Changsha County is selected as the research object.Relevant data such as the basic situation and hidden dangers of the typical line are calculated and analyzed.The characteristics of the lightning line are also studied.The corresponding simulation circuit is constructed by using the electromagnetic transient simulation software,so as to simulate the lightning transmission line and to detect the earth current and the line over-voltage of the towers in various levels.Besides,the steps and requirements for the design of differential grounding of transmission towers are also put forward.This paper studies the transformation scheme of the grounding resistance of Huang YeXian line and conducts economic analysis and comparison with the non-differential grounding resistance,and thus the recommendation of differential tower grounding is proposed.Simulation experiments and studies show that when the lightning current occurs,during the transmission of lightning current along the transmission line,with the increase in the grade of towers,the earth current and the over-voltage of the transmission line tend to gradually reduce and that the reduction also appears in the lightning current and lightning over-voltage amplitude of towers in various levels.By simulation experiments and analysis of the line,the application of differential decrease of the grounding resistance of incoming line towers can,to a large extent,reduce the amplitude of lightning current and restrict the transmission of lightning current into transformers,which therefore provides better protection.Through the grounding resistance transformation of the HuangYeXian line by using the differential tower grounding technology,it is possible to ensure the reliability and effectiveness of the lightning protection measures and to avoid unnecessary waste of manpower and financial resources,and finally to reduce the lightning strikeout rate and improve the line lightning protection level.This paper provides reference for units and corporations engaged in the design,management and operation of transmission lines.