Patent ID: 8882460

Claim:
A method for operating a wind turbine with a variable-speed rotor, a control system and a safety system, comprising the steps of: activating the safety system for braking the rotor when a rotational speed of the rotor exceeds either a second threshold value (n s1 ) or a third threshold value (n s2 ), the second threshold value (n s1 ) being less than the third threshold value (n s2 ), wherein when the rotational speed of the rotor exceeds the second threshold value (n s1 ), the safety system is activated only if the control system has not initiated a control system braking procedure in response to the rotational speed of the rotor being greater than a first threshold value (n c1 ) that is less than the second threshold value (n s1 ); and wherein when the rotational speed of the rotor exceeds the third threshold value (n s2 ), the safety system is activated even if the control system has initiated the control system braking procedure in response to the rotational speed of the rotor being greater than the first threshold value (n c1 ).