Universidade da Coruña. UDCDspace
(405 recursos)
UDCDspace é o repositorio dixital da Universidade da Coruña, un sistema que proporciona de xeito estable e seguro a preservación de documentos dixitais produto da actividade científica e institucional da UDC, e facilita a súa accesibilidade en Internet.
Mostrando recursos 1 - 20 de 77
1.
Analytical integration techniques for earthing grid computation by boundary
element methods - Navarrina Martínez, Fermín; Colominas Ezponda, Ignasi; Casteleiro Maldonado, Manuel
Analysis and design of substation earthing involves computing the equivalent resistance of grounding systems, but also distribution of potentials on the
earth surface due to fault currents [1]. While very crude approximations were
available in the sixties, several methods have been proposed in the last two
decades, must of them on the basis of intuitive ideas such as superposition of
punctual current sources and error averaging [2,3]. Although these techniques
represented a significant improvement in the area of earthing analysis, a number
of problems have been reported. Namely: large computational requirements, unrealistic results when segmentation of conductors is increased, and uncertainty
in the margin of error [3].
In...
2.
A validation of the boundary element method for grounding grid design and
computation - Colominas Ezponda, Ignasi; Navarrina Martínez, Fermín; Casteleiro Maldonado, Manuel
Several widespread intuitive techniques developed during the last two decades for substation grounding analysis, such as the Average Potential Method
(APM), have been recently identified as particular cases of a more general Boundary Element formulation [1]. In this approach, problems encountered with the
application of these methods [3] can be explained from a mathematically rigorous point of view, and innovative advanced and more eficient techniques can be
derived [2].
Numerical results obtained with low and medium levels of discretization
(equivalent resistance and leakage current density) seem to be reasonable. However, these solutions still have not been validated. Unrealistic results are obtained when domain discretization is...
5.
A BEM approach for grounding grid computation - Colominas Ezponda, Ignasi; Navarrina Martínez, Fermín; Casteleiro Maldonado, Manuel
16th International Conference on Boundary Element Methods, 1994, Southampton, England
6.
Numerical computation of grounding grids - Colominas Ezponda, Ignasi; Navarrina Martínez, Fermín; Casteleiro Maldonado, Manuel
Grounding systems are designed to preserve human safety and grant the integrity
of equipments under fault conditions. To achieve these goals, the equivalent electrical
resistance of the system must be low enough to ensure that fault currents dissipate
(mainly) through the grounding electrode into the earth, while maximum potential
gradients between close points on the earth surface must be kept under certain
tolerances (step and touch voltages) [1,2].
In this paper we present a Boundary Element approach for the numerical computation of grounding systems. In this general framework, former intuitive widespread
techniques (such as the Average Potential Method) can be identified as the result
of specific choices for...
7.
"Una formulación general de elementos de contorno para el diseño asistido por
ordenador de tomas de tierra en subestaciones eléctricas - Colominas Ezponda, Ignasi; Navarrina Martínez, Fermín; Casteleiro Maldonado, Manuel
La puesta a tierra de una instalación eléctrica es imprescindible para
garantizar su seguridad cuando tienen lugar situaciones de fallo. Para su correcto
diseño se requiere la determinación de una serie de magnitudes tales como
el cálculo de la resistencia equivalente de la toma de tierra y la distribución
del potencial originado en la superficie del terreno como consecuencia de una
derivación de corriente al mismo [1]. Tradicionalmente, los estudios sobre el
cálculo de tomas de tierra se han planteado con el fin de obtener fórmulas sencillas
y rápidas (a partir de mediciones experimentales en modelos de laboratorio o
como resultado de la experiencia acumulada por los técnicos...
8.
A boundary element numerical approach for substation grounding in a two
layer earth structure - Colominas Ezponda, Ignasi; Aneiros Blanco, Juan M.; Navarrina Martínez, Fermín
Analysis and design of substation grounding requires computing the distribution of potential
on the earth surface (for reasons of human security) and the equivalent resistance of the earthing
system (for reasons of equipment protection) when fault conditions occur (Sverak et al.,1981).
A new Boundary Element approach for the numerical computation of substation grounding
systems in nonuniform soils is presented in this paper. The formulation is specially derived for
two-layer soil models, which are widely considered as adecquate for most practical cases. The
feasibility of this BEM approach is demonstrated by solving a real application problem, in which
accurate results for the equivalent resistance and the potential distribution...
12.
High order shape design sensitivity: an unified approach - Navarrina Martínez, Fermín; López Fontán, Santiago; Colominas Ezponda, Ignasi; Bendito Pérez, Enrique; Casteleiro Maldonado, Manuel
4th World Congress on Computational Mechanics, 1998, Buenos Aires
15.
A 2D numerical model for the transport of pollutants. The influence of
Boundary Conditions - Bonillo Martínez, Juan José; Fe Marques, Jaime Miguel; Rodríguez-Vellando Fernández-Carvajal, Pablo; Puertas Agudo, Jerónimo
The pollutants transport phenomena in a 2D unsteady free surface flow has been studied. The weighted residual method has been used for the integration of the transport equations, appying the Galerkin formulation for the spatial integration and a differentiation scheme for the time integration. The variation of the dispersion coefficient with the direction has been taken into account by the use of a dispersion tensor. The code allows to impose Dirichlet, neumann, Mixed and Open boundary condition types. Several solutions have been carried out for a numerical test with know analytical solution so as to validate the numerical model and...
16.
A Finite element formulation for the resolution of the unsteady incompressible
viscous flow for low Reynolds numbers - Rodríguez-Vellando Fernández-Carvajal, Pablo; Puertas Agudo, Jerónimo; Bonillo Martínez, Juan José; Fe Marques, Jaime Miguel
The following paper shows a Finite Element formulation for the resolution of the local and convective acceleration terms including- Navier-Stokes equations, which
gives analytical response to the problem of viscous, incompressible, unsteady flows.
The integration of the resulting non-linear system of first order ordinary differential
equations, is made upon a successive approximation algorithm together with an
implicit backward time integrating scheme. The interpolation of the spatial domain is
made in terms of a Q1/P0 pair (bilinear velocity-constant pressure). The usage of a
Bubnov Galerkin formulation in the process of obtaining a weak form implies that
flows of a certain velocity need the employment of a very refined...
19.
A stabilized finite element approach for advective-diffusive transport
problems - Figueroa Álvarez, Carlos Alberto; Colominas Ezponda, Ignasi; Mosqueira Martínez, Gonzalo; Navarrina Martínez, Fermín; Casteleiro Maldonado, Manuel
As it is well-know, the numerical simulation in fluid mechanics is quite difficult specially when the velocity of the fluid is important. These problems are reflected in the apparearance of numerical oscillations when Finite Element approaches with Galerkin weighting are used. In last years, some alternative formulations have been proposed in order to overcome these problems: Streamline Upwind Petrov Galerkin Methods, Space-time Galerkin Least Squares Methods, Subgrid Scale Methods, Characteristic Galerkin Method, etc. In this paper, we focuse our attention in the advective-diffusive transport differential equation, and its application to engineering problems. Thus, we present a brief review of the...
20.
A meshless numerical approach for the analysis of earthing systems in
electrical installations - Colominas Ezponda, Ignasi; Mosqueira Martínez, Gonzalo; Chao López, Mar; Navarrina Martínez, Fermín; Casteleiro Maldonado, Manuel
In the last three decades some numerical formulations have been developed for solving potential problems in electrical engineering applications. In the particular case of the grounding analysis area, in recent years we have developed a general numerical approach based on the Boundary Element Method for homogeneous and isotropic soil models, which has been succesfully applied to the analysis of large grounding systems. This numerical approach has been recently extended for the study of earthing grids embedded in stratified soils, which enables to solve some frequent practical cases, such as the two-layered soil models. Nevertheless, boundary element approaches imply a considerable...
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