Gearboxes in wind turbines (WTs) are located in nacelle between rotor and generator. It is a heavy part of gondola; the mass is up to 60,000 kg or 60 tons. Bearings are used in various places of the nacelle: rotor shaft, gearbox, generator, yaw gearbox, yaw slewing table, blade pitch revolving seat, and hydraulic pump. Contaminants in gearbox oil may be generated internally. These particles are usually wear debris from gears, bearings, splines, or other components resulting from micropitting, macropitting, adhesion, abrasion, or fretting corrosion wear modes. WTs in desert environments are exposed to airborne dust during the hot season and moisture during the rainy season. Solid particle contaminants vary in hardness, friability, and ductility, depending on the composition of the particle. Small amounts of water are usually found in lubricating oils. Offshore turbines are constantly exposed to moisture, which may penetrate into gearboxes.