Timely damage diagnosis of wind turbine rolling elements is a keystone for improving
availability and eventually diminishing the cost of wind energy: from this point of view, it is a
priority to integrate high-level practices into the real-world operation and maintenance of wind
farms. On this basis, the present study is devoted to the formulation of reliable methodologies for the
supervision of wind turbine bearings, which possibly can be integrated in the industrial practice. For
this reason, this study is a collaboration between a company (ENGIE Italia), the University of Perugia
and the Politecnico di Torino. The analysis is based on the exploitation of the data types which are
available to wind farm managers from industrial control systems: SCADA (Supervisory Control
And Data Acquisition) and TCM (Turbine Condition Monitoring). Due to the intrinsic sampling
time difference between SCADA and TCM data (a few minutes the former, up to the millisecond for
the latter), the proposed methodology is designed as multi-scale. At first, historical SCADA data
are processed and the behavior of the oil filter pressure is analyzed for all the wind turbines in the
farm: this provides preliminary advice for identifying presumably healthy wind turbines from those
suspected of damage. A second step for the SCADA analysis is then represented by the study of the
temperature trends of the bearings through a Support Vector Regression: the incoming damage is
individuated from the analysis of the mismatch between measurements and estimates provided by
the normal behavior model. Finally, the healthy units are selected as the reference and the faulty as
the target for the analysis of TCM vibration data in the time domain: statistical features are computed
on independent chunks of the signals and, using a Novelty Index, it was possible to distinguish the
damaged wind turbines with respect to the reference ones. In light of the interest in application of
the proposed methodology, good practice criteria in selecting and managing the data are discussed
as well