Study on the Performance of Current Differential Protection in UHVDC Hierarchical Connection Mode

Abstract

UHVDC hierarchical connection mode resulting in a very close electrical coupling between the AC and DC hybrid systems, with a very complex fault characteristic. In order to analyze the adaptability of line differential protection in the UHVDC hierarchical access AC grid, a certain ± 800 kV UHVDC hierarchical access project is taken as the research object. The equivalent model of AC system, the characteristics of equivalent power frequency variation and harmonics in equivalent model are analyzed. Then the adaptability of steady-state current differential protection is analyzed. Finally, the analysis results is verified based on PSCAD / EMTDC simulation.