Rotor blades are some of the most highly stressed components of a wind turbine. Gusts of wind, storms, ice and lightning can all cause minor damage that is often only discovered during routine checks. In a worst-case scenario, the defects will have progressed so far by this stage that a costly replacement of the rotor blades will need to be carried out. As a result, the installation will be at a standstill for weeks in order to prevent any consequential damage, and will not be generating any power. This is where Predictive Maintenance comes in.
Excellent detective work
BLADEcontrol® from Weidmüller continually records the condition of each individual rotor blade and detects even minor changes such as loose parts in the blade and tears or delamination of the aerodynamic surface covering. Damage to the support structure of the blade constitutes a critical form of damage. If this damage is not detected in good time, not only do the repair costs increase, but so does the risk of tower contact or blade breakage.
In order to detect changes, BLADEcontrol® records the natural vibration behaviour of the rotor blades, and
makes a distinction between measurements towards the front and rear edge as well as towards the surface of the blade. The structure-borne sound from the entire blade is also recorded. Various algorithmic approaches are used to filter out any irregularities or deviations from within this data. In the event of ice, the vibration frequency of the rotor blade will be somewhat reduced due to the extra weight. Depending on the ice distribution, BLADEcontrol® can achieve a measurement resolution for the thickness of the ice in the millimetre range.
For any detected damage, BLADEcontrol® will immediately transmit the relevant data to a Monitoring Centre, where it will be evaluated by experts who will then put together a list of concrete action recommendations for the operator
Knowing when a situation becomes critical
The key feature of the Weidmüller system is the two-dimensional acceleration sensor with its own temperature measurement channel. BLADEcontrol® collects the data from the rotor blades together in the hub, and transfers it to the nacelle. An evaluation unit that can be installed in the foot of the tower, for example, analyses the data, classifies any damage based on severity, passes on this information and signals recommendations to the control unit. In the event of risk, the installation’s control unit immediately initiates a system shut-down. If there is ice on the rotor blades, the system detects when there are no longer critical ice thickness levels, even when the installation is at a standstill, and sends a signal to restart the installation. “This enables us to achieve much better installation availability, which leads to a noticeable revenue increase in the long term,” explains Dr John Reimers, Head of Marketing and Sales at Weidmüller Monitoring Systems.
Act instead of react
BLADEcontrol® transmits all detected damage to the turbine, usually via Modbus TCP. “In principle though, BLADEcontrol® supports all standard protocol types,” Reimers adds. The protocol provides BLADEcontrol® with important information such as the wind speed and pitch angle of the rotor blade, allowing it to work out the operating area where there is a deviation, and to draw conclusions on the cause of this deviation where necessary. The Monitoring Centre can also communicate with the installation, and can transmit additional measured data to be investigated during post-processing, for example. The system can also signal notifications of serious damage directly to the turbine.
The experts in the Monitoring Centre respond to the deviations detected by the systems immediately. The first step involves creating a helpdesk entry in the ticket system for the affected turbine. The client will then receive a detailed notification via email. In order to ensure that the relevant information is received immediately in the event of serious damage, a telephone call will also be made to notify the client of the damage.
4,000 machine years of experience
“Thanks to our over 4,000 machine years of monitoring experience, we have a huge amount of data and the corresponding empirical knowledge to help propose recommendations for action and to remedy any errors,” says Dr Daniel Brenner, Head of Monitoring at Weidmüller Monitoring Systems. There are over 1,600 systems online and more than 2,000 sold all over the world.
The BLADEcontrol® hardware consists of sturdy acceleration sensors as well as measurement and evaluation computers that can easily be retrofitted into existing installations
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Operate wind turbines efficiently with BLADEcontrol® and other solutions
Published in May 2017
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