Torque Monitoring During Rotor Orientation
A novel torque/force monitoring safety feature for rotor orientation on non-geared wind turbines has been developed by Ørsted.
Problem to be Solved
During installation, replacement, and repair activities, it can be necessary to rotate (re-orient) a turbine rotor. This may occur with a balanced rotor (all blades installed) or an unbalanced rotor (e.g., only 1–2 blades installed), where the required torque to rotate can be significantly higher due to gravitational and aerodynamic contributions.
During installation, replacement, and repair activities, it can be necessary to rotate (re-orient) a turbine rotor. This may occur with a balanced rotor (all blades installed) or an unbalanced rotor (e.g., only 1–2 blades installed), where the required torque to rotate can be significantly higher due to gravitational and aerodynamic contributions.
Figure 1 – a wind turbine showing the rotation of blades in an unbalanced and balanced arrangement
Between rotation activities, the rotor is typically secured using one or more rotor locks that connect the stationary part of the turbine (nacelle) to the rotating part (rotor). A critical failure mode arises if personnel attempt to rotate the rotor while the rotor lock is still engaged or only partially disengaged. In that scenario, the externally applied rotation loads can be unintentionally transferred into the turbine structure and/or components (potentially including blades on non-geared turbines), causing severe damage. Relying only on manual procedures to ensure the lock is fully disengaged is therefore a high-risk human-factor dependency.
Figure 2 – Examples of positioning of a rotor lock of a wind turbine
Ørsted’s Concept
Ørsted’s solution introduces an automatic, measurement-based verification that the rotor lock(s) are fully disengaged before (and during) rotor rotation on non-geared turbines.
The steps of the core idea are as follows:
This idea has been developed by Michael Kastrup and Peter Fynbo.
Ørsted’s solution introduces an automatic, measurement-based verification that the rotor lock(s) are fully disengaged before (and during) rotor rotation on non-geared turbines.
The steps of the core idea are as follows:
- Determine the expected torque required to rotate the rotor for the given situation (balanced/unbalanced configuration, azimuth, number of blades, blade mass and centre of gravity, pitch angle, wind speed, and related parameters).
- Convert the expected torque into an expected interface force at the point where an external means applies the turning moment on the low-speed rotor side (e.g., via lifting yoke, lifting bag, or other interface connected to a crane/hoist).
- Measure the actual interface force using a load cell (or multiple load cells) integrated into, or attached to, the interface between the hoisting mechanism and the turbine/blade.
- Continuously compare measured vs expected force during the rotor-orientation operation.
- Trigger an alarm and stop operation in response to the measured force exceeding an allowable threshold (e.g., expected force plus margin, or a limit based on component capacity such as WLL of the lifting yoke). The threshold indicates that loads are not being used to rotate the rotor as intended (e.g., because a rotor lock is still carrying load or clearance is not achieved).
This idea has been developed by Michael Kastrup and Peter Fynbo.
Figure 3 – Examples of measurement of force applied to a blade of a wind turbine
Advantages of the Solution
- Directly detects the hazardous condition (unexpectedly high force/torque demand consistent with a locked/partially locked rotor) rather than relying only on lock status indicators and procedures.
- Reduces risk of severe structural/component damage during rotor orientation on non-geared turbines, especially in unbalanced rotor conditions where required torque is high.
- Supports multiple operational setups (lifting yoke, lifting bag, or other low-speed-side rotation interfaces) and can be adapted across turbine variants by parameterising the expected-force model.
Example System
A method of rotating a rotor of a wind turbine, the wind turbine comprising a rotor lock configured to restrain rotation of the rotor, the method comprising:
applying a rotational moment to the rotor using an external hoisting mechanism coupled to a rotor-side interface;
measuring, using at least one load sensor, a force associated with the applied rotational moment;
determining an expected force associated with rotating the rotor based on one or more turbine and/or environmental parameters;
comparing the measured force to the expected force; and
generating a signal when the measured force exceeds an allowable threshold.
The generated signal may be an alarm, and/or cause a forced stop of the rotation
The step of determining the expected force may comprise computing an expected torque contribution from gravity and an expected torque contribution from aerodynamic loading using one or more inputs comprising rotor configuration, blade mass properties, azimuth angle, pitch angle, and wind speed.
The rotor-side interface may comprise a lifting yoke, lifting bag, or other device configured to couple the hoisting mechanism to a blade or rotor. The at least one load sensor may comprise a load cell configured to continuously monitor the force during the rotation.
A system capable of enacting the above-described method is also envisaged.
The ideas and concepts are published in an effort to show them to all interested companies that may be able to build on Ørsted’s efforts, to create implementable solutions. We welcome an open dialogue with these companies.
Jonathan Foster
Lead IP Specialist
A method of rotating a rotor of a wind turbine, the wind turbine comprising a rotor lock configured to restrain rotation of the rotor, the method comprising:
applying a rotational moment to the rotor using an external hoisting mechanism coupled to a rotor-side interface;
measuring, using at least one load sensor, a force associated with the applied rotational moment;
determining an expected force associated with rotating the rotor based on one or more turbine and/or environmental parameters;
comparing the measured force to the expected force; and
generating a signal when the measured force exceeds an allowable threshold.
The generated signal may be an alarm, and/or cause a forced stop of the rotation
The step of determining the expected force may comprise computing an expected torque contribution from gravity and an expected torque contribution from aerodynamic loading using one or more inputs comprising rotor configuration, blade mass properties, azimuth angle, pitch angle, and wind speed.
The rotor-side interface may comprise a lifting yoke, lifting bag, or other device configured to couple the hoisting mechanism to a blade or rotor. The at least one load sensor may comprise a load cell configured to continuously monitor the force during the rotation.
A system capable of enacting the above-described method is also envisaged.
The ideas and concepts are published in an effort to show them to all interested companies that may be able to build on Ørsted’s efforts, to create implementable solutions. We welcome an open dialogue with these companies.
Jonathan Foster
Lead IP Specialist