Rotor drive system assisted disengagement of the rotor-lock mechanism

A method of constructing or dismantling a wind turbine rotor of a wind turbine, the method comprising:

• engaging a rotor-lock of the wind turbine to fix the rotor in a locked orientation about a horizontal axis;
• adding a wind turbine blade to or removing a wind turbine blade from the rotor such that, due to gravitational pull, the rotor is subjected to a rotor torque which is opposed by a rotor-lock counter-torque from the rotor-lock;
• and
• disengaging the rotor-lock, wherein disengaging the rotor-lock comprises:
• a) determining a direction of the rotor torque with a sensor system, wherein the sensor system comprises one or more sensors arranged in the wind turbine blade,
• b) applying a rotor-drive counter-torque to the rotor with a rotor-drive system, wherein the rotor-drive counter-torque acts to oppose the rotor torque and causes the rotor-lock counter-torque to reduce;
• c) during or after the application of the rotor-drive counter-torque, disengaging the rotor-lock;
• wherein the step of determining the direction of the rotor torque comprises applying a torque restriction to the rotor-drive system based on the determined direction of the rotor torque, the torque restriction preventing the application of the rotor-drive counter-torque to the rotor by the rotor-drive system in the same direction as the rotor torque.

A wind turbine comprising:

• a rotor having one or more wind turbine blades;
• a rotor-lock engageable to lock the rotor in a fixed orientation about a rotational axis of the rotor, wherein, due to gravitational pull, the rotor is subjected to a rotor torque which is opposed by a rotor-lock counter-torque from the rotor-lock;
• a sensor system including one or more sensors arranged in each of the one or more wind turbine blades configured to generate rotor data, the rotor data indicating a direction of the rotor torque;
• a rotor-drive system configured to apply a rotor-drive counter-torque to the rotor and
• a control system configured to cause disengagement of the rotor lock by:
• a) determining the direction of the rotor torque with the sensor system,
• b) applying the rotor-drive counter-torque to the rotor with the rotor-drive system, wherein the rotor-drive counter-torque acts to oppose the rotor torque and causes the rotor-lock counter-torque to reduce;
• c) during or after the application of the rotor-drive counter-torque, disengaging the rotor-lock;
• wherein the step of determining the direction of the rotor torque comprises applying a torque restriction to the rotor-drive system based on the determined direction of the rotor torque, the torque restriction preventing the application of the rotor-drive counter-torque to the rotor by the rotor-drive system in the same direction as the rotor torque.