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Yayın Evaluation of alternative maintenance strategies on a complex system in thermal power systems(Işık Üniversitesi, 2020-08-12) Türkali, Busenur; Özgür Ünlüakın, Demet; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Endüstri Mühendisliği - Yöneylem Araştırması Yüksek Lisans ProgramıIn recent years, due to the continuous development of the industry and the rapid increase in the system complexity, maintenance policies have become more important. Unplanned downtimes due to unexpected failures may lead to huge problems in almost all industry branch. However, carrying out maintenance more than the required to prevent unexpected failures increases maintenance cost signicantly. Thus, balancing the number of reactive and proactive maintenance is very important. The aim of this thesis is to develop maintenance methods under the reactive, condition-based and proactive maintenance strategies using dynamic Bayesian networks (DBNs) in thermal power plants. DBNs which are are probabilistic graphical models, are selected to model the system because they are very effective to formulate the stochastic and structural dependencies between the components. In this study, we evaluate alternative maintenance strategies on a complex systembased on two factors: total number of maintenance and total maintenance cost in a given planning horizon. The proposed maintenance methods are simulated on a multi-component thermal power plant system which has a very complex structure with hidden components among which there are stochastic and structural dependencies. Scenarios are designed considering the maintenance dependability of parallel systems during proactive activities and different reactive cost structures. As a result, performances of all proposed maintenance strategies and methods are compared and analysed under each scenario and the most promising ones are highlighted.
