| With the increasing scale of power grid construction,the transmission line span and voltage level are also increased correspondingly.The risk of lightning strikes on transmission lines is increasing.The economic losses and security risks of regional power grid caused by lightning disasters are more serious.However,passive lightning protection has some shortcomings,such as weak pertinence and high investment cost.Therefore,it is very important to carry out active lightning protection.To study the lightning trip characteristics of transmission lines in regional power grid,accurately evaluate the lightning risk level of transmission lines and realize the pre-warning of lightning trip,it has become an urgent problem to reduce the losses caused by lightning accidents and lightning protection costs of transmission lines.In this paper,the characteristics of lightning tripping and active lightning protection of a power grid in Guangdong Province are studied in depth.A real-time lightning risk assessment and lightning trip warning model for transmission lines are established.The main contents are as follows:(1)The direct lightning overvoltage and induced lightning overvoltage in the process of lightning trip-out of transmission lines are analyzed theoretically.The lightning strike tower,the lightning strike lightning shield line and the lightning strike conductor in direct lightning overvoltage,as well as the generation process and characteristics of electrostatic and electromagnetic components of induced lightning overvoltage are described in detail from two overvoltages.The statistical analysis method is used to describe the regional distribution characteristics,time distribution characteristics,related features of lightning activity and related features of line ontology factors in the fault characteristics of lightning strikes.(2)Based on the mechanism of lightning strike fault,a real-time risk assessment model for transmission line lightning strike is proposed in this paper.Firstly,the probability distribution of extreme lightning current amplitude is fitted by screening and statistics of historical lightning monitoring data.Then,the lightning resistance level of tower is calculated by the regulation method.Through real-time collected lightning data,the calculation model of lightning flashover probability based on GEV distribution is established.The real-time risk assessment of lightning strike from tower to line is realized by combining the calculation model of shielding flashover probability established by improved electrical geometry model and the method of line lightning risk classification.The validity of the model is verified by a practical example.(3)Based on the characteristics of lightning trip faults,the main characteristic quantities affecting transmission line trip are extracted,and a lightning trip prediction model based on GA-BP neural network is established for the line spacing section.The real-time trip prediction is made for all the spacing sections of the line to be warned,and the total trip times of the line are accumulated.The corresponding trip threshold is used to divide the warning level,and the lightning trip warning from the spacing section to the entire transmission line is realized.The validity of the model is verified by the analysis of the actual transmission line warning situation. |
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