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Showing papers on "Electric power system published in 1975"


Journal ArticleDOI
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



Journal ArticleDOI
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.

99 citations


Journal ArticleDOI
R. F. Woll1
TL;DR: In this article, the authors focus on the problem of unbalanced voltage at the point of utilization of a three-phase induction motors and the effect of such voltage imbalance on the operation of the motors.
Abstract: Three-phase electric power systems generally provide voltage supply at the generating station that is well balanced in both magnitude and displacement. For varying reasons, however, some degree of voltage unbalance occurs at the point of utilization, and, depending upon the amount of unbalance, this can have an adverse effect upon the operation of polyphase induction motors. A major cause of unbalanced voltage at the point of utilization is that single-phase loads on a system are not uniformly applied to all three phases. This is particularly true for some rural electric power systems, and it can also occur in large urban power systems where heavy single-phase demands are imposed by facilities such as extensive shopping plazas. A large manufacturing plant may have well balanced incoming supply voltage, but unbalance can develop within the plant from its own single-phase power requirements if these are not uniformly spread among the three phases. Regardless of the cause, unbalanced voltage is harmful to three-phase induction motors. The paper to follow concentrates upon that aspect of unbalanced voltage.

98 citations


Book
01 Jan 1975
TL;DR: Extensions of the Z-Matrix Short-Circuit Program to Include Very Large Systems Single-Phase Short Circuits and Calculations for Contingency Evaluation and Maximum Interchange Capability Determinations are presented.
Abstract: General Background Matrix Algebra Extensions of the Z-Matrix Short-Circuit Program to Include Very Large Systems Single-Phase Short Circuits State-Estimation Load Flow Solutions The Economics of Operating a Power System Optimum Load Flow Transient Stability High-Speed Reduced-Accuracy Power Flow Calculations for Contingency Evaluation and Maximum Interchange Capability Determinations Appendixes Index.

73 citations


Journal ArticleDOI
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.

70 citations



Journal ArticleDOI
Osamu Saito1, K. Koizumi, M. Udo, M. Sato, H. Mukae, T. Tsuji 
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.

60 citations


Journal ArticleDOI
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.

51 citations


Patent
07 Jul 1975
TL;DR: In this paper, a cycloconverter having at the input a source of higher frequency than at its output is used as a static reactive power generator to correct displacement angle in an alternating current power system when coupled to a power system at the output.
Abstract: A naturally commutated cycloconverter having at the input a source of higher frequency than at its output is used as a static reactive power generator to correct displacement angle in an alternating current power system when coupled thereto at the output. Reactive power correction is obtained with such "high frequency link" by automatically controlling the output voltage of the cycloconverter so as to deviate by a required amount from the AC power system voltage. At the same time, a circulating current is established between the positive and negative banks of thyristors of the cycloconverter of such a magnitude as to compensate for the variations of the lagging quadrature component of the input current of the cycloconverter caused by output current variations, thereby permitting optimization of the high frequency link. The concept of generating controllable reactive power with a naturally commutated cycloconverter is used (1) with one cycloconverter as a controllable source of reactive power coupled to a power system; (2) with two cycloconverters tying a power system with a load, or two power systems together. In either instance, the output voltage of the cycloconverter is controlled for automatic compensation in the line power factor, and concurrently a circulating current is established in the single or in the two cycloconverters for automatic correction against variations in the lagging current at the cycloconverter input when the load conditions at the output thereof vary.

48 citations


Journal ArticleDOI
TL;DR: In this paper, a comparison of the various energy storage systems is presented in terms of performance on electric power systems, and cost, and a brief review of the Los Alamos Scientific Laboratory program on superconducting magnetic energy storage is included.
Abstract: As the cost of fossil fuel has increased and the load factors on electric utilities have decreased, the need for efficient, reliable energy storage systems has increased. Although pumped hydro storage is now used extensively on those utility systems having the appropriate resources nearby, it is only 65% efficient. Superconducting magnetic energy storage which promises to be more than 90% efficient and easily sited may become a competitive energy storage technology. A comparison of the various energy storage systems is presented in terms of performance on electric power systems, and cost. Emphasis is given to the various technologies involved in the development of large superconducting magnets. A brief review of the Los Alamos Scientific Laboratory program on superconducting magnetic energy storage is included.

Journal ArticleDOI
TL;DR: In this article, a new approach to the stability analysis of large scale power systems using vector Lyapunov functions is introduced, by decomposing the composite power system into a number of low-order subsystems, and using this function together with the stability properties of individual subsystems and the nature of interactions between subsystems criteria for the stability of the overall system are derived.

Journal ArticleDOI
TL;DR: In this paper, the experience obtained with series-compensated power systems, particularly in Sweden, where internally fused capacitor units and simple system designs have contributed to the good results.
Abstract: The paper reviews the experience obtained with series-compensated power systems, particularly in Sweden, where internally fused capacitor units and simple system designs have contributed to the the good results. It also introduces new approaches for meeting future demands, e.g., optronic protection and a high-speed flip-flop reinsertion system.

Journal ArticleDOI
TL;DR: A mathematical programming model is described for the economic planning of generation and transmission systems by iterating between the simulation of operating conditions and the combined costs model the number of constraints are reduced by up to one hundredth of those required for early linear programming models.
Abstract: A mathematical programming model is described for the economic planning of generation and transmission systems. By iterating between the simulation of operating conditions and the combined costs model the number of constraints are reduced by up to one hundredth of those required for early linear programming models.

Journal ArticleDOI
TL;DR: In this article, an algorithm for calculating apparent transmission line impedance to the point of a fault is presented as an approach to distance type protection via a dedicated digital computer, where phase voltages and currents are sampled asynchronously approximately 24 times per cycle and operated on to yield apparent resistances and reactances.
Abstract: An algorithim for calculating apparent transmission line impedance to the point of a fault is presented as an approach to distance type protection via a dedicated digital computer. Phase voltages and currents are sampled asynchronously approximately 24 times per cycle and operated on to yield apparent resistances and reactances. Descrimination between phase to phase, phase to ground and two phase to ground faults is considered. The effects of disturbances such as transformer magnetizing inrush currents, assymetrical currents, sensor response, as well as results which can be expected when the power system frequency is higher or lower than nominal are discussed. The reach accuracy of the system is reported using simple statistical measures obtained from simulating the operation of the digital relay on an IBM 360/65 computer. These simulations verify the approach is feasible.

Journal ArticleDOI
TL;DR: In this article, the authors present a feasibility study of a technique for identifying dynamic equivalents of portions of a power system from measurements made only within a restricted study system without intentional perturbation of the system.
Abstract: This paper presents the results of a feasibility study of a technique for identifying dynamic equivalents of portions of a power system from measurements made only within a restricted Study System without intentional perturbation of the system. The Maximum Likelihood technique is used to identify parameter values for a specified equivalent structure which is suitable for direct use in standard transient stability programs. The identifier was tested using measurements from simulations tuned to match field measurements. The field measurements, identification algorithm, and program test results are described. The expected benefit of this technique is in overcoming a major block in the development of an on-line technique for the evaluation of transient stability contingencies by power system operators.


Patent
19 May 1975
TL;DR: An extremely low frequency (ELF) communication system is disclosed for worldwide communication from land to receiving stations thousands of miles away using the existing DC power transmission lines of the Pacific Intertie power transmission system as the antenna as mentioned in this paper.
Abstract: An extremely low frequency (ELF) Communication System is disclosed for worldwide communication from land to receiving stations thousands of miles away using the existing DC power transmission lines of the Pacific Intertie power transmission system as the antenna. An ELF communication system requires a very long uninterrupted antenna or a series of long parallel antennas. The transmission lines of the Pacific Intertie DC power system lend themselves to be used as the required long antenna for the disclosed ELF system. The DC lines together with the associated ELF transmitter and coupling devices comprise the global ELF communication system disclosed herein.

Journal ArticleDOI
TL;DR: In this paper, the feasibility of a series connection of stations in a multiterminal HVDC transmission system is demonstrated, and the operation of the system is studied on a large power system simulator.
Abstract: The feasibility of a series connection of stations in a multiterminal HVDC transmission system is demonstrated. Techniques were developed to control this system, and the operation of the system was studied on a large power system simulator. The performance of the system was shown to be similar to conventional point to point systems with most control functions being carried out by local controls. An overall system control is shown to be necessary only for optimizing load distributions. Given adequate tap changer ranges on the converter transformers the increase in valve damping and system reactive power requirements are shown to be moderate. The series connected multitermimal system is shown to have a number of advantages over the alternative parallel connected system for certain applications.

Journal ArticleDOI
P.L. Noferi1, L. Paris
TL;DR: In this paper, a method for the reliability evaluation of a power generation and transmission system, when considering, together with the constraints on the active power capability of elements, the voltage constraint in network nodes, is presented.
Abstract: The paper deals with a method for the reliability evaluation of a power generation and transmission system, when considering, together with the constraints on the active power capability of elements, the voltage constraint in network nodes. The approach suggested is an extension of a previous method for the reliability evaluation when considering only the active power capability constraints. The method is based on the approximate evaluation, by means of linear computation methods, of the reactive power flows and of the consequent voltage values in network nodes. This evaluation is performed starting from the approximate evaluation of the active power flow derived with the classic method of d.c. load-flow computation. The system performance, as a consequence of voltage constraints, is quantitatively evaluated by means of two indices: the first being the power disconnected in the nodes as a consequence of unacceptable voltage values or lack of reactive generation, the second being the irregularity of the voltage Service.

Journal ArticleDOI
TL;DR: In this article, a frequency deviation transducer using solid-state circuitry has been developed for continuous record of power system frequencies and power system governor application with a high order of accuracy.
Abstract: A frequency deviation transducer using solid-state circuitry has been developed. The device is based on digital - analogue technique and is suitable for continuous record of power system frequencies and governor application with a high order of accuracy. No initial adjustments are required and no reset problems are faced. Depending on application requirements, the transducer may be used alone for direct measurement or in combination with other control equipment for automatic load frequency control, excitation control, load shedding and in acceleration relay applications etc.

Journal ArticleDOI
TL;DR: In this article, the authors describe the development, validation and use of a non-linear dynamic model developed for the study of automatic generation control and economic dispatch structures within a large multi-company interconnected electric power system.
Abstract: This paper describes the development, validation and use of a non-linear dynamic model developed for the study of automatic generation control and economic dispatch structures within a large multi-company interconnected electric power system. The model constitutes a unique tool for the realistic evaluation of the dynamic performance of newly developed system control and dispatch strategies. The improvements obtainable with these strategies and the determination of sufficient response reserves are demonstrated.

Proceedings ArticleDOI
A. Fouad1
01 Dec 1975
TL;DR: A survey of the criteria of stability used in the power system transient stability problem is made in this article, where the status of progress in the use of these methods is given, and the areas of difficulty are outlined.
Abstract: A survey of the criteria of stability used in the power system transient stability problem is made. The status of progress in the use of these methods is given, and the areas of difficulty are outlined.

Journal ArticleDOI
TL;DR: A review and comparative study of the various optimisation methods applied to electrical power systems and it is shown that the suboptimal control using feedback of a selected number of variables derived by Liapunov method can be equally effective.
Abstract: A review and comparative study of the various optimisation methods applied to electrical power systems is made in this paper. The linear optimal control derived by solving the matrix Riccati equation requires feedback of all the state variables. It is shown that the suboptimal control using feedback of a selected number of variables derived by Liapunov method can be equally effective. Under certain conditions optimal control derived from lineamised system equations can give improved system perfommance following large disturbances. However to achieve maximum improvement it is necessary to retain all the system nonlinearities in the optimisation procedure. A method of optimising a system for a nonlinear mode of operation retaining the advantages of closed loop control is described. Finally, the feasibility of practical implementation is investigated by incorporating the various optimal controls derived in a laboratory micromachine system.

Patent
05 Dec 1975
TL;DR: In this article, a standby power supply system utilized for continuously supplying alternating current power at a regulated value to a load independent of the line power amplitude of continuity is described, where direct current feedback circuitry is provided for improving the AC-DC synchronization, minimizing the drain on the source and holding the direct current relatively constant.
Abstract: A standby power supply system utilized for continuously supplying alternating current power at a regulated value to a load independent of the line power amplitude of continuity. The standby power supply includes an inverter utilizing a direct current source. Direct current feedback circuitry is provided for improving the AC - DC synchronization, minimizing the drain on the source and for holding the direct current relatively constant thereby reducing the requirements of the direct current source.

Journal ArticleDOI
F. Saccomanno1
TL;DR: The sensitivity of the characteristic roots of a linear time-invariant dynamic system, versus parameter perturbations, may be defined in terms of the transfer matrix residuals as discussed by the authors.

ReportDOI
04 Feb 1975
TL;DR: In this paper, the authors provide formulas and data for evaluating coupling of the high-altitude electromagnetic pulse (EMP) to electric power systems and to facilities served with commercial electric power.
Abstract: : The handbook provides formulas and data for evaluating coupling of the high-altitude EMP to electric power systems and to facilities served with commercial electric power. The subjects covered include coupling to power transmission and distribution lines, transient coupling through transformers, lightning-arrester firing characteristics, and coupling through the service entrance. Grounding, EMP protective measures, and testing are also discussed. The emphasis of the handbook is on the EMP effects of concern to the power user, but much of the information contained in the handbook can also be used to evaluate the effects of the EMP on electric power systems.

Journal ArticleDOI
TL;DR: The application of superconductors in the field windings of large steam-turbine generators appears to offer a number of significant economic and operational advantages, most of which are a consequence of the relatively low per-unit synchronous reactance that is characteristic of these machines.
Abstract: The application of superconductors in the field windings of large steam-turbine generators appears to offer a number of significant economic and operational advantages. The principal advantage offered by such machines appears to be a potentially large reduction in size, weight, and cost for a given power rating. In addition, superconducting alternators also appear to have a number of unique and potentially advantageous operational characteristics, most of which are a consequence of the relatively low per-unit synchronous reactance that is characteristic of these machines. This paper reviews the reasons for the low synchronous reactance attributable to the use of superconducting field winding, and compares the expected performance characteristics of a superconducting alternator in the 1000 MVA range with those of a conventional power system generator of comparable rating. Among the specific topics discussed are performance with regard to dynamic stability, transient stability, voltage regulation, and excitation control. The principal operational advantages of a superconducting alternator appear to be 1) the absence of a dynamic stability limit within its MVA capability, 2) significantly greater transient stability when operating at leading power factors, 3) superior voltage regulation, and 4) no degradation of dynamic stability due to automatic voltage regulator action. Consequently, superconducting alternators appear to be ideally matched to modern power system applications that require operation of generators at leading power factors.

Patent
16 Jul 1975
TL;DR: In this article, a flywheel is mounted in an evacuated housing and is driven by a plurality of wheels powered by DC electric motors, which receive current from an input power source.
Abstract: A system is disclosed for storing electrical energy and for converting DC power to AC power. The system includes a very large flywheel which is mounted in an evacuated housing and is driven by a plurality of wheels powered by DC electric motors which receive current from an input power source. An independent plurality of wheels coupled to AC generators selectively engage the rotating flywheel to withdraw energy from the rotating mass of the flywheel in the form of alternating current. Control systems are provided for adjusting the radial position of the drive and output wheels in dependence upon the speed of the flywheel. Additional control systems are provided to change the number of driving motors or output generators in contact with the flywheel depending upon the input power available or output power required.