Single-end traveling wave protection method in flexible DC transmission line based on dominant frequency attenuation characteristics

Abstract

The conventional traveling wave protection (TWP) for flexible DC transmission lines suffer from low-sensitivity problem in far-end high-impedance faults. Also, they are lack of theoretical basis in threshold setting. In this paper, the initial traveling wave is analysed considering the frequency attenuation law and discrepancy between internal and external faults. Then, the frequency domain expressions of the initial traveling wave are analysed deeply. By enhancing the influence of high-frequency components in energy calculation reasonably, the initial traveling wave dominant frequency (ITWDF) is constructed, which can reflect the fault location and the attenuation characteristics of the boundary. The expressions of the ITWDF show that the ITWDF decreases with the increasing fault distance, and the ITWDF is significantly different between the internal faults and the external faults. On this basis, a single-ended TWP method based on the attenuation characteristics of the ITWDF is proposed. The method is immune to the fault impedance, and the expressions of the ITWDF provide a theoretical basis for protection threshold setting as well. The simulation results show that the proposed method can fast and correctly identify line faults, even with 1000 Ω fault impedance. The ITWDF can reflect the fault location effectively, and the threshold setting is simple. Moreover, the proposed method is high-adaptability in different network topologies.