Models of Wind-Turbine Main Shaft Bearings for the Development of Specific Lightning Protection Systems

One of the main cause of damages for wind turbine power plants is certainly constituted by lightning. Direct and indirect events can indeed produce damages and malfunctions of electrical and mechanical components. Concerning mechanical components, blades and bearings are the most involved parts. In particular, lightning-damages produced at bearings positioned at the mechanical interface between rotating parts of the wind turbine, can result in high costs, considering the difficulties involved in the replacement of such components. The paper presents a numerical and an analytical model of wind turbine main shaft bearings aimed at calculate their electrical impedance along with their experimental validation. These models provide useful criteria for the design of wind turbines lightning protection systems (LPS). In this respect, the paper presents also the development of a specific LPS for the protection of wind turbine bearings and the relevant effectiveness analysis obtained by means of experimental tests.