Efficient procedure to evaluate electromagnetic transients on three-phase transmission lines

This paper presents a hybrid way mixing time and frequency domain for transmission lines modelling. The proposed methodology handles steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behaviour. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents an easy and practical procedure to model a three-phase transmission line directly in time domain, without the explicit use of inverse transforms. The proposed methodology takes into account the frequency-dependent parameters of the line, considering the soil and skin effects. In order to include this effect in the state matrices, a fitting method is applied. Furthermore the accuracy of proposed the developed model is verified, in frequency domain, by a simple methodology based on line distributed parameters and transfer function related to the input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust analytic integration procedure to solve the state equations, enabling transient and steady-state simulations. The results are compared with those obtained by the commercial software Microtran (EMTP), taking into account a three-phase transmission line, typical in the Brazilian transmission system.

Integration Methods Used in Numerical Simulations of Electromagnetic Transients

This paper made an analysis of some numerical integration methods that can be used in electromagnetic transient simulations. Among the existing methods, we analyzed the trapezoidal integration method (or Heun formula), Simpson's Rule and Runge-Kutta. These methods were used in simulations of electromagnetic transients in power systems, resulting from switching operations and maneuvers that occur in transmission lines. Analyzed the characteristics such as accuracy, computation time and robustness of the methods of integration.

Using Universal Line Model (ULM) for Representing Electromagnetic Transients in Three-Phase Transmission Lines

The second-order differential equations that describe the polyphase transmission line are difficult to solve due to the mutual coupling among them and the fact that the parameters are distributed along their length. A method for the analysis of polyphase systems is the technique that decouples their phases. Thus, a system that has n phases coupled can be represented by n decoupled single-phase systems which are mathematically identical to the original system. Once obtained the n-phase circuit, it's possible to calculate the voltages and currents at any point on the line using computational methods. The Universal Line Model (ULM) transforms the differential equations in the time domain to algebraic equations in the frequency domain, solve them and obtain the solution in the frequency domain using the inverse Laplace transform. This work will analyze the method of modal decomposition in a three-phase transmission line for the evaluation of voltages and currents of the line during the energizing process.

Spurious transients of projection methods in microflow simulations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação de tanques de escorva utilizados em substituição à válvula-de-pé em instalações de bombeamento

A maioria das instalações de abastecimento de água utiliza bombas hidráulicas do tipo turbobombas, requerendo que o interior de sua carcaça e da tubulação de sucção esteja preenchido com água (escorvados) para que a sucção da água possa ser efetivada. O escorvamento das bombas pode ser efetuado instalando-as abaixo do reservatório de captação (bomba afogada). Quando a bomba está acima do reservatório e o escorvamento é manual, é necessário usar válvulas-de-pé, que são suscetíveis ao mau funcionamento, limitando a confiabilidade do sistema, principalmente em caso de automação. Como alternativa à válvula-de-pé, neste trabalho, foram estudados dois tanques escorva, testados no Laboratório de Hidráulica e Irrigação da FCAV/UNESP - Jaboticabal, avaliando-se situações de altura manométrica de sucção de bomba centrífuga e relações entre volume útil do tanque e volume do tubo de sucção, tendo-se concluído: a) o volume do tanque de escorva é função do volume do tubo de sucção da instalação de bombeamento e da altura manométrica de sucção; b) o volume do tanque de escorva pode ser calculado seguindo-se a Lei de Boyle, com percentagem de acréscimo que, neste estudo, foi de 10% para um modelo de tanque e de 30% para o segundo modelo.

Representação de linhas de transmissão por meio de variáveis de estado levando em consideração o efeito da freqüência sobre os parâmetros longitudinais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Decomposição modal de linhas de transmissão a partir do uso de duas matrizes de transformação

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Proposal of an alternative transmission line model for symmetrical and asymmetrical configurations

This article shows a transmission line model for simulation of fast and slow transients, applied to symmetrical or asymmetrical configurations. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents a practical procedure to model three-phase transmission lines directly in time domain, without the explicit or implicit use of inverse transforms. In three-phase representation, analysis modal techniques are applied to decouple the phases in their respective propagation modes, using a correction procedure to set a real and constant matrix for untransposed lines with or without vertical symmetry plane. The proposed methodology takes into account the frequency-dependent parameters of the line and in order to include this effect in the state matrices, a fitting procedure is applied. To verify the accuracy of the proposed state-space model in frequency domain, a simple methodology is described based on line distributed parameters and transfer function associated with input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust integration procedure to solve the state equations, enabling transient and steady-state simulations. The results obtained by the proposed methodology are compared with several established transmission line models in EMTP, taking into account an asymmetrical three-phase transmission line. The principal contribution of the proposed methodology is to handle a steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behavior, by a practical procedure applied directly in time domain for symmetrical or asymmetrical representations. (C) 2011 Elsevier Ltd. All rights reserved.

Alternative Model of Three-Phase Transmission Line Theory-Based Modal Decomposition

In this paper is shown the development of a transmission line, based on discrete circuit elements that provide responses directly in the time domain and phase. This model is valid for ideally transposed rows represent the phases of each of the small line segments are separated in their modes of propagation and the voltage and current are calculated at the modal field. However, the conversion phase-mode-phase is inserted in the state equations which describe the currents and voltages along the line of which there is no need to know the user of the model representation of the theory in the field lines modal.

Proposal of a Transmission Line Model Based on Lumped Elements: An Analytic Solution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Analysis of the Electrical Characteristics of an Alternative Solution for the Brazilian-Amazon Transmission System

This article analyzes the electrical parameters of a 3-phase transmission line using a 280-m-high steel tower that has been proposed for the Amazon transmission system in Brazil. The height of the line conductors and the distance between them are intrinsically related to the longitudinal and transverse parameters of the line. Hence, an accurate study is carried out in order to show the electrical variations between a transmission line using the new technology and a conventional 3-phase 440-kV line, considering a wide range of frequencies and variable soil resistivity. First, a brief review of the fundamental theory of line parameters is presented. In addition, by using a digital line model, simulations are carried out in the time domain to analyze possible and critical over-voltage transients on the proposed line representation.

Alternative proposal for Modal Representation of a Non-transposed Three-Phase Transmission Line with a Vertical Symmetry Plane

The objective of this paper is to show an alternative representation in time domain of a non-transposed three-phase transmission line decomposed in its exact modes by using two transformation matrices. The first matrix is Clarke's matrix that is real, frequency independent, easily represented in computational transient programs (EMTP) and separates the line into quasi-modes a, b and zero. After that, Quasi-modes a and zero are decomposed into their exact modes by using a modal transformation matrix whose elements can be synthesized in time domain through standard curve-fitting techniques. The main advantage of this alternative representation is to reduce the processing time because a frequency dependent modal transformation matrix of a three-phase line has nine elements to be represented in time domain while a modal transformation matrix of a two-phase line has only four elements. This paper shows modal decomposition process and eigenvectors of a non-transposed three-phase line with a vertical symmetry plane whose nominal voltage is 440 kV and line length is 500 km.

Structural characterization of wild rubbers, microstructure of the rubber extracted from ficus elastica by C-13-NMR

Low molecular weight fractions of polyisoprene extracted from Ficus elastica Herb. ex Hornem. were studied by C-13-NMR. The identification of 2-3 trans terminal units at the end of the polymer chain needed the acquisition of more than 17 000 transients. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

Período de recuperação do investimento em bomba hidráulica de melhor rendimento em sistemas de bombeamento na tarifa horossazonal verde

Neste trabalho, ajustou-se um modelo matemático para quantificar o efeito da variação do rendimento da bomba hidráulica na variação dos custos de um sistema de bombeamento, na estrutura tarifária horossazonal verde (subgrupo A4) e o tempo de recuperação do capital investido no equipamento de maior rendimento. em seguida, o mesmo foi aplicado a um sistema de bombeamento para suprimento de um sistema de irrigação do tipo pivô central. As opções de rendimento da bomba hidráulica foram: 69,5% (bomba 1), 73% (bomba 2) e 78% (bomba 3), cujos custos de aquisição foram, respectivamente, R$ 6.176,00, R$ 8.479,00 e R$ 15.509,00. Os resultados da aplicação do modelo mostraram que: i) a substituição da bomba 1 pela bomba 2 foi viável, sendo o período de recuperação de capital 3,4 anos; ii) a substituição da bomba 1 pela bomba 3 foi viável, sendo o período de recuperação de capital 9,2 anos; iii) a substituição da bomba 2 pela bomba 3 foi inviável, sendo o período de recuperação de capital 21,1 anos superior ao período de amortização do investimento na avaliação econômica, considerado 15 anos.

Multiple effects of sibutramine on ejaculation and on vas deferens and seminal vesicle contractility

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)