A travelling wave protection scheme for bipolar HVDC line

The detection and fast clearance of faults in the HVDC lines are important. A traveling wave protection scheme for a bi-polar HVDC line is proposed in this paper. The identification of internal and external faults is based on the magnitude comparison criteria of the backward and forward travelling waves detected at the relay location. The modal analysis method is adopted to transform pole quantities to two independent modal components, including one earth mode and one aerial mode, to remove the mutual coupling effect between pole lines. The polarity of earth and aerial component of backward travelling wave is used to determine the faulty pole. Extensive simulation studies using RTDS indicate that the proposed scheme is reliable for rapid and correct identification of various fault cases.