A Novel Fault-location Method for HVDC Transmission Lines Based on the Ratio of Two-terminal Traveling Wave Frequency Difference

High voltage direct current (HVDC) overhead transmission lines have the characteristics of long length, high failure rate, large corona loss, and serious disturbance caused by lightning and harmonic waves; and the true value of line length also varies. As a result, it is more difficult to perform accurate fault locating. The study indicates that both the equal interval frequency difference of the natural frequency spectrum of the fault traveling wave and the free oscillation components have the exact mathematical expression related to the fault distance. And the frequency difference is not affected by the boundary conditions of DC transmission or the inconsistent wave velocity at different sub-frequency. A fault location approach for HVDC transmission lines based on the frequency difference ratio of the two-terminal traveling wave was proposed. The fault locating equation has eliminated the influence of traveling wave velocity’s attenuation, and is independent of two-terminal clock synchronization. The proposed method made a breakthrough in identifying the traveling waves’ wavefront in time domain and precisely calibrating the arrival time of traveling waves. The reliability and accuracy are not affected by traveling wave dispersion, lightning corona, harmonic interference, line length variation or other factors. Massive digital simulation and field data record test show that the proposed method is precise and robust, which is not affected by physical boundary components of the line, and has good tolerance to high impedance faults. © 2022 Chin. Soc. for Elec. Eng.