Condition Monitoring of Wind Turbines How Weidmüller Detects Cracks in Rotors with Sensors

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Sensors instead of just drones: EDF Power Solutions relies on continuous vibration monitoring in California to detect structural damage to wind turbines at an early stage and plan necessary repairs.

A steady, fresh wind blows from the Pacific over the Californian coast and drives the turbines of an onshore wind farm near Rio Vista. The turbines there produce around six million kilowatt hours of electricity a year, enough to meet the needs of 1,500 households. The farm is operated by EDF Power Solutions, a global low-carbon energy company. However, generating green electricity is only half the battle; the real challenge lies in maintaining the huge plant structures under extreme mechanical loads over the long term.

Until now, the company has primarily relied on drones for inspections. The aircraft scanned the surfaces of the rotor blades for cracks or fractures. During one of these routine inspections, the experts discovered an H-shaped crack near the center of gravity of a blade. Such a finding is critical: in the worst-case scenario, damage at this central point can cause rotor blades to buckle or fall off during operation. EDF Power Solutions reacted immediately, took the turbine off the grid and looked for a technological solution that went beyond the selective snapshot of a drone.

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Precision Through Acceleration Sensors

This is where electronics specialist Weidmüller came into play. Instead of simply observing the crack superficially, the technicians installed the Bladecontrol system. At the heart of this solution are biaxial accelerometers located directly in the rotor blades. These sensors detect the slightest changes in the vibrations of the blades. As structural integrity problems almost always correlate with a change in vibration behavior, the system provides a digital image of the mechanical condition. In combination with the web-based visualization software Webvis, operators can track the measured values directly in the browser and monitor the system remotely.

After the installation, EDF put the affected wind turbine back into operation. The sensor technology enabled those responsible to record the development of the damage seamlessly over the course of an entire year. Instead of immediately initiating the repair under time pressure, the team was able to observe exactly how and when the crack expanded under load. This allowed for optimized planning of the repair measures. The success of the subsequent repair was also documented in black and white: Following the work, Bladecontrol recorded a four-fold reduction in vibrations.

A Model for Predictive Maintenance

The focus is thus shifting away from purely mechanical inspection towards deeply integrated electronics that permanently monitor the "skeleton" of the turbine. Phil Gauthier, Senior Manager Wind Technology Strategy at EDF Power Solutions, draws a positive conclusion about the hardware: "Weidmüller's Bladecontrol has a robust system design with solid housings, high-quality components with integrated protection systems and comprehensive documentation. Although the wired sensors required special work inside the rotor blades during installation, the result was a system that delivered highly accurate data combined with high data availability throughout the test period. The sophisticated data visualization platform for data monitoring and alerting allowed us to track the evolution of the damage throughout the rotor blade repair campaign."

Weidmüller's portfolio for the wind industry is not just limited to blade monitoring. With systems such as Boltcontrol for detecting broken bolts or special Twincap sensors, the entire system becomes a networked measuring instrument. For engineers and electronics developers, the "twist" lies in the fact that the operational safety of complex mechanical systems today depends largely on the reliability and precision of the embedded electronic components. Continuous data availability replaces the principle of hope with fact-based maintenance strategies. (mc)