Analysis of protection operation for ultra-high voltage multi-terminal hybrid flexible DC transmission projects

As an important safety barrier in EHV multi terminal hybrid flexible DC transmission system, DC overvoltage protection ensures the safe, reliable and stable operation of the whole multi terminal DC transmission project. In this context, ± 800kV kunbei converter station, as the first transmission station of UHV multi terminal hybrid flexible DC transmission project, its operation status directly affects the safety and efficiency of the whole power grid. However, in the actual operation process, the DC overvoltage open circuit protection of the converter station has abnormal action. In this paper, the cause of the abnormal action is systematically explored through fault recording data tracking, protection logic simulation verification, and field test. On this basis, targeted optimization strategies and improvement measures are proposed.