Transient pilot protection based on directional traveling wave principle for wind power transmission line

The short-circuit current from the new energy power generator presents special characteristics such as frequency shift, restricted amplitude, unequal positive and negative sequence impedance, high percentage of harmonic content, etc., resulting in the risk of misoperation or rejection of conventional protection. By analyzing the propagation characteristics of traveling wave in the transmission line after the fault, this paper reveals difference between traveling wave waveforms at both ends of the line under internal fault and external fault. The similarity between forward traveling wave and reverse traveling wave at both ends of line is higher when an external fault occurs, while the similarity between the forward traveling wave and reverse traveling wave is lower after internal fault. According to this difference, a pilot protection algorithm based on discrete Frechet distance is proposed, which can calculate similarity coefficient of forward traveling wave and reverse traveling wave at both ends of line to construct protection criteria, and then identify internal and external fault. Through the analysis of PSCAD/EMTDC and experiment platform of hardware-in-the-loop test verify that the proposed protection algorithm can accurately and reliably distinguish internal and external fault.