Operation and maintenance costs constitute an average of more than 30% of the total cost per kWh produced by a new wind turbine. Manufacturers are increasingly seeking to develop new maintenance approaches to bring down these costs.
TWI, in partnership with RTS International, worked to support this aim through the CM Project, a research programme funded by Innovate UK, within the competition ‘Emerging Energy Technologies’.
The project sought to establish the feasibility of using a non-contact acoustic pressure sensor to monitor the condition of machinery in an onshore wind turbine. This was achieved through experimental field trials in a 2MW turbine lasting over a month.
Figure 1. Wind farm location for experimental trials
Acoustic sound and vibration monitoring
Vibrations from all the rotating components within the nacelle were monitored through the airborne noise generated by the surface vibrations of the machinery.
Figure 2. Sensing instrumentation
The noise was detected by acoustic pressure sensors (microphones) mounted at the nacelle inner surface.
Unlike contact sensors, which cover only the small portion of their contact area, these microphone sensors are able to monitor up to 75% of the noise emitted from the machine surfaces. The developed non-contact sensor array consists of a group of five acoustic pressure sensors arranged in a manner which allow its easy installation and set-up.
Figure 3. Sensor array installed in the wind turbine nacelle
To determine the feasibility of the non-contact technique, acoustic sound and vibration monitoring were carried out during the UK-based turbine’s normal operation. An array of five acoustic pressure sensors and two accelerometers was installed. In addition to acoustic sound and vibration data, parametric data, ie wind speed and power output, were obtained for correlation with the acquired data, as shown in Figure 4.
Figure 4. Root mean square of the acoustic signals versus power
For further information about the project, please visit the project website: www.cmdrive.co.uk.
If you would like further details, please contact us.
TWI Ltd (The Welding Institute)