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- A power amplifier system for testing of distance relay operating characteristicPublication . Marçal, Rui; Rodrigues, Ricardo; Fortunato, Carlos; Martins, L. Sousa; Pires, V. FernãoThis paper describes a power amplifier system for testing of distance relay operating characteristic. This power amplifier is based on two three phase inverters with a neutral wire. The output power currents and voltages are controlled by a sliding mode controller. A developed matlab/simulink digital simulator generates the test signals. This test signals are converted in current and voltage references using a microcontroller to connect the digital simulator to the power converter amplifier. Experimental results from a laboratory prototype are presented and discussed.
- A current differential line protection using a synchronous reference frame approachPublication . Martins, L. Sousa; Fortunato, Carlos; Pires, V. FernãoThis paper presents a new approach for a current differential protection of the transmission lines. This approach is based on the Park transformation or ABC-dqo transformation. Using the ABC-dqo transformation the three phase quantities are transformed into a synchronous rotating reference frame. In this way, the line currents of the three phase system are measured and transformed into three dc components. So, immunity to problems such as sampling misalignment and time delay of the communication channel will be improved. Several test results are presented in order to show the effectiveness of the proposed approach.
- Transmission lines protection based on the current eigenvalues differential conceptPublication . Pires, V. Fernão; Guerreiro, M.; Fortunato, Carlos; Martins, L. SousaThis work presents a new approach for a current differential protection of the transmission lines. The proposed approach is based on the Clarke-Concordia transformation and principal component analysis. First the acquired current signals are transformed into “αβo” components by applying the Clarke-Concordia transformation. This allows obtaining typical patterns. To identify these patterns a principal component analysis is performed. Several tests under different fault conditions were performed. The obtained results allow verifying the effectiveness of the proposed approach.
- Euronet Lab, A Cloud V-Lab EnviromentPublication . Correia, Raúl Cordeiro; Fonseca, José ManuelIn this paper we present a proposal for the creation of a European V-labs web space. In its essence it would result in an open online laboratory, with a primarily practical nature. In this laboratory students will have the opportunity to develop skills in the “know-how-to-do” area, enabling them to conduct a series of practical experiences in “try-out” philosophy that will substantiate and consolidate all knowledge that the students acquired in lectures. It is quite possible that these resources aren’t available in all universities and institutions, specifically in the university where the student is. This environment provides substance to the Directive stated in the declarations of Bologna and Prague that expresses “the teaching process is therefore student-centered”, strengthening the final pedagogical aim of “learning to learn”, as lifelong learning is assumed as an indispensable stage. What we propose is the creation of a virtual environment for e-learning where a series of virtual labs in many areas of electronics, automation and robotics are available, in this environment it will do possible for any student of any of these universities to scheduling of experience in any institution that belongs to this cloud, and thus can perform is work for anytime that will be available and with technical resources available or not available in its own university.
- Energy and quality of service management in wireless multimedia sensor networksPublication . Pereira, Paulo; Gonçalves, José; Grilo, António; Fortunato, Carlos; Nunes, Mário; Casaca, AugustoSensor networks are composed of resource constrained nodes that capture data from the environment, preprocess it and then transmit it to a sink node. This paper presents a scenario for monitoring an electricity distribution network, an energy analysis of the used sensor nodes and an intelligent energy and quality of service (QoS) manager. This manager continuously adapts the provided QoS according to the energy level of the nodes.
- A wireless sensors suite for Smart Grid applicationsPublication . Grilo, António; Sarmento, Helena; Nunes, Mário; Gonçalves, José; Pereira, Paulo; Casaca, Augusto; Fortunato, CarlosThis paper presents a demonstrator of a Wireless Sensor and Actuator Network (WSAN) for Smart Grid applications, developed in the context of project WSAN4CIP. This WSAN is formed by WSAN nodes equipped with sensors and a wireless radio interface, which monitor key parameters of power grid equipments belonging to the Medium Voltage (MV) and Low Voltage (LV) segments. The measurements are reported to the SCADA system and constitute the basis of both safety and security services to improve the power grid distribution dependability. This paper describes the hardware of the sensor nodes and presents the respective performance results, attesting the feasibility of the proposed solutions.
- Physical Layer Aware Network Architecture for the Future InternetPublication . Cardoso, Filipe; Correia, Luís; Mannersalo, Petteri; Frantti, Tapio; Serrador, António; Nunzi, Giorgio; Genay, Naveena; Le Rouzic, EstherIn this article, physical layer awareness inaccess, core, and metro networks is addressed,and a Physical Layer Aware Network Architec-ture Framework for the Future Internet is pre-sented and discussed, as proposed within theframework of the European ICT Project4WARD. Current limitations and shortcomingsof the Internet architecture are driving researchtrends at a global scale toward a novel, secure,and flexible architecture. This Future Internetarchitecture must allow for the co-existence andcooperation of multiple networks on commonplatforms, through the virtualization of networkresources. Possible solutions embrace a fullrange of technologies, from fiber backbones towireless access networks. The virtualization ofphysical networking resources will enhance thepossibility of handling different profiles, whileproviding the impression of mutual isolation.This abstraction strategy implies the use of wellelaborated mechanisms in order to deal withchannel impairments and requirements, in bothwireless (access) and optical (core) environ-ments.
- Ontology: a support structure for a V-Labs Network, the Euronet - LabPublication . Correia, Raúl Cordeiro; Fonseca, José Manuel; Donnellan, AndrewThis paper presents work on the establishment of a virtual laboratories network, based on the concept of Virtual Closet that will contain all the elements and parts required to build the different experiences available in a vlabs network (that we call Euronet-Lab). To build this complex network it is necessary to find an adequate support. The large database of v-labs and independent elements that can integrate this structure allows the “recycling” of elements for purposes diverse from those they were originally created. This means to “re-use” the same element several times in different scenarios. In order to do this, it is necessary to have a structure that allows multiple instances of the same component. This paper will discuss the ontology essential to the establishment of such a network in order to standardize concepts and create uniform components description that supports the interaction between heterogeneous systems using shared parts or circuits.
- A computer-based testing system to evaluate protective relays as a tool in power system protection educationPublication . Martins, L. Sousa; Fortunato, Carlos; Pires, V. FernãoTeaching power system relaying is a fundamental issue in a power system high-level course. However, for an effective instruction of this topic an experience with real equipments can be considered as fundamental. To achieve this purpose, in this paper a new approach for the practical learning of power system relaying is presented. This consists of a computer-based testing system of relay-operating characteristic. Different relay types and developed specific software are also an important piece of the laboratory practice. Using this system it is possible to understand the performance and limitations of different protective relay systems and to test a real relay disoperation. The benefit of using this system is not available through traditional lectures and textbooks.
- A wireless sensor and actuator network for improving the electrical power grid dependabilityPublication . Grilo, António; Casaca, Augusto; Pereira, Paulo; Buttyan, Levente; Gonçalves, José; Fortunato, CarlosThis paper presents an overview of a Wireless Sensor and Actuator Network (WSAN) used to monitor an electrical power grid distribution infrastructure. The WSAN employs appropriate sensors to monitor key grid components, integrating both safety and security services, which improve the grid distribution dependability. The supported applications include, among others, video surveillance of remote secondary substations, which imposes special requirements from the point of view of quality of service and reliability. The paper presents the hardware and software architecture of the system together with performance results.