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Santa Clara, Cuba

The University "Marta Abreu" of Las Villas " is a university located in Santa Clara, Cuba. It was founded in 1952 and is organized in 12 Faculties and special Mountain Faculty located in Topes de Collantes, the heart of the Escambray Mountain Range. Wikipedia.

Perez Abril I.,University "Marta Abreu" of Las Villas
IEEE Latin America Transactions | Year: 2010

The measurements registered in eight of the 50 primary distribution circuits of Santa Clara city (Cuba), shown the presence of a 29.8% of phase currents unbalance and a 51.5% of neutral current as average. The phase current unbalance increases the energy losses in primary circuit and contributes to voltages unbalance on the different buses. On the other hand, the presence of a high neutral current on normal operation make it difficult the detection of earth faults by neutral over current relays. The main purpose of this work is to develop a method that determines the minimal reconnection operations needed for the two-phase three-wire and the single-phase twowire circuit laterals, as well as for the three-phase transformers banks and the single-phase distribution transformers, to minimize the energy losses on the primary distribution circuit and reduce the neutral current to an accepted level. A successful application example of the presented methodology is achieved in a distribution circuit of the Santa Clara city. The results show the energy saving benefits as well as the neutral current reduction on the circuit. Source

Abril I.P.,University "Marta Abreu" of Las Villas
International Journal of Electrical Power and Energy Systems | Year: 2016

The primary distribution systems are among the more unbalanced three-phase networks. The unbalance of the phase currents causes two fundamental problems in the circuits: the increase of energy losses in the primary feeders and the presence of a high neutral current in normal operating status that makes it difficult the detection of ground faults by corresponding protections. These circuits are always protected at the substation. Nevertheless, other protections can also be located downstream in some sections or laterals of the circuit. Additionally, a circuit or some section of it can be supplied from another adjacent circuit in emergency conditions. In all the points where a ground fault protection is used, the maximum current of imbalance must be reduced to a minimum considering the several operating conditions that can change the circuit topology. This paper formulates the problem of phase balancing as a multi-objective optimization problem that minimizes: the neutral current at the desired points of the circuit, the energy losses in the primary feeders and the number of reconnected elements to achieve these objectives. The Non-dominated Sorting Genetic Algorithm (NSGA-II) has been used to develop the optimization application, which has shown a very successful performance in the solution of the phase balancing problem. A test example with all the needed data is solved to show the advantages of the presented approach. © 2016 Elsevier Ltd. All rights reserved. Source

Frias M.,CSIC - Eduardo Torroja Institute for Construction Science | Garcia R.,Unidad University | De La Villa R.V.,Unidad University | Villar E.,University "Marta Abreu" of Las Villas
Construction and Building Materials | Year: 2013

This paper presents for the first time the influence of mixing different thermally activated paper sludges (APS) and fly ash (FA) on the pozzolanic reaction kinetics in APS-FA-Ca(OH)2 systems as a previous step to manufacture the future commercial ternary blended cements. In this study, two paper sludge wastes from different origins and activation conditions (laboratory (LS) and industrial (IS) scale) have been investigated, once mixed with fly ash at a ratio of 1:1 by weight. The results indicated that binary blends of pozzolans exhibited a high pozzolanic activity, showing that the hydrated phases produced during the pozzolanic reaction depend on the origin and activation conditions of clay wastes. At all times of reaction, the predominant phase turn out to be the LDH structures when LS pozzolan was used; meanwhile for the IS pozzolan the C4ACH12 along with the LDH were the main phases during the first 28 days. © 2012 Elsevier Ltd. All rights reserved. Source

Santos-Fernandez E.,University "Marta Abreu" of Las Villas | Scagliarini M.,University of Bologna
Journal of Statistical Software | Year: 2012

Manufacturing processes are often based on more than one quality characteristic. When these variables are correlated the process capability analysis should be performed using multivariate statistical methodologies. Although there is a growing interest in methods for evaluating the capability of multivariate processes, little attention has been given to developing user friendly software for supporting multivariate capability analysis. In this work we introduce the package MPCI for R, which allows to compute multivariate process capability indices. MPCI aims to provide a useful tool for dealing with multivariate capability assessment problems. We illustrate the use of MPCI package through both simulated and real examples. Source

Roque Diaz P.,University "Marta Abreu" of Las Villas | Benito Y.R.,Pontifical Catholic University of Rio de Janeiro | Parise J.A.R.,Pontifical Catholic University of Rio de Janeiro
Energy | Year: 2010

Design and operation of complex systems for combined cooling, heating and power generation (CCHP) are always a matter of matching performance and demand characteristics of a thermal system set to supply electrical, cooling and heating loads, according to specific usage demands. Equipment selection and operation require the characterization of power, heating and cooling load demands, and their time variation during years, seasons, months and even hours or minutes. The paper aims at utilizing a general model for complex CCHP systems. The proposed model is based on the general theory of exergy cost and structural coefficients of internal links. A general model is presented, and a simple hypothetical cogeneration case is studied. The system operates with two heat engines, with waste heat recovery driving a chiller, in order to meet electrical power and refrigeration loads. © 2010 Elsevier Ltd. Source

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