Abstract :Wind turbines are generally used in a more severe environment and therefore have relatively higher failure rates than those used in conventional electric power plants such as gas, steam, and hydro turbines. Consequently, the statistics of the failures likely to ester the wind turbines should be studied by taking into account two criteria, their frequencies and their downtimes caused, in order to deduce the failures to take priority into account in a context of predictive maintenance. However, access to these statistics is not always authorized by the manufacturer and it is completely understandable.The Wind turbines experience mechanical vibrations and electrical fluctuations that are not completely damped. The speed of the air flow around the wind turbine causes the minimization of the reliability of the various mechanical parts. The main failure modes in the different mechanical parts, for example the bearing, the speed-increasing electric motor, the blade, etc.Among the big problems in wind power systems are faults in the bearings. A bearing is a mechanical element which is interposed between two parts of a machine, one of which is rotating, and the other is fixed.The various defects that can be seen on the bearings are manifested by the appearance of periodic shocks at specific frequencies. To make an effective prognosis from a certain spectrum, it is therefore possible to use a certain number of characteristic frequencies or fault frequencies.Localized faults in a rolling element bearing may occur in the outer race, the inner race, the cage, or a rolling element. High frequency resonances between the bearing and the response transducer are excited when the rolling elements strike a local fault on the outer or inner race, or a fault on a rolling element strikes the outer or inner race. Keywords : Wind system, Wind speed, Faults in the bearings, Frequency, Vibration method
