Search results for "Reliability engineering"
showing 10 items of 224 documents
Comparing different control strategies for indoor thermal comfort aimed at the evaluation of the energy cost of quality of building
2010
Abstract The rapid improvement in the standard of living requires more detailed and sophisticated methods of evaluating comfort conditions. But, maintaining thermal comfort conditions in confined environments may require complex regulation procedures and the proper management of heating, ventilating and air conditioning (HVAC) systems. In turn, the requirements for indoor thermal comfort do not necessarily coincide with those of energy saving purposes, which in the last years are becoming a crucial issue owing to the enactment of the European Energy Performance of Buildings Directive (EPBD). The aim of this work is to compare different indoor control thermal comfort strategies in view of th…
Controlled Fault-Tolerant Power Converters for Power Quality Enhancement
2013
Power quality depends generally on the interaction of electrical power with electrical equipments. If electrical equipments operate correctly and reliably without being damaged or stressed, a suitable level of power quality is assured. On the other hand, if the electrical equipment malfunctions, is unreliable, or is damaged during normal usage, power quality is poor and probably the economical loss could be important like the technical one. In the scenario of the Distributed Generation, power quality issues will be moreover important because an higher dissemination of power conditioning equipment will be requested and this obviously increases the sources of vulnerability of the electrical s…
Using semantics to facilitate data integration of offshore wind farms
2012
Operation and maintenance play an important role in extracting power from the wind, especially, in offshore wind energy where wind farms are located far off the shore and under harsh weather conditions. Improved operation and maintenance is likely to reduce costs as well as hazard exposure of the employees. Implementation of advanced information technology is thus crucial for operating offshore wind farms effectively and efficiently and hence improves operation and maintenance. However, information availability and reliability are key issues for their use in the offshore wind domain. In addition, the semantic of information has not been exploited thoroughly. This paper describes the develop…
Impact of increasing penetration of photovoltaic (PV) systems on distribution feeders
2015
This paper investigates impact of increasing photovoltaic (PV) penetration on distribution feeders. The main focus of this work is on ‘how PV systems penetration can influence operation of the protective devices in the distribution feeder?’. PV systems' impact, in a distribution feeder, for 3Φ fault has been analyzed. It considers fault location and protective devices (PDs) settings (e.g. time of PDs operation before a fault gets cleared by it). This paper is also emphasizing on ‘how the penetration of PV can affect voltage quality / unbalance in the distribution feeder’. The considered distribution feeders are supplying residential network and therefore loading on different phases are goin…
Error and Uncertainty Analysis of Non-Uniform Residual Stress Evaluation by Using the Ring-Core Method
2016
Like other mechanical methods used for the residual stress evaluation on a generic structural component, the Ring-Core Method (RCM) is potentially subjected to various error sources that in some particular experimental conditions can lead to significant errors and/or uncertainties on the computed residual stresses. The accuracy of the residual stresses computed by the RCM can be improved by a proper error analysis that allows the user to correct the systematic errors, as well as to evaluate the remaining stress uncertainty due to the random errors. Therefore, in order to give a contribution to the accuracy of the RCM, in the present work the list of the main error sources is presented and t…
A RELIABILITY MODEL FOR OPTIMAL ALLOCATION OF SPARE TOOLS IN FMS
1989
ABSTRACT A model for the dynamic management of the tool set of an FMS workstation is developed. The proposed approach processing the on-line recorded tool failure data updates the estimate of the parameters of the probability density functions of tool life and selects, at the occurence of each failure, the code of the tool to be allocated in the workstation storage devices in order to maximize its reliability over a planned horizon.
Load management for voltage security using probabilistic fuzzy decision tree method
2016
During contingency, load management is most important in planning, monitoring and controlling of power system. In transmission system, there is limit for controlling the reactive power in large size power network. In order to manage heavy loading on transmission, load management is necessary to avoid voltage collapse. This paper presents a methodology for load management considering voltage security assessment using probabilistic fuzzy decision tree (PFDT) technique. By using probabilistic fuzzy decision tree method, the load management is calculated in optimal manner in real time and insecure operating conditions are observed. With the help of this method, a real time load management plan …
A Comparative Analysis of the Reliability of Simple and Two-Level Checkpointing Techniques in two Different Distributed Industrial Control System Arc…
2003
In Distributed industrial control systems it is necessary to guarantee certain reliability level. In this sense, Checkpointing and Rollback techniques offer interesting possibilities to achieve fault tolerance without appreciable cost and complexity increment. Several Checkpointing techniques have been proposed. Most of them suppose the presence of stable storage in the system. But distributed industrial control systems usually do not dispose of this kind of storage. So, another storage strategy has to be employed. If Checkpoints were locally stored (Simple Checkpointing), the system tolerates only transient faults. If Checkpoints were locally, at the same node, and, additionally, at anothe…
Reliability assessment of granular filters in embankment dams
2006
SUMMARY Empirical criteria have been used successfully to design filters of most embankment large dam projects throughout the world. However, these empirical rules are only applicable to a particular range of soils tested in laboratory and do not take into account the variability of the base material and filter particle sizes. In addition, it is widely accepted that the safety of fill dams is mainly dependent on the reliability of their filter performance. The work herein presented consists in a new general method for assessing the probability of fulfilling any empirical filter design criteria accounting for base and filter heterogeneity by means of first-order reliability methods (FORM), s…
A Robustness Approach to Reliability
2012
Reliability of products is here regarded with respect to failure avoidance rather than probability of failure. To avoid failures, we emphasize variation and suggest some powerful tools for handling failures due to variation. Thus, instead of technical calculation of probabilities from data that usually are too weak for correct results, we emphasize the statistical thinking that puts the designers focus on the critical product functions. Making the design insensitive to unavoidable variation is called robust design and is handled by (i) identification and classification of variation, (ii) design of experiments to find robust solutions, and (iii) statistically based estimations of proper safe…