Performance can be optimised by careful monitoring of turbine behaviour and analysis for imminent failures.

The performance of a site is a complex issue, and will generally evolve over time. In this context, a utility or a site owner goes through several challenges for maintenance as the project progresses.

During the early stages of a project it is common to experience a number of teething problems, which may include component failures. With time, these will decrease. It is in this secondary stage that the site and the wind farm can best be understood in terms of establishing benchmarks for performance in real site conditions. Later, the individual components will begin to wear out as the wind farm reaches the end of its operational lifetime. This may coincide with the end of warranty for the turbines.

“At all stages of the wind farm life, performance can be optimised by careful monitoring of turbine behaviour and analysis for imminent failures and slow power degradation,” says Dr. Joanna McKenzie, Renewable Energy Consultant, SgurrEnergy Ltd.

The most common methods of monitoring performance are through in-depth statistical SCADA analysis, known as performance monitoring, and using condition monitoring systems to identify abnormalities in system vibrations or other systems. These two techniques are complementary: while condition monitoring provides a detailed look at individual component behaviour in real-time and can hence alert imminent failures with a good success rate, performance monitoring is less intrusive, less costly and monitors actual turbine output – power – rather than secondary indicators.

Availability of spare parts

As the end of the warranty period approaches, it is more crucial than ever to maintain a detailed inventory of available spare parts, said Dr. McKenzie.

“This reduces lead time on repairs when critical failures occur, and hence reduces the impact of failure on wind farm performance,” added Dr. McKenzie.

According to her, typically an owner/operator of a site can face lengthy delays and downtime if awaiting the supply of a component, particularly if the failure has not been predicted.

“As such, a small number of options are open to them; procure from the turbine manufacturer at typically inflated costs; procure from the OEM who has typically supply chain commitments (mainly to the turbine manufacturer); procure a refurbished or retrofitted component supplier; or reengineer or fix 'in-house'. The storage and maintenance of spare parts remains a challenge for an operator,” according Dr. McKenzie.

Experience

Access to suitably trained and competent labour resources and competing within industry and similar industries to minimise churn is another obstacle that must be overcome.

“A combination of gaining experience at a site and allowing input from those with experience at other sites allows the best balance for ongoing and long term operating and maintenance strategies and experience,” said Dr. McKenzie.

She added that growth, development and evolution of industry safety and technical practices allows industry experience to make the necessary changes to a site’s practices and methods, however this all comes at the cost of retraining, implementation and changes in attitudes, mentalities and processes.

Approach towards training

It is vital to have a properly trained staff in O&M practices, according to Keith Plantier, program manager for Texas Wind Energy Institute at Texas State Technical College.

“Any time a company can step up and plan maintenance actions as opposed to reacting to any problem that comes along to ensure their assets will last longer and improve efficiency.  If you are in a reactive mode, the damage has potentially already occurred and your costs will skyrocket with repair or replacement,” said Plantier.

Plantier recommends that companies’ expertise in areas such as blade repair, generator/gearbox repair, etc should be honed with additional training provided by the company. 

“This can be attained by attending conferences, allowing individuals to have access to the latest technology available or corporate training using the expertise of those persons within the companies’ profile.  Areas which could/should be outsourced are the basic training for wind technicians and other management duties,” he added.  

The O&M team should have a comprehensive, well thought out planned maintenance activity which address the time of year a scheduled outage should occur as well as a systematic approach to completing the maintenance. 

“All parts necessary for a planned maintenance activity should be available with the ordering of those parts and lead times scheduled into the plan,” said Plantier.  

He added, “Material history for each turbine should be kept along with logs and data, trends, etc. to help the team identify why components are failing more frequently.  Be it for poor design or bad maintenance practices or transient events or component failure etc. - any time a fault occurs on a turbine; it should be added to material history and investigated as to why something occurred.”

Short term, this may not provide much insight but over the long haul, the material history will become critical into root cause for fatigue, corrosion and other failures common to turbines.