Automatic mechanical fault assessment of small wind energy systems in microgrids using electric signature analysis

A microgrid is a cluster of power generation, consumption and storage systems capable of operating either independently or as part of a macrogrid. The mechanical condition of the power production units, such as the small wind turbines, is considered of crucial importance especially in the case of islanded operation. In this paper, the fault assessment is achieved efficiently and consistently via electric signature analysis (ESA). In ESA the fault related frequency components are manifested as sidebands of the existing current and voltage time harmonics. The energy content between the fundamental, 5th and 7th harmonics (referred as residual value - RV) is measured and sent to the central microgrid controller. The controller compares RV to three predefined limits where inspection, maintenance and shut down of the turbine are the corresponding actions. The method is tested based on a finite element model where dynamic eccentricity and bearing outer race defect are simulated under varying fault severity and electric loading conditions.