Travelling Wave Based Pilot Directional Protection for HVDC Line

In order to improve the performance of conventional traveling wave protection used in high voltage direct current(HVDC) lines,a novel traveling wave based pilot directional protection is proposed based on the fact that amplitude of the backward traveling wave is greater than that of the forward traveling wave on both ends of line under internal zone fault.If the two relays at both ends of HVDC line detect a forward direction fault,then control action is to retard the rectifier firing control into full inverter operation mode.RTDS simulation results show that the proposed scheme can discriminate internal and external zone faults rapidly and reliably.It has some advantages such as: easy setting,specific protective zone and high resistance grounding fault recognition.The protection scheme is feasible as a complement of conventional main protection of HVDC line.