Abstract: Considering the low voltage ride through（LVRT）requirement and weak-infeed feature of wind farms,the fault characteristics of a centralized wind farm is analyzed firstly based on doubly-fed wind power generation system.Since the Crowbar protection contributes to the positive and negative sequence impedances,especially the former,the wind farm weakinfeed characteristics are strengthened.On that basis,the performance of distance protection of wind farm grid connection line is analysed.The results show that the Crowbar and weak-infeed property of wind farm may cause wrong phase selection and affect the precision of impedance protection relay.Some countermeasures are also proposed.Finally,a doubly-fed wind farm is simulated,and the simulation results demonstrate the validity of the theoretical analysis.