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Brasília, Brazil

Hallwass G.,Federal University of Rio Grande do Sul | Lopes P.F.,Federal University of Rio Grande do Norte | Juras A.A.,Eletronorte | Silvano R.A.M.,Federal University of Rio Grande do Sul
Environmental Management

The management of small-scale freshwater fisheries in Amazon has been based usually on surveys of urban markets, while fisheries of rural villages have gone unnoticed. We compared the fishing characteristics (catch, effort and selectivity) between an urban market and five small villages in the Lower Tocantins River (Brazilian Amazon), downstream from a large reservoir. We recorded 86 and 601 fish landings in the urban market and villages, respectively, using the same methodology. The urban fishers showed higher catch per unit of effort, higher amount of ice (related to a higher fishing effort, as ice is used to store fish catches) and larger crew size per fishing trip, but village fishers had a higher estimated annual fish production. Conversely, urban and village fishers used similar fishing gear (gillnets) and the main fish species caught were the same. However, village fishers showed more diverse strategies regarding gear, habitats and fish caught. Therefore, although it underestimated the total amount of fish caught in the Lower Tocantins River region, the data from the urban market could be a reliable indicator of main fish species exploited and fishing gear used by village fishers. Monitoring and management should consider the differences and similarities between urban and rural fisheries, in Amazon and in other tropical regions. © Springer Science+Business Media, LLC 2010. Source

Rosolem J.B.,Brazilian Center for Research and Development in Telecommunications | Floridia C.,Brazilian Center for Research and Development in Telecommunications | Sanz J.,Eletronorte
43rd International Conference on Large High Voltage Electric Systems 2010, CIGRE 2010

Classical systems for monitoring hydro generators normally use the following variables: •Turbine: pressure of spiral duct, cover and discharge; •Generator: copper, core and cooling water temperature, partial discharges, core vibrations, cooling water pressure; •Bearings: axis oscillations, cover vibrations, metal and oil temperatures; •Excitation system: slip ring temperature, current, voltage, rotor temperature, electric field. In these systems, electric variables and temperatures are transmitted from the supervisory system by means of communication device. The other variables as oscillations, vibrations, pressures, partial discharges and electric field are available by means of specific sensors, connected directly or through electronic devices to a computer, which condition and organize the data. This structure of monitoring systems, despite its important use to predict failures, has important installation cost and requires periodic calibration of the measurement chains. The development of sensors based on fiber optics technology offers new capabilities for the monitoring systems: the first available sensors are of the direct or intrinsic type, namely that the sensor is inlaid in the fiber, such as temperature, pressure, vibrations sensors. Eletronorte, a Brazilian utility company located in the Amazon region, interested in monitoring systems that are simple, more trustworthy and less onerous, decided to invest in the development of the two more required and not yet available sensors in the market: a sensor for oscillation of shaft and other for partial discharges. As the rotor is a component of the generator without supervision, Eletronorte also developed an optic communication system for the data measured at the rotor (temperature mainly) with optic sensors that transmit the measured data to the part fixed on the stator. The sensor of axis oscillation is of the indirect or extrinsic type, when the transducer acts in the fiber, using the magnetic properties of the sensor to intervene with implanted grid of Bragg in the fiber. The partial discharges sensors are of the hybrid type, when the fiber takes the information of the transducer, an antenna type minder that catches the induced impulses of partial discharges, transforms them into luminous impulses, which are then transmitted by the fiber. The communication system of data measured in the rotor consists of two collimators, one installed at the rotor that receives the measurements carried out by the rotor embarked optic sensors, and the other in the stator, that catches the measured signals each time that the mobile collimator passes in front of it, enabling the direct measurement of the temperature of the polar regions and the wheel deformation. Considering that the current technology allows to place 80 optic sensors in a fiber loop, and that a total monitored hydro generator would need approximately 150 measurement points, two optical-fiber loops can transmit the monitored data; therefore for reliable measurement, the number of loops can be increased decreasing the points distributed in each loop, in a way to get a control system and optoelectronic measurement multipoint and multiloop. Optic measurements are made by an interrogator module and converted into electronic and digital signals, enabling its treatment by a computer. A total optical system in the hydro generator environment guarantees an improved reliability because of its immunity to electromagnetic interferences. Source

Pereira C.S.,Federal University of Para | Almeida A.D.C.,Federal University of Para | Rocha B.R.P.,Federal University of Para | Frota W.M.,Eletronorte
Electric Power Systems Research

The vulnerability under lightning conditions of stretches of the 1500 km long electrical transmission line Tucurui-Oriximina-Manaus over dense Amazon forest canopy and river crossings is evaluated using a leader progression model (LPM) called ModSalto. We find vulnerability windows (low protection or unsafe) in all crossing stretches that use high towers to comply with environmental restrictions. The values of lightning flashover rates (LFR) reach 0.8277 flashover/year or an equivalent period of 14.49 months for stretches of river crossings, and 0.3403 flashover/year or an equivalent period of 35.26 months for stretches of forest canopy crossing. These numbers are above the computed equivalent ANEEL bidding figure of 0.15 flashover/year for that TL. This methodology uses a map of yearly lightning frequency produced with data from STARNET and SIPAM LLS and the level of lightning protection was evaluated with the electro-geometric model (EGM). © 2014 Elsevier B.V. All rights reserved. Source

Zimath S.L.,Reason Tecnologia | Ramos M.A.,Furnas Centrais Eletricas | Filho J.S.,Furnas Centrais Eletricas | Beck J.M.,Eletronorte | Mueller N.,Reason International
2010 63rd Annual Conference for Protective Relay Engineers

Transmission utility companies continuously strive for high availability of their lines. When a line is off service following a permanent fault, a significant amount of the time during the restore the line can be attributed to locating the point of the fault. This paper shows how this time can be significantly reduced using highly accurate traveling wave (TW) fault locators. It describes location results of several faults in three separated transmissions lines. The collected data are compared to those obtained by considering one- and two-end impedance location algorithms for the same faults. It also highlights the unique characteristics of Reason fault locators to overcome common problems of other TW solutions existing in the market. ©2010 IEEE. Source

Nogueira F.G.,Federal University of Ceara | Barra W.,Federal University of Para | Da Costa C.T.,Federal University of Para | Barreiros J.A.L.,Federal University of Para | De Lana J.J.,Eletronorte

In this paper, the application of linear parameter-varying (LPV) identification and control methods for designing and performance evaluation of an adaptive power system stabilizer (PSS) is presented. The target control objective is to improve the damping of the dominant electromechanical oscillating mode in the power system. The performance of the LPV PSS controller has been assessed by means of experimental tests carried out on 10 kVA small-scale power system. For design purposes, an LPV ARX model was estimated from experimental tests, for a wide range of operating conditions. The LPV controller was tuned via an optimization problem, in the form of a Parameterized Linear Matrix Inequality (PLMI). The solution was obtained through a sum-of-squares relaxation. Both the LPV model and the LPV-PSS have an explicit dependency on system scheduling variables, namely the active and reactive powers measurements. Therefore, the LPV-PSS was designed to ensure stability and performance for a wide range of operating conditions, an objective usually difficult to obtain by using fixed parameter controllers. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Source

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