“…This keyword also has the highest centrality, a measurement index which reflects a node's importance by calculating its number of shortest paths in a knowledge mapping to which a given node belongs (Chen, 2006;Li, Porter, & Wang, 2017). In those articles which related to "Offshore wind farm", a review given by Franck (Franck, 2011) is mostly cited (296 times till 2018), mentioned that the remote renewable energy like offshore wind power had brought HVDC (high-voltage direct current) multi-terminal systems, which had been once a research hotspot in 1980s (Billon, Taisne, Arcidiacono, & Mazzoldi, 1989;Morin, Bui, Casoria, & Reeve, 1993), to the technology of interest again, and regarded the HVDC circuit breakers as the essential determinant to a dc power grid system by ensuring its efficiency, reliability, and controllability (Bergstrom, Juhlin, Liss, & Svensson, 1978;Greenwood, Kanngiessner, Lesclae, Margaard, & Schultz, 1995, 1996Kanngiesser, Ring, & Wess, 1991). The following article (Yang, Fletcher, & O'Reilly, 2012), also stated that VSC-HVDC (voltage-source converter-HVDC) had been typically embodied in OWP, and has proposed a fault location method to identify and define the major faults of VSC-HVDC, where the ground resistance and the distance to the fault location is the key to this method.…”