Method and apparatus for operating a wind turbine

A control system for use with a wind turbine, the wind turbine including a rotor with at least one rotor blade, said control system being adapted for operating the wind turbine, said control system being configured to:

• determine an actual value of at least one of a first variable indicative of a failure state of the wind turbine and of a second variable of the wind turbine correlated to a status of the wind turbine or an ambient status;
• estimate an occurrence of a detrimental overspeed state of the wind turbine from at least one of the determined actual values, wherein a variable speed limit is adjusted based on the result of said estimation;
• and,
• operate said wind turbine having regard to the variable speed limit.

A wind turbine, comprising a:

• a) a rotor with at least one rotor blade;
• and
• b) a control system for operating said wind turbine, the control system being configured to:
• determining an actual value of at least one of a first variable indicative of a failure state of the wind turbine and a second variable of the wind turbine correlated to a status of the wind turbine or an ambient status,
• estimating an occurrence of a detrimental overspeed state of the wind turbine from at least one of the determined actual values, wherein a variable speed limit is adjusted based on the result of said estimation;
• and,
• operating said wind turbine having regard to the variable speed limit.