Complexity and uncertainty have impacted wind power systems and their applications.Commercial wind power asset exhibits complex system behaviour due tostochastic loading characteristics of its installation context. However, differentstakeholders’ practices in whole life cycle processes try to treat multi-disciplinarycomplexity issues. Moreover, wind power system failures, stoppages, faults, supportdelays and human/organizational errors provide a clear proof of increasingthe needs for dependability. Therefore, dependability is considered as an aggregatetheory for RAMS (Reliability, Availability, Maintainability, Safety & Supportability)in order to cope with complex systems (i.e. physical systems and their assetmanagement systems) and their behaviour phenomenon. Consequently, to addresswind power practical problem as one of the modern complex and interdependentsystems, it is worth to enhance both the way of how we look at dependability andthe method of inquiry. Technical system complexity, system interdependency andsystem learn-ability are the main challenges within system dependability field.Therefore, this research work is done to integrate both terotechnology and systemsengineering methodologies to enhance systems dependability theory and practices.In particular, it focuses on three main aspects within systems dependability engineering:challenges, practitioners’ concepts and system-level methodologies.The research methodology of this thesis has utilised the mixed research approachof qualitative and quantitative methods to extract the empirical findings that arerequired to validate the dependability theory developments. Qualitative survey isused to identify the challenges of dependability theory within wind power applications.Grounded theory is used to define the practical understanding of windpower stakeholders concerning to dependability and asset management concepts.Case study is implemented to validate the systems dependability engineering, ascross edge theory of dependability and systems engineering. Moreover, the phenomenographymethod is used to capture the individual experiences and understandingof purposefully selected stakeholders, due to different site-specific circumstancesfor each wind farm.In general, the thesis contributes to the body of knowledge of five fields: dependability,terotechnology, asset management, systems engineering and wind energy.In particular, the focus of thesis contributes with retrospective review to be as referenceline for system dependability theory. Simultaneously, on basis of empiricalfindings, it contributes to be a pivot point for further enhancements from both theacademic contributions and industrial developments.

The thesis covers studies conducted during 1976-79 under a Science Research Council contract to examine the uses of reliability information in decision-making in maintenance in the process industries. After a discussion of the ideal data system, four practical studies of process plants are described involving both Pareto and distribution analysis. In two of these studies the maintenance policy was changed and the effect on failure modes and frequency observed. Hyper-exponentially distributed failure intervals were found to be common and were explained after observation of maintenance work practices and development of theory as being due to poor workmanship and parts. The fallacy that constant failure rate necessarily implies the optimality of maintenance only at failure is discussed. Two models for the optimisation of inspection intervals are developed; both assume items give detectable warning of impending failure. The first is based upon constant risk of failure between successive inspections 'and Weibull base failure distribution~ Results show that an inspection/on-condition maintenance regime can be cost effective even when the failure rate is falling and may be better than periodiC renewals for an increasing failure situation. The second model is first-order Markov. Transition rate matrices are developed and solved to compare continuous monitoring with inspections/on-condition maintenance an a cost basis. The models incorporate planning delay in starting maintenance after impending failure is detected. The relationships between plant output and maintenance policy as affected by the presence of redundancy and/or storage between stages are examined, mainly through the literature but with some original theoretical proposals. It is concluded that reliability techniques have many applications in the improvement of plant maintenance policy. Techniques abound, but few firms are willing to take the step of faith to set up, even temporarily, the data-collection facilities required to apply them. There are over 350 references, many of which are reviewed in the text, divided into chapter-related sectionso Appendices include a review of Reliability Engineering Theory, based on the author's draft for BS 5760(2) a discussion of the 'bath-tub curves' applicability to maintained systems and the theory connecting hyper-exponentially distributed failures with poor maintenance practices.