Diagnostics and Condition Based Maintenance

In the wind energy industry, condition based maintenance is preferred if it is foreseen that a component needs to be maintained or replaced regularly, but if it is unclear when. Condition based maintenance requires a proper determination and prognosis of the health of the system, so-called condition monitoring. Depending on the type of system and component, a wide variety of condition monitoring methods and techniques is available. For instance offline, one can perform periodic visual inspections, analyse oil samples, or vibration measurements. Another option is to permanently install systems that are dedicated to perform certain measurement and analysis tasks and that automatically report analysis results and events (alarms, warnings) to operators. Such systems are referred to as online condition monitoring systems. Another source of information for health determination is operational data from SCADA systems, e.g. the number of starts and stops, development of temperatures over time, or occurrence of alarms. With adequate diagnostics, unplanned shutdowns and total component failures can be avoided.

Within the EU project CONMOW (CONdition Monitoring of Offshore Wind turbines), ECN has carried out research to assess the adequacy of most commonly used condition monitoring systems for wind turbine engineering.

At present, ECN’s research is focussing on the development of low cost and reliable methods for load counting in offshore wind farms, assuming that the loads are the primary cause for component degradation and failures. Operators may use the information to prioritise their inspection and maintenance schemes. ECN’s research deals with the following topics.

• Fibre Optic Blade Monitoring (FOBM)
• Flight Leader Concept for Wind Farm Load Counting
• Development of “PROcedures for TESTing and measuring wind energy systems” (PROTEST)