4 research outputs found

    Preliminary Design of a Multilevel Converter Based De-Icing Application on the Italian Sub-Transmission Grid

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    The safe operation of high voltage overhead lines (OHLs) can be hampered by the accumulation of ice and snow on conductors. In this regard, the high voltage OHLs that cross the mountainous regions of the Alps and Apennines in Italy are of particular concern. Numerous utilities have also experienced this problem, requiring effective solutions to avoid and minimize the damages. The solution proposed by Terna S.p. A, the Italian Transmission System Operator, focuses on the relatively short (20-40 km) 132 kV and 150 kV OHLs of the Italian sub-transmission grid in the Alps and Apennines, which are generally equipped with small (15.75-22.8 mm diameter) conductors. The de-icing procedure is provided by a cascade connection of two multilevel neutral point clamped converters, capable to supply up to 1200 A at very low frequency. With the possibility to operate directly on the transfer bus of the substation with power electronic converters, this configuration exhibits high compactness and efficiency. This paper deals with the design of the multilevel converters based de-icing system operating across the Italian sub-transmission network in the Alps and Apennines. The electrical performance of the system is evaluated through a detailed model developed with the software ATP-EMTP. The thermal analysis of the de-icing procedure is also envisaged

    N-3 fatty acids in patients with multiple cardiovascular risk factors

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    Are all people with diabetes and cardiovascular risk factors or microvascular complications at very high risk? Findings from the Risk and Prevention Study

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    N-3 fatty acids in patients with multiple cardiovascular risk factors

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    BACKGROUND: Trials have shown a beneficial effect of n-3 polyunsaturated fatty acids in patients with a previous myocardial infarction or heart failure. We evaluated the potential benefit of such therapy in patients with multiple cardiovascular risk factors or atherosclerotic vascular disease who had not had a myocardial infarction. METHODS: In this double-blind, placebo-controlled clinical trial, we enrolled a cohort of patients who were followed by a network of 860 general practitioners in Italy. Eligible patients were men and women with multiple cardiovascular risk factors or atherosclerotic vascular disease but not myocardial infarction. Patients were randomly assigned to n-3 fatty acids (1 g daily) or placebo (olive oil). The initially specified primary end point was the cumulative rate of death, nonfatal myocardial infarction, and nonfatal stroke. At 1 year, after the event rate was found to be lower than anticipated, the primary end point was revised as time to death from cardiovascular causes or admission to the hospital for cardiovascular causes. RESULTS: Of the 12,513 patients enrolled, 6244 were randomly assigned to n-3 fatty acids and 6269 to placebo. With a median of 5 years of follow-up, the primary end point occurred in 1478 of 12,505 patients included in the analysis (11.8%), of whom 733 of 6239 (11.7%) had received n-3 fatty acids and 745 of 6266 (11.9%) had received placebo (adjusted hazard ratio with n-3 fatty acids, 0.97; 95% confidence interval, 0.88 to 1.08; P=0.58). The same null results were observed for all the secondary end points. CONCLUSIONS: In a large general-practice cohort of patients with multiple cardiovascular risk factors, daily treatment with n-3 fatty acids did not reduce cardiovascular mortality and morbidity. Copyright © 2013 Massachusetts Medical Society
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