01 Nov 2011 11:11:59
Electrical systems faults number 1 cause of offshore turbine downtime
The latest research from Wind Energy Update reveals that despite the huge amount of attention given to gearbox failure, electrical faults are a leading cause of offshore wind turbine downtime. Failures of electrical and controls systems are the root cause of wind turbine repairs in 50% of cases, and operators should expect an electronic or electrical subassembly failure every 2 to 2.5 years, according to Wind Energy Update's offshore operations and maintenance report 2011, released today.
According to the report's authors, while the failure rate event of electrical system and control faults/failures may not have the highest associated downtime, a higher frequency of occurrence translates into the highest mean annual downtime.
"Electrical systems and components continue to cause relatively high rates of failure, and often result in unplanned servicing campaigns, because they are not as predictable as other types of failures," explain the authors. This is because generators, converters, conductors and transformers components require particular attention, and because condition-monitoring techniques are not always reliable enough to successfully conduct in-time prognosis.
With balance-of-plant outages, alone, taking from 1 to 8 months to solve, an exhaustive list of components failure, covering export cables, power collectors, converters, switchgears and substations makes this report an indispensable guide to offshore turbine maintenance.
Downtime resulting from an electrical fault or failure is often lengthened by access difficulties, owing to vessel shortage and limited weather windows. Limited weather windows serve only to exacerbate extremely high freight and charting costs, which can tally up to €300,000 per day. Due to significant wave height and wind speeds, the timing and execution of O&M operations is often very constrained, say the authors.
Helicopter access is often considered an alternative in order to gain quicker, safer access and to increase the working time. But at €50 per minute, this option doesn't come cheaply.
Providing a thorough treatment of access options, vessel types, and charter rates, the Wind Energy Update offshore operations and maintenance report will greatly assist operators in balancing costs for planned and unplanned offshore turbine maintenance.
Know thy enemy
The cost of operating a wind farm is linked directly to the cost of operation and maintenance activities. Today, however, considerable uncertainty surrounds the operating expenditure required to maintain high turbine availability.
With estimated annual O&M costs at €100,000 to €300,000 per 2MW–3MW offshore turbine and at €200,000 to €720,000 for larger turbines (according to a previous Wind Energy Update report), operators need access to more reliable data, stresses the report.
The authors call for more product quality assurance from OEMs, as well as greater transparency on the servicing frequency and reliability data for the various turbine components and systems. "A project's size, conditions at sea, reliability of the systems, subsystems and components, the maintenance and access strategy and the distance to shore, are all variables that must be factored into an efficient O&M plan", stress the authors.
By providing a comprehensive overview of today’s offshore wind turbine component failure landscape and the subsequent impact on O&M activities, the latest Wind Energy Update offshore O&M report provides developers and operators with a blueprint for a bullet proof O&M action and contingency plan.
For further information, including details on how to get a copy of the report, please send an enquiry to Scott Macdonald.