1,721,039 research outputs found
Power system components reliability assessment and bayes estimation in the presence of switching voltage surges using a Weibull stress-strength model
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Approccio stocastico alla sicurezza: definizione di indici di sicurezza in ambito tecnologico
No full textI concetti di rischio e sicurezza sono strettamente legati
alla possibilità che al verificarsi di un evento accidentale
si presenti una situazione di pericolo per persone
o cose, e la sua definizione è legata alla valutazione delle
probabilità di occorrenza di tali eventi e delle loro conseguenze. Nel presente lavoro, illustrata una metodologia
stocastica adeguata alla definizione di indici di sicurezza validi
in ambito tecnologico, si presentano 2 indici, validi rispettivamente
per sistemi “con memoria” e “senza memoria”
Theoretical and Practical Aids for the Proper Selection of Reliability Models for Power System Components
No full textThis paper gives theoretical and practical aids for the proper selection of reliability models for power system components. Firstly, the most adopted reliability models in the literature about electrical components are reviewed and the classical 'direct reliability assessment' is described. Then, phenomenological and physical models for the estimation of ageing and life of electrical insulation (the weakest part of many devices) are illustrated. Finally, numerical and graphical examples show that seemingly similar reliability models can possess very different lifetime percentiles and hazard rates. Thus model selection must be accomplished very carefully, since it involves completely different maintenance actions and costs
The Log-logistic model for reliability characterization of power system components subjected to random stress
No full textBayes Parametric Estimation of Insulation Reliability under Distorted Voltage
No full textEstimating the useful life of power system components is of considerable importance both in planning, to properly assess the costs, and in the management of such systems, to effectively schedule maintenance programs. The paper discusses the reliability of the insulation of power system components on the basis of well-known life models of such devices, with the aim of parametric statistical estimation of such models. With particular reference to insulated cables for traction systems under distorted regime, an experimentally-based and commonly adopted mathematical relationship between the lifetime of a given insulation affected by non-sinusoidal voltage and the levels of the harmonic voltages applied to such insulation is adopted, that is of the kind of the well-known Inverse Power Model (IPM). A Bayesian inference method for the estimation of the above model is illustrated, when the Gamma Exponential prior distribution - a new model here proposed - holds for the basic parameters of the above Inverse Power Model. The performance of these estimators are empirically analyzed through extensive numerical simulations under a wide range of parameter values. All the results show the feasibility and efficiency of such Bayes estimation, especially for very small sample sizes, as requested for the above applications
Negative Log-Gamma distribution for data uncertainty modelling in reliability analysis of complex systems
No full textArtificial Neural Network Application in Power Systems: Steady State Security Evaluation
No full textValutazione della sicurezza in chiave stocastica. Calcolo degli indici di sicurezza in ambito tecnologico
No full textQuesto lavoro è connesso e consequenziale ad
un precedente articolo [1] che tratta i concetti
di rischio e di sicurezza in ambito tecnologico.
In [1] si è dapprima discussa la distinzione semantica
tra security (sicurezza riferita a sistemi o apparati
tecnologici) e safety (sicurezza riferita all’incolumità delle
persone), mostrando che entrambe sono legate al concetto
di rischio [2, 3]; poi ci si è concentrati sulla security, esaminando
in tale ambito la definizione di rischio e sicurezza.
Si è poi illustrata la definizione di rischio e sicurezza in
due casi di interesse pratico per la progettazione e l’esercizio
di sistemi tecnologici: il caso di danno cumulativo e
quello di danno istantaneo (o “massimo”), pervenendo alla
definizione di un indice di sicurezza, designato come security
index (SI).In questo lavoro tali concetti sono brevemente
richiamati per applicarli alla valutazione del SI in alcuni
casi pratici di interesse tecnologico-ingegneristico,
con particolare riferimento ai sistemi elettrici
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