Condition Monitoring of Wind Turbine Towers and Blades

Operation and maintenance costs constitute a sizeable share of the total annual costs of a wind turbine. For a new machine, these costs might easily have an average share over the lifetime of the turbine, of more than 30% of the total cost per kWh produced. The increase of the wind turbines and their size, in combination with remote locations where off-shore farms are built, means that these maintenance costs will see an unprecedented increase in the future. Therefore manufacturers are seeking to develop new maintenance strategies. The use of Conditional Monitoring allows maintenance to be scheduled, or other actions to be taken to avoid the consequences of failure, before the failure occurs.

Project Deliverables

The project is structured in six work packages (WP) covering all the aspects in the project. The end-user requirements and system specifications are included in WP1. WP2 and WP3 cover the development of the software and hardware. The development of training material for the understanding of the system is covered by WP4. Trials and validations of the system form WP5 and finally the dissemination and exploitation activities are included in WP6.

All the relevant information from these work packages will be included in the eleven deliverables developed.

Project Summary

The “Systems and methodologies for condition monitoring of wind turbine towers and blades” project will develop a condition monitoring system for early fault detection in order to increase the reliability of the wind turbine, preventing any unexpected break down or power outages. Acoustic Emission and vibration techniques will be used. The process of Structural Health Monitoring (SHM) will be used, which consists of using damage-sensitive features to monitor the integrity of a structure.

Additional Project Information

This project is collaboration between the following organisations: The University of Newcastle, CMR UK Ltd, Applied Inspection Ltd, TBG solutions Ltd, TWI Ltd and the National Renewable Energy Centre (Narec).

It is part of the 4-project programme:

“Offshore Wind Turbine Fabrication and Condition Monitoring – Knowledge Generation and Transfer to Industry”.

This programme comprises four activities. Three of these involve research and development relating to new technologies and the forth one is technology transfer activity to take the results of these developments, and other related developments, to individual companies:

novel fabrication methods for wind turbine towers
the development and automated application of 40 year life coatings for wind turbine structures
systems and methodologies for condition monitoring of wind turbine towers and blades
technology transfer

This project will produce an advanced system for condition monitoring of wind turbine towers and blades utilising two techniques, specifically designed for wind turbines and their components:

The Acoustic Emission (AE) technique for condition monitoring is an active area of research primarily due to the requirement for complex signal processing to extract and identify the signals of interest from a noisy background. Additional complexity arises from the fact that the AE signals are strongly non-stationary (frequency varies as a function of time as in a chirp) which leads to errors if classical signal processing techniques are employed (such as Fourier analysis). The particular strength of AE is its ability to directly detect the processes associated with wear and degradation (including friction, impacts, crushing, cracking, turbulence, etc,). This is achieved by detecting the surface component of stress waves that these processes invariably generate. These stress waves travel all over the structure’s surface.
The Operational Modal Analysis (OMA) technique focuses on the analysis of the system’s dynamic behaviour when excited by an input. In this case the structure is excited by its normal vibration while operating and the input is considered to be stochastic which suits the case of large structure excitation like buildings and bridges. Sustained vibrations in the operational spectrum can cause excessive sustained oscillatory motion beyond the static loading condition. This will ultimately lead to structural failure. Modes describe the resonances of a system and can be used to describe the overall system dynamics. Every system response can be assembled by a superposition of weighted modal participation. Modal analysis is used in order to acquire the necessary parameters of each mode. These are the natural frequency, the mode shape (or deflection shape), and the modal damping.

For more information, please email contactus@twi.co.uk.

For more information please email:

contactus@twi.co.uk