A pilot protection based on Zero-Sequence voltage ratio for AC lines in hybrid Multi-Terminal HVDC transmission system

•A fault analysis model for the AC faults occurring at the receiving terminal of hybrid multi-terminal high-voltage direct-current (HVDC) transmission system is established.•Based on the fault analysis model, a novel protection based on zero-sequence voltage ratio for AC lines in hybrid multi-terminal HVDC transmission system is proposed.•A test model of hybrid multi-terminal HVDC transmission system is constructed in PSCAD, and the effectiveness of the proposed protection is verified by extensive simulations.•The proposed protection can correctly identify internal and external faults. Meanwhile, it is immune to commutation failure, and has a good tolerance to high-resistance faults. And it has no requirement for two-terminal data synchronization.