This paper considers the problem of grid integration of wind power. The integration level, i.e., the amount of wind power that can be connected to a given point of the grid while complying with certain interconnection requirements is determined for 6 different cases of induction generator based wind turbines, both with fixed and variable speed. Acceptable terminal voltage variation, power transfer margin, and acceptable range for the internal voltage angle are taken as criteria for the analysis of the attainable integration level, which is provided in terms of the point-of-common-connection parameters, namely the shortcircuit power and the X/R ratio. Results show the profile of the limits imposed by each individual criterion on the wind power integration level, as a function of the X/R ratio. The set of integration levels satisfying all criteria simultaneously is characterized as a safe integration region. The 6 cases considered are compared regarding the attainable integration level.