Wind turbine cut-out wind speed is much more important than cut-in wind speed. Wind turbine cut-out speed means, the highest predicted wind speed at which an operating wind turbine stops producing power due to excess wind. The cut-out wind speed is designed to apply the breaking system to slow down or stop the turbine from spinning and protect your equipment from damage.
The wind speed is usually monitored by the turbine control system and no power will be generated above the cut-out wind speed. There are several ways to stop a wind turbine in high wind. In some wind turbines, speed sensors are installed to automatically apply a built-in braking system. Other (large) turbines twist the blades away from incoming wind also known as "pitching the blades" to allow the wind to pass through thus reducing the wind turbine speed.
Some wind turbines use drag flaps that are mounted on the blades of the wind turbine to reduce blade speed or the hub itself will automatically activate drag flaps at high rotor RPM's. Also, some wind turbines are mechanically activated by spring loaded devices which turns the machine away from the wind stream. Usually wind turbines resume operation when the wind speed drops back to a safe level below the cut-out wind speed.
Wind turbines make use of cut-out wind speed for damage prevention. Regardless of the method used, if your rotor or power electronics are not equipped with cut-out wind speed function, serious damage may occur to your wind turbine or electronic equipments. You should not be confused between wind turbine cut-out wind speed and wind turbine cut-in speed.