Adaptability Analysis of Travelling Wave Protection for Hybrid LCC-MMC HVDC Transmission Lines

To investigate the adaptability of existing traveling wave protection in the Baihetan-Jiangsu Ultra High Voltage Hybrid DC Transmission System, theoretical analysis of the propagation characteristics of fault traveling waves at both ends of the DC line during line faults was performed. It was found that there are differences in boundary propagation characteristics after external faults in the forward zone compared to traditional DC systems. Further analysis of the traveling wave protection criteria revealed that the reflection coefficient on the rectification side and the refraction coefficient on the inverter side have an impact on the protection criteria. In comparison to traditional DC systems, the Baijiang project exhibits larger voltage changes during external faults in the forward zone, making traveling wave protection more susceptible to maloperation. Finally, a simulation model was constructed using PSCAD to validate the theoretical analysis.