Voltage Collapse
Mostrando 13-24 de 24 artigos, teses e dissertações.
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13. Avaliação das condições de operação de sistemas eletricos de potencia com relação a estabilidade de tensão utilizando redes neurais artificiais / Voltage stability assesment via artificial neural networks
As mudan¸cas no setor eletrico tem influ?do de maneira dr´astica nas condicoes de operacao dos sistemas, levando-os a operar proximos da sua maxima capacidade. Por esta razao, estimar a proximidade do ponto de operacao da rede aos limites do sistema de forma eficiente tem se tornado uma tarefa fundamental na operacao de sistemas el´etricos de pot?encia. D
Publicado em: 2005
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14. MODELLING SPECIAL EQUIPMENTS OF TRANSMISSION NETWORK FOR VOLTAGE SECURITY ASSESSMENT / MODELAGEM DE EQUIPAMENTOS ESPECIAIS DA REDE DE TRANSMISSÃO PARA AVALIAÇÃO DA SEGURANÇA DE TENSÃO
With the extreme use of the transmission lines, the voltage stability problem, or more properly, the voltage security problem has appeared. The voltage security condition assessment is achieved using the computational program ESTABTEN. The calculated indexes are based on a system operation point and on a linear model of load flow equations, likewise the ANAR
Publicado em: 2003
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15. ANÁLISE DO CONGESTIONAMENTO EM REDES DE TRANSMISSÃO APLICADA AO PROBLEMA DO REFORÇO DE SEGURANÇA DE TENSÃO / TRANSMISSION CONGESTION ANALYSIS APPLIED ON VOLTAGE SECURITY REINFORCEMENT PROBLEM
After a number of collapses due to the extreme use of the transmission lines, the voltage stability, or voltage security, became an important issue. This work was developed in order to contribute to a voltage security reinforcement method. The method calculates control actions to decrease the power flowing through the critical branch of the most loaded trans
Publicado em: 2003
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16. ÍNDICES E MARGENS PARA AVALIAÇÃO DA SEGURANÇA DE TENSÃO / INDEXES AND MARGINS FOR VOLTAGE SECURITY ASSESSMENT
Apresenta-se uma abrangente ferramenta de avaliação das condições de segurança de tensão, composta de índices com significado físico / matemático, propícia para uso na operação em tempo real. A ferramenta identifica se a solução de tensão para uma carga conectada à barra i está na parte superior, na inferior e a distância ao máximo carrega
Publicado em: 2003
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17. VOLTAGE STABILITY REINFORCEMENT ON ELETRIC POWER SYSTEMS / REFORÇO DAS CONDIÇÕES DE ESTABILIDADE DE TENSÃO NA OPERAÇÃO DO SISTEMA ELÉTRICO
As the electric power transmission networks became more interconnected, the thermal limits of lines and transformers restrict less the power transmission. Similarly, the use of static systems of reactive power compensation increases the power transmission capacity in systems whereas before they were limited by problems of angular stability. Actually, transmi
Publicado em: 2002
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18. CONTINGENCY SCREENING AND RANKING FOR VOLTAGE SECURITY ASSESSMENT / SELEÇÃO E ORDENAÇÃO DE CONTINGÊNCIAS PARA AVALIAÇÃO DAS CONDIÇÕES DE SEGURANÇA DE TENSÃO
O uso de compensação de potência reativa, embora permita um carregamento mais elevado do sistema elétrico, leva-o a operar próximo de situações de colapso de tensão. Portanto, tornou-se necessário analisar o comportamento do sistema quanto a esse fenômeno na ocorrência de contingências. Neste trabalho alguns métodos existentes são estudados par
Publicado em: 2002
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19. Metodos de solução do fluxo de potencia otimo reativo e tratamento das restrições de desigualdade
The Reactive Optimal Power Flow (ROPF) is a computational optimization tool that dispatches all reactive power sources of an electrical power system. It is extremely important in power system planning, operation and voltage collapse simulation. Its mathematical modeling involves nonlinear nonconvex equality constraints and linear and nonlinear nonconvex ineq
Publicado em: 1999
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20. AN ASSESSMENT OF THE VOLTAGE COLLAPSE PHENOMENON / UMA AVALIAÇÃO DO FENÔMENO DO COLAPSO DE TENSÃO
Investiments on new generators and transmission lines for electrical power systems have been limited due to economical and environmental constraints. This dissertation established the operational characteristics of the voltage collapse phenomenon, as well as pointed out similarities and differences in relation to the angular stability problem. Voltage collap
Publicado em: 1990
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21. Effect of colicins Ia and E1 on ion permeability of liposomes.
Colicins Ia and E1 are shown to inhibit the formation and bring about the collapse of a potassium diffusion potential imposed across the membrane of liposomes prepared from soybean or Escherichia coli phospholipids. Such depolarization results from a colicin-induced increase in membrane ion permeability. Colicins E2 and E3 do not depolarize such membranes. I
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22. Identification of a Transport Mechanism for NH4+ in the Symbiosome Membrane of Pea Root Nodules.
Symbiosome membrane vesicles, facing bacteroid-side-out, were purified from pea (Pisum sativum L.) root nodules and used to study NH4+ transport across the membrane by recording vesicle uptake of the NH4+ analog [14C]methylamine (MA). Membrane potentials ([delta][psi]) were imposed on the vesicles using K+ concentration gradients and valinomycin, and the siz
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23. A potential role for guanine nucleotide-binding protein in the regulation of endosomal proton transport.
The effects of guanosine 5'-triphosphate (GTP) and GTP-gamma-S, known activators of GTP binding proteins, on proton transport were investigated in endosome-enriched vesicles (endosomes). Endosomes were prepared from rabbit renal cortex following the intravenous injection of FITC-dextran. The rate of intravesicular acidification was determined by measuring ch
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24. Independent pathways regulate the cytosolic [Ca2+] initial transient and subsequent oscillations in individual cultured arterial smooth muscle cells responding to extracellular ATP.
Stimulation with extracellular ATP causes a rapid initial transient rise followed by asynchronous periodic oscillations in cytosolic calcium ion activity ([Ca2+]i) in individual aortic smooth muscle cells in either HEPES-buffered or HCO3(-)-buffered saline. The dose at which one-half of the cells display an initial rise in cytosolic calcium is 0.11 microM AT