Nowadays, due to global warming and the depletion of petroleum reserves, renewable energies have gained special prominence. At the moment, wind energy is the most successful renewable energy resource, and the technology to convert this wind energy into electricity has been very developed. As a consequence, the costs per kWh of generation have decreased and it has become a competitive alternative for conventional fossil-fuel power plants to generate electricity. However, a lot of factors and variables are involved in wind power generation. In the rst part of this document, some of this factors like the Betz limit, the classi cation of wind turbines and its components, and the power curve of a wind turbine are explained. In the second part, the performance of a real wind farm is studied. The wind farm is called Es Mil a, and it is located in an island called Minorca, in Spain. Firstly, a description of this wind farm and the energy and electricity in Minorca is made. Then, with meteorological and power data of 2007 a thorough study of its performance is completed. In this study, rst of all some meteorological aspects like wind direction, wind velocity and its distribution are discussed. After that, the study focuses on electricity production, looking at the power curve, at the expected and the real production, and trying to explain a little of the reactive power.