Maintenance management of wind power systems

The wind power industry has experienced a large growth the past years. The growth mainly focus on a growing market, better economical conditions for wind power because of political decisions and the development of large wind turbines and offshore farms. A goal is to increase reliability for turbines. The topic is even more important for offshore farms where service is difficult and expensive. The answer for the wind power industry, for better maintenance management and increased reliability, could be Condition Monitoring Systems (CMS). Such systems are commonly used in other industries. They continuously monitor the performance of the wind turbine parts e.g. generator, gearbox and transformer, and help determine the best time for a specific maintenance work. How these systems could support the wind power user is investigated in this report. The further step could be to implement CMS as a part of Reliability Centered Maintenance (RCM).RCM is a structured approach that focus on reliability aspects when determining maintenance plans, that is to find a balance between preventiveand corrective maintenance. Preventive maintenance is maintenance carried out before failures occur and corrective maintenance is maintenance carried out after failures occur. Condition Monitoring can consist of e.g. vibration analysis and oil analysis. In these two different analyses there are several methods that can be used. The components that are of interest of condition monitoring are the gearbox, generator and the main shaft. The component of most interest, and that it has been shown is a critical component due to its impact on system availability, is the gearbox. Life Cycle Cost (LCC) analyses have been made to calculate if it is profitable to implement CMS. The total cost, LCC including additional costs for implementing CMS, is compared for different alternative maintenance strategies. For a single turbine onshore versus an average turbine offshore in three strategies, and for a farm offshore where maintenance is planned using CMS in three strategies. The LCC without costs for CMS is called the basic case. The first three strategies studied for the separate turbine onshore gave the following results when a CMS cost is added to the basic case; to compensate for the additional cost the preventive maintenance has to be decreased by 23 %. To compensate for the additional cost the preventive and corrective maintenance together have to be decreased by 3,5 %. The same results for the farm offshore, where an average turbine was observed, were 4,5 % and 2,5 % respectively. Decreased corrective maintenance is needed to motivate CMS, at least for the turbine onshore. The following three strategies studied for the farm offshore gave the following results: a change from corrective maintenance to preventive maintenance with 47 % would be enough to make CMS profitable. The availability would not have to be increased with more than 0,43 % to get a reduction in cost for production loss that would cover the cost for CMS.