Backup-Protection Scheme for Multi-Terminal HVDC System Based on Wavelet-Packet-Energy Entropy

DC fault protection is a major issue in multiterminal high-voltage DC current transmission systems. Most studies have focused on primary protection, which considers a different theory. However, the poor sensitivity of primary protection under high-resistance fault and maloperation still affect the protection feasibility to a certain extent. Thus, backup protection is definitely required to enhance the stability of an entire system considering the limit in primary protection. This paper proposes a backup-protection strategy based on wavelet-packet-energy entropy as mitigation for primary protection. The pole-to-ground (PG) fault with high resistance is highlighted because detecting the fault transient of PG fault with high resistance is difficult in the most primary relay. Fault detection and classification are achieved using the proposed backup-protection method based on theoretical study and simulation verification. The proposed method also presents the expected robustness of fault resistance, fault distance, and different operating conditions.