Field measurements for wind turbine main bearings
Measurements have been done on a significant set of wind turbines in the field. Observations of electrical stray current in wind turbine main bearings seem to correlate with bearing failures.
When troubleshooting problems with main bearings, mechanical conditions such as excessive motions are often proposed as root causes. This study looks at field measurements on wind turbines identified with such problems. Evidence of excessive motions was typically not found. However, stray current was frequently observed through the main bearings.
The measurements indicate that electric pitching installations may sometimes induce current through main bearings and gearboxes. Other sources of stray current are also indicated by the measurements. It is well known from other industrial sectors that stray current through bearings reduces bearing life significantly. This presentation hypothesizes that stray current is a source of main bearing damage in some wind turbines.