Single Ring Theorem Based Pilot Protection Method for HVDC Transmission Lines

For the high impedance faults caused operation failure in the high voltage direct current (HVDC) transmission lines, this paper proposes a pilot protection scheme for HVDC transmission lines based on the single ring theorem. Firstly, the singular value equivalent matrix is formed consisting of the fault components of the current at both ends of the line, with which the internal and external faults can be distinguished. Then, the faulted end of a line can be determined by the ratio difference obtained from the sum of the transient energies in the specific frequency bands of the fault components of the current at both ends of the line through the generalized S transform. Finally, a pilot protection scheme is given. Simulation results in a HVDC system show that the proposed protection acts accurately for fault judgement with high transition resistance, which can effectively work in a variety of operating modes of the bipolar HVDC system and various fault conditions. © 2021, Power System Technology Press. All right reserved.