Showing papers in "IEEE Power & Energy Magazine in 1983"
TL;DR: In this paper, the frequency and rate-of-change of frequency at the bus can also be determined from the positive sequence voltage phase angle, and the theoretical basis of these computations and results of experiments performed in the AEP power system simulation laboratory are also outlined.
Abstract: With the advent of Substation Computer Systems dedicated to protection, control and data logging functions in a Substation, it becomes possible to develop new applications which can utilize the processing power available within the substation. The microcomputer based Symmetrical Component Distance Relay (SCDR) described in the references cited at the end of this paper possesses certain characteristics which facilitate real-time monitoring of positive sequence voltage phasor at the local power system bus. With a regression analysis the frequency and rate-of-change of frequency at the bus can also be determined from the positive sequence voltage phase angle. This paper describes the theoretical basis of these computations and describes results of experiments performed in the AEP power system simulation laboratory. Plans for future field tests on the AEP system are also outlined.
906 citations
TL;DR: In this paper, a simulation and digital computer modeling effort is described in which a wind turbine- generator system is adapted for stability evaluation using a large scale transient stability computer program, which provides the capability of simulating a wide variety of wind variations, in addition to the usual network disturbances.
Abstract: A simulation and digital computer modeling effort is described in which a wind turbine- generator system is adapted for stability evaluation using a large scale transient stability computer program. Component models of the MOD-2 wind generator system are described and their digital model equations are provided. A versatile wind velocity model is described, which provides the capability of simulating a wide variety of wind variations, in addition to the usual network disturbances. Computed results obtained from runs of the enhanced stability program are provided that illustrate the wind turbine-generator system dynamic performance for changes in wind velocity.
605 citations
TL;DR: In this article, a method for determining the impact of wind generation on system reliability is developed, which combines the effects of wind turbine forced outage rates and varying power output due to wind speed variations.
Abstract: A method for determining the impact of wind generation on system reliability is developed. This method combines the effects of wind turbine forced outage rates and varying power output due to wind speed variations. Since individual wind turbines on a windfarm all have an output related to wind speed, each turbine's output cannot be assumed to be independent random variables. Because of this situation, special steps must be taken in der to arrive at the cumulative distribution function for the windfarm. This distribution function may be combined with the system distribution function using simple convolution and so the windfarm can be easily incorporated into a Loss of Load Expectation computer program. The method can then be used to determine the effective load carrying capability of a windfarm and also to supply better estimates of the benefits of wind generation to the overall system.
490 citations
TL;DR: In this paper, a branch-and-bound approach is presented for solving the unit commitment problem based on branch and bound techniques. But it does not require a priority ordering of the units.
Abstract: A new approach is presented for solving the unit commitment problem based on branch-and-bound techniques. The method incorporates time-dependent start-up costs, demand and reserve constraints and minimum up and down time constraints. It does not require a priority ordering of the units. The method can be extended to allow for a probabilistic reserve constraint. Preliminary computational results are reported.
430 citations
TL;DR: A new Lagrangian relaxation method is proposed, which produces optimal solutions for unit commitment and the flexibility of the algorithm is such that numerous developments can be envisaged, such as simultaneous management of pumping units, probabilistic determination of the spinning reserve, etc.
Abstract: Unit commitment is a complex problem which, until now and for real size systems, has been solved using heuristic methods only. This paper proposes a new Lagragian relaxation method, which produces ??-optimal solutions. The flexibility of the algorithm is such that numerous developments can be envisaged, such as simultaneous management of pumping units, probabilistic determination of the spinning reserve, etc.
428 citations
TL;DR: In this paper, it has been confirmed analytically and by simulations that the multiple load flow solutions are likely to appear under the heavy-loaded conditions, and that the individual solutions of the solution pair have different features from each other, from the standpoint of stability, although they are close to each other.
Abstract: There have been observed several voltage instability phenomena in electric power systems where receiving end voltages oscillate remarkably or get much lower than the nominal values. Those phenomena tend to occur in heavy loaded conditions and seem to be related to the multiple load flow solution problem for the following reasons. It has been confirmed analytically and by simulations that the multiple load flow solutions are likely to appear under the heavy-loaded conditions, and that the individual solutions of the solution pair have different features from each other, from the standpoint of stability, although they are close to each other.
377 citations
TL;DR: In this paper, the perturb and observe method of power control migrates considerably from peak power whenever the insolation varies randomly as a result of cloud cover, and an alternate power tracking method is also examined.
Abstract: An important consideration in the operation of grid connected photovoltaic power systems is a means of adjusting the photovoltaic array voltage so that maximum output power is achieved for the given atmospheric conditions. The dynamic behiavior of a specific photovoltaic power system which utilizes the well known perturb and observe method of power tracking is examined. Using measured insolation data, it is demonstrated that the perturb and observe method of control migrates considerably from peak power whenever the insolation varies randomly as a result of cloud cover. An alternate method of power tracking is also examined. It is shown that the photovoltaic power system, utilizing the proposed method of power tracking, is able to track accurately peak power conditions during periods of randomly varying insolation.
350 citations
TL;DR: In this paper, the characteristics of induction motors having more than three phases are presented. And the effect of the stator coil pitch on these inductances is explained, showing that some of these harmonics cannot induce rotor currents in motors having many phases, thereby reducing the torque pulsations and rotor I2R loss below the values for three-phase motors.
Abstract: The characteristics of induction motors having more than three phases are presented. The sequence sets of the symmetrical component method are used to determine the inductances with time harmonics in the source waveform such as for inverter sources. The effect of stator coil pitch on these inductances is explained. It is shown that some of these harmonics cannot induce rotor currents in motors having many phases, thereby reducing the torque pulsations and rotor I2R loss below the values for three-phase motors. Other advantages are lower current per phase and the ability of the motor to start and run with one phase open. Six and nine-phase motors are found to be especially attractive.
292 citations
TL;DR: A knowledge based system for automatic control of a power system in the restorative state is developed, and efforts are made to represent heuristics by a set of knowledge the goal of which is to restore the power supply without overloading any transmission line.
Abstract: A knowledge based system is developed for automatic control of a power system in the restorative state. System operator's heuristics seem to play a central role during the course of system restoration. So efforts are made to represent those heuristics by a set of knowledge the goal of which is to restore the power supply without overloading any transmission line. While the overload check is a numerical computation, reasoning in the knowledge based system is a symbolic computation. A method to link these two different types of computation is proposed. The knowledge based system is expected to serve managing a large scale power system in the restorative state.
275 citations
TL;DR: The increasing rate of depletion of conventional energy resources and the ability of induction generators to convert mechanical power over a wide range of rotor speeds have given rise to an interest in the possible contribution of wind energy to provide fuel displacement as discussed by the authors.
Abstract: The increasing rate of depletion of conventional energy resources and the ability of induction generators to convert mechanical power over a wide range of rotor speeds have given rise to an interest in the possible contribution of wind energy to provide fuel displacement.
234 citations
TL;DR: In this paper, a technique for rapid measurement of the distance to a fault using fault-initiated travelling waves is presented. But the measurement uses the time it takes a given surge to travel from the relaying point to the fault and back.
Abstract: A technique is presented for rapid measurement of the distance to a fault using fault initiated travelling waves. The measurement uses the time it takes a given surge to travel from the relaying point to the fault and back. A correlation technique is used to recognise the surge returning from the fault and distinguish it from other surges present on the system. For a three phase transmission line, the modal components describing the incident wave are delayed and cross-correlated against the respective components reflected by the fault. Maximum output occurs when the delay corresponds to twice the fault distance.
TL;DR: In this article, a wind energy conversion scheme using an induction machine driven by a variable speed wind turbine is described, where a single value capacitor and a thyristor controlled inductor are employed for energy conversion.
Abstract: A wind energy conversion scheme using an induction machine driven by a variable speed wind turbine is described. Excitation control has been obtained by employing a single value capacitor and thyristor controlled inductor. Wind speed cube law is proposed to be followed in loading the induction machine for maximising energy conversion. Performance characteristics of the generation scheme have been evaluated over a wide speed range. Harmonic analysis of the proposed scheme shows that harmonic currents and their associated power loss is negligible.
TL;DR: In this paper, the authors describe a very simple alternative method, with considerably improved bad data detection properties, based on evaluating the coherency between the measurement with the largest normalized residual and the remainder of the measurement system.
Abstract: The weighted least squares performance index test (J(x?) test) conventionally used in power system static state estimation has poor reliability for detecting the presence of measurement errors in the range 3 to 20 standard deviations. This paper describes a very simple alternative method, with considerably improved bad data detection properties, based on evaluating the coherency between the measurement with the largest normalized residual and the remainder of the measurement system. In fact, the detection and identification phases of bad data processing become combined. Inanexistent state estimator using normalized residuals, the cost of implementation of the new method is negligible. The new method has been tested extensively on several power systems, and compared with the J(x?) test.
TL;DR: The paper gives a unified derivation and analysis of compensation methods for the efficient solution of network problems involving matrix modifications, including the removal, addition and splitting of tiodes.
Abstract: The paper gives a unified derivation and analysis of compensation methods for the efficient solution of network problems involving matrix modifications. These methods have a very wide range of practical application, and many of the better ones appear tobe little known in the power field. General and specific cases are dealt with, including the removal, addition and splitting of tiodes. The choice between themany compensation versions is seen to be highly problem dependent, and although space precludes the treatment of specific applications, guidelines are offered for the comparison of versions with each other and with matrix refactorization.
TL;DR: In this paper, the effects of saturation of the main flux path can be incorporated in the generalized equations of alternating current machines in which the currents are deliberately chosen as the state variables.
Abstract: This paper shows how the effects of saturation of the main flux path can be incorporated in the generalized equations of alternating current machines in which the currents are deliberately chosen as the state variables. In the conventional equations linear magnetic conditions are assumed and the forms taken by these equations in various reference frames are well known. When saturation of the main flux path is taken into account, some parameters have to be modified and additional terms introduced; stator (and rotor) self inductances in orthogonal axes are no longer equal. These are the consequence of intersaturation - sometimes called cross-saturation; a phenomenon which has been mentioned in the literature but has not been subjected to general analysis. New forms of generalized equations are derived and their application to the analysis of induction motor starting transients described.
TL;DR: In this article, the authors present a technique which computes and uses flux-current relationship of the transformer to obtain the restraint function, which can be implemented on a microcomputer of modest capability.
Abstract: The paper begins with a review of techniques for computer based protection of multi-winding three-phase power transformers. After reviewing the principles of harmonic-restraint and voltage-restraint current differential protection, the paper develops a technique which computes and uses flux-current relationship of the transformer to obtain. the restraint function. It is shown that this protection technique requires fewer computations as compared to the harmonic current computation, and hence can be implemented on a microcomputer of modest. capability. The principle has been tested. in the'laboratory on a model power transformer. The relay based on this flux-restraint principle performs well on all the system phenomena simulated in the laboratory. It is expected that a relay based on this principle will be tested in the field on a power transformer.
TL;DR: In this paper, the authors studied the charge accumulation and its mechanisms based on the experiments of post and conical epoxy spacers subjected to high dc voltages in compressed SF 6 gas.
Abstract: The charge accumulation and its mechanisms are studied based on the experiments of post and conical epoxy spacers subjected to high dc voltages in compressed SF 6 gas. The charge measurement is performed using electrostatic probe and dust figure techniques. The charge accumulation is strongly influenced by the surface condition of epoxy spacer. Heterocharge deposits locally on the surface of untreated spacer. The flashover voltage of highly charged spacer decreases considerably at the time of polarity reversal. In the case of epoxy surface treated with horning, only a small quantity of charge is deposited uniformly on the surface of spacer. The mechanism of inhomogeneous surface conduction is suggested by the local surface charging on the untreated spacer. Field emission is also found as the other charging mechanism on the conical spacer set in rough finish electrode system.
TL;DR: In this article, a combined observability/measurement placement algorithm that both tests the measured network for observability and evaluates pseudo measurement sites as to the desirability of their inclusion into the measurement set is presented.
Abstract: Measurement system failures and modeling constraints may make it impossible for the power system state estimator to estimate bus voltage magnitudes and angles at every bus in the power system from the available real-time measurements. Such a measurement deficiency may be remedied by adding pseudo measurements of estimated bus loads. This paper presents a combined observability/measurement placement algorithm that both tests the measured network for observability and evaluates pseudo measurement sites as to the desirability of their inclusion into the measurement set.
TL;DR: In this article, the impact of electric vehicle deployment on load management strategies primarily occurs in two areas: (i) reduction in effectiveness of load factor improvement of either EV deployment or load management strategy due to the action of the other and (ii) inadvertent addition to peak demand by electric vehicle load.
Abstract: The future penetration of electric vehicles into the transportation sector is unknown. However, if off peak recharging of electric vehicles is employed, considerable improvement in daily load factor is possible. Similarly, load management methods to shift peak load to off-peak periods will also improve load factor. The impact of electric vehicle deployment on load management strategies primarily occurs in two areas: (i) reduction in effectiveness of load factor improvement of either electric vehicle deployment or load management strategies due to the action of the other and (ii) inadvertent addition to peak demand by electric vehicle load. These and other factors are considered in this paper and several practical considerations of recharging of electric vehicles are summarized.
TL;DR: In this paper, a finite element analysis is employed to model the constituent parts of a grounding system, which enables the computation of the transient response of substation grounding systems to fast or slow waves striking the substation.
Abstract: This paper addresses the problem of computing the ground potential rise of grounding systems during transients. Finite element analysis is employed to model the constituent parts of a grounding system. Short lengths of earth embedded electrodes are characterized as transmission lines with distributed inductance, capacitance and leakage resistance to earth. Leakage resistance to earth is accurately computed with the method of moments. The other parameters of the finite element, namely inductance and capacitance, are computed from the resistance utilizing Maxwell's equations. This modeling enables the computation of the transient response of substation grounding systems to fast or slow waves striking the substation. The result is obtained in terms of a convolution of the step response of the system and the striking wave. In this way the impedance of substation systems to 60 cycles is accurately computed. Results demonstrate the dependence of the 60 cycle impedance on system parameters. The methodology allows to interface this model of a substation ground mat with the Electromagnetic Transient Analysis Program thus, allowing explicit representation of earth effects in electromagmatic transients computations.
TL;DR: In this article, a small induction motor connected for six phases and for nine phases was tested with a balanced source and with one phase open, and the motor was subjected to source voltages having harmonics and the measured currents show good agreement with theoretical values.
Abstract: Experimental tests have been carried out on a small induction motor connected for six phases and for nine phases. These include torque measurements over the entire speed range and load tests with balanced source and with one phase open. Some of the machine impedances, including sequence impedances, were measured and these generally agree with predicted values. The motor was subjected to source voltages having harmonics and the measured currents show good agreement with theoretical values based on the analysis in a companion paper.
TL;DR: In this article, an approach to the modeling and performance for the preliminary design phase of a large (6.2 MW) horizontal axis wind turbine generator (WTG) is discussed.
Abstract: This paper discusses an approach to the modeling and performance for the preliminary design phase of a large (6.2 MW) horizontal axis wind turbine generator (WTG). Two control philosophies are presented, both of which are based on linearized models of the WT mechanical and electrical systems. The control designs are compared by showing the performance through detailed non-linear time simulation. The disturbances considered are wind gusts, and electrical faults near the WT terminals.
TL;DR: In this article, a detailed circuit representation of a six phase synchronous machine with mutual leakage couplings between the two sets of three phase stator windings is described, and the main modes of power transfer of a 6 phase machine with sinusoidal inputs are examined.
Abstract: This paper describes a detailed circuit representation of a six phase synchronous machine wherein mutual leakage couplings between the two sets of three phase stator windings are included. The main modes of power transfer of a six phase machine with sinusoidal inputs are examined. A harmonic phasor method of steady-state analysis to obtain the current, voltage and torque waveforms of a six phase machine with mixed AC-DC stator connections is described. It is shown that the output waveforms for various operating conditions from a digital computer program using the harmonic phasor method agree remarkably well with those obtained from an established detailed analog simulation.
TL;DR: In this article, the optimal preventive maintenance scheduling problem (OMSP) is addressed and the importance of OMSP is due to the fact that system reliability and operating cost of an electric utility are affected by the maintenance outage of generating facilities.
Abstract: This paper addresses the optimal preventive maintenance scheduling problem (OMSP). The importance of OMSP is due to the fact that system reliability and operating cost of an electric utility are affected by the maintenance outage of generating facilities.
TL;DR: In this paper, a unified survey of methods appropriate for solving the state estimation problem in large-scale electric power systems is presented, and the most suitable among them are described, examined and compared.
Abstract: This paper intends to give a unified survey of methods appropriate for solving the state estimation problem in large-scale electric power systems After a first overview of the various approaches proposed up to now, the most suitable among them are described, examined and compared The comparisons are carried out on the basis of selected criteria evolving estimation properties of the resulting algorithms, along with their organization possibilities and their capabilities of handling some important satellite functions
TL;DR: In this paper, the state of knowledge on the behavior of ground wire electrodes under impulse currents due to lightning strokes is outlined. And the influence of ground characteristics, size of buried conductors, and current wave-shape and intensity are discussed.
Abstract: The state of knowledge on the behavior of ground wire electrodes under impulse currents due to lightning strokes is outlined. The influence of ground characteristics, size of buried conductors, and current wave-shape and intensity are discussed.