The (n-1) reliability criterion is the mostly widely used adequacy criterion in conventional transmission system planning. The rapid growth of wind power, and the need to deliver this intermittent source of power from a location with rich wind resources to the power grid has created new challenges to determine adequate and economic transmission facility. This paper presents a probabilistic method to illustrate that the (n-1) criterion is not suitable for wind power transmission planning. However, probabilistic techniques that require complex statistical tools and considerable amounts of data are not readily applied in practice. This paper presents a simplified wind speed model that can generate wind speed probability distributions for wind farm sites if their annual mean wind speed and standard deviation values are known. The developed wind speed model can be combined with the wind turbine generator characteristics to obtain a wind farm generation model that can be further modified to incorporate the effect of the transmission line on wind power delivery. The results of adequacy studies on test systems are presented. The presented methods and discussions should be useful to power system planners and policy makers.