905 / 2019-04-30 15:45:03

AC protection in the context of AC/DC hybrid lines

AC/DC hybrid line, AC/DC protection coordination, electromagnetic coupling, intersystem faults, VSC-HVDC

AC/DC hybrid lines are transmission systems with AC and DC systems on the same support structure. The added DC system has a significant influence on the parallel AC systems, and especially on the AC protection. Studies of this aspect are not found in the literature. Therefore, all relevant fault types are examined and an overview of the influencing factors on the protection of the parallel AC lines is given. The analysis of pure DC faults shows that an unwanted trip of the earth fault detection can occur due to the electromagnetic coupling. On the other hand, the difficulties of the AC protection in detecting certain intersystem faults are presented. Finally, current issues and challenges on the way to safe operation of AC/DC hybrid lines are outlined.