Research On Fault Location Algorithm For Hybrid Transmission Line Consisting Of Power Cable And Overhead Line

With the acceleration of urbanization,the scarcity of land resources and the requirement of beautifying the city,the single overhead transmission line for power transmission line has gradually developed to the cable-overhead line.Due to the inconsistent speed of the overhead line and cable and the discontinuity of the wave impedance,the existing fault location algorithm cannot be directly applied to the hybrid transmission line for fault location.The fault distance measurement technology of hybrid transmission lines can reduce the losses and negative effects caused by power outages,increase the success rate of re-closing,and accelerate the restoration of power supply.Therefore,it is of great significance to study the fault location technology of hybrid transmission lines.For high-voltage hybrid transmission lines,the fault segmentation algorithm is used to determine the fault occurrence zone.According to the different segments,corresponding fault location algorithms are proposed to improve the accuracy of fault location.The main work of this article is as follows:Analyze the refraction and reflection of traveling wave on hybrid transmission lines of any structure.The fault occurrence time is deduced according to the fault occurrence section,the time when the traveling wave reaches both ends of the transmission line,and the wave speed of the traveling wave.According to the different segments,corresponding fault location algorithms are proposed to improve the accuracy of fault location.In order to discriminate the fault occurrence section of A-type transmission line and B-type transmission line,three fault section identification methods are proposed:The main idea of first method is to determine the fault occurrence time and the total length of the transmission line based on the assumed fault occurrence section,the time when the fault traveling wave reaches both sides of the transmission line and the traveling wave speed.The total length of the calculated transmission line is equal to the total length of the actual transmission line in the error range,and the fault occurs in the assumed zone.The second method compares the time difference between the initial fault wave arriving at both ends of the transmission line and time difference between cable connection points reaching both ends of the transmission line,and then determines whether the fault occurs on the overhead line segment or the cable segment.The third method uses the time difference between the initial traveling wave reaching the two ends of the transmission line and the time difference between the midpoint of the cable,the midpoint of the overhead line,and the cable connection point to the end of the transmission line to construct the fault segment identification function.The positive and negative relationships determine the fault occurrence section.Aiming at fault location of hybrid transmission lines,two fault location algorithms for transmission lines are proposed:The first solution is to use the single-end traveling wave distance measurement method to calculate the fault distance after the fault section is determined.The second solution proposes an improved fault distance calculation for hybrid transmission lines with irrelevant cable section wave speeds.In this paper,the combination of traveling wave is used to quickly identify the fault section of the hybrid transmission line and accurately fault location.The simulation results show that the fault location method proposed in this paper can reliably locate the fault point of the hybrid transmission line,and has a good prospect of engineering application.