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Article
Publication date: 1 June 2004

Guzmán Díaz González, Javier Gómez‐Aleixandre Fernández and Pablo Arboleya Arboleya

In the past years, there has been an increasing concern about turn‐to‐turn faults in power transformers, due to the high costs that unexpected outages cause. It is not always…

630

Abstract

In the past years, there has been an increasing concern about turn‐to‐turn faults in power transformers, due to the high costs that unexpected outages cause. It is not always possible to analyse the transformer behaviour under such faults at rated conditions, since the tests are largely destructive. Therefore, models are of great importance to avoid severe damage to machines. In this paper, a model based on flux rearrangement around the damaged turn is presented. Two roles are assigned simultaneously to the damaged turn – i.e. the turn is seen as damaged but segregated from winding, and virtually undamaged belonging to the winding – and the damaged turn leakage flux is considered to be a coupling flux between the two roles. Thus, complex relations of magnetic couplings between the turn and the rest of the transformer are avoided, resulting in a very fast model, easy to develop further, which has been validated through a comparison with a finite element model.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 September 2005

Guzmán Díaz, Pablo Arboleya and Javier Gómez‐Aleixandre

Differential relaying is one of the most widely used techniques for protecting power transformers. The purpose of this paper is to discuss and cover a developed methodology for…

509

Abstract

Purpose

Differential relaying is one of the most widely used techniques for protecting power transformers. The purpose of this paper is to discuss and cover a developed methodology for analyzing the signals obtained from the differential protection of power transformers.

Design/methodology/approach

The differential signal obtained from the protective relays of power transformers is analyzed in this paper, in order to establish a relation between time‐dependent symmetrical components and space vectors. As a result of the formulation of such a relation, specific patterns are obtained and classified for the plot of the space vector during fault and inrush conditions.

Findings

What was found in the course of the work? This will refer to analysis, discussion, or results. It has been found that the discrimination between inrush and fault conditions is possible by observing a characteristic asymmetry in the plots of the space vector. A method for dealing with the said asymmetries based on the absolute value of the space vector as obtained from the differential signal is proposed and discussed. The theoretical approaches given in the paper are further validated through finite element simulations and laboratory tests, which include linear and non‐linear loads, in order to account for more severe exploitation conditions.

Research limitations/implications

A complete protective algorithm can be developed from the analysis of the methodology proposed, which avoids the spectral analysis, since the methodology is based in pattern analysis rather that in the latter technique.

Practical implications

The methodology provides faster identification of the fault during inrush condition, since the spectral analysis is prevented.

Originality/value

It may be stated that the major contribution of the paper is the methodology proposed for identifying internal faults in power transformers using pattern characterization of the plot of the space vector.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 June 1999

Eileen Oliver

Cuba’s 1959 Revolution brought about dramatic changes not only in that island‐nation but also in the USA. Cubans, and later Cuban‐Americans, have changed the face of Miami and…

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Abstract

Cuba’s 1959 Revolution brought about dramatic changes not only in that island‐nation but also in the USA. Cubans, and later Cuban‐Americans, have changed the face of Miami and south Florida. The economic and social successes of Cuban‐Americans, the third largest Latino group in the USA, are prevalent in scholarly and popular literature. In this annotated bibliography, the author presents journal articles, chapters in books, books, and human rights reports, published between 1990 and 1998, as well as World Wide Web sites, that discuss the Cuban‐American experience. Articles from the popular literature are not included, nor are materials that deal primarily with Cuba or Cuba‐USA relations.

Details

Reference Services Review, vol. 27 no. 2
Type: Research Article
ISSN: 0090-7324

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