Study on Protection Strategy for Monopole Grounding in Offshore Wind DC Grid Based on Zero-Mode Component Correlation

With the rise of deep-sea wind power, interest in all-DC wind farms is growing, but protection methods are under-researched. This paper analyzes fault characteristics of all-DC deep-sea wind power networks during single-pole grounding faults using modal decomposition. It derives analytical expressions for current and voltage, showing mainly capacitive relationships. A floating characteristic starting criterion based on voltage rate of change and voltage difference rate of change is proposed, along with a single-ended protection line selection algorithm using the Pearson correlation coefficient. A pole selection method is also introduced. A PSCAD/EMTDC simulation model verifies the proposed protection algorithm, showing good speed, selectivity, and strong tolerance to transition resistance.