Traditional primary transformer protection and outgoing line protection of wind farm taken more consideration of system perspective, the selectivity and sensitivity of protection operation maybe not reliable. Then, the adaptability of transformer and outgoing line protection needs to be studied further, especially for the collection station which is a cluster of wind power connected to grid. For this reason, based on Xinjiang actual grid structure, and considering characteristics of fault current and voltage of double-fed wind farm, this paper analyzes theoretically the impact of fault current frequency offset for differential protection, simulates the impact of phase differential and sampled value differential protection for transformer and types of protection for outgoing line, under the cluster of double-fed wind farm connected to grid. Finally, it proposes the measures for collection station transformer and its outgoing line protection, which provides a reference for solving practical problems faced by the current grid.