Research On Distributed Traveling Wave Fault Location Algorithm For Transmission Lines

With the rapid expansion of power grid scale and higher requirements of power users for power supply reliability,transmission lines,as an important component of the power system,play a key role in energy transmission.The traditional transmission line traveling wave location method uses the single-end method or double-end method to calculate the distance from the fault point to the substation.For a single transmission line,there is still a large ranging error.As the transmission line gradually develops from a single transmission line to an overhead line-cable hybrid line,a more complex traveling wave refraction phenomenon will appear at the cable connection point,making it difficult to accurately identify wavehead information or even cause traveling wave ranging failure.To address the shortcomings of the traditional ranging methods,this paper proposes a transmission line fault location algorithm that is independent of wave speed by installing a distributed traveling wave detection device on the line,determining the interval location of the fault point,and calculating the accurate wave speed of the fault traveling wave in each zone online.The main work of this paper is as follows:(1)The basic principle of single and double-ended traveling wave ranging based on substations on both sides of the line is introduced.For the problems of traditional traveling wave ranging methods,such as the inability to identify the source of waveheads and the attenuation of wave speed during the propagation of traveling wave distance,distributed traveling wave detection devices are used,and then the number and location of distributed traveling wave detection devices are determined.(2)For the problem of interval identification after the line is divided into multiple intervals by the traveling wave detection device,the Pearson correlation coefficient is applied to the fault location and used as the basis for fault interval discrimination.Because the cable and the overhead line in their respective structures,characteristics are very different that the mixed transmission lines in their wave impedance discontinuity,wave speed is not equal,so on the basis of Pearson correlation coefficient to identify the fault interval,summarize the traveling wave in the mixed line propagation polarity change law,and then through the combination of the two to accurately identify the fault interval.(3)The accurate measurement of traveling wave speed is one of the important factors affecting the accuracy of traveling wave fault location.To address the problem that the traveling wave velocity affects the ranging accuracy,a new formula for transmission line fault location,which is not affected by wave velocity,is derived by using distributed structure combined with known line length for online wave velocity calculation,thus improving the accuracy of transmission line fault location.(4)The PSCAD/EMTDC software is used to build an AC transmission line model and perform fault simulation on its transient process;meanwhile,the unique advantages of singular value decomposition(SVD)in line wave singularity detection are analyzed with the help of MATLAB platform,and the simulation data are processed.The single-variable method is used to analyze the influence on the traveling wave ranging accuracy by setting different fault types,fault locations,ground resistance and other factors,and to analyze the applicability and universality of the proposed method.The simulation results show that the proposed method can effectively determine the fault section,perform online traveling wave velocity calculation,and reduce the fault traveling wave ranging error.Finally,we summarize the work done for fault ranging on highvoltage transmission lines and provide an outlook on the application of the method to actual transmission lines.