| Lightning strikes are one of the important causes of overhead transmission line failures.The development of lightning protection of transmission lines depends on a sound lightning risk assessment system.At present,the main indicator for evaluating the lightning damage risk of transmission lines is the lightning trip rate.Therefore,accurate calculation of the lightning trip rate is of great significance for the safe and stable operation of transmission lines.At the same time,it is very important to conduct lightning protection research for specific transmission lines and propose scientific lightning protection measures.This paper has first discussed the principles of lightning strike discharge and overvoltage.Then it has introduced several methods for the calculation of transmission line shielding strikes: the regulation method,the electrical geometric model method,the shielding strike probability model method,and discusses the influence of complex terrain and complex tower structures on the calculation of the electrical geometric model method,using the exposure distance method and The exposure projection method has been used to calculate the tripping rate of the shielding strike,and the electrical geometric model method has been improved by considering the strike distance formula,the strike distance coefficient and the distribution of the incident angle.The trip rate has been calculated and compared.Then,several methods for calculating the counterattack of the transmission line have been studied: the regulation method,the Monte Carlo method,the fault tree method,the EMTP method,and the lightning current waveform and the lightning channel wave impedance,the transmission line model,the pole and tower,which are mainly considered in the calculation method of the EMTP counterattack,have been discussed.Model,insulator flashover model,grounding resistance model,induced voltage calculation of these six calculation models,using the regulation method and the EMTP method to calculate the counterattack of the 110 k V tower.Finally,for a 220 k V transmission line in our country,a comprehensive assessment of its lightning flashover risk has been carried out,and the overall lightning protection level of the line has been evaluated.The circuit’s shielding and counterattack reconstruction scheme is put forward.The research content of this paper can provide a corresponding basis for the accurate calculation of the lightning strike trip rate,and is of great significance to the evaluation of the lightning protection performance of the transmission line and the proposal of the lightning protection transformation scheme of the line. |
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