S-Transform Based Traveling Wave Directional Pilot Protection for Hybrid LCC-MMC-HVDC Transmission Line

In this paper, the traveling wave protection issue of a hybrid high-voltage direct-current transmission line based on line-commutated converter and modular multilevel is investigated. Generally, voltage variation criterion, rate criterion current applied lines as primary protection. There are two issues that should be addressed: (i) it has no fault direction identification capability which may cause wrong operation regarding external faults; (ii) does not consider difference between rectifier station topology inverter topology. Therefore, novel directional pilot principle for proposed S-transform. Firstly, data processing S-transform described. Secondly, typical propagation process studied. Thirdly, proposed. Eventually, PSCAD/EMTDC, ±400 kV system used case study to verify its robustness against location, resistance type.