مقاله انگلیسی رایگان در مورد قابلیت اطمینان بر اساس طرح سیستم قدرتی مایع – وایلی 2017

Wind turbines play a significant role in the present utilization of renewable energy sources, and an increase in investment of new installations is expected.1 The cost of energy produced by wind turbines must decrease, to meet future expectations. The key factors for decreasing the cost of energy are low cost, high efficiency and high availability. Because wind turbines are designed to operate as autonomous energy converters, high availability depends on efficient maintenance and high reliability. However, in real life, turbines suffer from unpredicted failures causing significant downtime, which reduce availability.2–6 The European ReliaWind study conducted on approximately . 350 turbines larger than 1 MW, shows that the pitch system contributes over 20% to both the overall turbine failure rate and downtime. This makes it the most unreliable subassembly of the turbine.4 The study includes wind turbines using either electrical or fluid power pitch systems with unknown distribution. However, indications are that half of the erected variable pitch turbines employ fluid power pitch systems.7 This paper focuses on the fluid power pitch systems. A recent study by Carroll et al. presents subassembly failure rate for approximately 350 offshore multi-megawatt turbines equipped with fluid power pitch systems.6 These results confirm that pitch systems are the largest contributors to total turbine failure rate. The associated downtime is not directly evident, but a similar indicator is found by combining the average repair time and average failure rate. Comparing turbine subsystems by this indicator shows the pitch system faults rank in the top four together with faults related to blades, generators and the gearboxes. A Dutch study on 36 Vestas V90 3 MW offshore turbines equipped with fluid power pitch systems shows that the pitch system accounts for over 20% of the production stops, only exceeded by the control system.3 The related total downtime is fourth longest outnumbered only by the gearbox, generator and control system. From the aforementioned studies, it is clearly evident that pitch systems contribute significantly to both the downtime and failures of modern multi-megawatt turbines. Hence, lowering the failure probability and downtime of such systems will have the potential to significantly increase the availability of wind turbines. In lowering the failure probability of pitch systems, an important basis is knowledge of failure modes and component failure rates. Two of the mentioned studies address the failure modes and failure rates for current fluid power pitch systems. Figure 1 shows a list of subjectively determined failure modes identified through the ReliaWind study.4 Component leakage and sensor faults are seen to be the dominating faults. Failure rate distribution for components and events are seen in Figure 2 obtained from the study by Carroll et al. 6 Here, failure rates related to oil, valves and accumulators faults show to make up a large portion of the total failure rate. The failure rates are categorized from field service reports where information can be inadequate. The Others category consists of these partially documented failures.