An enhanced distance protection algorithm based on characteristics-travelling waves measured from the current for HVDC Lines

It is a vital challenge to perfectly and reliably position high impedance faults and remote end faults in high-voltage direct current (HVDC) transmission lines. Also, distance protection systems are very vulnerable to maloperation under power swing situations and noise interference. These challenges are essential for system stability. This paper succeeded in these challenges with high accuracy, reliability, and stability and without delay in protection startup for single pole-to-ground faults and pole-to-pole faults during ultra-high-speed. The paper presents new employment for the 2nd order of the sequential overlapping difference (SOD) tool to capture transient component characteristics of both terminals of the DC-TL, calculate the fault distance, and identify the faulted pole. Also, it presents novel employment of external disturbances to estimate the fault location. This employment protects the proposed technique from the errors resulting from the mistakes in knowing the transmission line parameters data. The paper studies a bipolar-HVDC-TL system established in (ATP/EMTP). Besides, the proposed algorithm is valid for both single-pole and two-pole operation modes. Also, it suggested an amplification process to magnify the stability margin between normal and abnormal operations. And, it verifies the decision by employing more than information. In addition, the distributed capacitance does not affect it.