scispace - formally typeset
Search or ask a question

Showing papers in "IEEE Transactions on Power Apparatus and Systems in 1971"


Journal ArticleDOI
Abstract: An essential component of a comprehensive, real-time control center for power systems is a method for the calculation of short-term load forecasts. This paper explores the use of general exponential smoothing to develop an adaptive forecasting system based on observed values of integrated hourly demand. A model is developed which offers high accuracy and operational simplicity. Forecasts of hourly MWH load with lead times of one to twenty-four hours are computed at hourly intervals throughout the week. A pragmatic viewpoint is maintained throughout the paper, which includes an analysis of two years of hourly load data, test results for the method developed, and discussions of adjustments for holidays and weather disturbances.

442 citations


Journal ArticleDOI
TL;DR: In this paper, a program for on-line steam unit dispatch that results in the minimizing of Nitrogen Oxide emissions is developed, where a unique mathematical representation of the steam generating units coupled with a Newton-Raphson convergence technique for dispatch produces base points and participation factors.
Abstract: A program has been developed for on-line steam unit dispatch that results in the minimizing of Nitrogen Oxide emissions. A unique mathematical representation of the steam generating units coupled with a Newton-Raphson convergence technique for dispatch produces base points and participation factors for any load level and any unit configuration. Emission reductions and corresponding cost increases are compared to standard economic dispatch.

295 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a bad data suppression (BDS) estimator which is based on a non-quadratic cost function but which reduces to the weighted least squares estimator in the absence of bad data.
Abstract: The presence of bad data points may severely degrade the performance of any of the power system static state estimators currently being proposed This paper discusses a BDS (bad data suppression) estimator which is based on a non-quadratic cost function but which reduces to the weighted least squares estimator in the absence of bad data In the presence of bad data, the BDS algorithm provides state estimates comparable to those provided by the weighted least squares method when all data is good Computer storage and computational requirements and convergence time are equivalent for the BDS and weighted least squares estimators

250 citations


Journal ArticleDOI
TL;DR: In this article, a new method of eliminating ac harmonic current is proposed, which is based on the principle of the magnetic flux compensation in a transformer core, by means of the new method, abnormal harmonics as well as normal harmonics can effectively be dealt with.
Abstract: A new method of eliminating ac harmonic current is proposed, which is based on the principle of the magnetic flux compensation in a transformer core. By means of the new method, abnormal harmonics as well as normal harmonics can effectively be dealt with. Considerations on the basic design of the new method are given.

209 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a method of distance-type protection suitable for on-line digital computer protection of transmission lines, based on the predictive calculation of peak fault current and voltage from a small number of sample values.
Abstract: The paper proposes a method of distance-type protection suitable for on-line digital computer protection of transmission lines. The basic principle is the predictive calculation of peak fault current and voltage from a small number of sample values. The magnitudes of various sources of error are discussed. The results of experimental work on a model transmission line and on a high- voltage transmission system are described. The calculation times for implementation in real time are estimated.

160 citations


Journal ArticleDOI
TL;DR: In this article, the authors report upon the development of a unit commitment method, and its implementation in program form on a 100 machine system, which satisfies the many operating constraints that are encountered in system operations.
Abstract: This paper reports upon the development of a unit commitment method, and its implementation in program form on a 100 machine system The method presented satisfies the many operating constraints that are encountered in system operations The unit commitment function is employed by operating personnel for both actual operations and for operations planning The paper discussed the elapsed computing time required to perform the commitment function in a process computer while executing higher priority functions and also the substantial savings realized in system operations over manual methods of commitment

153 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical approch to the construction of power system dynamic equivalents for use in stability calculations and dynamic simulations is presented, which is capable of accurately representing the dynanlical effects of generator field and amortisseur windings, voltage regulators, and speed governors.
Abstract: This paper presents an analytical approch to the construction of power system dynamic equivalents for use in stability calculations and dynamic simulations. The method presented is capable of accurately representing the dynanlical effects of generator field and amortisseur windings, voltage regulators, and speed governors. Experimental evaluation of equivalents constructed by this method is reported in a companion paper.

153 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe techniques for keeping the solution time in networks with such elements as low as possible, by using the compensation method or network equivalents, and they describe how to simulate the effects of lightning arresters, transformer saturation, circuit breakers and other nonlinear and time-varying effects.
Abstract: Simulation programs for electromagnetic transients must provide models for lightning arresters, transformer saturation, circuit breakers and other nonlinear and time-varying effects. This paper describes techniques for keeping the solution time in networks with such elements as low as possible, by using the compensation method or network equivalents.

144 citations


Journal ArticleDOI
TL;DR: In this article, a load-frequency control problem for interconnected systems is considered from the viewpoint of optimal stochastic system theory, and a control algorithm is developed which provides improved power system performance in both large and small signal modes of operation.
Abstract: The load-frequency control problem for interconnected systems is considered from the viewpoint of optimal stochastic system theory. A control algorithm is developed which provides improved power system performance in both large and small signal modes of operation. An especially attractive feature of the proposed control scheme is that it requires as inputs only the variables currently used, i. e., frequency deviations and scheduled interchange deviations. The classical two-area power system is used as a base system for comparative studies relating the response of an interconnected power system using the new control algorithm to the response obtained using conventional control strategy.

129 citations


Journal ArticleDOI
Thomas A. Lipo1
TL;DR: In this paper, an analytic method for predicting the steady-state performance of an induction motor with variable voltage control is presented, which is well suited to the evaluation of proposed motor designs when used in conjunction with thyristor voltage control.
Abstract: The application of thyristor switching to induction motor speed control has resulted in a number of unconventional supply systems. One such technique, which has been successfully employed in a number of applications, is variable voltage control by means of symmetrically triggered thyristors in the stator phases of a wye-connected machine. In this paper, an analytic method for predicting the steady-state performance of such a system is presented. The solution is obtained in closed form without the necessity for iteration to obtain the proper boundary conditions. In addition, it is shown that the symmetry of the solution permits an additional reduction in the computation time. Since matrix techniques are utilized throughout the analysis, the equations can be easily implemented into a digital computer program. Hence, the method is well suited to the evaluation of proposed motor designs when used in conjunction with thyristor voltage control. Measured torque-speed characteristics of a typical drive system are included and the results compared to an analytical solution. It is demonstrated that a computed solution will favorably predict the performance of an actual system.

127 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show how LTC transformers and variable phase-shifting transformers may be automatically adjusted by the Newton algorithm, thus complementing a previous inclusion of the area interchange control variables within the Newton method.
Abstract: In recent years, Newton's method has been generally accepted as a superior algorithm for solving power flow problems. But the introduction of generator var limits, area-interchange control, load-tap- changing (LTC) transformers, and variable phase shifting transformers has significantly increased the solution times (compared with a fixed system). This paper shows how LTC transformers and variable phase-shifting transformers may be automatically adjusted by the Newton algorithm, thus complementing a previous inclusion of the area interchange control variables within the Newton algorithm [1]. Tests of the new method for adjusting LTC transformers and phase shifters indicate a significant overall saving in solution time.

Journal ArticleDOI
D. R. Albright1
TL;DR: In this article, an effective method of detecting interturn short circuits on round rotor windings is described, which is based on measuring the rate of change of the air-gap flux density wave when the rotor is at operating speed and excitation is applied to the field winding.
Abstract: An effective new method of detecting interturn short circuits on round rotor windings is described. The approach used is to measure the rate of change of the air-gap flux density wave when the rotor is at operating speed and excitation is applied to the field winding. The measurements are obtained by the use of a small stationary search coil positioned near the rotor surface. The voltage outputs are recorded by Polaroid pictures from an oscilloscope screen and can be analyzed based on the information presented. The sensitivity obtained from these methods is far superior to previous methods. The data obtained at operating speed identify the coils and slots which have shorted turns, and provide a good indication of the number of turns shorted in a coil if more than one short exists.

Journal ArticleDOI
TL;DR: In this article, a comparison is made of a lower-order linear model and a high-order non-linear system modelled as a single machine-infinite bus as well as multi-machine systems.
Abstract: The stabilization of power systems with excitation control using speed or power signals has been very well developed,1-6 while the application of optimal control to power system stability study is relatively new.7 Both are based on linear models. In this paper, a comparison is made of these two techniques. Signals derived from a lower order linear model are tested on a high order non-linear system modelled as a single machine-infinite bus as well as multi-machine systems.

Journal ArticleDOI
TL;DR: In this paper, the nonlinear quasi-Poisson equation that describes static magnetic fields in saturable iron is solved approximately by minimizing the corresponding nonlinear energy functional, performed by means of the method of finite elements, using firstorder elements and a quadratically convergent iterative solution method.
Abstract: The nonlinear quasi-Poisson equation that describes static magnetic fields in saturable iron is solved approximately by minimizing the corresponding nonlinear energy functional. The minimization is performed by means of the method of finite elements, using firstorder elements and a quadratically convergent iterative solution method. The method is applied to a turboalternator and used to predict all the normal shop-floor test results. Excellent agreement is found between experimental and computed values. Computing times are found to be extremely fast, and it is concluded that this method is capable of producing results comparable to those obtained by finite difference methods, but at very much reduced cost.

Journal ArticleDOI
TL;DR: A tracking static state estimator is a digital feedback loop (a computer algorithm) which uses real time measurements of voltage magnitudes, watt flows, and var flows to track the static state (voltage at all buses) as it varies during the daily load cycle as discussed by the authors.
Abstract: A tracking static state estimator is a digital feedback loop (a computer algorithm) which uses real time measurements of voltage magnitudes, watt flows, and var flows to track the static state (voltage at all buses) as it varies during the daily load cycle. The design and performance of simple gain matrices suitable for wide ranges of operating conditions are discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors present some of the basic principles which should be considered in the application of a load shedding and load restoration program and describe the philosophy which led to the frequency actuated load shedding, and the method of program implementation and management is presented in a companion paper.
Abstract: During the last few years, there has been expanded effort throughout the country to install frequency actuated load shedding programs for the purpose of providing means to safeguard a power system should a condition of declining frequency occur. Hand in hand with a load shedding program a convenient means must be provided for restoring load after the system returns to a normal state. In this series of papers, the authors will present some of the basic principles which should be considered in the application of a load shedding and load restoration program and will describe the philosophy which led to the frequency actuated load shedding and load restoration program being implemented on the American Electric Power System. As part of this presentation, the various analytical studies which were carried out to determine the load management programs for the AEP system will be described in detail. In addition, the method of program implementation and management is presented in a companion paper.

Journal ArticleDOI
TL;DR: In this article, a method is described for determining the most economical generating commitment policy and loading schedule for a day's operation of an electric utility system while maintaining a desired level of system reliability.
Abstract: A method is described for determining the most economical generating utiit commitment policy and loading schedule for a day's operation of an electric utility system while maintaining a desired level of system reliability.

Journal ArticleDOI
TL;DR: In this paper, the optimal output feedback control of a synchronous machine, consisting of constant output feedback gains from only those states which are physically available for measurement, is considered, and an integral quadratic performance index of outputs and controller inputs is minimized for impulse type disturbances occurring in the system.
Abstract: The optimal output feedback control of a synchronous machine, consisting of constant output feedback gains from only those states which are physically available for measurement, is considered in this paper. An integral quadratic performance index of outputs and controller inputs is minimized for impulse type disturbances occurring in the system. This gives a physically realizable control system which optimally "stabilizes" the excitation and input power to the synchronous machine. Numerical examples are included to show the application of the theory to a thermal and a hydraulic machine equipped with static exciters, and connected to an infinite bus. It is found that it is desirable to control a synchronous machine using both exciter and input power control gates with both power angle and speed fed back. A reduction in the value of the index of performance by a factor as large as 66 may be achieved using this control configuration instead of the conventional control configuration.

Journal ArticleDOI
TL;DR: The paper develops a-method of determining the minimum amount of reactive power capacity installation required to satisfy constrained system voltage conditions, and linear programming is used to obtain the solution.
Abstract: The paper develops a-method of determining the minimum amount of reactive power capacity installation required to satisfy constrained system voltage conditions. The solution gives both location and amount of reactive sources. Sensitivity parameters are the basis of the model, and linear programming is used to obtain the solution. The method is practical and static operating constraints are naturally included. Numerical examples illustrate the application of the method.

Journal ArticleDOI
TL;DR: In this article, the electrical discharge characteristics of SF6 are discussed theoretically in relation to the field dependence of the ionization coefficient a and the electron attachment coefficient, and a simple theoretical formulation of breakdown or corona inception voltages of gaps in SF6 is derived.
Abstract: The electrical discharge characteristics of SF6 are discussed theoretically in relation to the field dependence of the ionization coefficient a and the electron attachment coefficient The results are compared with the characteristics of air. A simple theoretical formulation of breakdown or corona inception voltages of gaps in SF6 is derived. The formulation has been examined by experiments on several electrode configurations. At low pressures of less than 4 atm, the agreement of the theoretical and the experimental results is fairly good. The breakdown voltage decreases from the theoretical estimation at higher pressure.

Journal ArticleDOI
TL;DR: In this article, the application of statistical methods to the field of cable dielectric strength is discussed on the basis of experimental results, and the results show that statistical methods can be used to obtain a better performance than traditional methods.
Abstract: The application of statistical methods to the field of cable dielectric strength is discussed on the basis of experimental results.

Journal ArticleDOI
TL;DR: A new method of scheduling thermal generating units to achieve minimum operating costs including both running and start-up costs while at the same time maintaining a desired level of system security is described.
Abstract: The paper describes a new method of scheduling thermal generating units to achieve minimum operating costs including both running and start-up costs while at the same time maintaining a desired level of system security.

Journal ArticleDOI
TL;DR: In this paper, the magnetic field distribution in saturated iron parts of electric machines is defined by a nonlinear quasi-Poisson equation, and the solution of this equation is equivalent to minimization of a non-linear energy functional.
Abstract: The magnetic field distribution in saturated iron parts of electric machines is defined by a nonlinear quasi-Poisson equation. Solution of this equation is equivalent to minimization of a nonlinear energy functional. A recent paper has proposed approximate minimization by means of a finite element method, using triangular finite elements and a quadratically convergent iteration scheme. This new method is now applied to a 5 KW d-c machine, whose no-load and on-load characteristics are predicted and compared with experimental measurements. Good agreement is obtained. Since the pole axis is not an axis of magnetic symmetry under load, a periodicity condition is introduced to relate all magnetic vector potentials to those one pole pitch away. This condition is enforced by means of a special connection matrix, whose derivation is shown in the paper. An automatic plotting program has been developed for graphical plotting of the flux distributions, and several field plots for the machine are shown.

Journal ArticleDOI
TL;DR: In this article, present practices within the utility industry in the economic operation of electric power systems are discussed and some shortcomings of present practices and areas requiring further development are discussed. But these practices are intended primarily as a reference for those new in this area of endeavor.
Abstract: This paper presents present practices within the utility industry in the economic operation of electric power systems. It is intended primarily as a reference for those new in this area of endeavor. It also discusses certain shortcomings of present practices and areas requiring further development.

Journal ArticleDOI
TL;DR: In this article, the problem of optimization of induction motor design is tackled as a nonlinear programming problem and the objective function or the cost function is formed taking only the material cost into account.
Abstract: The problem of optimization of induction motor design is tackled as a nonlinear programming problem The objective function or the cost function is formed taking only the material cost into account The specifications like pull out torque, starting torque etc are put as constraint functions These functions are expressed in terms of important dimensions of the machine which are assumed to be continuously variable The sequential unconstrained minimization technique for nonlinear programming is used to obtain an optimum design Analysis and synthesis programs needed for the problem have also been developed The method is applied to a line of small single cage integral horsepower motors

Journal ArticleDOI
TL;DR: In this paper, radio noise measurements made near overhead power lines from 2.4 to 345 kV in the frequency range of 60 Hz to 1 GHz and on radio noises measurements made on 7.2, 345, 525, 735, and 765kV ac lines and on an 800-kV dc test line up to 10 GHz.
Abstract: This paper presents radio noise measurements made near overhead power lines from 2.4 to 345 kV in the frequency range of 60 Hz to 1 GHz and on radio noise measurements made on 7.2, 345, 525, 735, and 765-kV ac lines and on an 800-kV dc test line up to 10 GHz. The measurements and their analysis show the important radio noise factors involved in the development and use of prediction techniques for the evaluation of communication site performance in the vicinity of overhead power lines.

Journal ArticleDOI
TL;DR: In this paper, a control of the convergence process is added to the normal Newton's method to obtain faster convergence than with the normal approach, and the method is derived by comparison with the non-linear programming approach to the solution of the load flow problem.
Abstract: Newton's method [1] is altered to obtain a faster convergence than with the normal approach. The method is derived by comparison with the non-linear programming approach [2]-[4] to the solution of the load flow problem. A control of the convergence process is an additional feature of the proposed algorithm. By means of this control, the method converges for cases when the normal Newton's method diverges. Numerical examples show evidence of these characteristics. The alteration is simple to implement on existing Newton programs.

Journal ArticleDOI
TL;DR: In this article, the performance of a polyphase reluctance machine is analyzed by direct and quadrature-axis components, by circle diagrams, and by machine admittance, and specific equations are deduced for pull-out out torque, maximum power factor, no-load current, and pullout current.
Abstract: Polyphase reluctance machine performance is analyzed by direct-and quadrature-axis components, by circle diagrams, and by machine admittance. Specific equations are deduced for pull-out out torque, maximum power factor, no-load current, and pull-out current. A method is given by which the entire motor performance may be calculated through knowledge of machine admittance. Comparisons are made between calculated and measured results.

Journal ArticleDOI
TL;DR: In this article, the problem of electromechanical equivalence is formulated, and a method of constructing EME equivalents is described, and the performance of these equivalents has been evaluated by a series of computational tests.
Abstract: This paper describes the development of dynamic power system equivalents for use in stability studies of interconnected systems. The problem of electromechanical equivalencing is formulated, and a method of constructing electromechanical equivalents is described. The performance of these equivalents has been evaluated by a series of computational tests. Theoretical material pertaining to electromechanical equivalencing is presented in a companion paper.

Journal ArticleDOI
TL;DR: In this paper, an electromagnetic model of the reluctance machine was proposed and the self-inductance Ld and La of a reluctance machine with flux barriers and cutouts was analyzed.
Abstract: Equations for the self-inductances Ld and La of a reluctance machine having flux barriers and cutouts are developed. An electromagnetic model of the reluctance machine is postulated. Flux densities are found in the air gap proper, the cutouts, and the barriers. A comparison is made between measured and calculated results.