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Power Systems, IEEE Transactions on

Issue 4 • Date Nov. 1995

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Displaying Results 1 - 25 of 43
  • A user-friendly simulation program for teaching power system operations

    Publication Year: 1995 , Page(s): 1725 - 1733
    Cited by:  Papers (29)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1098 KB)  

    This paper describes a user-friendly power simulation program for teaching power system operations and control. The motivation for the development of the program is to provide students with a simple and useable tool for gaining an intuitive feel for power system operations. This Microsoft Windows based program simulates power system operation over a specified time period (of typically several hours to a day). Students dynamically interact with the simulated system through various windows, including a one-line display. The use of data files and option windows allows the program to simulate a wide variety of different power systems and operating problems. Efficient programming results in a modest program size of just 450 k, allowing for easy distribution to students. View full abstract»

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  • Developing static reactive power compensators in a power system simulator for power education

    Publication Year: 1995 , Page(s): 1734 - 1741
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    This paper describes a newly installed laboratory module microcomputer-based static reactive power compensator (SVC) in detail to teach students how an SVC affects system voltage, load balancing, power factor, and transmission line losses. The SVC is merged into an old power system simulator for extensive power engineering education. The structure of the SVC is thyristor controlled reactors with fixed capacitors (TCR-FC). Two control algorithms, feedback control and feedforward control, are developed and compared. For the purpose of program flexibility and portability, a VME-Bus based microcomputer is used to synthesize the controller of the SVC. Several suggested experiments are given to show the effects of the SVC on distribution system compensation. The SVC greatly promotes the performance of the power system simulator. View full abstract»

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  • A Windows based graphical package for symmetrical components analysis

    Publication Year: 1995 , Page(s): 1742 - 1749
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (665 KB)  

    A Microsoft Windows graphical package to facilitate the teaching and learning of power system symmetrical components is described in this paper. This package is written in Microsoft Visual Basic 3.0. This software calculates and displays graphically, the ABC sequence and the corresponding symmetrical component phasors. Students can manipulate the graphical displays by keyboard input or by mouse operation. The objective of this package is to help the students to better understand the various aspects of symmetrical components' analysis through a user-friendly graphical user interface. View full abstract»

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  • A multiobjective approach to the short-term scheduling of a hydroelectric power system

    Publication Year: 1995 , Page(s): 1750 - 1755
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    This paper is concerned with the short-term scheduling of the Iguacu river hydroelectric power system, in Southern Brazil. The system comprises four power plants with an unusual high coupling, held by two different utilities. Even though government regulations establishes operation guidelines, electric utilities have their own interests. A multiobjective framework is adopted to study the operation of the power system. Dynamic programming is used to find optimal solutions, with an implementation based on the concept of differential dynamic programming. A case study shows the possibility of obtaining energetic gains with the adoption of nonconventional operation rules and the need of negotiation to avoid wasting energy. View full abstract»

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  • Measured and predicted cold load pick up and feeder parameter determination using the harmonic model algorithm

    Publication Year: 1995 , Page(s): 1756 - 1764
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (885 KB)  

    This paper presents theory of the "cold load harmonic", CLHARM, model algorithm for simulation of power feeder currents resulting from both cold load pickup, CLPU, and the "step voltage test", STEPV. The STEPV method is also presented. Feeder parameters obtained from field STEPV measurement are used to predict CLPU on that feeder using the CLHARM algorithm. STEPV test measurements and actual measured CLPU currents on the same feeder are compared with computer predictions. The CLHARM aggregates feeder thermostatically controlled load to simulate regain of diversity during outage restoration. All feeder weather sensitive load is lumped in CLHARM, using mean parameter values of a simple thermodynamic model. The ultimate objective of this work is experimentally obtained feeder "signatures" for CLPU prediction as a feeder design tool. View full abstract»

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  • Evaluation of harmonic impacts from compact fluorescent lights on distribution systems

    Publication Year: 1995 , Page(s): 1772 - 1779
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (982 KB)  

    Compact fluorescent lamps (CFLs) have the potential to increase the overall harmonic distortion levels on distribution systems. Measurements of the harmonic characteristics of different types of CFLs are presented and the possible impacts on a distribution system are analyzed. The analysis uses a combination of EMTP simulations and conventional harmonic analysis simulations to predict the distribution system distortion levels as a function of system characteristics, the CFL characteristics, and the CFL penetration level. View full abstract»

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  • Predicting harmonic problems resulting from customer capacitor additions for demand-side management

    Publication Year: 1995 , Page(s): 1765 - 1771
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1657 KB)  

    The use of capacitors to correct for poor power factor is a well-established and cost-effective means of reducing demand and system losses. Utilities routinely apply capacitors on transmission and distribution systems. Additional gains may be made by installing capacitors in customer facilities and many utilities are encouraging such installations for demand-side management (DSM) purposes. Unfortunately, many industrial customers have serious problems with capacitor installations because of interactions with harmonic distortion from plant loads. Capacitors may cause one or more harmonics to be accentuated through resonance. The capacitors themselves may be damaged or the resulting voltage distortion may make it impossible to operate some process equipment. It is often difficult to predict which capacitor installations will be troublesome, particularly when there are numerous capacitors and harmonic-producing loads scattered over a plant's power system. A simplified approach that depends on less input data is described. The method is based on the voltage distortion at the main bus and the currents in the capacitors. Two test cases are presented. View full abstract»

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  • Load modelling in studies of power system damping

    Publication Year: 1995 , Page(s): 1781 - 1788
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (861 KB)  

    This paper considers the significance of load voltage dynamics in studies of power system damping. A generic model of dynamic loads is used to investigate the influence of active and reactive power dynamics on the damping of oscillations in a multimachine power system. The interaction between the load and the power system is explored in terms of load and system transfer functions. It is shown that the power system transfer function is composed of a static part and a dynamic part. The static part is derived from the power flow Jacobian. The investigations indicate that load voltage dynamics can significantly influence the damping of modal oscillations. Static load models can give quite misleading predictions of damping when loads actually exhibit dynamic behaviour. View full abstract»

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  • A time-domain approach to transmission network equivalents via Prony analysis for electromagnetic transients analysis

    Publication Year: 1995 , Page(s): 1789 - 1797
    Cited by:  Papers (16)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    This paper presents a method of obtaining transmission network equivalents from the network's response to a pulse excitation signal. The proposed method is based on modal decomposition representation for the large-scale interconnected system. In this framework we use Prony analysis to identify the network function of the system and to decompose the large system into a parallel combination of simple first-order systems. As a result the network function of the transmission network can be identified easily, and a Thevenin-type of discrete-time filter model can be generated. It can reproduce the driving-point impedance characteristic of the network. Furthermore, the proposed model can be implemented into the EMTP in a direct manner. The simulation results with the full system representation and the developed equivalent system showed a good agreement. View full abstract»

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  • An online dispatcher training simulator function for real-time analysis and training

    Publication Year: 1995 , Page(s): 1798 - 1804
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    Today's power systems have become so complex that it is not easy for the system dispatcher to realistically predict the results of outages. The situation is compounded whenever the power grid is not in its "normal" configuration due to maintenance switching or equipment failure. The authors feel that the dispatcher training simulator (DTS) is an excellent tool that can be used to teach the dispatcher how to react under these conditions. In this paper, the authors present an on-line implementation of the DTS which allows the user to: initialize the DTS to an EMS disturbance using data that was captured at the time of the disturbance; and place the DTS in a playback mode and go back to specific times in the scenario. The former feature allows the analyst to investigate EMS disturbances and then train the various dispatchers to be able to recognize such disturbances and to recover from them when they occur. The latter feature allows the instructor (with the trainee) to review and re-experience desired portions of the scenario. It is the authors' feeling that these two features will help the EMS operational staff understand their power system better and help their dispatchers in dealing with operational problems associated with the proper running of the system. View full abstract»

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  • Expert system application for the loading capability assessment of transmission lines

    Publication Year: 1995 , Page(s): 1805 - 1812
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (782 KB)  

    This paper describes the application of an expert system for the evaluation of the short-term thermal rating and temperature rise of overhead conductors. The expert system has been developed using a database and Leonardo expert system shell which is gaining popularity among commercial tools for developing expert system applications. The expert system has been found to compare well when evaluated against site tests. A practical application is given to demonstrate the usefulness of the expert system developed. View full abstract»

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  • Multi-objective generation dispatch using bi-criterion global optimisation

    Publication Year: 1995 , Page(s): 1813 - 1819
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    This paper proposes a bi-criterion global optimisation approach to determine the most appropriate generation dispatch solution taking into account fuel costs, environmental costs and security requirements of power networks. The approach is based on the simulated annealing technique and the formation of a bi-criterion objective function. Its effectiveness is demonstrated through an example, in which the sample test system is a three-area interconnected and longitudinal power system. View full abstract»

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  • Intelligent on-line decision support for distribution system control and operation

    Publication Year: 1995 , Page(s): 1820 - 1827
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (994 KB)  

    Significant improvements have been taking place in the power and extent of the monitoring and control systems employed by electrical power utilities, with the result that strategic decisions are having to be made concerning the use of the increased data now available. The evolutionary changes being made to power systems are introducing increased expectations of the performance of system management and control. However, more effective system control can only be exercised if the increased volume of data is matched by an increased capacity to interpret system conditions from the control room. The decision support system described in this paper makes use of expert system techniques in order to provide intelligent reasoning based on the incoming alarm data. Both the readily available benefits, and the advance towards the next generation of power systems which this type of system will afford shall be presented along with a description of the decision support system. View full abstract»

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  • Large scale transmission network planning using optimization and heuristic techniques

    Publication Year: 1995 , Page(s): 1828 - 1834
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (685 KB)  

    Pursuing optimal solutions for large scale transmission network planning problems is a formidable task due to their combinatorial nature and also due to the nonconvexities involved. Successful approaches using hierarchical Benders decomposition incur in a high computational cost mainly due to the need to solve a large integer program (the investment sub-problem) for every Benders iteration. In this work the authors propose to use heuristics within the decomposition framework, therefore avoiding to solve to optimality each integer sub-problem. The global computational effort is substantially reduced, and allows coping with large problems that would be intractable using classical combinatorial techniques. Case studies with the 6 bus Garver test system and a reduced Southeastern Brazilian power network are presented and discussed. View full abstract»

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  • Value-based transmission planning and the effects of network models

    Publication Year: 1995 , Page(s): 1835 - 1842
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (932 KB)  

    A value-based automated transmission system planning model is presented in this paper and the impact of the various network representations on the results of the model is discussed. Value-based integrated resource planning provides a "societal cost" (utility operation and investment costs plus customer outage costs) minimizing composite generation-transmission system expansion plan. The model trades-off and compares the costs and benefits of alternative generation and transmission resources using a consistent economic and engineering criterion in order to determine an "optimal" resource expansion plan. The generalized Benders decomposition algorithm with "importance sampling" used to solve the problem enables the model to estimate certain average information about scenarios or contingencies by examining only a very small fraction of all the scenarios or contingencies. The impacts of system resources upon both real and reactive power can be analyzed when using the AC power flow equations. It is concluded that for transmission system planning where reactive power flows and voltage constraints are important, it is imperative that an AC power flow model be used. The combination of AC power flow and linearized power flow models, with linearization about the solution of the AC power flow model, was found to be a promising compromise between accuracy and computation time. View full abstract»

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  • Optimization method for reactive power planning by using a modified simple genetic algorithm

    Publication Year: 1995 , Page(s): 1843 - 1850
    Cited by:  Papers (57)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (866 KB)  

    This paper presents an improved simple genetic algorithm developed for reactive power system planning. Successive linear programming is used to solve operational optimization sub-problems. A new population selection and generation method which makes the use of Benders' cut is presented in this paper. It is desirable to find the optimal solution in few iterations, especially in some test cases where the optimal results are expected to be obtained easily. However, the simple genetic algorithm has failed in finding the solution except through an extensive number of iterations. Different population generation and crossover methods are also tested and discussed. The method has been tested for 6 bus and 30 bus power systems to show its effectiveness. Further improvement for the method is also discussed. View full abstract»

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  • Improved secondary and new tertiary voltage control

    Publication Year: 1995 , Page(s): 1851 - 1862
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1231 KB)  

    In this paper the basic role of a secondary (regional level) voltage control in a multi-regional electric power system is reviewed. Specifically, certain limitations of presently implemented control schemes are described. Next an improved secondary voltage control (ISVC) scheme is proposed. In the second part of the paper, possible enhancements of a multi-regional power system operation by means of scheduled, tertiary voltage control (TVC) interactions are proposed. It is shown that the prime role of a TVC is in managing limits on voltage control devices, such as generators. The theoretical developments are illustrated on two regions of the French electric power network. View full abstract»

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  • Impact of under-excitation limit control on power system dynamic performance

    Publication Year: 1995 , Page(s): 1863 - 1869
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    Several control functions, in addition to terminal voltage control, are performed by the excitation systems of the synchronous machines in a power plant. The under-excitation limit (UEL) is one of these. In this paper, the authors deal with the effect of such control on the dynamic performance of power systems. Certain simulation results properly characterize UEL action which, depending on the nature and severity of the contingency, can be relatively fast. Their objective is to encourage representation of the under-excitation limit control function in synchronous generator AVR modeling for power system dynamic studies. Essentially, the control acts by precluding excessively binder-excited conditions. In practice, it is applied to prevent both operation beyond the steady-state stability limit and the large magnetic losses produced by leakage fluxes in stator winding end-of-turns during machine operation with very small field circuit excitation. View full abstract»

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  • Modelling regional end user price/cost relationships in a widespread interconnected power system

    Publication Year: 1995 , Page(s): 1870 - 1878
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (887 KB)  

    A combined programming and regression modelling approach is developed to analyse regional retail price/cost relationships for a widespread interconnected power system characterised by low population density and uniform (regulated) retail tariffs. The programming model is designed to calculate on the hour the delivered cost of electricity from 5 thermal power stations and one pumped storage hydrostation to end users in 8 distribution regions. A simultaneous equation regression model then analyses the link between retail prices charged end users, regional demand and supply characteristics, industry financial objectives and departures from economically efficient pricing. The electricity supply industry in Queensland Australia is used as a framework. View full abstract»

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  • Summary of the panel session "Coordination Between Short-Term Operation Scheduling and Annual Resource Allocations"

    Publication Year: 1995 , Page(s): 1879 - 1889
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1223 KB)  

    This paper summarizes the discussions of the panel session entitled "Coordination Between Short-Term Operation Scheduling and Annual Resource Allocations" which was held during the 1994 IEEE PES Winter Meeting at New York. The panel discussions focused on the need of coordinations, the conceptual framework to achieve effective coordinations, and electric utilities' experiences in coordinating resource (e.g. fuel, emission, hydro) allocation decisions and short-term operation scheduling decisions. View full abstract»

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  • Application of artificial neural networks in voltage stability assessment

    Publication Year: 1995 , Page(s): 1890 - 1896
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (763 KB)  

    Voltage stability problems have been one of the major concerns for electric utilities as a result of system heavy loading. This paper reports on an investigation on the application of ANNs in voltage stability assessment. A multilayer feedforward artificial neural network (ANN) with error backpropagation learning is proposed for calculation of voltage stability margins (VSM). Based on the energy method, a direct mapping relation between power system loading conditions and the VSMs is set up via the ANN. A systematic method for selecting the ANN's input variables was developed using sensitivity analysis. The effects of ANN's training pattern sensitivity problems were also studied by dividing system operating conditions into several loading levels based on sensitivity analysis. Extensive testing of the proposed ANN-based approach indicate its viability for power system voltage stability assessment. Simulation results on five test systems are reported in the paper. View full abstract»

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  • Demand forecasting using fuzzy neural computation, with special emphasis on weekend and public holiday forecasting

    Publication Year: 1995 , Page(s): 1897 - 1903
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (755 KB)  

    This paper describes the implementation and forecasting results of a hybrid fuzzy neural technique, which combines neural network modeling, and techniques from fuzzy logic and fuzzy set theory for electric load forecasting. The strengths of this powerful technique lie in its ability to forecast accurately on weekdays, as well as, on weekends, public holidays, and days before and after public holidays. Furthermore, use of fuzzy logic effectively handles the load variations due to special events. The fuzzy-neural network (FNN) has been extensively tested on actual data obtained from a power system for 24-hour ahead prediction based on forecast weather information. Very impressive results, with an average error of 0.62% on weekdays, 0.83% on Saturdays and 1.17% on Sundays and public holidays have been obtained. This approach avoids complex mathematical calculations and training on many years of data, and is simple to implement on a personal computer. View full abstract»

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  • A new method of evaluating system margin under various system constraints

    Publication Year: 1995 , Page(s): 1904 - 1911
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (781 KB)  

    This paper presents a concept of system margin for evaluation of adequacy of a composite power system. It can be a useful index for planning a desirable power system. An efficient methodology to calculate maximum supplying capability is introduced. It uses DC load flow analysis and linear programming to obtain a solution which is approximate but accurate enough for first stage planning studies. The proposed method can evaluate the power system margin under various constraints which consist of power flow, frequency in case of system separation, synchronous stability and voltage stability. The validity and effectiveness of the developed methodology is confirmed through the simulation of a model system. View full abstract»

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  • Pooling generating unit data for improved estimates of performance indices

    Publication Year: 1995 , Page(s): 1912 - 1918
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    The purpose of this paper is to present and explain some fundamental concepts of pooling data to improve estimators of generating unit performance indices. These concepts were developed by a Task Force of the Application of Probability Methods Subcommittee of the Power System Engineering Committee. This paper delineates the two major reasons for pooling estimators: (1) to obtain improved estimators of unit performance when the units are homogeneous; and (2) to obtain good estimators of system performance when the system contains heterogeneous units. The paper recommends the correct method for pooling in both cases. View full abstract»

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  • Large-scale economic dispatch by genetic algorithm

    Publication Year: 1995 , Page(s): 1919 - 1926
    Cited by:  Papers (105)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (866 KB)  

    This paper presents a new genetic approach for solving the economic dispatch problem in large-scale power systems. A new encoding technique is developed. The chromosome contains only an encoding of the normalized system incremental cost in this encoding technique. Therefore, the total number of bits of chromosome is entirely independent of the number of units. The salient feature makes the proposed genetic approach attractive in large and complex systems which other methodologies may fail to achieve. Moreover, the approach can take network losses, ramp rate limits, and prohibited zone avoidance into account because of genetic algorithm's flexibility. Numerical results on an actual utility system of up to 40 units show that the proposed approach is faster and more robust than the well-known lambda-iteration method in large-scale systems. View full abstract»

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Aims & Scope

Covers the requirements, planning, analysis, reliability, operation, and economics of electric generating, transmission, and distribution systems for general industrial, commercial, public, and domestic consumption.

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Editor-in-Chief
Antonio J. Conejo
The Ohio State University