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Showing papers in "IEEE Transactions on Power Delivery in 1992"


Journal Article•DOI•
TL;DR: In this article, a power-flow-minimum heuristic algorithm for determining the minimum loss configuration of radial distribution networks is presented. But the algorithm is based on the concept of optimum flow pattern which is determined by solving the KVL and KCL (Kirchoff's voltage and current laws) equations of the network.
Abstract: The authors report a power-flow-minimum heuristic algorithm for determining the minimum loss configuration of radial distribution networks. The algorithm is based on the concept of optimum flow pattern which is determined by solving the KVL and KCL (Kirchoff's voltage and current laws) equations of the network. The optimum flow pattern of a single loop formed by closing a normally open switch is found, and the flow pattern is established in the radial network by opening a closed switch. This process is repeated until the minimum loss configuration is obtained. A simple, fast and approximate power flow method has also been developed to assist the reconfiguration algorithm. The proposed reconfiguration algorithm has been found to give better network configuration than those obtained by some other methods. >

627 citations


Journal Article•DOI•
TL;DR: In this article, a method for the computation of fault location in two and three-terminal high voltage lines is presented based on digital computation of the three-phase current and voltage 60/50 Hz phasors at the line terminals.
Abstract: A method for the computation of fault location in two- and three-terminal high voltage lines is presented. It is based on digital computation of the three-phase current and voltage 60/50 Hz phasors at the line terminals. The method is independent of fault type and insensitive to source impedance variation or fault resistance. Furthermore, it considers the synchronization errors in sampling the current and voltage waveforms at the different line terminals. The method can be used online following the operation of digital relays or offline using data transferred to a central processor from digital transient recording apparatus. The authors start with a two-terminal line to explain the principles and then present the technique for a three-terminal line. The technique was first tested using data obtained from a steady-state fault analysis program to evaluate the convergence, observability, and uniqueness of the solution. The technique was then tested using EMPT-generated transient data. The test results show the high accuracy of the technique. >

366 citations


Journal Article•DOI•
TL;DR: Undervoltage load shedding is an economical solution (or partial solution) to the voltage stability challenges facing electric utilities as mentioned in this paper, but it is not an efficient solution for large-scale systems.
Abstract: Undervoltage load shedding is an economical solution (or partial solution) to the voltage stability challenges facing electric utilities. Simulations for an equivalent system and for large-scale representation of the Puget Sound (Seattle) area of the Pacific northwest led to several concepts for an undervoltage load-shedding program. Application factors such as undervoltage relay settings and time delay are discussed. Pacific northwest utilities are implementing undervoltage load shedding for the 1991-2 winter operation period. >

297 citations


Journal Article•DOI•
P.G. McLaren1, R. Kuffel, R.P. Wierckx, J. Giesbrecht, L. Arendt •
TL;DR: The structure and performance of a real-time digital simulator (RTDS) for testing relays are described and examples are given of tests on a commercial distance relay.
Abstract: The structure and performance of a real-time digital simulator (RTDS) for testing relays are described. The RTDS uses parallel processing architecture based on a state-of-the-art digital signal processor (DSP) to run power system simulations in real time with a time step of 50-100 mu s. Physical devices such as relays, energy monitors for MOVs, or power system stabilizers can be fed with the appropriate signals from the RTDS and the output from the physical device can be fed back into the simulation. Examples are given of tests on a commercial distance relay. >

210 citations


Journal Article•DOI•
TL;DR: In this paper, the performance of reactive compensation systems based on gate-turnoff thyristors offers potential benefits compared to conventional compensators, such as increased steady-state loadability of heavily stressed systems, improving the security of systems with heavy motor loads, and improving the transient stability of systems experiencing large power swings.
Abstract: The performance of reactive compensation systems based on gate-turnoff thyristors offers potential benefits compared to conventional compensators. The authors describe these benefits in applications involving increased steady-state loadability of heavily stressed systems; in improving the security of systems with heavy motor loads; in improving the transient stability of systems experiencing large power swings; and in adding damping to power swings. These performance benefits lead to the ability to solve specific application problems with less rating and with better stability than with conventional devices. >

189 citations


Journal Article•DOI•
R.S. Gorur1, George G. Karady1, A. Jagota1, M. Shah1, A.M. Yates1 •
TL;DR: In this article, a hypothesis for aging produced by dry band arcing in silicone rubber material used for outdoor insulation is presented and experimentally proven, and the analytical techniques used to study the permanent changes are Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, XRD, and surface roughness measurement.
Abstract: A hypothesis for aging produced by dry band arcing in silicone rubber material used for outdoor insulation is presented and experimentally proven. Aging is indicated by permanent changes. The analytical techniques used to study the permanent changes are Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and surface roughness measurement. The authors highlight the fact that there are permanent changes occurring in the material that lead to progressive degradation in the long run, even though there can be a complete recovery of surface hydrophobicity in a short time. >

177 citations


Journal Article•DOI•
TL;DR: In this article, a microprocessor-based system for online identification of magnetizing inrush and internal fault conditions in three-phase transformers is presented, using a digital algorithm which is based on a transformer model and can be used irrespective of whether or not it is possible to measure winding currents.
Abstract: The authors present a microprocessor-based system for online identification of magnetizing inrush and internal fault conditions in three-phase transformers. The system uses a digital algorithm which is based on a transformer model and can be used irrespective of whether or not it is possible to measure winding currents. The only parameters needed by the algorithm are positive and negative sequence impedances of the transformer. These parameters are usually a part of the name-plate data. The proposed algorithm has been implemented on a Texas Instrument TMS320C25 digital signal processor. The hardware and software of the system are described. The ability of the system to identify magnetizing inrush and internal faults was tested by using a 15 kVA three-phase transformer. Some test results are reported. >

164 citations


Journal Article•DOI•
TL;DR: In this paper, the possibility of nonoperation of second-harmonic restraint differential protection in the case of internal faults of power transformers was studied and modified schemes for improved operation for internal faults were presented.
Abstract: The possibility of nonoperation of second-harmonic restraint differential protection in the case of internal faults of power transformers was studied. The smaller the setting for harmonic restraint, the longer will likely be the time delay in the operation of the relay. To study this aspect, various internal faults and inrush conditions were tested on a physical model of a three-phase transformer in the laboratory. The data were analyzed by different protection algorithms. Based on the results of these studies, modified schemes for improved operation for internal faults are presented. >

162 citations


Journal Article•DOI•
L.W. Pierce1•
TL;DR: In this article, a comprehensive test program was performed using a winding assembly with embedded thermocouples, and steady-state and transient tests were performed for natural and non-directed forced oil calculation.
Abstract: Manufacturers may be required to design transformers to overload specifications. Oil viscosity changes and loss variation with temperature are not accounted for in the industry loading guide. A comprehensive test program was performed using a winding assembly with embedded thermocouples. Steady-state and transient tests were performed for natural and nondirected forced oil calculation. The temperature distribution in the winding was not linear with height as usually assumed. A large number of temperature sensors is required to determine the hot spot location. The location of the hot spot was found to be different and less predictable for natural oil calculation than for nondirected forced oil circulation, especially during overload conditions. Improved loaded guide equations were developed to account for oil viscosity, resistance change, cooling duct oil rise and location of the hot spot. >

148 citations


Journal Article•DOI•
TL;DR: In this paper, the impact of voltage harmonics on a power system can be minimized by using active filters to inject distortion-canceling currents, but a network objective function must be specified before the optimum filter injection currents can be determined.
Abstract: The impact of voltage harmonics on a power system can be minimized by using active filters to inject distortion-canceling currents. However, a network objective function must be specified before the optimum filter injection currents can be determined. The authors illustrate the application of a distortion-minimizing procedure with each of the following four network correction strategies, total harmonic voltage distortion, telephone influence factor, motor load-loss function, and single-bus sine wave correction. It is also pointed out that, as with any active device, care must be taken when sitting and controlling an APLC (active power line conditioner) to ensure maximum improvement in network distortion. If a network approach is not used, a poorly located APLC could have an overall negative impact. >

137 citations


Journal Article•DOI•
G. Manchur1, C.C. Erven1•
TL;DR: In this paper, a single-phase arc furnace model is proposed for use on digital simulation programs such as the EMTP or other appropriate commercial software simulation programs, based on actual furnace input data are included to show the validity of the model.
Abstract: Owing to the characteristics of electric-arc phenomena electric arc furnace loads can result in serious electrical disturbances on a power system. Low level frequency modulation of the supply voltage of less than 0.5% can cause annoying flicker in lamps and invoke public complaints when the frequency lies in the range of 6-10 Hz. There is a need therefore to develop better techniques to predict flicker effects from single and multiple arc furnace loads and the effects of compensation schemes. The authors discuss the nature of arc furnace loads, and describe the instrumentation, field measurements, and signal analysis techniques which were undertaken to develop an arc furnace model. A single-phase furnace model is proposed suitable for use on digital simulation programs such as the EMTP or other appropriate commercial software simulation programs. Representative results based on actual furnace input data are included to show the validity of the model. >

Journal Article•DOI•
TL;DR: The need for a distribution current limiting device (DCLD) by the utility industry is addressed in this paper, where an evaluation was made of what specifications would be acceptable and what DCLD technique would fill the utilities' needs.
Abstract: The need for a distribution current limiting device (DCLD) by the utility industry is addressed. An evaluation was made of what specifications would be acceptable and what DCLD technique would fill the utilities' needs. Using this survey and a distribution system analysis, a DCLD that could limit a 20 kA fault to 10 kA in a 15 kV circuit was shown to be the primary candidate for further development. The study showed that gate turn-off thyristors (GTOs) are the best technology available that could be developed into a practical DCLD. A recommendation was made to develop a DCLD using GTOs. >

Journal Article•DOI•
TL;DR: In this paper, the authors proposed a new treatment of insulation thermal life which recognizes the effects of more significant parameters and would enable users to make more realistic judgements about the impact of loading on functional life.
Abstract: The author offers recommendations for a new treatment of insulation thermal life which recognizes the effects of more significant parameters and would enable users to make more realistic judgements about the impact of loading on functional life. Background tutorial material from the published literature is presented as an aid to understanding the basis for the change. In the proposed method of treatment of insulation life in loading guides, a single aging rate constant would be used for all distribution and power transformers to calculate life consumption during any given loading condition relative to continuous operation at a reference temperature. The definition of absolute 'insulation life' would be influenced by the moisture and oxygen content of the insulation system and the life end-point criterion selected. >

Journal Article•DOI•
TL;DR: In this article, improved models for current transformers (CT), potential transformers, and capacitive voltage transformers were presented for a relay software library based on the nonlinear power curve formulation of J.R. Lucas (1988).
Abstract: Improved models for current transformers (CT), potential transformers, and capacitive voltage transformers (CVT) for a relay software library are presented. The magnetizing characteristic in each of these transformers is based on the nonlinear power curve formulation of J.R. Lucas (1988). The flux-current loops of the transformer core are self-generated rather than predetermined or based on look-up tables. The results presented show that the models developed for the transformers behave as expected, and agree with reported field investigations. Models for the CT and CVT give acceptable results, including those under remanent conditions and ferroresonant conditions. These models are thus necessary components for relay studies carried out with electromagnetic transient programs whether offline or in real time. >

Journal Article•DOI•
Peter Vaessen1, E. Hanique2•
TL;DR: In this article, a novel frequency response analysis (FRA) method is described, which is being used on power transformers at the KEMA laboratories, and is applied to digitally recorded time signals, is easy to use, and provides high-resolution frequency spectra for both magnitude and phase.
Abstract: A novel frequency response analysis (FRA) method is described which is being used on power transformers at the KEMA laboratories. This frequency domain method is applied to digitally recorded time signals, is easy to use, and provides high-resolution frequency spectra for both magnitude and phase. This tailor-made FRA method uses a low voltage special impulse source to avoid aliasing. Results from several measured transformers are presented. >

Journal Article•DOI•
TL;DR: In this paper, a feed-forward three-layer perceptron was trained by high-impedance fault, fault-like load, and normal load current patterns, using the backpropagation training algorithm.
Abstract: The authors present an arcing fault detector, motivated by the advances in neurocomputing in pattern recognition, that uses a simple preprocessing algorithm. A feedforward three-layer perceptron was trained by high-impedance fault, fault-like load, and normal load current patterns, using the backpropagation training algorithm. The neural network parameters were embodied in a high-impedance arcing fault detection algorithm, which used a simple preprocessing technique to prepare the information input to the network. The algorithm was tested by traces of normal load current disturbed by fault currents on dry and wet soil, an arc welder, computers, and fluorescent lights. The algorithm showed good performance in identifying faults disrupted by arc noise as well as good discrimination between faults and fault-like loads. >

Journal Article•DOI•
TL;DR: Very efficient procedures for computing elementary parameters (turn leakage inductances and capacitances) in a transformer are presented in this paper, where turns are used as a calculation base to permit modeling at very high frequencies.
Abstract: Very efficient procedures for computing elementary parameters (turn leakage inductances and capacitances) in a transformer are presented. The turns are used as a calculation base to permit modeling at very high frequencies. Turn-to-turn (or loop) leakage inductances are obtained by an image method. The charge simulation method is used for finding the capacitances between turns and from turns to ground. The new methods are very efficient compared with the use of the technique of finite elements and are also remarkably accurate. Thus, the short circuit (or test) leakage inductance can be obtained from turn-to-turn information. Examples of calculated parameters are given for illustration. For validation, the results are compared with the parameters obtained using finite elements and tests. The elementary parameters can be used to create reduced-order computational models for the calculation of transient phenomena. >

Journal Article•DOI•
TL;DR: In this article, it is shown that the frequency distribution of the front duration, the tail duration, and the front steepness can be approximated by a logarithmic normal distribution.
Abstract: Long-term observation of winter lightning has been conducted on the Japan Sea Coast since 1978. From various kinds of observations, the results of lightning current measurement by an automatic lightning current recording system are reported. It is shown that winter lightning current has wide variations in its waveform, but the frequency distribution of the front duration, the tail duration, and the front steepness can be approximated by a logarithmic normal distribution. Positive polarity lightning current tends to have much longer front and tail duration than negative lightning current. The ratio of the positive to the negative polarity is one to two in winter lightning, which is much higher than that of summer lightning. The cumulative frequency distribution of the winter lightning current peak agrees with that of the summer lightning current. The fractional distribution was proposed for winter lightning protection design. >

Journal Article•DOI•
TL;DR: In this paper, the authors describe the development by EPRI of digital coupling capacitor voltage transformer (CCVT) models that are intended for digital simulation of fault transients Experimental techniques for laboratory measurements of the CCVT parameters are outlined.
Abstract: The authors describe the development by EPRI of digital coupling capacitor voltage transformer (CCVT) models that are intended for digital simulation of fault transients Experimental techniques for laboratory measurements of the CCVT parameters are outlined A sensitivity study was performed to identify the influence of various CCVT parameters on the transient behavior relevant for the relaying studies Digital models of three different CCVTs are given and their transient behavior is compared to the behavior of the actual transformers >

Journal Article•DOI•
TL;DR: The functional dependency approach is seen to be more flexible and more powerful than the graph theoretic schemes, and holds out much promise for the development of efficient computer-aided design tools for the protection engineer.
Abstract: The concept of functional dependency is applied to the problem of relay coordination in protection systems. An algorithm is developed for the identification of a minimal break point set (BPS) of relays of a protection topology. This algorithm is an improvement over existing algorithms in that it identifies a minimal BPS within a time period that is a polynomial function of the number of relays, while the earlier algorithms had exponential time behavior. In the case of large protection schemes, the saving in computation costs is considerable. An algorithm is developed for the selection of a relative sequence matrix; this algorithm also has polynomial time complexity. The functional dependency approach is seen to be more flexible and more powerful than the graph theoretic schemes, and holds out much promise for the development of efficient computer-aided design tools for the protection engineer. >

Journal Article•DOI•
TL;DR: A novel method for predicting power system voltage harmonics with an artificial neural network based on the backpropagation learning technique for feedforward neural networks is presented.
Abstract: A novel method for predicting power system voltage harmonics with an artificial neural network is presented. The method is based on the backpropagation learning technique for feedforward neural networks. The promise of the proposed method in harmonics prediction is shown. In order to demonstrate its effectiveness, the proposed method is applied to voltage harmonics observed through a personal computer based measurement system and the performance is compared with that of conventional methods. >

Journal Article•DOI•
TL;DR: In this paper, a complete model for transformers is derived on the basis of very efficiently calculated elementary (turn-to-turn) parameters, and a high-order turn-toturn model is constructed for the windings.
Abstract: A complete model for transformers is derived on the basis of very efficiently calculated elementary (turn-to-turn) parameters. A high-order turn-to-turn model is constructed for the windings. This model is reduced to a lower order by operating on the resulting matrices. An electric equivalent circuit for the core is obtained from the principle of duality. By the use of test turns the winding model is interfaced with the iron-core. For validation, the frequency response of the model has been compared with test results. The model for the calculation of transients has the form of a Norton equivalent circuit and it can easily be incorporated in a power system transients program such as the EMTP. Examples of calculated transients are given for illustration and further validation. >

Journal Article•DOI•
TL;DR: In this paper, the authors describe the quasi-static and radiation fields of simple three-dimensional sources and proceed to a two-dimensional source, and show that the quasistatic approximations result in an error of 0.000002% for fields at 100 m or less from the power line.
Abstract: The authors describe the quasi-static and radiation fields of simple three-dimensional sources and proceed to a two-dimensional source. It is shown that the quasi-static approximations result in an error of 0.000002% for fields at 100 m or less from the power line. This is followed by a discussion of how the quasi-static fields are coupled together by Maxwell's equations. It is shown that the electric field of a power line can formally be determined from the magnetic fields, but this cannot be done practically. The electric and magnetic fields are assumed to be independent and are related respectively to voltage and current. The conditions under which electric and magnetic fields are related by the free space impedance are discussed. In general, they are not for power line fields. Poynting's theorem is applied to the power line fields to describe the bulk power transferred along the power line as a result of the quasi-static fields and to calculate the insignificant amount of power radiated laterally away from the power line. >

Journal Article•DOI•
TL;DR: In this article, four reactive power meters, operating on different principles, were tested under nonsinusoidal conditions and compared with four nonsinoidal reactive powers and the first harmonic reactive power, to verify whether these readings can be interpreted as approximate measures of the different definitions.
Abstract: Four reactive power meters, operating on different principles, were tested under nonsinusoidal conditions. Different definitions of the reactive power are discussed. Because the definition and meaning of the nonsinusoidal reactive power are still being actively debated, the readings of the tested meters were compared with four nonsinusoidal reactive powers and the first harmonic reactive power, to verify whether these readings can be interpreted as approximate measures of the different definitions. A digital instrument, programmed to measure each of these powers, was used as a reference. >

Journal Article•DOI•
TL;DR: In this article, a microprocessor-based high-speed relay that correctly detects transformer winding faults is presented, instead of relying on the presence of harmonics to identify magnetizing inrush, it uses a nonlinear model of the transformer to determine the state of its health.
Abstract: The authors present the design, implementation and testing of a microprocessor-based high-speed relay that correctly detects transformer winding faults. Instead of relying on the presence of harmonics to identify magnetizing inrush, it uses a nonlinear model of the transformer to determine the state of its health. One version of the relay is suitable for protecting single-phase transformers, whereas another version is for protecting three-phase transformers. A three-phase delta-wye 15 kVA transformer was used to test the relay for a variety of operating conditions. The results show that the relay performs well. >

Journal Article•DOI•
TL;DR: In this paper, a three phase rectification scheme that draws line currents with reduced distortion and provides a regulated DC output voltage is analyzed, which employs two boost DC-DC converters to modulate the DC link currents.
Abstract: A three phase rectification scheme that draws line currents with reduced distortion and provides a regulated DC output voltage is analyzed. The scheme employs two boost DC-DC converters to modulate the DC link currents. The modulation current is injected into the AC side through an impedance network consisting of series tuned L-C branches. The theoretical analysis and the basic simulation results, which can be used to carry out the design of a system based on this approach, are presented. >

Journal Article•DOI•
TL;DR: In this paper, a saturation model for a single phase shell-form transformer based on 3D finite-element analysis is used to calculate the excitation currents and the variation of excitation current harmonics over an extended range of geomagnetically induced currents bias is determined.
Abstract: Harmonic characteristics of transformer excitation currents under DC bias caused by geomagnetically induced currents (GICs) are presented. A saturation model for a single phase shell-form transformer based on 3-D finite-element analysis is used to calculate the excitation currents. As a consequence, the variation of excitation current harmonics over an extended range of GIC bias is determined. The results of this study are useful in understanding transformers as harmonic sources and their impact on power systems during a solar magnetic disturbance. >

Journal Article•DOI•
M. Runde, T. Aurud, L.E. Lundgaard, G.E. Ottesen1, K. Faugstad •
TL;DR: In this paper, a noninvasive technique for assessing the condition of circuit breakers by considering the acoustic signals generated during nonenergized switching is described, which can be detected as changes in this acoustic signature.
Abstract: A noninvasive technique for assessing the condition of circuit breakers by considering the acoustic signals generated during nonenergized switching is described. Mechanical malfunction, wear, and other types of abnormal behavior can be detected as changes in this acoustic signature. Digital signal processing techniques known from speech recognition were successfully applied to extract, compare, and present the information from the breaker signatures. A fault in the release mechanism which developed over time and eventually rendered one pole of a circuit-breaker inoperative was detected in an early stage, demonstrating the efficiency of this diagnostic technique. >

Journal Article•DOI•
TL;DR: In this article, a thorough analysis of the second harmonic resonance problem using an eigenvalue and frequency domain approach is presented, which explains the mechanism of the excitation of second harmonic instability by the presence of HVDC converters.
Abstract: The Chateauguay HVDC back-to-back scheme with interconnections to the 765 kV transmission to the USA and to Beauharnois generators can exhibit, under certain operating conditions, second harmonic resonance problems. The author presents a thorough analysis of the problem using an eigenvalue and frequency domain approach. The analysis explains the mechanism of the excitation of the second harmonic instability by the presence of HVDC converters. The influence of changing the control parameters of the static VAr compensator at the Chateauguay terminal is also studied. Finally, an assessment is made of the effectiveness of present countermeasure schemes, namely the auxiliary DC stabilizing controls and the installation of second harmonic filters. >

Journal Article•DOI•
TL;DR: In this article, an efficient computer-based method for evaluation of an optimal two-layer soil model from Wenner four probe test data is presented, which is based on recently developed finite expressions for computation of potential in two layer soil.
Abstract: An efficient computer-based method for evaluation of an optimal two-layer soil model from Wenner four probe test data is presented. The method is based on recently developed finite expressions for computation of potential in two-layer soil. The coefficients of the formulae have been readjusted to suit the present application. A computer program SPEF (Soil Parameters Estimation using Finite Expressions) based on the proposed method is described. The accuracy and efficiency of the method are established by determining two-layer soil models for several sets of apparent resistivity data. SPEF is shown to be much more efficient and convenient than programs based on infinite series expressions. >