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Power Tech Proceedings, 2001 IEEE Porto

Date 10-13 Sept. 2001

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  • 2001 IEEE Porto Power Tech Proceedings [front matter]

    Page(s): 1 - 348
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    Freely Available from IEEE
  • Author index

    Page(s): 435 - 446
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    Freely Available from IEEE
  • Integrated AC transmission systems with nonintrusive control

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (634 KB) |  | HTML iconHTML  

    Problems related to controllable transmission paths in an AC system are intensive planning studies and redesign of control and protection systems, adverse control interactions with other controllers and a lack of optimization potential due to predefined devices. These problems can be eliminated by applying a control architecture which enables the operation of a controlled transmission path without affecting the rest of the system. This nonintrusiveness is the key issue of the proposed Non Intrusive System Control (NISCTM) architecture. In this paper the basic requirements and structure of this new control architecture are described first. A second focus is given to the problem of controller interactions in abnormal operation situations where the NISCTM architecture helps to avoid malfunctioning or adverse reactions. The overall efficiency and robustness is shown in connection with a case study View full abstract»

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  • Transient stability simulation of power system including wind generator by PSCAD/EMTDC

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    Induction machines are mostly used as generators in wind power stations. Since induction machines also have a stability problem, it is important to analyze the transient stability of the power system including wind power stations. This paper presents simulation analyses of transient stability of a power system including an induction generator performed by PSCAD/EMTDC View full abstract»

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  • Efficiency of the linear induction motor (LIM) performance under constant voltage feeding-additional finite elements considerations

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    The aim of this work is to present a mathematical model for the linear induction motor, this model allows estimation of its efficiency, considering the winding space harmonics. This work followed the strategy of research among rotary machines to find the one which could be the base of all the studies. The machine found, was the rotary three-phase asymmetrical induction motor. This is justified by the inherent asymmetry characteristic of LIM that comes from building aspects. Experimental procedures with a LIM prototype makes viable the theoretical against experimental tests to make the validation for the proposed model. A special section is dedicated to electromagnetic aspects of the LIM through finite element analysis View full abstract»

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  • Identification of synchronous machine parameters using constrained optimization

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB) |  | HTML iconHTML  

    In order to investigate transient performance problems in isolated power systems an accurate system dynamic model is required. Real measurements, under specific system operational conditions, have been used for the identification of the conventional generator unknown parameters. Frequency and power variations, resulting from the formulation model using the estimated parameters, are compared with the frequency and power deviations, measured during the corresponding real operational conditions in order to demonstrate the successful performance of the proposed methodology View full abstract»

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  • New energy storage devices for an improved load managing on distribution level

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    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, electronic equipment and domotic systems are very sensitive to deviations in mains voltage. To avoid these problems, one can use power supplies which are redundant during normal mains supply, but become active in the case of voltage sags or in cases of total loss of power. All these systems are based on the storage of energy. During recent years, more powerful techniques like superconducting magnetic storage systems (SMES) and systems with supercapacitors, as alternatives for the conventional solutions, have become attractive. Recently, redox flow batteries gave another alternative. A literature study is carried out to present an overview of the advantages and drawbacks of these new storage systems against the existing systems, and to study their usefulness in the distribution grid View full abstract»

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  • Forecasting methods used for performance's simulation and optimization of photovoltaic grids

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    The energy-efficiency statistical model presented below is an acceptable and quickly method of photovoltaic grid behavior forecasting, for specific photovoltaic energy producing application. Using the standard method of efficiency evaluation, a statistical model for photovoltaic grids is proposed, transposing collected data in the specified model pattern of the exponential smoothing and autoregressive integrated moving average statistical techniques. These aims were included in a prospective software program (EnergOptimizer), which provide advanced features of designing, forecasting and three-dimensional shading prediction tool. Therefore, a systematic analysis of the photovoltaic grids, in energy-efficiency respect, following this conception will bring benefits in the simulation and optimization background of photovoltaic projects View full abstract»

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  • General model for sag-tension calculation of composite conductors

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    A new computer model is presented for precise calculation of sag and tensions of composite conductors for overhead lines. All the effects known to increase the sag are accounted for: residual deformations, evolution of creep with time, compression in aluminum layer of ACSR conductors at high temperature, etc. This general model can also be applied for the simpler cases of one-material conductors and messengers supporting multiples or telecommunication cables View full abstract»

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  • Gas turbine model using in design of heat and power stations

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    This paper presents prime mover models suitable for island operation simulation. It deals with the design principles of a power station with gas unit from power station-network interaction point of view View full abstract»

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  • Flexible simulation tool for planning and optimization of decentralized power systems with renewables based sources and energy storage

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    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»

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  • Modeling of linear induction motors as linear drives

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    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 lumped parameters is provided. The most representative models capable of simulating transients of LIMs are described and applied to a laboratory prototype. Finally, the results obtained are compared to experimental data View full abstract»

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  • Large scale integration of wind power in an island utility-an assessment of the likely variability of wind power production in Ireland

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    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 power system are emphasized. The methodology of an ongoing study to assess the likely variability of wind power production is described. The results presented show the benefits of geographic dispersion of the wind power generating capacity and the critical importance of the limit set by the power system operators on the ratio of instantaneous wind power to system demand View full abstract»

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  • Electrical integration assessment of wind turbines into industrial power systems: the case of a mining unit

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (429 KB) |  | HTML iconHTML  

    Onsite diesel-based power generation is a common practice within the industry, not just for supplying private demands but also as a solution to power quality problems. Although diesel generation has benefits, the cost of running such systems is rather high. In favoured locations, especially geographically-remote sites, wind-powered generation is an attractive, cost-effective option. This paper focusses on the development of individual generator models and some simulation results to assess the electrical integration of wind turbines into industrial power systems. Also, an insight into the assessment procedure and the proposed case study are also introduced View full abstract»

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  • High-temperature conductors: a solution in the uprating of overhead transmission lines

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (554 KB) |  | HTML iconHTML  

    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 detected and its coming into service amply exceeds the time regarded as permissible by the utility. In upgrading the capacity of a line, the possible options include installing a larger conductor on existing structures, increasing the operating voltage, increasing operating temperature, etc. Also, uprating process using high-temperature conductors is another possible solution. This paper presents the most important results of the COALPRET research project, whose dual aim has been to carry out a general study of the characteristics of electrical conductors with high temperature performance and low sag, and apply these studies to the specific overhead transmission line View full abstract»

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  • A new wide area protection system

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    As a result of recent developments in power markets, power utilities are forced to increase the reliability and profitability of their power systems. Their networks have to be operated closer to limits, which may lead to frequent outages due to unreliable assessment of stability limits. A new wide area protection system is introduced to extend the system operational limits, i.e. operate the system closer to the physical limits, without any investments in high voltage equipment. The system protects the entire power system against blackouts due to several kinds of instabilities. With dynamic supervision of the system's stability and the optimization of transmission capability, it is a cost-effective system that complements installed protection and control systems. Phasor measurement information is transmitted to a system protection center, where snapshots of the transient system status are online available. This dynamic system's view opens up new applications to assess and actively remain system's stability in case of voltage or angle instability and oscillations. After the introduction of the system setup of the new wide area protection system, a new voltage stability prediction algorithm for transient system states and cascaded contingencies is presented. The applicability of the algorithm is shown with the example of a test system and a real power system View full abstract»

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  • Initialization of wind turbine models in power system dynamics simulations

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (513 KB) |  | HTML iconHTML  

    As a result of increasing environmental concern, increasing amounts of electricity are generated from renewable sources. One way of generating electricity from renewable sources is to use wind turbines. A tendency to erect more wind turbines can be observed. As a result of this, in the near future wind turbines may start to influence the behavior of electrical power systems. To investigate the impact of increasing wind turbine penetration, power system dynamics studies need to be carried out. To this end, power system dynamics simulation software is used, in which wind turbine models must be integrated to enable the investigation of increasing wind turbine penetration on power system behavior. If wind turbine models are to be integrated into power system dynamics simulation software, it must be possible to calculate the initial conditions of the dynamic model from load flow data to be able to initialize the dynamic simulation correctly. In this paper, a solution to this problem is presented View full abstract»

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  • Study of the dynamic behavior of the Greek mainland system after the opening of the Greece-Bulgaria interconnection

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    This paper presents studies carried out on the Hellenic system in order to assess the effect of the existence of only one main interconnection with the rest Balkan system, the Bulgaria interconnection. The dynamic behavior is analyzed for selected disturbances and shows that for large generation loss in the Greek network there is isolation of the Greek system, due to the short activation time of the Bulgaria overload protective device. In this case load shedding is necessary for safety reasons. In general it is concluded that the Greek system remains stable, even in large disturbances View full abstract»

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  • An integrated approach to substation automation problem based on multifunctional protective relays

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB) |  | HTML iconHTML  

    In recent years the utility business has faced changes related to privatization, deregulation and internationalization. The diversification and complexity of functions required by most distribution utilities becomes a strong trend of evolution. At the same time the integration of an increasing number of functions in digital devices provides resources for new and more complex schemes. Thus advanced automation algorithms can be implemented associating extra processing power with powerful communication networks. Modern software packages conceived to interface protective relays also play an important role in the global solution. This paper proposes a highly integrated approach for control and automation in distribution substations, based on the modern EFACEC protective relays and its SCADA system. The integration in these units of control functions such as automatic reclosing, automatic voltage regulation, load shedding and restoration, circuit breaker failure protection and other control and supervision functions is analyzed. The improvement of classical algorithms and the definition of new methods for automation based on the interaction among different units through the local area network are described. The conclusions are based on an economical and technical analysis, where potential advantages and benefits combined with new possibilities are evaluated View full abstract»

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  • Analysis of system-inherent oscillations in power systems with several load models

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    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 bifurcation theory is considered. A useful tool for the research of oscillatory states is developed and initial tests on different load models are carried out View full abstract»

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  • Magnetic flux density measurement techniques to analyze 345kV circuit breaker maintenance operations

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (455 KB) |  | HTML iconHTML  

    The paper presents magnetic flux density and current measurement principles and procedures during 345 kV circuit breaker maintenance operations. Field and scale model measurement techniques are described and discussed. Two case studies are presented; they are related to vertical-plane magnetic flux density measurements during the maintenance of a deenergized live-tank SF6 circuit breaker in a 345 kV substation. Field and scale model measurements, and calculations are compared and discussed View full abstract»

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  • A frequency dependent model for Δ-Y0 coupled distribution transformers

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    The paper describes some of the investigations made in order to evaluate the possibilities for defining a model valid for a class of distribution transformers (10/0.4 kV) covering the frequency range from the operational frequency to above the most dominating disturbing frequencies. The work reported covers both an analytical description of the semi-ideal Δ-Y0 coupled transformer; measurements in the lab giving the nodal admittance matrix for a 400 kVA transformer; the development of an EMTP96 model for the transformer; some transfer-functions for the very same transformer giving a possibility to test the model, and, finally, the results of measurements made on a group of "identical" 100 kVA transformers, i.e. transformers from the same batch are presented. It is shown that it will be possible to use such models with sufficient accuracy for classes of transformers View full abstract»

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  • On-line power transformer monitoring at Electricite de France

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (551 KB) |  | HTML iconHTML  

    This article presents an online monitoring system for power transformers developed and evaluated on several transformers at EDF. It combines acoustic, electrical and chemical measurements of partial discharges to establish a diagnostic of the transformers and generate an alarm if admitted thresholds are exceeded. This system is modular and can be used for monitoring for several months or to make a diagnosis in a few days View full abstract»

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  • Possibility of fuel cell fast charger and its arrangement problem for the infrastructure of electric vehicles

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB) |  | HTML iconHTML  

    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 concept for constructing the infrastructure of EV by fuel cell chargers. This unique application is simulated by the scenario analysis as an arrangement problem. The approach uses the modified weighted Voronoi Diagram providing a proper allocation of the chargers for electric vehicle (EV). The simulation presents a suitable distribution and the possible implementation number of EVs when 100 chargers, including the fast charger and the parking charger, are introduced in Tokyo metropolitan area View full abstract»

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  • Testing EHV secondary arcs

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    The protection of the environment requires compact EHV tower constructions. This trend results in decreasing the clearances and phase-to-phase distances. It is expected, that both the number of faults and the amplitude of the secondary arc current will grow in the future. All these make it necessary to improve the efficiency of single-phase reclosing. Secondary arc duration values gained at field tests show a big spread and therefore they do not provide a reliable basis for selecting a suitable dead time. Analyzing the main processes affecting the secondary arc duration, the authors conclude that traveling wave phenomena arising in the intermittent period of secondary arcing have a determining effect on the arc duration. Considering the difficulties connected with field tests and the big influence of the weather conditions on the secondary arc duration, the authors propose to complete laboratory test circuits by such components, which affect the simulation of the wave processes. A method for the detection of the secondary arc extinction on 750 and 400 kV lines is mentioned, which offers a possibility to prevent inefficient reclosures View full abstract»

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