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Sacavem, Portugal

REN - Redes Energéticas Nacionais, SGPS, S.A. is a Portuguese energy sector company which is the current concession holder of the country's two main energy infrastructure networks: the National Electricity Transmission Grid and the National Natural Gas Transportation Grid . It is responsible for the planning, construction, operation, maintenance and global technical management of both these grids and associated infrascrutures. Its stated mission is to provide a guarantee of an uninterrupted and stable supply of energy while ensuring equal rights of grid access to the remaining participants in the energy market, including consumers, generators and distributors.The company is also involved with the storage and transportation of liquefied natural gas, and owns and operates an LNG regasification terminal located at Sines. Wikipedia.

Giner-Reichl I.,REN - Rede Electrica Nacional
Energy Research and Social Science | Year: 2015

Energy is slowly accepted as a key dimension of sustainable development and a key factor for emerging frameworks of global and regional governance. This bodes well for the development of countries in Sub-Saharan Africa where energy poverty is a key component of extreme poverty. © 2014 Elsevier Ltd All rights reserved. Source

Dos Santos A.,University of Lisbon | Dos Santos A.,REN - Rede Electrica Nacional | De Barros M.T.C.,University of Lisbon
IEEE Transactions on Power Delivery | Year: 2016

The performance of three commonly used busbar protection architectures (centralized, decentralized, and redundant) is compared, taking into account the reliability indices (failure rate and mean time to repair) of their components. The protection system performance is analyzed, considering that the probability of successful fault clearance is given by system availability. The different architectures were applied to a double busbar with a bus coupler substation. The busbar protection architectures are described by reliability graphs, and the availabilities are computed by Monte Carlo simulation. Key performance indicators are introduced and the influence of the substation size on the protection system performance is analyzed. A comparative study is carried out, allowing to quantify the benefits of the different design options. © 1986-2012 IEEE. Source

Pinto De Sa J.L.,University of Lisbon | Cartaxo R.,REN - Rede Electrica Nacional
IEEE Transactions on Power Delivery | Year: 2011

This paper shows how cooperative automatic control functions in transmission substations, specified by Petri Nets (PN), fit the IEC 61850 standard. In the PN model, each automaton is specified by an interpreted state machine communicating with others through shared conditions, featuring operational improvements and still ensuring good behavior, as it can be proven through formal analysis. However, to avoid jeopardizing the good properties of the model in a distributed implementation, a few rules on how to split the functions in concurrent tasks must be followed, particularly on how some runtime conflicts have to be resolved. Although the IEC 61850 environment provides a set of communication services for the substations functions, implementing PN specifications on it is not a straightforward process. Therefore, a new class of logical nodes is proposed to model the functions required for that purpose. © 2011 IEEE. Source

Barcia P.,New University of Lisbon | Pestana R.,REN - Rede Electrica Nacional
International Journal of Electrical Power and Energy Systems | Year: 2010

Consider an electrical power system and let G denote the set of nodes with net generation, L the set of nodes with a net load and assume the DC model of the network. Our aim is to determine how much power is each node of G sending to each node of L in such a way that the flow decomposition arising from this assignment is such that each branch flow is broken in parcels of the (as much as possible) same orientation in order to provide a sensible tool for transmission cost allocation. © 2009 Elsevier Ltd. All rights reserved. Source

REN - Rede Electrica Nacional | Date: 2011-07-07

A multi-abrasive tool is constituted by a support on which abrasive elements are present. Such abrasive elements are arranged in a manner so as to form one or more paths along which the successive abrasive elements have grain size sequentially increasing or decreasing by an arbitrary quantity when passing from on element to the next. Such principle gives rise to abrasive tools with different conformation both for polishing machines and for grindstones. For roto-orbital and planetary polishing machines, and optionally orbital, such support is circular and the grain sequence is circumferential, or radial, or in both directions. A first tool is constituted by contiguous (or non-contiguous) circular rings, that are differently abrasive. A second tool comprises differently abrasive elements arranged along the circular peripheral edge. A third tool comprises differently abrasive elements arranged along a spiral path of 360 starting from the edge. A fourth tool comprises two 180 spiral paths with reversed roughness sequences. A fourth tool comprises pairs of differently abrasive small cylinders fixed to a plate on concentric circumferences. A fifth tool is obtained directly on the plate of the polishing machine by means of reliefs and spacers for fixing differently abrasive sectors. For linear polishing machines, the abrasive support is a belt along which differently abrasive rectangular or oblique zones follow each other. For alternative polishing machines, the abrasive support is a plate shaped like the aforesaid belt. For tools to use with grindstones, the multi-abrasive element has a cylindrical rotation symmetry, or conical with rounded tip, or spherical symmetry.

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