Search results for "Reliability engineering"
showing 10 items of 224 documents
An imprecise Fault Tree Analysis for the estimation of the Rate of OCcurrence Of Failure (ROCOF)
2013
Abstract The paper proposes an imprecise Fault Tree Analysis in order to characterize systems affected by the lack of reliability data. Differently from other research works, the paper introduces a classification of basic events into two categories, namely Initiators and Enablers . Actually, in real industrial systems some events refer to component failures or process parameter deviations from normal operating conditions ( Initiators ), whereas others refer to the functioning of safety barriers to be activated on demand ( Enablers ). As a consequence, the output parameter of interest is not the classical probability of occurrence of the top event, but its Rate of OCcurrence (ROCOF) over a s…
A new methodology for distribution systems faults identification, location and characterization
2005
PurposeIdentify a new methodology for fault characterization, identification and location in electrical distribution systems, based on the use of matrix algebra.Design/methodology/approachThe developed diagnostic methodology is based on a high precision analytical model of the network using a distributed parameters representation.FindingsTest results have proved the approach to be efficient and precise, while providing a generalized quadripolar model of a line affected by the most common kinds of fault.Research limitations/implicationsGeneralization to a greater number of fault cases, experimental tests.Practical implicationsUtilities are quite interested in such items, since the new requir…
The New Nino Capability Index for Dynamic Process Capability Analysis
2013
The process capability analysis is a crucial activity to evaluate if the process outcome meets the design specifications. Classically, such analysis is performed by verifying the in-control condition of the process and evaluating suitable capability indices, by assuming the process in-control steady-state condition. However, the in-control period of the process characterizes only a part of the system functioning cycle, the one with the lower defective rate. In particular, the system functioning cycle is also characterized by the out-of-control period, during which a greater defective rate is produced, and such increasing is not considered by the widely adopted capability indices. As consequ…
Investigating the effect of distributed generators on traditional protection in radial distribution systems
2013
The recent changes in power network structure, development in green energy technologies and increased attention on environmental concerns have led to increase the installation of renewable energy based distributed generations (DG) in distribution networks. The increasing penetration of distributed generation in the distribution power system creates new technical and economical challenges; protection is one important topic of these challenges. High penetration of DG will have unfavorable impact on the traditional protection methods; the impact depends on the number, location and size of injected DG. To ensure safe and selective protection devices coordination, the impact of DG should be take…
The Quest for Global Safety
2007
The authors present a systematic study on the factors that have influence on the establishment of the safety conditions ensuring the rise of Global Earthing Systems. Starting from the definition of Global Earthing System given by CENELEC Document HD 637 SI and from the results of the studies done on the last years on the interconnected earthing systems inside MV networks, the paper proposes some directions of deepening on the topic of Global Safety. Some of the themes whom the paper deals with are: the correct definition of proximity, interconnection and quasi-equipotentiality of the earth electrodes belonging to a Global Earthing System; the influence of the presence of HV/MV stations on h…
Applicational Aspects of a New Diagnostic Methodology for Fault Location in MV Networks: Problems, Solutions and Improvements
2005
The electrical energy market liberalization has encouraged utilities to make new investments at distribution level so as to attain higher quality levels. Service continuity is one of the aspects of greater importance in the definition of the quality of the electrical energy, for this reason, the research in the field of faults diagnostic for distribution systems is spreading ever more. The Authors have just developed a new methodology for diagnostic management of automated distribution systems. The technique is based on the use of circuital models of the electrical system resulting from the composition of quadripoles. In this paper, after a brief description of the proposed approach, the is…
A composite indicator for water meter replacement in an urban distribution network
2012
In water supply management, volumetric water meter are typically used to measure users' consumption. With water meters, utilities can collect useful data for billing, assess the water balance of the system, and identify failures in the network, water theft and anomalous user behaviour. Despite their importance, these instruments are characterised by intrinsic errors that cause so-called apparent losses. The complexity of the physical phenomena associated with metering errors in aging water meters does not allow meter replacement to be guided by single parameters, such as the meter age or the total volume passed through the meter. This paper presents a meter replacement strategy based on a c…
Cost benefits of flexible hybrid cloud storage : Mitigating volume variation with shorter acquisition cycle
2016
The hybrid cloud storage is investigated as a case of concurrent sourcing.The paper introduces an analytical model for hybrid cloud storage costs.We study the role of acquisition cycle and volume variation in hybrid cloud costs.Shortening the reassessment interval reduces the volume non-stationarity.Shortening the reassessment interval reduces the total hybrid costs. Hybrid cloud storage combines cost-effective but inflexible private storage along with flexible but premium-priced public cloud storage. As a form of concurrent sourcing, it offers flexibility and cost benefits to organizations by allowing them to operate at a cost-optimal scale and scope under demand volume uncertainty. Howeve…
An execution, monitoring and replanning approach for optimal energy management in microgrids
2011
abstract This work develops a new approach for optimal energy management of electrical distribution ‘smart-grids’. Optimality aims at improving sustainability through the minimization of carbon emissions and atreducing production costs and maximizing quality. Input data are the forecasted loads and productionsfrom renewable generation units, output data are a set of control actions for the actuators. Theconsidered electrical distribution system includes storage units that must be considered over a 24 h timeinterval, to consider an entire charge and discharge cycle. The objectives for the optimal management ofdistributed (renewables and not) generation are technical, economical and environme…
Technical and Economical Analysis of Different Measures for Efficient Operation of a Distribution Network in a Mediterranean Island
2006
The paper performs a technical and economical comparison of different measures to improve the efficiency of a MV system for power distribution in the Mediterranean island of Lampedusa. The study takes into consideration three possible measures: 1) rated voltage increase from 10 kV to 20 kV; 2) reactive power compensation with fixed capacitor banks; 3) reactive power compensation with switchable capacitor banks. While the study of the first two considered measures is carried out with classical design methods, the optimal reactive design with switchable capacitor banks is carried out by means of a specific software set up at the DIEET and implementing the multiobjective optimization genetic a…