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Power Systems, IEEE Transactions on

Issue 4 • Date Nov 1991

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Displaying Results 1 - 25 of 33
  • Security-constrained OPF: influence of fixed tap transformer fed loads

    Page(s): 1366 - 1372
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    The behavior of the conventional security-constrained optimal power flow (OPF) solutions is studied in the presence of loads not controlled by under load tap changing (ULTC) transformers. modified versions of the AEP/IEEE 30 bus system with exponential-type load models were used to create a variety of test situations. The study reveals that with loads not controlled by ULTC transformers, the solution to a conventional security-constrained OPF can be different from its practically observed version. This conclusion is similar to that obtained for OPF neglecting contingencies. In the present case, since the voltages are usually higher than for OPF neglecting contingencies, it follows that an increase in fuel costs, power demand, and total and net revenue can be expected in more cases than in the previous study. Moreover, limit violations in the present case are observed mainly during contingencies View full abstract»

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  • An experiment in real time pricing for control of electric thermal storage systems

    Page(s): 1356 - 1365
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    The authors present the results of an experiment designed to test the economic benefits of real-time pricing (RTP) used to schedule electric thermal storage (ETS) systems in a New York utility's service territory during the winter of 1989-1990. Three customers with EST systems were placed on an experimental RTP rate for their heating load only. A complete automated RTP-based control system was designed and retrofitted in place of the existing time-of-use (TOU)-based control system. The design, development, and implementation of the experimental RTP rate, customer response algorithms, and the energy management systems are described. Costs to the utility of the provision of service went down by about 10% beyond savings achieved under the TOU-based control system for a system with no storage View full abstract»

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  • An approach for explicitly modeling the protective relaying system in substation reliability evaluation studies

    Page(s): 1373 - 1379
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    The authors present an approach for evaluating the reliability of a power system substation taking into account its associated protective relaying system. The method employs the technique of minimum cutsets to compute the frequency and duration of a fault with respect to the criterion of continuity of electric service. The protective relaying system is accounted for by explicitly incorporating its elements into a new functional model developed for their associated circuit breakers. The approach was implemented in the form of a computer program and used to compare the reliability of several substation arrangements. These comparisons as well as some details on the practical implementation of the approach are also presented View full abstract»

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  • The ELCOM utility communication concept

    Page(s): 1411 - 1417
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    An electric utility communication concept for providing services at the application layer is described. Specific protocols were developed for the application and presentation layer. Standardized ISO protocols for both connection-oriented and connectionless communication were used on lower layers. A possible migration to full ISO compatibility is described. The first version of the concept was specified in 1983 (ELCOM-83). The first implementation was installed in 1985 for communication between a background computer and a SCADA system. Additional facilities (supervisory control, text messages, transport service, etc.) were added in the next version (ELCOM-90). The implementation of ELCOM in a SCADA environment is discussed View full abstract»

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  • Effect of sequential reclosure of multi-phase system faults on turbine-generator shaft torsional torques

    Page(s): 1380 - 1388
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    The authors present a method of reducing the high torsional torques induced in turbine-generator shafts during high-speed reclosure of multiphase system faults. The method is based on the sequential reclosing of the faulted circuit. In this context, investigations have been conducted on two turbine-generator units of different designs for various multiphase system faults. The results of both the three-phase-to-ground and double-line-to-ground faults are reported, and the effectiveness of the method is illustrated through parametric studies and simulation results. The effects of the reclosing time and the fault incidence instant on the effectiveness of the method have also been investigated View full abstract»

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  • Introduction of professional software into the curriculum of an undergraduate power system analysis course

    Page(s): 1584 - 1588
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    The author presents sophisticated professional software for power system analysis to be applied to the curriculum of an undergraduate program. As a consequence, an unfolding process takes place. The author defines unfolding as the learning process by which the students learn the principles of a subject with the perspective of developing their understanding through exposure to practical problems currently being investigated. Discovery in the learning process is based on interactive analysis. In this particular experiment, students were able to learn about energy losses on a distribution system while using recently developed techniques for minimizing losses View full abstract»

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  • Simulation and analysis of small and medium size power systems containing wind turbines

    Page(s): 1453 - 1458
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    A method of simulation and analysis of small or medium-sized power systems with high wind penetration is presented. The computer program developed provides the capability to consider separately the existence of wind turbines dispersed on the radial distribution networks or concentrated in wind parks. The repercussions of their operation for the power generation or the distribution system are calculated, taking into account the composition and the reaction of the system loads. The program was applied to the study of the transient behavior of a small power system typical of the ones existing in small- and medium-sized islands in Greece View full abstract»

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  • A reliability test system for educational purposes-spinning reserve studies in isolated and interconnected systems

    Page(s): 1578 - 1583
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    Operating reserve in a system is required to make the system capable of handling unforeseen load changes and possible outages of generation. The basic results of an assessment of operating reserve requirements in a small reliability test system are presented. Results are presented for both isolated and interconnected configurations. The results provide a basic understanding of probabilistic assessment of operating reserve requirements and can be included in a power system reliability teaching program View full abstract»

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  • Inter-utility communications within WSCC

    Page(s): 1345 - 1348
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    The development of real-time interutility data communications capabilities has resulted in many implementations in the western United States. The current state of these implementations and the future plans for additional capabilities spanning the entire Western Systems Coordinating Council (WSCC) are presented. In 1982, the WSCC formed a group to develop a protocol and a set of guidelines for real-time interutility data exchange. All the major utilities within the WSCC now have or are planning implementations based on the guidelines. Other implementations outside the WSCC are discussed. The impetus for this move is economic benefits realized by reduced hardware installation, better power system modeling that allows optimal use of existing resources, visibility outside a utility's control area, better restoration coordination, and the ability to quickly match power system resources to markets at mutually beneficial prices View full abstract»

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  • Use of Monte Carlo simulation in teaching generating capacity adequacy assessment

    Page(s): 1571 - 1577
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The authors present a range of generating capacity adequacy studies for a small educational reliability test system, RBTS, based on Monte Carlo simulation. They briefly illustrate the increasing importance and utilization of Monte Carlo simulation in power system reliability evaluation and its used in teaching the basic concepts. The emphasis is on its utilization in generating capacity reliability evaluation. The results were obtained using the simulation program developed by the power systems research group at the University of Saskatchewan View full abstract»

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  • Stabilization of multimodal electromechanical oscillations by coordinated application of power system stabilizers

    Page(s): 1439 - 1445
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    The author presents a hybrid methodology which utilizes modal sensitivity and frequency-domain analysis to coordinate power system stabilizers in multimachine systems. The approach permits robust stabilization of multimodal electromechanical oscillations by the minimal number of coordinated stabilizers. For the monitoring of nonlinear system response, a spectral technique is proposed which provides an insight into the time-frequency distribution of energy of electromechanical oscillations. This monitoring technique is used for the fast examination of the damping efficiency and robustness of coordinated stabilizers in the well-known ten-machine test system View full abstract»

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  • Power system reliability planning practices in North America

    Page(s): 1485 - 1492
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    The authors present selected results from a recently completed research project for the Electric Power Research Institute. One component of the project was intended to develop and test methodologies for gathering data on how utility customers value service reliability, as measured by either the cost of outages or the willingness to pay for reliability. Another component of this project involved a survey of current and emerging reliability planning practices in the North American utility industry, especially regarding interest in value-based reliability planning. The results of the survey, including the survey design and methodology, are given. The authors briefly discuss potential applications of interruption costs in generation and composite system reliability planning View full abstract»

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  • Application independent interactive environment for power systems education

    Page(s): 1418 - 1424
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The authors present an interactive software package for the simulation of power system stability studies. The package is intended as a supplementary tool for the teaching of power system stability courses at the graduate level. The development of the package was done exclusively for IBM-PC and compatible computers. The hardware mainly requires VGA display and 640 kbyte of memory. Professional libraries used for the development of the package include Meta Windows, graphics Menu, and Object Professional. The authors describe the methods used for the integration of various analysis programs and the organization of the data and information pertinent to a system study View full abstract»

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  • Real time complete model estimation for contingency study: field experience

    Page(s): 1480 - 1484
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    The authors describe field experience with external network modeling for real-time contingency analysis. Contingency simulations using an unreduced external modeling approach were conducted in a real-time environment. The response of the external network model to outages of major 345 kV lines was compared to data obtained by measurement. The real-time contingency test results obtained by using the latest state-estimation-based external network modeling approach are superior to those obtained by the previously used load-flow-based approach View full abstract»

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  • Effect of bus load uncertainty and correlation in composite system adequacy evaluation

    Page(s): 1522 - 1529
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    A tabulating technique of normal distribution sampling is used to simulate bus load uncertainty and a correlation sampling technique is utilized to simulate bus load correlation including those situations in which bus loads are completely dependent or independent. These techniques have been incorporated in the MECORE computer program developed at the University of Saskatchewan for composite system reliability evaluation. Case studies include comparisons between the normal distribution sampling technique and a discrete interval enumeration model, effects of bus load uncertainty and correlation on annualized and annual indices for different systems, and effects of different load uncertainty standard deviations and different degrees of bus load correlation on the inadequacy indices View full abstract»

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  • Cost of electric power interruptions in the agricultural sector-statistical analysis

    Page(s): 1432 - 1438
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    The authors describe the methodology and results of statistical analyses of data collected to estimate the losses incurred by the farm sector as a result of electric power system interruptions. The project was sponsored by the Canadian Electrical Association and employed a postal survey to estimate the costs to electric customers resulting from electric power outages. The survey included interruption cost estimation questions based on three principles: direct estimate of losses, an economic principle of substitution, and a willingness-to-accept method. The results of these questions together with the others included in the questionnaire were subjected to rigorous statistical analysis. The analysis presented unexpected challenges due to the peculiarities of the data. The difficulties associated with data analysis, the methodology used, and the results are discussed View full abstract»

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  • Turbogenerator torsional mechanical modal parameter identification from on-line measurements

    Page(s): 1389 - 1395
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    A method for measuring the torsional mode parameters of a turbogenerator is investigated. The advantages of this measurement technique are that it allows the direct measurement of the mode inertia. In addition, it makes possible the determination of the mechanical damping (excluding the electrical effects) while the turbogenerator is synchronized. The process involves the measurement of the generator's electrical torque and shaft speed. Results from digital computer simulations are presented as evidence that the method is successful. The method was used to identify specific torsional mode parameters of a laboratory multi-inertia microalternator View full abstract»

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  • A priority vector based technique for load forecasting

    Page(s): 1459 - 1465
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    The priority-vector-based load forecasting technique uses pairwise comparisons to extract relationships from presorted historical hourly load and weather records for up to two years. The presorting is done to identify seasonal boundaries and to categorized the day types. The technique is adaptive in that it internally generates the coefficients of relationships among the governing variables (weather parameters) and the load. As these relationships change over time, such coefficients are automatically updated. The resulting linear method is robust and fairly accurate. This technique was used to forecast the hourly loads for a week, using a 168 h lead time, in different seasons. The only forecast variable used was the dry-bulb temperature. When tested for historical data in the service area of a Virginia electric utility for four weeks in different seasons of the year, the average forecast error remained mostly under 4%. Only 23 individual errors, out of a total of 672 cases, exceeded 6% View full abstract»

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  • A new index extracted from line flow fluctuation to evaluate power system damping

    Page(s): 1473 - 1479
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    The authors propose an index to evaluate the damping effect of a power system on a dominant mode of electromechanical oscillation. The index is obtained from numbers of line flow fluctuations in which the dominant mode is strongly observed even in the normal state of the system. To extract the index from the fluctuations, a combined technique is developed which is based on FFT (fast Fourier transform) processing and principal component analysis. The technique is applied to the field data which have been acquired at a single tie-line of a power system in Japan. The regression analysis with respect to the index and the total generation of the system shows that the damping effect of the system becomes strong with an increase of the total generation. This property, which is called a droop characteristic, could be used to determine the steady-state stability region and to identify whether the system is in the normal or alert state View full abstract»

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  • A gradient-based algorithm for the state initialization of control systems

    Page(s): 1349 - 1355
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    The authors present an efficient algorithm for the state variable initialization of the network and control system. This algorithm is suitable for slow transient studies in AC/DC systems. It uses gradient methods to update the integrator inputs. The network is solved by the load-flow and the control system by the Gauss-Seidel method. Following the simultaneous steady-state solutions of the combined network and control system, the initial values of the state variables describing the dynamics for each component are calculated. A computer program was developed on the basis of the proposed algorithm for the initialization of slow transient studies in AC/DC systems. Results from the initialization of a typical AC/DC system are given View full abstract»

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  • Improved techniques for power system voltage stability assessment using energy methods

    Page(s): 1446 - 1452
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    An improved method of assessing power system voltage stability using energy techniques is presented. The concept of an energy function providing a localized measure of voltage security in a particular portion of the system is developed. A crucial factor in the use of the energy function method is the ability to rapidly determine the appropriate low-voltage solution to use in the energy measure calculation. Also, an improved method of locating power alternative solutions with low associated energy measures is presented. Techniques are demonstrated on the IEEE 118 bus system and a 415-bus system View full abstract»

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  • A canonical model for the study of faults in power systems

    Page(s): 1493 - 1499
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    The authors introduce a general class of fault conditions encompassing all possible faults in a power system, e.g., simultaneous symmetrical and unsymmetrical short circuits, line interruptions, and predicted breaker operations at different locations. The influence of mutually coupled lines, static VAR systems and/or faults at several busbar systems are also considered. The fault conditions are described in both the (three) phase and sequence domains, with the same simplicity. The proposed model of a faulted power system, is in a canonical form, over the general class of fault conditions. It is found that its effectiveness is equal in both domains. The authors also present the model solution procedure for various fault conditions in the general frame of the study of faults. They present the derivation of the canonical model and numerical examples. The application of the canonical model to faults that include buses of distinct voltage levels is stressed View full abstract»

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  • Analysis of the inter-area mode phenomenon in power systems following large disturbances

    Page(s): 1515 - 1521
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    The authors analyze interarea mode phenomena in stressed power systems, following large disturbances. It is shown that the interarea mode phenomenon could occur as a result of a nonlinear interaction of the natural modes of oscillation in the system. A technique for determining the interaction is developed and the machines participating in the interaction are identified. A procedure for predicting the onset of the interarea mode is presented. The technique was tested on two realistic sample test systems: a 50 generator system and a 126 generator system. The results of this analysis indicate that the procedure can detect the onset of the interarea mode phenomenon and also detect the machines which participate in the interacting natural modes of oscillation View full abstract»

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  • New digital control of forced commutation HVDC converter supplying into load system without AC source

    Page(s): 1425 - 1431
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    The authors describe a digital control technique for a forced commutation converter applied to HVDC transmission systems with loads which have no AC sources. The technique used direct calculation of the firing angle of the inverters. The results of simulator experiments and computer simulations show good performance for the regulation of the AC voltage of a load system without an AC source. In particular, it works well when a ZnO arrester is installed to suppress overvoltage which occurs when the load in the receiving system is suddenly rejected. The results show that the control technique drastically shortens the overvoltage duration and decreases the amount of energy absorbed by a ZnO gapless arrester installed at the inverter station View full abstract»

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  • A synchronous machine model for three-phase harmonic analysis and EMTP initialization

    Page(s): 1530 - 1538
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    A three-phase synchronous machine model is developed for unbalanced harmonic load flow analysis and for initializing EMTP (electromagnetic transient program) transient simulations. Two nonlinear effects, the frequency conversion and saturation, are represented in conjunction with the machine load flow constraints. The model is in the form of a frequency-dependent three-phase equivalent circuit. It can therefore be easily incorporated into existing harmonic programs for systemwide harmonic analysis. Thus, the generation of harmonies by synchronous machines under various load flow conditions and the harmonic interaction between machines and other harmonic sources can readily be analyzed 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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Meet Our Editors

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