Showing papers in "IEEE Transactions on Power Apparatus and Systems in 1975"
TL;DR: In this article, the state estimation problem in electric power systems consists of four basic operations: hypothesize structure; estimate; detect; identify, which is addressed with respect to the bad data and structural error problem.
Abstract: The state estimation problem in electric power systems consists of four basic operations: hypothesize structure; estimate; detect; identify. This paper addresses the last two problems with respect to the bad data and structural error problem. The paper interrelates various detection and identification methods (sum of squared residuals, weighted and normalized residuals, nonquadratic criteria) and presents new results on bad data analysis (probability of detection, effect of bad data). The theoretical results are illustrated by means of a 25 bus network.
608 citations
TL;DR: The paper presents a new approach to the calculation of transients on transmission lines with frequency-dependent parameters to obtain significant computer-time savings by avoiding convolutions by approximating all line and ground distortions and also time variable characteristic admittances by exponential functions.
Abstract: The paper presents a new approach to the calculation of transients on transmission lines with frequency-dependent parameters. Its purpose is to obtain significant computer-time savings by avoiding convolutions. This is achieved by approximating all line and ground distortions and also time variable characteristic admittances by exponential functions, i.e. solutions of linear differential equations. The method produces a simple Norton-type line equivalent which permits its incorporation into an existing system representation like the B.P.A. program for the calculation of transients. The program has been tested on systems of different degrees of complexity and proved to be superior, in terms of speed and accuracy, to other advanced methods.
391 citations
TL;DR: It is shown that in load flow calculations performed by Newton's method one can estimate, as a by-product of the solution, the steady-state stability of the operating condition in question, and to make this estimate more reliable and to improve convergence of the iterative solution it is expedient to use a modified Newton's algorithm.
Abstract: The paper shows that in load flow calculations performed by Newton's method one can estimate, as a by-product of the solution, the steady-state stability of the operating condition in question. In order to make this estimate more reliable and to improve convergence of the iterative solution it is expedient to use a modified Newton's algorithm - supplemented with proper alterations of the iterative corrections. The practical ways to determine the steady-state stability limits are also described in the paper.
293 citations
TL;DR: The results of the subsynchronous resonance test conducted on the number 2 turbine-generator at the Southern California Edison Company Mohave Generating Station are presented and discussed in this paper.
Abstract: The results of the subsynchronous resonance test conducted on the number 2 turbine-generator at the Southern California Edison Company Mohave Generating Station are presented and discussed Comparisons are made between measured and calculated torsional natural frequencies and mode shapes, and the damping associated with each torsional mode stimulated is presented at various loads In addition, the methods of stimulating the mechanical torsionals of the turbine-generator set are discussed along with a description of the instrumention system that was used to obtain the data
225 citations
TL;DR: A method for calculating the effect of the propagation of data inaccuracies through the load flow calculations, thus obtaining a range of values for each output quantity that encloses the operating conditions of the system.
Abstract: The load flow study has been at the center of studies made for designing and operating power systems for many years. It is well known that forecasted data used in load flow studies contain errors that affect the solution, as can be evidenced by running many cases perturbing the input data. This paper presents a method for calculating the effect of the propagation of data inaccuracies through the load flow calculations, thus obtaining a range of values for each output quantity that, to a high degree of probability, encloses the operating conditions of the system. The method is efficient and can be added to any existing load flow program. Results of cases run on the AEP system are included.
217 citations
TL;DR: An algorithm of this type is developed which is guaranteed to find a schedule satisfying problem constraints, if one exists, and which will accept any of an important class of optimality criteria, not just levelness of reserve.
Abstract: The generator maintenance scheduling problem is formulated as a 0-1 integer linear program. Although previous papers have considered a rigorous integer programming approach intractable, an algorithm of this type is developed which (1) is guaranteed to find a schedule satisfying problem constraints, if one exists; (2) is guaranteed to find the optimal feasible schedules; and (3) will accept any of an important class of optimality criteria, not just levelness of reserve. Particular attention is directed to a new criterion incorporating dollar costs/benefits incurred by delaying or advancing maintenance on a unit.
203 citations
TL;DR: In this article, the problem of planning distribution substation locations, sizes, and service boundaries is discussed. And the results of the discussed techniques will lead to a configuration of substations that will minimize distribution feeder losses and substation construction costs.
Abstract: The problem discussed in this paper is the planning of distribution substation locations, sizes, and service boundaries. The technique discussed uses operations research methods to simultaneously optimize substation sizes and service boundaries, given alternative locations for the substations and reliability constraints. The results of the discussed techniques will lead to a configuration of substations that will minimize distribution feeder losses and substation construction costs. Adherence to the results will lower long-range distribution expenses.
142 citations
TL;DR: A piece-wise compromising method of solution is presented, which conveniently groups generating units and uses successive approximations dynamic programming and the grouping criterion presented appears to be the cornerstone of the superior performance of the proposed method.
Abstract: Host currently used thermal-generator maintenance scheduling methods schedule each unit at a time, leading in many cases to a poor local optimum or to an unfeasible solution. Considering simultaneously all units in the scheduling process, a computationally impractical method results. In this paper a piece-wise compromising method of solution is presented, which conveniently groups generating units and uses successive approximations dynamic programming. The optimal maintenance scheduling problem is formulated by employing a suitable state-space representation; most common constraints used in practice are described and a multiple objective function is presented. The effectiveness of the optimizing method is illustrated by solving a problem with data obtained from a real system. The grouping criterion presented appears to be the cornerstone of the superior performance of the proposed method.
138 citations
TL;DR: In this article, the authors present the results of a study into the application and performance of the offset mho distance relay for the loss of excitation protection of synchronous generators.
Abstract: This paper presents the results of a study into the application and performance of the offset mho distance relay for the loss of excitation protection of synchronous generators. Included is information on the loss of excitation characteristics of modern generators, on relay performance during transient swings and low frequency disturbances and on generator protection.
130 citations
TL;DR: In this article, the authors developed a computer program which calculates the potential in earth, the resistance and the required potential probe position in field resistance measurements for any complex electrode in a two layer earth structure.
Abstract: The authors have developed a computer program which calculates the potential in earth, the resistance and the required potential probe position in field resistance measurements [1], for any complex electrode in a two layer earth structure. The first part of the study describes the theoretical basis of the programs and compares the two analytical methods of potential calculations, the summation and the integration methods. The second part contains essentially a comparison between the theoretical calculations derived in this paper, experimental results obtained in scaled down model [2], and other theoretical calculations currently used in the industry [3]. The final part will discuss the efficiency of different usual electrode configurations and will introduce new configurations.
124 citations
TL;DR: In this article, a 1400MW dynamic braking resistor installed at the Bonneville Power Administration's (BPA) Chief Joseph Substation enhances system stability in the Pacific Northwest (PNW).
Abstract: A 1400-MW dynamic braking resistor installed at the Bonneville Power Administration's (BPA) Chief Joseph Substation enhances system stability in the Pacific Northwest (PNW). The capacity of the Pacific Northwest-Southwest (PNW-SW) Intertie is increased by the use of resistor braking for faults in the PNW. The need of and benefits from the use of the brake are discussed. The physical and electrical characteristics of the brake are described as well as the control system for its operation.
TL;DR: In this article, a method of forecasting the heat sensitive portion of electrical demand and energy utilizing a summer weather load model and taking into account probability variation of weather factors is discussed in this paper.
Abstract: A method of forecasting the heat sensitive portion of electrical demand and energy utilizing a summer weather load model and taking into account probability variation of weather factors is discussed in this paper. The heat sensitive portion of the load is separated from base load and historical data is used to determine the effect of weather on the system load. This method is based on regression analysis of historical load and weather information and the establishment of system load characteristics based on historical or survey information. The method has been determined primarily for forecasting demands and energy for the intermediate range of from 3 to 10 years. However, it is applicable for monthly and annual peak forecasting, but probably not applicable for short terms such as hour to hour or day to day forecast. It may also be helpful in long term forecasting with appropriate forecast of future quantities of heat sensitive load on the system. Separate weather load models are used for determining the heat sensitive portion of electric energy and demand independently. These correlation studies were made when the author was located in Birmingham, Alabama and all of the studies reported here are on systems in that general area. The author hopes to continue these weather-load correlation studies in the northeast area in the near future.
TL;DR: In this article, a Graetz bridge converter is used in dc transmission to provide an ideal interface between the three-phase power system and the superconductive magnet or inductor.
Abstract: Large magnets with superconductive windings could serve to perform a power system function analogous to pumped storage hydro. A conventional Graetz bridge converter as used in dc transmission provides an ideal interface between the three-phase power system and the superconductive magnet or inductor. Such Inductor-Converter or I-C units, when properly controlled, provide significant power system benefits. Power reversibility is achievable within a few cycles without switching. Power system electromechanical oscillations can be damped effectively. Computer studies reveal that this damping capability may be useful even with smaller inductor sizes when energy storage in large amounts is not the primary objective. In sizes greater than 1,000 MWh, economic studies show promise.
TL;DR: In this article, it is shown that an accurate determination of these points is not necessary and using the analogy of 1-mechine-infinite bus example, (2n-1-1) u.p.'s can be approximately obtained.
Abstract: One of the major difficulties in using the Lyapunov method for on-line transient stability is the determination of the critical value of the V-function which describes the stability boundary. In one method the V critical is taken to be the minimum value of the V-function evaluated at (2n-1-1) unstable equilibrium points (u.e.p.). In this paper it is shown that an accurate determination of these points is not necessary and using the analogy of 1-mechine-infinite bus example, (2n-1-1) u.e.p.'s can be approximately obtained. Two multimachine systems (4 and 9- machine) are used as examples. The error in the stability boundary by using approximate method is shown to be acceptable. The use of Newton-Raphson method to calculate the post-fault stable equilibrium point is suggested. Also the type of mathematical model which is sufficient to represent both uniformly and non-uniformly damped multimachine systems is discussed.
TL;DR: In this paper, a quantitative relation between the practical breakdown threshold and gas pressure times maximum surface roughness is derived, based on the streamer theory of breakdown, which is applied to microscopic field regions associated with roughness.
Abstract: Electrode surface roughness can cause a large reduction of the threshold for break down in SF 6 insulated apparatus. This effect is discussed by applying the streamer theory of breakdown to the microscopic field regions associated with surface roughness. A quantitative relation is derived between the practical breakdown threshold and gas pressure times maximum surface roughness.
TL;DR: In this article, first-order triangular finite elements are derived for the nonlinear diffusion equation in the general form which includes both time-dependent and notional terms, and applied to a simplified model of a single-sided linear induction motor, for which the finite element equations are solved by an implicit method in time and iteratively in space.
Abstract: Following the Galerkin projective technique, first-order triangular finite elements are derived for the nonlinear diffusion equation-in the general form which includes both time-dependent and notional terms. The method is applied to a simplified model of a single-sided linear induction motor, for which the finite element equations are solved by an implicit method in time, and iteratively in space. The results suggest that the screening effect of eddy currents in the iron is quite strong.
TL;DR: In this paper, the accuracy of the digital methods for protection of high voltage transmission lines under transient fault condition on a long line was explored and an improved method for future digital protection schemes.
Abstract: This paper explores the accuracy of the digital methods for protection of high voltage transmission lines under transient fault condition on a long line and describes an improved method for future digital protection schemes. With this method it is possible to calculate R and L of high voltage transmission lines so that any number of harmonics on the current and voltage waveforms can be eliminated and it is shown to be suitable for distance protection during the first cycle of fault occurrence.
TL;DR: In this article, a new power flow model has been developed for the steady state behavior of large complex power systems, it allows the study of power flow under abnormal conditions as well as normal conditions.
Abstract: A new power flow model has been developed for the steady state behavior of large complex power systems, it allows the study of power flow under abnormal conditions as well as normal conditions. It is also shown how Newton's method can be efficiently applied to the model to provide exact and practicable solutions for a new steady state following the disturbance. Advanced applications are introduced which show how the steady state model can be combined with a dynamic simulation program.
TL;DR: In this article, the harmonic restraint differential relay concept has been enlarged upon to provide a new static multiple-winding transformer differential relay, which includes simplification of the frequency selective circuits and new techniques for rapidly determining the harmonic content of the applied currents.
Abstract: Established harmonic restraint differential relay concepts have been enlarged upon to provide a new static multiple-winding transformer differential relay. The resulting design includes simplification of the frequency selective circuits and new techniques for rapidly determining the harmonic content of the applied currents. The relay is shown to have improved sensitivity, to be responsive to internal transformer winding faults in less than two cycles, and to the more severe type of fault in less than one cycle. Full security against inrush currents and overexcitation as well as to external faults is demonstrated. Poor performance of current transformers is shown not to adversely affect either the security or dependability of the relay. Heavy current test results are presented which confirm the relay principles.
TL;DR: In this article, a new algebraic expression for critical sparkover voltage (CSOV) subair insulation submitted to positive switching impulses was established for all practical gap configurations in the distance range 1 to at least 30 m.
Abstract: A new algebraic expression has been established for the critical sparkover voltage (CSOV) afair insulation submitted to positive switching impulses. By using the concept of the gap factor, the expression is found to be valid for all practical gap configurations in the distance range 1 to at least 30 m. Based on these considerations, an absolute limit of 2.4 MV is foreseen for the rated voltage of AC systems. Sparkover voltages under A.C. or lightning impulses are also predictable. Complementary investigations concerning the physics of discharge are needed for further improvements.
TL;DR: In this paper, the authors take the view that the predominant problem of load frequency control (LFC) resides in the low frequency domain assosiated with bulk generation change and which is dominated by limited generation response capability.
Abstract: This paper takes the view that the predominant problem of load frequency control (LFC) resides in the low frequency domain assosiated with bulk generation change and which is dominated by limited generation response capability. In this setting LFC is formulated as a tracking problem in which energy source dynamics and load following play a central role. It is shown how load prediction and coordination of area generation in a multi-area interconnection can effectively improve the regulation of inter-area power flows.
TL;DR: This paper relates to on-line security assessment and determination of optimal preventive measures of power system, which the authors have developed by using two methods, digital and digital-analog hybrid.
Abstract: This paper relates to on-line security assessment and determination of optimal preventive measures of power system, which the authors have developed by using two methods, digital and digital-analog hybrid. The description includes the power system of the Tokyo Electric Power Co., Inc. (TEPCO) for the security assessment; the software configuration for the on-line security assessment; fast calculating methods for the assessment, with emphasis on the study of transient stability; methods for determinating optimal preventive measures to improve transient stability; performance test of the digital method for an actual bulk power system; and a model hybrid security monitoring system for a comparatively small power system and its performance test.
TL;DR: In this article, the effect of virtual current chopping which can lead to line to line overvoltages is described and the phenomena are explained for simplified conditions, more complex situations are handled by digital computer studies.
Abstract: Switching of three phase load currents with low power factors, such as encountered in arc furnace installations can result in a series of reignitions and clearings. Depending on the switch performance and system parameters the switching transients may involve one, two, or three phases. The effect of virtual current chopping which can lead to line to line overvoltages is described. The phenomena are explained for simplified conditions, more complex situations are handled by digital computer studies.
TL;DR: In this paper, the problem of determining the best measurement to add to a given set is solved by showing that the poorest observability is in the direction of the eigenvector associated with the smallest eigenvalue of an observability matrix.
Abstract: Power system static state estimators usually employ more measurements than the minimum number necessary to completely define the state of the system. This paper solves the problem of determining the best measurement to add to a given set. This is done by showing that the poorest observability is in the direction of the eigenvector associated with the smallest eigenvalue of an observability matrix. Added new measurements in this direction are shown to improve observability and the best possible observability is shown to be where all the eigenvalues of the observability matrix are equal. The addition of measurements for determining the static state of a power system should improve observability. The technique for applying this concept to a power system is illustrated by a numerical example. The observability matrix and the smallest eigenvalues are found and the measurement to be added is determined by examining the components of the associated eigenvector. The improvement of this measurement over any other is verified by use of the Kalman filter.
TL;DR: In this paper, a detailed study of the influence of electrodes and earth parameters on grounding performance is analyzed for different types of practical electrodes and a brief analysis and discussion of new electrodes configuration is also included.
Abstract: In a previous paper [1] the authors have presented the theoretical basis of their computer program which determines grounding electrodes performance. In this last paper of the series presented, a detailed study of the influence of electrodes and earth parameters on grounding performance is analysed for different types of practical electrodes. A brief analysis and discussion of new electrodes configuration is also included.
TL;DR: In this article, a linear flow network is used to model the transmission interconnections and an efficient graph theory algorithm is applied to find critical minimal cuts in the network to determine the probability of failure.
Abstract: This paper presents the results of an investigation of a technique for the evaluation of the reliability of supplying power in a system with a number of interconnected load-generation areas. There is no restriction as to how the areas may be interconnected. Most previous techniques using analytical methods (as opposed to Monte Carlo simulations) have been limited to systems with a maximum of three interconnected areas. Systems with more areas have been analyzed assuming that the interconnecting electrical network did not contain any loops. The application of straightforward enumerative methods to systems with more complex interconnections than these can result in an improbably large number of computations. The method of analysis described in this paper is based upon the use of a linear flow network to model the transmission interconnections and makes use of an efficient graph theory algorithm to segregate the failure states by finding critical minimal cuts in the network. The probabilities of failure to supply the various loads are computed by evaluating the various combined event probabilities associated with these critical minimal cuts. For the cases tested, the technique reduces the number of probability evaluations required by about one to two orders of magnitude in comparison with complete state enumeration methods. The tested method provides reliability measures (i.e., the probability of failure to meet the load) for each individual area and the total system, and also allows the computation of the probability that each "link" (transmission line or source) is a member of a critical minimal cut. The latter will facilitate the application of the method to the design of systems and specifically to the problem of evaluating the reliability benefits of increased transmission capacity versus added generation.
TL;DR: In this article, a different approach to the design of power stabilizers for damping out tie-line power oscillations in power systems is described, which can be applied directly to systems characterized by lightly damped oscillations and gives an explicit indication of the amount of improvement in system damping for different combinations of stabilizer parameters.
Abstract: This paper describes a different approach to the design of power stabilizers for damping out tie-line power oscillations in power systems. The technique described in this paper was successfully applied at a generating station of the Saskatchewan Power Corporation System with the results from these tests included in the latter part of this paper. The technique can be applied directly to systems characterized by lightly damped oscillations and gives an explicit indication of the amount of improvement in system damping for different combinations of power stabilizer parameters. This procedure allows for a graphical approach to the design of power stabilizers and serves as a synthesis procedure when the design constraints are relaxed so that the speed stabilizer is required to provide an improvement in system damping.
TL;DR: In this paper, the system and transformer characteristics which can result in overvoltages and ferroresonance when energizing grounded-wye/groundwye distribution transformers from a remote location with single-pole switches are defined.
Abstract: The system and transformer characteristics which can result in overvoltages and ferroresonance when energizing grounded-wye/ grounded-wye distribution transformers from a remote location with single-pole switches are defined. A qualitative analysis of a system typical of those installed today is presented to show how the overvoltages can occur during single-pole switching. Full-scale laboratory tests were conducted to determine maximum overvoltages and obtain a better understanding of the phenomenon. The results show that distinct responses occur during the single-pole energization, and ferroresonance can occur contrary to statements appearing in many references.