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  • 1.
    Besnard, Francois
    et al.
    KTH, School of Electrical Engineering (EES).
    Nilsson, Julia
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling, Lina
    On the economic benefits of using condition monitoring systems for maintenance management of wind power systems2010In: 2010 IEEE 11th International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2010, 2010, p. 160-165Conference paper (Refereed)
    Abstract [en]

    The large growth in the wind power industry in the past years mainly focuses on a growing market and the development of large turbines and offshore farms. The high technical availability of wind turbines comes with a high need for frequent maintenance. Current maintenance planning is generally not optimized, and it is possible to make maintenance more efficient. Condition Monitoring Systems (CMS) are commonly used in other industries and can reduce the consequential damage at failure and provides advantages for the planning of the maintenance. It is of interest to determine if the wind industry would benefit of the use of CMS. This paper shows results from Life-Cycle-Cost (LCC) evaluated with probabilistic methods and sensitivity analysis to identify the benefit of using CMS. The results highlight that there is a high economic benefit of using CMS, as well as benefits on the risk. The benefit is highly influenced by the reliability of the gearbox.

  • 2.
    Nilsson, Julia
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    On maintenance management of wind and nuclear power plants2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Electrical production in Sweden today is mainly from nuclear and hydro power. However, there is large increase in renewable energy like wind power and the installed new capacity goals are large. Several electrical production sources are important for the sustainability of the energy system. Maintenance is an approach for keeping a system sustainable. The importance of structured maintenance for reliable electrical production systems triggers the development of qualitative and quantitative maintenance management methods. Examples of these methods are Reliability-Centered Maintenance (RCM) which is a structured qualitative approach that focuses on reliability when planning maintenance, and Reliability Centered Asset Management (RCAM) which is a development of RCM into a quantitative approach with the aim to relate preventive maintenance to total maintenance cost and system reliability.

    This thesis presents models, as applications of RCAM, based on the methods of Life Cycle Cost (LCC) and mathematical optimization, applied to wind and nuclear power plants. Both deterministic and stochastic approaches have been used and the proposed models are based on the Total Cost model, which summarizes costs for maintenance and production loss, and the Aircraft model, which is an opportunistic maintenance optimization model. Opportunistic maintenance is preventive maintenance performed at opportunities. The wind power applications in this study show on different ways to cover costs of condition monitoring systems (CMS) and further on economic benefits of these when uncertainties of times to failure are included in the model. The nuclear power applications show on that the optimization model is dependent on the discount rate and that a high discount rate gives more motivation for opportunistic replacements. When put into a stochastic framework and compared to other maintenance strategies it is shown that an extended opportunistic maintenance optimization model has a good overall performance, and that it, for high values of the constant cost of performing maintenance, is preferable to perform opportunistic maintenance. The proposed models, applied to wind and nuclear power plants, could be extended and adapted to fit other components and systems.

  • 3.
    Nilsson, Julia
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling, Lina M.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Maintenance management of wind power systems using condition monitoring systems - Life cycle cost analysis for two case studies2007In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 22, no 1, p. 223-229Article in journal (Refereed)
    Abstract [en]

    The large growth in the wind power industry in the past years. mainly focuses on a growing market and the development of large turbines and offshore farms. The high technical availability of wind turbines comes with a greater need for frequent maintenance. Current maintenance planning is not optimized, and it is possible to make maintenance more efficient. Condition monitoring systems (CMS) could resolve the growing wind power industry's need for better maintenance management and increased reliability. Such systems are commonly used in other industries. CMS could continuously monitor the performance of the wind turbine parts and could help determine specific maintenance timing. This paper presents a life cycle cost (LCC), analysis with strategies where CMS improved maintenance planning for a single wind turbine onshore and a wind farm offshore. Case studies are based on real data from Olsvenne2 at Nasudden (Gotland, Sweden) and Kentish Flats, in the U.K. The main conclusion is that CMS benefits maintenance management of wind power systems. Improvements can be especially shown for offshore wind farm maintenance planning.

  • 4.
    Nilsson, Julia
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wojciechowski, A
    Strömberg, A-B
    Patriksson, M
    Bertling, L.
    An evaluation approach for opportunistic maintenance optimization models for nuclear power plants2010In: Power and Energy Society General Meeting, 2010 IEEE, IEEE , 2010Conference paper (Refereed)
    Abstract [en]

    Nuclear power constitutes one of the main electricity production sources in several countries, e.g. in Sweden, with about half of today's electricity production. Driving forces for cost-efficiency have pushed the development of new methods for maintenance planning and optimization forward. Reliability Centered Asset Management (RCAM) is one of these new approaches, and maintenance optimization is one way to perform quantitative analysis which is a feature of RCAM. This paper proposes a stochastic framework for evaluating opportunistic maintenance optimization models for the generation of replacement schedules for shaft seals in feed-water pump systems in nuclear power plants. Results show that the extended discounted model has a good overall performance, when compared to other strategies. Moreover, it is shown that it is the best strategy for high values of the constant cost for maintenance and the second best for lower values of the constant cost.

  • 5.
    Nilsson, Julia
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wojciechowski, A.
    Strömberg, A-B
    Patriksson, M.
    Bertling, L.
    An Opportunistic Maintenance Optimization Model for Shaft Seals in Feed-Water Pump Systems in Nuclear Power Plants2009In: 2009 IEEE Bucharest PowerTech: Innovative Ideas Toward the Electrical Grid of the Future / [ed] Toma L; Otomega B, New York: IEEE , 2009, p. 2962-2969Conference paper (Refereed)
    Abstract [en]

    Nuclear power is one of the main electricity production sources in Sweden today. Maintenance management is one tool for reducing the costs for operation of a power plant. Driving forces for cost-efficiency has pushed the development of new methods for maintenance planning and optimization forward. Reliability Centered Asset Management (RCAM) is one of these new approaches, and maintenance optimization is one way to perform quantitative analysis which is a feature of RCAM. This paper proposes a model for opportunistic maintenance optimization where replacement schedules for shaft seals in feed-water pump systems in nuclear power plants are constructed. The feed-water pump system is important for the availability of the entire nuclear power plant. Results show that the optimization model is dependent on e.g. the discount interest and a limit for when the optimal solution goes from non-opportunistic to opportunistic is calculated. The circumstances for which opportunistic maintenance could be used have been investigated given different values of discount rates and remaining life at start of the planning period.

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