LAUSR

This article proposes a new backup protection algorithm for bipolar high voltage alternative current (HVdc) lines using two-end synchronized sampled currents. Unlike traditional differential protection, the proposed algorithm can be applied to detect and recognize the faulted poles directly without the requirements for long time delay. The currents at both line ends are sampled at 1 kHz and the noise in the current signals is removed utilizing the stationary wavelet transform. To activate the proposed backup protection algorithm, initialization unit is proposed. In addition, the internal faults can be discriminated from external faults and the faulted poles can be recognized using adaptive signed correlation indices. Comprehensive studies are simulated on PSCAD/EMTDC software considering several cases for external and internal faults. In addition, the frequency dependent phase model is employed to simulate the HVdc transmission line. The simulation results assure the satisfactory performance of the proposed backup protection algorithm for several fault locations, all fault types, and several fault resistances up to 1000 Ω.