The Research Of Traveling Wave Fault Location Method For Overhead Line-Cable Hybrid Transmission Lines

With the continuous transformation and upgrading of the power grid, there are more and more overhead line-cable hybrid transmission lines. For hybrid transmission lines, due to the complex reflection phenomenon at the connection point of the traveling wave, and the different traveling wave propagation speed in two lines of overhead line and cable,these factors have caused that traveling wave fault location method suitable for uniform transmission line is difficult to be applied in hybrid line fault location.At present, for high voltage hybrid transmission lines, the two terminal fault location method is widely used in the field. The fault section is selected first, and then the distance measurement results are given by the two methods. Its disadvantage is that the accuracy of the measurement is affected by the given length error of the line and the error of the synchronous clock. According to the high voltage hybrid transmission lines with different structure, a corresponding combined traveling wave ranging method is proposed in this paper, and the ranging result is given by the single end principle, as well as the ranging accuracy is high. The main work of this paper is as follows:(1) The characteristics of reflection of the fault traveling wave in A type hybrid transmission line and B type hybrid transmission line were analyzed in this paper, and the changes of amplitude and polarity of traveling wave were derived when it transmitted from the cable line through the connecting point between cable and overhead line to the side of the overhead line and from the overhead line through the connecting point between cable and overhead line to the side of the cable line. On the basis of the analysis, the characteristics of the reflection of the traveling wave were analyzed.(2) For hybrid transmission lines with arbitrary structure, a combined traveling wave fault location method of hybrid transmission line based on multi-terminal information was presented in this paper. First of all, using the initial traveling wave arrival time difference measured on both sides of the hybrid line to determine that the fault occurred in the overhead line segment or cable segment, and the fault information collected by the measurement equipment on both sides of the fault section was used to carry out the preliminary fault location, by which the result of single ended ranging was selected.(3) For A type hybrid transmission line and B type hybrid transmission line, a combined traveling wave fault location method of hybrid transmission line based on two terminal information was presented in this paper. Firstly, using the initial fault traveling wave arrival time errors on both sides of the line to determine the fault zone, and thengiving accurate distance measuring results by a single-ended method.(4) The simulation model of the A type hybrid transmission line and B type hybrid transmission line was established by PSCAD respectively. Simulating separately the ground fault occurred in different position to obtain the fault information which was processed by MATLAB software programming, and Simulating hybrid line combined traveling wave fault location method which was presented in this paper.The proposed combination of traveling wave fault location method can give accurate fault location results by single terminal fault location method, and have a high accuracy of ranging. After the fault occurs in the hybrid lines, it can reliably locate the fault point, and has a good engineering application prospect.