Nowadays, the global warming issue necessitates to think about alternative resources for supplying electric power. Fossil fuels have been burnt in the power plants for many years and this is the predominant approach for generating electricity. Due to the environmental considerations, exploitation of renewable energy sources is enhanced in recent years. Utilization of wind energy is in the vanguard of development in comparing with other renewable energy sources. Intermittent behavior of wind speed cause to variability of output power in the wind farms and due to this fact, wind farms affects many aspects of power systems. High penalty cost of outages and power markets enhance the role of reliability studies. reliability indices scrutinize the risk level of power systems. Adequacy indices describe the ability of power system to prepare an adequate supply for the demand. Large and small wind farms are integrated to power systems and this issue motivates conducting research about the effects of wind farms on adequacy indices of power system. Many methods have been proposed to model the wind farms from reliability point of view. Primary part of these method is the wind speed modeling. In this thesis, wind farm is modeled with Markovian approach. Considering the probability of transition between output power states is the cornerstone of this method. Probability distribution function based method neglect this characteristic of wind speed. Hourly average of wind speed data, for Khaf, Ahar, Aphriz, Fadashk, are used for modeling and the effect of wind resource selection on adequacy indices is studied. Wind farm is a part of generation system so the modeled wind farms is added to RBTS. Wind turbines constituting the wind farms affects the output power so the effect of wind turbine selection is also considered in this study. Wind farms improve the adequacy indices to a certain point. This fact necessitate to propose the critical capacity concept for the wind farms. An algorithm is also proposed to determine the appropriate rated power of wind farms for a certain wind site based on this concept. Five year scenarios are performed to scrutinize the effect of wind farm expansion on adequacy indices and this effect is compared with the effect of thermal power plant as an ordinary power stations on the adequacy indices. Keywords: Renewable energy sources, wind farm, reliability of power system, adequacy assessment
