Research On Fault Location Algorithm For Combined Transmission Lines

With the wide application of the combined transmission line composed by cable and overhead line, it’s fault location is a problem that is concerned a lot.Based on comprehensive reading of references about transmission line fault location, the thesis does some research on fault location for combined transmission line. At first the paper introduces the history and the new directions of fault location. Then it has also made the analysis of forming power circuit model and some technique of signal sampling. Finally the paper presents a novel phase comparison method and a new double-terminal fault location algorithm. They are both based on the distributed parameter model.The principle of the phase comparison is:The residual phase voltage at the fault point should have the same phase angle as the current through fault branch due to the pure resistive characteristics of the fault path impedance. By virtue of searching the minimum phase angle difference between the phase voltage along the transmission line and the fault-component current measured at the side equipped with protection, the fault distance can be located.The new two-terminal fault location algorithm based on distribution parameter model of combined transmission lines can discriminate the fault whether happened in overhead lines or power cables. Then the fault location can be determined by using the transmission lines parameter and post-fault voltages and currents from the two terminals. The algorithm does not require the synchronized data of two terminals, and it isn’t affected by fault resistance, fault type and fault location.Besides, the algorithms are based on power-frequency voltages and currents. Therefore, it can be implemented in the existing protection devices easily. The EMTP simulation results have shown the effectiveness of the algorithms.