Study Of Fault Location Algorithm For Hybrid Transmission Line Composed By High Voltage Cable And Overhead Line

Being the frequent fault area, transmission lines which have long distance always crossmountains. When fault occurred in transmission lines, it is hard to locate the fault area. It isimportant to protect transmission lines, in order to ensure power system safety and steadily.Nowadays, with the hybrid transmission lines which composed by high voltage cablesand overhead lines have been widely used, an increasing number of researchers pay closeattention to fault location for hybrid transmission lines. But inconsistent traveling velocity andno-matching impedance exists in hybrid transmission lines caused hard to distinguish thetraveling wave. For these problems, the fault location algorithm based on variable of time hasbeen used in this thesis.Compared current transformer to voltage transformer, it can be found that currenttransformer has wildly cut-off frequency band, which can be used in transient signalextraction. After frequency dependence of impedance analysis, it has been shown clearly thatpositive sequence impedance change more slowly than zero sequence impedance; therefore,line model component with stable parameters can be adopted as measurement signal.Wavelet transform has ability to analyze the fault transient information in time-frequencydomain. Cubic b-spline has been used in fault signal decomposition which can make balancebetween signal de-noising and singularity detection.Through the ATP-draw simulation and data processing by Matlab, several simulationshave been done, and the results show that the algorithm is accurate and feasible.