2001 IEEE Porto Power Tech Proceedings (Cat. No.01EX502)

The fuel cell is a very promising energy production system to supply electricity and heat with high efficiency and low impact to the environment. Presently, the effort is paid both to applications for dispersed generator and automobile energy source. However, the infrastructure for fueling of pure hydrogen has been still discussing and investigating. In this paper, the authors propose a new concep... View full abstract»

For a few years, problems regarding power quality issues in general have become of increasing interest. They have their own negative influence on several aspects of modern society. The problems in industry have been addressed for a longer period of time. However, home and nonmanufacturing industries also suffer from a lack of power quality. Besides the visual disadvantages, such as flicker, electr... View full abstract»

The aim of the present work is to analyse the behaviour of the Fourier, sine and cosine digital filtering algorithms in impedance calculation, considering a distorted current signal due to severe saturation of the CT. To this aim we consider the effect caused by data window length variation, and the analogue anti-aliasing filter on the algorithm output. The current signals considered in this work ... View full abstract»

This paper, introduces a new concept of robust protective relays based on unique type of self-organized neural network. An advanced approach for protective relay testing and evaluation is presented as well. The proposed relaying solution detects and subsequently classifies the faults. A new interactive simulation environment based on MATLAB is selected as the main software environment for synthesi... View full abstract»

Corresponding to the increasing capacity utilization of power systems, a systematic use of the load-flow controlling capabilities of multifunctional FACTS devices can increase the available transfer capability (ATC) enabling additionally demanded power transits. For an effective power transit control, the aptitude of possible locations of FACTS devices is assessed by a sensitivity analysis based o... View full abstract»

The electric power system in Ireland is undergoing a period of great change. The drivers of this change i.e. market liberalization, high growth in demand, shortage of generation, the need for greenhouse gas emissions abatement are briefly described. The status and plans for wind power developments are outlined. The particular difficulties in the large scale integration of wind power into an island... View full abstract»

In this work, the authors present the results of transient stability studies, which are accomplished when assessing the effects of the connection of wind farms in a power system. For the execution of those studies, a software environment for stability simulation was developed in MATLABTM with a friendly user interface, that allows the execution of different cases studies, e.g. sudden di... View full abstract»

A capacity of installed wind power of 40 GW in Europe, control areas with a wind power production exceeding the maximum load-these are serious plans that may come true in several years. Due to the high fluctuations and the limited predictability of wind power, this development will cause a severe change in the demands on the power reserve. Therefore, this paper introduces an investigation that qua... View full abstract»

Most High-Speed railway systems around the world used single-phase voltage source as power supply for trains, therefore, adopted some special transformers to convert 3-phase source to single phases. The differential relays used for this situation most be restudied for understanding their operation changes in a high harmonic content environment. This research aims at the study of effects of harmoni... View full abstract»

The study of circular maps of induction machines is one of the classical subjects dealt with in literature about electrical machines and it is fairly interesting from a didactical point of view as well as from its practical applications. This paper presents a new and general method that allows for, among other things, the analytical way of obtaining center coordinates and the radius of any of the ... View full abstract»

In the paper the results of investigation are presented on application of artificial neural networks to protection of synchronous machines against out-of-step conditions. The new ANN-based protection ensures faster and more secure detection of generator loss of synchronism when compared to traditional solutions. To determine the most suitable network topology for the recognition task a genetic alg... View full abstract»

Energy market opening, with higher net utilization, and increasing competition are urgently requiring a solution to strongly limit loop flows. This paper presents an approach to manage loop flow problem in liberalized power systems. This methodology, which involves implementation of FACTS devices, also applies network reduction models towards a solution of the problem in the real networks. A UPFC ... View full abstract»

When looking on how transients and communication signals are transferred through the distribution network, a broadband model of the whole distribution system is necessary. In this relation a broadband model of the four-wire cables with sector shaped conductors is needed. Such a model for the series impedance is set up in this paper, whereas the shunt impedance will be reported in another paper. Th... View full abstract»

A flexible simulation tool for decentralized electric/thermal power systems was developed. It is easy to parameterize and provides a comfortable operational surface, allowing to interactively "operate" the particular system under investigation. The characteristic components and features of the simulation tool are described and examples of the performance given View full abstract»

In this paper, nondamping oscillations, that are difficult to be identified nowadays in transmission power systems, are analyzed. Therefore, the most important considerations to be taken into account in the use of models and calculation procedures that appropriately represent these oscillations are proposed. Among other subjects, the application of nonlinear analysis techniques, such as bifurcatio... View full abstract»

There is a large bibliography in simulation models for linear induction motors (LIMs). However, most of them only consider steady state performance. LIMs working as linear drives generally operate under transient conditions. The aim of this paper is to investigate the suitability of different mathematical models to simulate LIMs as linear drives. A study of most major techniques of calculating lum... View full abstract»

The present paper aims at assessing the effects produced on the distribution system by dispersed generators directly connected to LV networks. In particular, the introduction of photovoltaic (PV) generation systems has been studied, since such systems are the only ones having a natural inclination to be easily integrated into high density urban LV distribution networks. In the proposed study some ... View full abstract»

The distribution capability for additional DECS-power of the existing distribution network is an important criteria for the soon-coming increasing installation of e.g. fuel-cell-systems for house supplying. In this paper, a method is described which allows the calculation of the maximum cumulated DECS-power of individual distribution networks. The calculation is based on an optimization problem, a... View full abstract»

The necessity for flexible electric systems, changing regulatory and economic scenarios, energy savings and environmental impact are providing impetus to the development of distributed generation, which is predicted to play an increasing role in the future electric power system; with so much new distributed generation (DG) being installed, it is critical that the power system impacts be assessed a... View full abstract»

The legislation currently in force that affects the construction of overhead electricity transmission or distribution lines establishes an extensive number of conditioning factors as regards licences, public exposition of projects, rights regarding the presentation of allegations, etc. For that reason, the period that can elapse between the time the need for the installation of a new line is detec... View full abstract»

An improved hybrid method is discussed, employing a finite-element method along with Faraday's law and standard circuit analysis, in order to predict the induced voltages and currents on a pipeline with defects on its coating, running parallel to a faulted line and remote earth. Such defects are a frequent situation especially when old pipelines are considered and are modeled as resistances, calle... View full abstract»

This paper deals with problems connected to distance protection of a double-circuit transmission lines. Because of the zero sequence mutual coupling of parallel circuits, the relay "sees" incorrect impedance. Behavior of distance relays, which protect multi-circuit lines, is that they underreach when the parallel circuits are in service and that they overreach when the parallel circuits are out of... View full abstract»

The brushless excitation of synchronous machines is an attractive solution for wound rotor machines, since no slip-rings are necessary. The paper investigates the rotating transformer method. For controlling the input voltage of the exciter AC chopper is proposed. Two kinds of the AC choppers are investigated, discussed and compared mainly considering the additional losses, which is important at t... View full abstract»