Abstract: In view of a false tripping event of the outgoing line switch in a wind farm, the cause analysis is carried out based on its protection action sequence and action conditions during the tripping period, and it is found that the event is caused by the improper setting of the small current grounding line selection device, and according to the actual situation of the line operation and maintenance, the treatment measures are proposed so as to offer reference for the small current grounding line selection device in its operation and maintenance.