A survey on relay protection for grid-connected wind farm at home and abroad is given. The fault characteristics and short-circuit currents characteristics of various types of wind turbine and wind farm as well as the factors impacting short-circuit current of wind farm are analyzed; the influence of wind farm integration on outgoing transformer and outgoing transmission line and the power distribution network protection is discussed; based on the performance of relay protection of wind power access system, the problems of relay protection non coordination in wind power system and the corresponding solutions are summarized. It is suggested that the researches in four aspects, such as solution to the low voltage ride through capability of relay protection and matching problems, strengthening the fault characteristics of wind power generation sets, paying attention to the coordination of the automatic control system of the wind farm and power network relay protection and safety automatic device, studying the coordination and cooperation of the protection of wind farm, to comprehensively solve the problem in the face of relay protection. This work is supported by National Natural Science Foundation of China (No. 51267019 and No. 51467019).