The Research Of Frequency-dependent Impedance In Rail Of Traction Power System

With the rapid development of railway,especially the high-speed railway,railway transportation has become one of the most important ways of travel.As an important part of the electrified railway,traction power supply system provides a continuous power for the whole electrified railway system.In order to ensure the high efficiency and reliability of traction power supply system,the research of the precise fault location system for traction power supply system is of great significance.At present,fault location accuracy is a common problem in the application of traveling wave fault theory in traction power supply system.Because the phenomenon of frequency-dependent impedance usually exists in rails and other transmission lines in traction power system,which resulting in the dispersion generated during the propagation of fault traveling wave,the distorted of wave head and the wave velocity can not be determined,and then affecting the accuracy of traveling wave fault location.In order to improve the accuracy of fault location,the research of the traction network transmission conductor chatter parameters become an important topic.The existing traveling wave fault location principle is analyzed and summarized,the influence of frequency variation parameters of traction network on transmission of traveling wave in traction network and interference on the accuracy of traveling wave fault location is also analyzed.As an important part of traction network,the rail is in electrification,which also transmits abundant traveling wave signals.Two major difficulties in the calculation of the frequency variation of rail and the characteristics of the rail are analyzed firstly in this paper.And then,summarize the feasible methods for calculating the frequency variation parameters of the rail,two kinds of schemes of finite element software modeling simulation and equivalent tubular conductor mathematical model are put forward to calculate the frequency variation parameters of rail.In the method of finite element software simulation to calculate the frequency variable parameter of rail.ANSYS finite element simulation software is used to model the rail with the ratio of 1:1,and the detailed setting method of the simulation steps in the modeling process is given,finally the simulation model of rail frequency parameters is obtained.The equivalent mathematical model of tubular conductor,according to the existing equivalent tubular conductor model is proposed for high frequency traveling wave frequency dependent parameters of simplified calculation mathematical model of tubular conductor,reduces the number of parameters calculation of equivalent tubular conductor model,the method to determine the required parameters and gives the simplified model calculation process.In the mathematical model of equivalent tubular conductor,a simplified mathematical model based on the existing equivalent tubular conductor model for the calculation of the frequency dependent parameters of rail for high frequency traveling wave have been proposed,which reduce the number of equivalent tubular conductor model parameters,and the determination of the parameters required in the calculation process is also given.After that,using these two methods to calculate the P50 rail,the results show that the frequency-dependent impedance of rail parameters is significant,and the fault traveling wave will produce serious dispersion in the process of transmission,which provide the reference value for the follow up study of the dispersion problem within traveling-wave fault location of traction power system.Finally,the paper summarizes the full text,and points out the existing problems and the future research.