Novel Traveling Wave Protection Method for High Voltage DC Transmission Line

The traveling wave protection performance of traditional DC transmission line can be influenced by fault conditions, so this paper proposes a traveling wave based directional pilot protection method. Analysis shows, for an internal DC line fault, that the forward traveling wave is less than the backward traveling wave at two ends of the proposed line within a short time of post-fault; but in the case of an external fault, the forward traveling wave is greater than the backward one at one end of the line while the forward traveling wave is less than the backward one at the opposite end. According to this characteristic difference, an integral criterion identifying fault direction is constructed here. By comparing the identification results of fault direction at both ends of the line, the internal fault can be distinguished from the external fault. For bipolar HVDC system, the faulted line can be determined according to the polarity difference between the aerial mode component and the zero mode component of the backward traveling wave. This paper builds a UHVDC line model, and the simulation results verify the validity of the proposed method.