Improved protection method of HVDC transmission line based on the analysis of traveling wave dispersion

The research on propagation characteristic of fault traveling wave are almost based on uniform lossless transmission line model, without considering the traveling wave dispersion resulted from the frequency dependent characteristic of transmission line, which distorts the wave front and increases the difficulty to detect the wave front. The traveling wave dispersion mainly affects the common mode component of traveling wave, whereas the differential mode component almost has no traveling wave dispersion problem. In order to eliminate the influence of traveling wave dispersion on protection, this paper uses only the differential mode of pole wave as the protection criterion. Based on the PSCAD/EMTDC simulation platform and practical HVDC transmission project, the performance of differential mode component criterion and the currently used DC line protection criterion is compared in this paper, which includes the steepness of wave front, the sensitivity to detect fault and the reliability with long fault location and high fault impedance. It is shown that the differential mode component criterion has better performance than the currently used DC line protection criterion, for the new protection criterion has steeper wave front and is more sensitive to detect the fault. For the same sensitivity requirement, the new protection criterion can act correctly under much higher fault impedance, and remoter fault location, which improves the reliability of protection.