*2.1. Wind Turbines*

A wind turbine is mainly composed of control systems, transmission mechanisms, generators, converters, blades, towers, power cables, converters and transformers. The internal transmission mechanisms include gearboxes, hubs and steering systems. The performance of wind turbines varies from one model to another.

As discussed previously, the installation site's climate conditions and the natural disasters which may occur affect wind turbines' operation, resulting in various causes of sudden failure, which is to be resolved by maintenance by prediction. In addition to these external factors, some wind turbines may have inherent (internal) drawbacks, such as inconsistent design specifications, low manufacturing quality and inappropriate design specifications for the sites on which they operate. All of these factors could cause them to operate in an unstable manner and accelerate the possible damage to their components, including the blades.

The reasons for fan-blade damage are manifold, but each can be categorised as either internal or external. Internal damage may be caused by kinetic or mechanical reasons. For example, machine wear due to operation over a long period will result in the deformation of parts due to stress. Also, during fan operation on normal days, the tower column will produce different deformations and displacements due to different operating conditions, tower conditions, and conditions of the base. External damage, by contrast, can result from the sudden occurrence of natural disasters, e.g., large typhoons and earthquakes. These are more harmful to the blades, and the consequences are usually unexpected. While the events causing damage are all occasional, they meet the condition that the tool provided by this study can address. See these further in Section 4.3.
