Simulation models of double-fed induction generator and permanent magnet direct driven wind generator are built based on PSCAD/EMTDC software. The fault characteristics of wind generation system are studied, and the performances of relays in power systems with wind farm integration are analyzed. It can be concluded that the fault currents fed by wind generation are limited comparing with conventional synchronous generators. And the positive and negative sequence impedance of wind farm is not equal which is different from conventional power transmission system. Some widely used protection principles are studied and it is found that the distance relay and fault phase selector will be influenced by wind farm integration. Finally, some field fault data from recorder are used to verify the studies and analysis. The results show that the study and analysis conducted will be useful for the protection system setting and operation in power system with wind farm integration.