A pilot protection method for direct-drive wind farm transmission lines based on the variance of high-frequency impedance

• Published in: International journal of electrical power & energy systems 2024-01, Vol.155, p.109534, Article 109534
• Main Authors: Ma, Jing, Geng, Ruonan, Liu, Chen, Ma, Ruichen, Xu, Yitong, Wang, Zengping
• Format: Article
• Language: English
• Subjects: Direct-drive wind farm; LCC-HVDC; Pilot protection; Transmission line
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2023.109534

•Pilot protection for wind farm outlet line based on variance of high-frequency impedance.•Can accurately identify internal faults and unaffected by control strategy of wind farm.•Only requires transmission of logic information and has low requirements on communication.•Establishing high-frequency fault supplementary networks of sending-end system.•Deriving matching relationship between high-frequency 1-mode impedances on two line ends. Concerning the difficulty in identifying faults on the transmission line of direct-drive wind farm connected to DC transmission system, a pilot protection method for the wind farm transmission line based on the variance of high-frequency impedance is put forward. First, the topologies of the transmission line farm-side converter and DC-side converter in different conducting states are analyzed, and combining the high-frequency characteristics of different system components, the equivalent high-frequency 1-mode models of the farm-side system and the DC-side system are built. Then, the high-frequency 1-mode fault models of the transmission line under internal faults and external faults are established, and the high-frequency 1-mode impedances on ends of two lines are derived. Finally, a protection criterion is constructed according to the matching relationhip between the high-frequency 1-mode impedances and different fault scenes. Experimental tests are conducted on the RT-LAB platform and verify that the method can accurately identify internal faults from external faults, unaffected by the control strategy of the wind farm.