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Out-of-step Protection Using Energy Equilibrium Criterion in the Time DomainPaudyal, Sumit 03 July 2008
<p>Disturbances in power systems are common and they result in electromechanical oscillations called power swing. The power swings could be severe and it may lead to loss of synchronism among the interconnected generators. This is referred to as out-of-step condition. The voltage and current swings during an out-of-step condition damage power system equipments and also cause unwanted operations of various protective devices. The protection systems require an effective algorithm for fast and accurate detection of out-of-step condition. </p>
<p>This research is focused on the development of a simple and effective out-of-step relay capable of detecting out-of-step condition in a complex power system. To achieve this, the research has gone through four distinct stages: development of an algorithm, simulation, hardware implementation and its testing. </p>
<p>An out-of-step algorithm is proposed based on equal area criterion in time domain. The equal area criterion in time domain is obtained by modifying the traditional equal area criterion in power angle domain. A single machine infinite bus system, a two machine infinite bus system and a three machine infinite bus system and a 17-bus multiple machines system are used as case studies and are modeled using simulation tool(PSCAD).
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<p>To test the effectiveness of the proposed algorithm, various out-of-step conditions are simulated by applying disturbances at various locations in the above chosen power system configurations. For hardware implementation and testing of the algorithm, a digital signal processing board (ADSP-BF533 from Analog Devices ) is used. To test the performance of the developed digital relay in a closed loop, real time power system signals are necessary and therefore for this purpose, a Real Time Digital Simulator (RTDS) available in the power research laboratory is used. The RTDS simulator mimics the actual power systems in real time. The signals required by the relays can be tapped from the RTDS and the signals coming from relay can be fed back into the RTDS, which makes the closed loop testing of the digital relay possible. This research has yielded a simple out-of-step algorithm and unlike the other out-of-step detection techniques proposed in the literature does not need offline system studies to arrive at a solution.The developed digital out-of-step relay is capable of making decisions based only on the information available from its point of installation, thus it avoids the communication devices which is advantageous for the out-of-step protection of a complex power system. Finally, the simulation results show that the proposed algorithm can be applied to any power configurations and is faster compared to the conventional concentric rectangle schemes used in the literature.</p>
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Out-of-step Protection Using Energy Equilibrium Criterion in the Time DomainPaudyal, Sumit 03 July 2008 (has links)
<p>Disturbances in power systems are common and they result in electromechanical oscillations called power swing. The power swings could be severe and it may lead to loss of synchronism among the interconnected generators. This is referred to as out-of-step condition. The voltage and current swings during an out-of-step condition damage power system equipments and also cause unwanted operations of various protective devices. The protection systems require an effective algorithm for fast and accurate detection of out-of-step condition. </p>
<p>This research is focused on the development of a simple and effective out-of-step relay capable of detecting out-of-step condition in a complex power system. To achieve this, the research has gone through four distinct stages: development of an algorithm, simulation, hardware implementation and its testing. </p>
<p>An out-of-step algorithm is proposed based on equal area criterion in time domain. The equal area criterion in time domain is obtained by modifying the traditional equal area criterion in power angle domain. A single machine infinite bus system, a two machine infinite bus system and a three machine infinite bus system and a 17-bus multiple machines system are used as case studies and are modeled using simulation tool(PSCAD).
</p>
<p>To test the effectiveness of the proposed algorithm, various out-of-step conditions are simulated by applying disturbances at various locations in the above chosen power system configurations. For hardware implementation and testing of the algorithm, a digital signal processing board (ADSP-BF533 from Analog Devices ) is used. To test the performance of the developed digital relay in a closed loop, real time power system signals are necessary and therefore for this purpose, a Real Time Digital Simulator (RTDS) available in the power research laboratory is used. The RTDS simulator mimics the actual power systems in real time. The signals required by the relays can be tapped from the RTDS and the signals coming from relay can be fed back into the RTDS, which makes the closed loop testing of the digital relay possible. This research has yielded a simple out-of-step algorithm and unlike the other out-of-step detection techniques proposed in the literature does not need offline system studies to arrive at a solution.The developed digital out-of-step relay is capable of making decisions based only on the information available from its point of installation, thus it avoids the communication devices which is advantageous for the out-of-step protection of a complex power system. Finally, the simulation results show that the proposed algorithm can be applied to any power configurations and is faster compared to the conventional concentric rectangle schemes used in the literature.</p>
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Uma proposta de interconexão de proteções para detecção de ilhamento em sistemas de geração distribuída / Proposal interconnection protection for islanding detection in distributed generation systemsMuraro, Matias Rossato 27 February 2014 (has links)
This work presents a methodology for detecting islanding in distributed generation
systems - DG - which use internal combustion engines as primary sources and synchronous
generators connected directly to grid. The proposed method considers the characteristics of this
type of DG, and is based on the analyses of the injected power and voltage level to disable or
enable the under/over frequency protection.
The proposed protection scheme considers the frequency as the main electrical signal,
and has three stages: the first stage is disabled when power injected oscillations are detected, in
the others cases, the stage is enabled; the second stage is normally disabled, it will be enabled
when a balanced voltage is detected after a unbalanced voltage condition and the third stage is
normally enabled and is used to detect large frequency deviations.
The proposed protection was tested over diferentes events, islanding with different load
and generation levels, temporary short-circuit and islanding during short-circuit. The results
show the efficiency and reliability in detecting islanding, presenting no false detections. / Esse trabalho apresenta uma metodologia para detecção de ilhamento e proteção de
sistemas de Geração Distribuída - GD - as quais utilizam motores de combustão interna como
fontes primárias e possuem alternadores síncronos conectados diretamente na rede elétrica. A
metodologia proposta leva em consideração as características desse tipo de GD, e baseia-se na
análise da potência gerada e nos níveis de tensão para bloquear ou habilitar proteção de sub e
sobre-frequência.
O esquema de proteção proposto utiliza a frequência como grandeza elétrica principal,
e possui três estágios: o primeiro é bloqueado quando oscilações na potência injetada na rede
pela GD forem detectadas, nos outros casos, o estágio permanece ativo; o segundo estágio
está normalmente bloqueado, sendo desbloqueado quando as tensões sofrerem desequilíbrios e
passarem a apresentar tensões de linha equilibradas e o terceiro estágio atua sem bloqueios para
grandes desvios de frequência.
A metodologia proposta foi testada para diferentes cenários, como ilhamento em
diferentes níveis de geração e carga, curtos-circuitos momentâneos e curtos-circuitos seguidos
de ilhamento. A metodologia mostrou-se eficiente e confiável na detecção de ilhamento, não
apresentando atuações indevidas.
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Algoritmo de alto desempenho para proteção numérica de linhas de transmissão imune a oscilações de potência / High-performance algorithm for numerical protection of transmission lines immune to power swingsMorais, Adriano Peres de 04 May 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This Doctoral Thesis proposes a new methodology for transmission line protection
tolerant to power swings. The algorithm developed has the ability to detect, classify and
locate all fault types with and without power swings, including those that produce high values
of fault resistance. In a first step, it is proposed a fault distance estimator based on the leastsquare
curve fitting. The fault locator, for protection proposes, was modeled by a series R-L
circuit and differential equations. In a second step, the main causes and consequences of
power swings in transmission lines distance relays are introduced. Also in this context,
techniques to minimize these effects are presented. Besides, computer simulations of power
swings, with different fault scenarios, were carried out to realize comparative analyses
between the methods. The results show that none of the methods is efficient in all scenarios.
Hence, there is still some concern about the performance of the protection methods against
power swings. In a third step, it was developed an algorithm for numerical protection in
transmission lines immune to power swings. The detection and classification steps are based
on Mathematical Morphology. In order to obtain a safer operation of the relay, especially in
the boundaries of threshold set, a counting strategy was developed. The main innovation of
the work is based on difference of behavior of the exponentially decaying component (dc
component) during a fault and during a power swing. The dc component, obtained by means
of morphological filter, is used as a tripping criterion. Finally, in order to evaluate the
algorithm performance, tests with different fault and power swings scenarios were performed.
The results show that the technique has the speed and safety required even during power
swings due to the simplicity of the algorithm used in mathematical operations. / Neste trabalho propõe-se uma nova metodologia de proteção de linhas de transmissão,
tolerante as oscilações de potência. O algoritmo desenvolvido tem a capacidade de detectar,
classificar e localizar todos os tipos de faltas, com e sem a presença de oscilações de potência,
inclusive aquelas que produzem altos valores de resistência de falta. Em uma primeira etapa
com o emprego do método de ajuste de curvas por mínimos quadrados desenvolve-se um
estimador para localizar a posição das faltas. Para fins de proteção, este é modelado por meio
de um circuito R-L série representado por suas equações diferenciais. Em uma segunda etapa
são apresentadas as principais causas das oscilações de potência, bem como suas
consequências para os relés de distância de linhas de transmissão. Ainda neste contexto, são
apresentadas, analisadas e comparadas algumas técnicas destinadas a minimizar estes efeitos.
Essas técnicas foram testadas por meio de simulações computacionais, sob condições de
oscilação de potência com e sem a presença de curtos-circuitos, considerando-se diversos
valores de carregamento e frequências de oscilação. Os resultados mostraram que nenhum
método é totalmente eficiente para todos os cenários. Desse modo, ainda há algumas
incertezas sobre o desempenho das técnicas de proteção contra as oscilações de potência
existentes. Em uma terceira etapa, foi desenvolvido um algoritmo para proteção numérica de
linhas de transmissão imune as oscilações de potência. A metodologia faz uso da Morfologia
Matemática nas etapas de detecção e classificação das faltas. De modo a se obter uma maior
segurança na operação do relé, especialmente na região próxima ao limiar de operação,
incorporou-se uma estratégia de contagem diferente das tradicionais. A principal contribuição
do trabalho relaciona-se com a análise da diferença comportamental da componente
exponencial decrescente (componente dc) para uma situação de falta e de oscilação de
potência. Ou seja, a componente dc, obtida por meio de um filtro morfológico, é utilizada
como critério de disparo do relé de distância. Para avaliar o desempenho do algoritmo
desenvolvido, uma série de testes com diferentes cenários de faltas com e sem a presença de
oscilações de potência foram realizadas. Devido à simplicidade das operações matemáticas
utilizadas no algoritmo, a técnica apresenta segurança e velocidade na sua operação, mesmo
durante oscilações de potência.
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