Research Of Fast Calculation Method Of Lightning Overvoltage In Transmission Lines Considering The Frequency-dependent Parameters

The transmission line is the main artery of the power system.It carries the important task of sending electricity in all directions.It is the link between every substation and every important user.With the increase of transmission voltage level and the height of transmission poles and towers,the lightning over voltage generated by lightning strike transmission lines is more and more harmful to the safe and reliable operation of power system.Therefore,the establishment of reasonable and accurate transmission line model and the efficient and convenient calculation of lightning over voltage are of great academic significance and practical application value for lightning protection design,engineering analysis and maintenance of power grid safe operation.In order to calculate the lightning over voltage of transmission line,the models of transmission line pole,tower,ground body and overhead transmission line are established.The model of lossless multi-surge impedance is used to simulate the pole tower,which has a clear formula and is easy to be applied.Taking into account the problem of circuit passivity,a four-port equivalent circuit for grounding body is established based on the Multiport Brune method.The results show that the transmission line has obvious frequency characteristics and fractional order characteristics due to the skin effect of wire and soil loss.In this paper,a fractional order model of transmission lines considering frequency variation parameters is established.This paper presents a new method to solve fractional calculus equation based on recursive convolution,which can simplify the calculation.In this paper,the formula of solving fractional calculus quickly based on recursive convolution method is deduced in detail,and compared with traditional numerical algorithm,the efficiency of recursive convolution algorithm is expounded and the example is proved.At the end of this paper,the accuracy and validity of the model and the proposed algorithm are verified by an experimental example compared with the results of ATP-EMTP simulation.