Showing papers in "IEEE Transactions on Power Delivery in 1990"
TL;DR: Active power line conditioning (APLC) as mentioned in this paper is a line conditioning technique that can potentially correct network distortion caused by power electronic loads by injecting equal-but-opposite distortion at carefully selected points in a network.
Abstract: Active power-line conditioning (APLC) is a concept that can potentially correct network distortion caused by power electronic loads by injecting equal-but-opposite distortion at carefully selected points in a network. Results are presented of an extensive literary survey on the subject of APLCs. Thirty-seven key publications are identified and reviewed. Existing and proposed line-conditioning methodologies are compared, and a list of the advantages and limitations of each is presented. >
573 citations
TL;DR: In this article, the development and application of a computer model for analyzing the transient performance of grounding systems based on electromagnetic field theory is described, where the use of a combination of numerical integration techniques, method of moments, adaptive interpolation, and fast Fourier transform constitutes the basis for the computation of various physical quantities such as the electric fields in the ground, longitudinal and leakage currents in ground conductors, and ground impedances.
Abstract: The development and application of a computer model for analyzing the transient performance of grounding systems based on electromagnetic field theory is described. The use of a combination of numerical integration techniques, method of moments, adaptive interpolation, and fast Fourier transform constitutes the basis for the computation of various physical quantities such as the electric fields in the ground, longitudinal and leakage currents in the ground conductors, and ground impedances. It is shown that the analysis of conductors energized by current waves can require computations at frequencies higher than the significant frequencies in the spectrum of the excitation signal, while simpler models may fail to predict accurately the transient performance. The main limitation of the computer model is the time required for the analysis of large or complex grounding systems. >
413 citations
TL;DR: A solution algorithm to the network reconfiguration problem, which is a constrained, multiobjective, nondifferentiable, optimization problem, that allows the designer to obtain a desirable, global noninferior point in a reasonable computation time.
Abstract: Using a two-stage solution methodology and a modified simulated annealing technique, the authors develop a solution algorithm to the network reconfiguration problem, which is a constrained, multiobjective, nondifferentiable, optimization problem. This solution algorithm allows the designer to obtain a desirable, global noninferior point in a reasonable computation time. Also, given a desired number of switch-on/switch-off operations involved in the network configuration, the solution algorithm can identify the most effective operations. In order to reduce the computation time required, the idea of approximate calculations is explored and incorporated into the solution algorithm, where two efficient load-flow methods are employed; one for high temperature and the other for low temperature. The solution algorithm has been implemented in a software package and tested on a 69-bus system with very promising results. >
379 citations
TL;DR: In this article, a two-stage solution methodology based on a modified simulated annealing technique and the epsilon -constraint method for general multiobjective optimization problems is developed.
Abstract: A new formulation of the network reconfiguration problem for both loss reduction and load balancing that takes into consideration load constraints and operational constraints is presented. The number of switch-on/switch-off operations involved in network reconfiguration is put into a constraint. The new formulation is a constrained, multiobjective and nondifferential optimization problem with both equality and inequality constraints. A two-stage solution methodology based on a modified simulated annealing technique and the epsilon -constraint method for general multiobjective optimization problems is developed. A salient feature of the solution methodology is that it allows designers to find a desirable, global noninferior solution for the problem. An effective scheme to speed up the solution methodology is presented and analyzed. >
341 citations
TL;DR: In this paper, a new method is presented for the solution of load flow in radially operated distribution networks, based on an electric equivalent and on the elimination of the voltage phase angle in the equations to be solved, which makes it possible to obtain the exact solution working only with voltage magnitudes.
Abstract: A new method is presented for the solution of load flow in radially operated distribution networks. The method is based on an electric equivalent and on the elimination of the voltage phase angle in the equations to be solved, which makes it possible to obtain the exact solution working only with voltage magnitudes. In this way, a simple and efficient method for the exact load flow solution for this type of network is obtained, allowing the modeling of voltage-dependent loads and the formulation of related problems like the radial load flow with voltage constraints. The method can easily be programmed and has good convergence characteristics, as shown by examples. >
308 citations
Enel1
TL;DR: In this article, a model of lightning-channel progression towards the Earth is given based on the latest knowledge on the physics of discharge in long air gaps, and the physical assessment of the electric field is done with the charge simulation method, which is adopted to input into a computer program all parameters involved in the progression of the negative downward channels toward the Earth and those involved in inception and propagation of upward positive channels from earthed structures.
Abstract: A model of lightning-channel progression towards the Earth is given based on the latest knowledge on the physics of discharge in long air gaps. The physical assessment of the electric field is done with the charge simulation method, which is adopted to input into a computer program all parameters involved in the progression of the negative downward channels towards the Earth and those involved in the inception and propagation of upward positive channels from earthed structures. Starting from the geometrical configuration of the earthed object and taking into account the orographic conditions, the lateral distance may be evaluated as a function of the severity of the lightning stroke in terms of impulse charge and thus of current amplitude. Provided the statistical distribution of the currents is given, the model therefore allows the number of lightning strokes to an object to be estimated, yielding an assumed ground flash density. Reference is made to the critical radius concept acquired with laboratory tests with long front surges. A check of the model with field data relevant to free-standing structures is presented and a reasonable agreement is found. >
275 citations
TL;DR: In this paper, a best-first tree search strategy based on heuristics is used to evaluate the various switching operations available and a rule-based system aimed at the reduction of the search space is presented as a means of implementing the above strategy.
Abstract: A method for feeder reconfiguration with the potential for handling realistic operating constraints is presented. The approach taken is to set up a decision tree to represent the various switching operations available. A best-first tree searching strategy, based on heuristics, is used to evaluate the various alternatives. Switching options which could result in overloads, voltage problems, or other operating constraints, such as those associated with system protection, are quickly eliminated as possibilities. The development of a rule-based system aimed at the reduction of the search space is presented as a means of implementing the above strategy. An example is used to illustrate the concepts described. >
271 citations
TL;DR: In this paper, the authors expanded on the physical meaning of the reactive power in nonsinusoidal situations, and showed that the total reactive power Q/sub F/ is composed from four distinctive types of elementary reactive powers.
Abstract: The author expands on the physical meaning of the reactive power in nonsinusoidal situations. The sinusoidal waveform case is surveyed, viewing the active current as a component of identical waveform with the voltage. This approach, when extended to nonsinusoidal waveforms, supports Fryze's model for apparent power, S/sup 2/=p/sup 2/+Q/sup 2//sub F/. It is proved that the total reactive power Q/sub F/ is composed from four distinctive types of elementary reactive powers. Each of the basic reactive powers is identified as the amplitude of an oscillation of instantaneous power. The separation of Q/sub F/ in Q/sub 1/, the reactive power at the system frequency, and in Q/sub H/, the reactive power at harmonic frequencies, is recommended as an effective mean for monitoring filter efficacy and power-factor compensation. Two major recommendations are supported by the results of this study: abolish the power model using distortion power, and measure the active power of the system frequency separately from the active power of the harmonics. >
265 citations
TL;DR: In this paper, a novel formulation of the general capacitor placement problem taking into consideration practical aspects of capacitors, the load constraints, and the operational constraints at different load levels is presented.
Abstract: A novel formulation of the general capacitor placement problem taking into consideration practical aspects of capacitors, the load constraints, and the operational constraints at different load levels is presented. This formulation is a combinatorial optimization problem with a nondifferentiable objective function. A solution methodology based on an optimization technique (simulated annealing) is proposed to determine the locations where capacitors are to be installed, the types and sizes of capacitors to be installed, and the control settings of these capacitors at different load levels. The solution methodology can offer the global optimal solution for the general capacitor placement problem. >
261 citations
TL;DR: In this paper, a new model for assessing the exposure of free-standing structures and horizontal conductors above flat ground to direct lightning strokes is introduced, and a recently developed criterion for positive leader inception modified to account for positive leaders initiated under the influence of a negative descending lightning stroke is discussed.
Abstract: A new model for assessing the exposure of free-standing structures and horizontal conductors above flat ground to direct lightning strokes is introduced. A recently developed criterion for positive leader inception modified to account for positive leaders initiated under the influence of a negative descending lightning stroke, is discussed. Subsequent propagation of the positive leader is analyzed to define the point of encounter of the two leaders which determines the attractive radius of a structure or the attractive lateral distance of a conductor. These parameters are investigated for a wide range of heights and return-stroke currents. A method for analyzing shielding failure and determining the critical shielding angle is also described. The predictions of the model are compared with field observations and previously developed models. >
258 citations
TL;DR: In this paper, a neural network strategy for the detection of high-impedance faults on electric power distribution feeders is described, which consists of collecting samples of substation current during normal and abnormal feeder operation and using these samples to teach a CNN the rules for fault detection.
Abstract: A neural network strategy for the detection of high-impedance faults on electric power distribution feeders is described. This approach consists of collecting samples of substation current during normal and abnormal feeder operation and using these samples to teach a neural network the rules for fault detection. The learning capability utilized in a neural network approach makes it possible to adapt partially trained fault detectors to individual feeders. The data preprocessing required to set up the training cases and the implementation of the neural network itself are described in detail. the potential of the neural network approach is demonstrated by applying the detection scheme to high-impedance faults simulated on a model distribution system. >
TL;DR: In this paper, the measured values of current harmonics at a staged high-impedance ground fault on sandy soil are presented, where the measured low-frequency spectrum is compared with current harmonic values recorded continuously for one week at the substation.
Abstract: The measured values of current harmonics at a staged high-impedance ground fault on sandy soil are presented. The measured low-frequency spectrum is compared with current harmonics recorded continuously for one week at the substation. This comparison was carried out to determine to what extent 120 Hz and 180 Hz components can be used to help detect a high-impedance fault. The field measurements are supported by a simple theoretical model and laboratory measurements. It is concluded that, for the studied feeder, detection of high-impedance arcing faults may be possible by monitoring of the second-harmonic current. >
TL;DR: In this article, an expert system using a two-stage artificial neural network is proposed to control in real-time multicap capacitors installed on a distribution system for a nonconforming load profile such that the system losses are minimized.
Abstract: An expert system using a two-stage artificial neural network is proposed to control in real time multicap capacitors installed on a distribution system for a nonconforming load profile such that the system losses are minimized. The required input data are directly obtained from online measurements which include the active and reactive line power flows, voltage magnitudes, and the current capacitor settings at certain buses. The optimum control does not involve any iteration procedure; therefore, it is computationally very efficient. Studies on a 30-bus distribution test system show the expert system to have quite satisfactory results. >
TL;DR: In this article, an algorithm for optimizing shunt capacitor sizes on radial distribution lines with nonsinusoidal substation voltages such that the RMS voltages and their corresponding total harmonic distortion lie within prescribed values is presented.
Abstract: An algorithm for optimizing shunt capacitor sizes on radial distribution lines with nonsinusoidal substation voltages such that the RMS voltages and their corresponding total harmonic distortion lie within prescribed values is presented. The problem is formulated as a combinatorial optimization problem with inequality constraints. A simple heuristic numerical algorithm that is based on the method of local variations is proposed to determine an optimal solution. An example shows that optimal capacitor sizes found by neglecting the harmonic components may result in unacceptable voltage distortion levels. >
TL;DR: In this article, a two-stage algorithm is proposed to estimate power system frequency deviation and its average rate of change during emergency operating conditions that may require load shedding, where an adaptive extended Kalman filter is used to calculate the frequency deviation, magnitude, and phase angle of the voltage phasor.
Abstract: A novel Kalman filtering-based technique is presented for estimating power system frequency deviation and its average rate of change during emergency operating conditions that may require load shedding. This method obtains the optimal estimate of the power system frequency deviation from noisy voltage samples and the best estimate of the mean system frequency deviation and its rate of change while accounting for low-frequency synchronizing oscillations which occur during large disturbances. The proposed technique is a two-stage algorithm which uses an adaptive extended Kalman filter in series with an adaptive linear Kalman filter. The extended Kalman filter calculates the frequency deviation, magnitude, and phase angle of the voltage phasor, which may change during the time period covered by the estimation window. Both the measurement noise variance and the system noise covariance associated with the voltage samples are calculated online. The instantaneous frequency deviation is used as the input to a linear Kalman filter, which models the frequency deviation as a random walk plus a random ramp process. The estimated average rate of frequency decay is represented by the slope of the random ramp. Results for both single and multiple measurements are reported. >
TL;DR: In this paper, an approach that accounts for the time-varying nature of the fundamental and harmonic components is developed to detect high-impedance faults accompanied by variations in the 60 Hz and harmonic component.
Abstract: High-impedance faults are accompanied by variations in the 60 Hz and harmonic components. An approach that accounts for the time-varying nature of the fundamental and harmonic components is developed. This approach is based on Kalman-filtering theory to obtain the best estimation of the time variations of the fundamental and harmonic components. Four actual recorded data sets for staged arcing fault on different types of soil are investigated by the proposed Kalman-filtering technique. The time variations of fundamental and low-order harmonic components significantly contribute to high-impedance fault detection using the features presented. >
TL;DR: In this paper, the wettability of aged surfaces and of the bulk of naturally aged silicone and EPDM (ethylene-propylene diener monomer) insulator housings and silicone elastomer insulator coatings was studied.
Abstract: The wettability of aged surfaces and of the bulk of naturally aged silicone and EPDM (ethylene-propylene diener monomer) insulator housings and silicone elastomer insulator coatings was studied. The samples were taken either directly from the insulators or treated by exposing them to corona discharges and/or to saline pollution. The results show that the contact angles of the silicone rubber insulator surfaces are larger than the contact angles of the RTV (room-temperature vulcanizing) silicone rubber coating and of the EPDM rubber insulator surfaces, especially when the surfaces are aged. When the insulators were exposed to corona discharges, the contact angles of the silicone rubber insulators are reduced but after exposure recover with time. The contact angles of the EPDM rubber insulators, however, continue to reduce after the exposure. When exposed to artificial saline pollution, the silicone rubber insulators show a limited recovery of their contact angles with time, while when exposed to corona discharge after saline pollution, they show a recovery of the contact angle after the exposure. The recovery time is dependent on the exposure time to the corona discharges. The EPDM samples do not show any recovery of their contact angles, either when left to rest after the salt deposition or, when after the salt deposition, they undergo a subsequent exposure to corona discharges. Furthermore, such an exposure may be deleterious for the EPDM polymer and the insulator surface may become completely hydrophylic. >
TL;DR: In this paper, a study on the loss and recovery of hydrophobicity of RTV (room-temperature vulcanizing) silicone-rubber insulator coatings in a salt-fog chamber is reported.
Abstract: The results of a study on the loss and recovery of hydrophobicity of RTV (room-temperature vulcanizing) silicone-rubber insulator coatings in a salt-fog chamber are reported. The results complement those previously reported on the ability of the coatings to suppress leakage current and insulator flashover. The temporary loss of hydrophobicity caused by dry-band arcing and the subsequent recovery are studied in depth. The gradual loss of hydrophobicity as determined from the leakage current and the contact-angle measurements is shown to be related to the physical changes to the coating brought about by dry-band arcing. >
TL;DR: A general solution algorithm based on simulated annealing for optimal capacitor placements in distribution systems is proposed and analyzed and can provide the global optimal solution for the capacitor placement problem.
Abstract: For pt.I see ibid., vol.5, no.2, p.634-42 (1990). A general solution algorithm based on simulated annealing for optimal capacitor placements in distribution systems is proposed and analyzed. The solution algorithm can provide the global optimal solution for the capacitor placement problem. The solution algorithm has been implemented into a software package and tested on a 69 bus system with very promising results. >
TL;DR: In this article, a general package for harmonic-domain computation is described, consisting of a set of routines which can be used by developers of programs for power system harmonic applications, and the most basic routines have been listed.
Abstract: A general package for harmonic-domain computation is described. It consists of a set of routines which can be used by developers of programs for power system harmonic applications. The most basic routines have been listed. The package represents nonlinear characteristics by fitting the characteristic with a polynomial, for which special harmonic domain processing via convolutions has been developed, or by directly applying a fast Fourier transform. A model in the form of a differential equation is derived for the electric arc. It is based on simple energy balance considerations and therefore is expected to be generally valid. The computational results compare well with existing measurements. The arc model can be used for discharge lamps or for arc furnaces. >
TL;DR: In this article, the authors investigated the mechanisms involved in the loss and subsequent recovery of surface hydrophobicity due to dry-band arcing and investigated various experimental techniques which could be used for characterizing surface hydophobicity.
Abstract: The results of a study on silicone rubber and ethylene propylene diene monomer (EPDM) polymers are presented. The study was done to understand the mechanisms involved in the loss and subsequent recovery of surface hydrophobicity due to dry-band arcing and to investigate various experimental techniques which could be used for characterizing surface hydrophobicity. The materials are subjected to dry-band arcing in a log chamber. Several techniques such as measurement of contact angle, determining surface composition using electron spectroscopy for chemical analysis (ESCA), and measuring crossover voltage (COV) using a scanning electron microscope are examined. The experimental results and theoretical calculations demonstrate that the mobile species in the polymer are responsible for the surface hydrophobicity. In terms of repeatability and simplicity of measurement, the COV determination appears to be the most suitable technique for hydrophobicity studies. >
TL;DR: In this article, the design, assembly, and testing results for prototypes of an optical current transformer (CT) and a voltage-dividing-type voltage transformer (PD) were described.
Abstract: The authors describe the design(, assembly(, and testing results for prototypes of an optical current transformer (CT) and a voltage-dividing-type voltage transformer (PD) The optical CT and PD were developed to be applicable to three-phase enclosed-type 300 kV gas-insulated switchgear (GIS) and air-insulated 168 kV substation systems Test results for the newly developed optical CT and PD showed that their basic properties conform with JEC 1201, the Japanese standard for electric-power instrument transformers >
TL;DR: In this paper, a method that minimizes the influence of harmonics in the system voltage when performing a harmonic analysis of the arrester leakage current is presented, where a field probe is introduced to compensate for the harmonics.
Abstract: Various methods of determining the condition of zinc oxide (ZnO) surge arresters by means of measuring their leakage current are discussed. A method that minimizes the influence of harmonics in the system voltage when performing a harmonic analysis of the arrester leakage current presented. The presence of harmonics in the voltage has presented a great problem to earlier methods based on harmonic analysis, since these harmonics may interfere with the harmonics generated by the nonlinear resistance of the arrester. The favorable effect of the method presented is achieved by introducing a field probe which allows a compensation for the harmonics in the voltage. The main advantage of the new method is the low sensitivity to harmonics in the system voltage. >
Enel1
TL;DR: In this article, an extensive application of the leader progression (LP) model to the relevant geometrical configurations has been carried out, together with the method of analysis of the lightning exposure of transmission lines located in different orographic conditions.
Abstract: For pt.I see ibid., vol.5, no.4, p.2009-22 (1990). To evaluate the lightning performance of transmission lines, extensive application of the leader progression (LP) model to the relevant geometrical configurations has been carried out. Basic configurations used in the LP computer program are presented together with the method of analysis of the lightning exposure of transmission lines located in the different orographic conditions of flat countries, ridges of hills, and along a mountain side. A computer program used to evaluate shielding efficiency and the total number of strokes to the line is considered. A set of application graphs referring to the different orographic locations and including wide ranges of line heights, shielding angles, and insulation levels are given. >
TL;DR: In this paper, an expression for the apparent resistivity in an earth structure with an arbitrary number of layers is derived for the Wenner four-electrode method, and the results showed good agreement, indicating that the proposed expression and parameter estimation technique could be practically applied to ground design problems.
Abstract: An expression for the apparent resistivity in an earth structure with an arbitrary number of layers is derived for the Wenner four-electrode method. The expression is arrived at by performing an analysis of apparent resistivity in a multilayer structure as an extension of studies that have concentrated on the two-layer model. Applying a series of parameter data to this expression enabled the preparation of rho -a curves for such a multilayer structure, and these curves were compared with actual rho -a curves obtained from two case studies. The results showed good agreement, indicating that the proposed expression and parameter estimation technique could be practically applied to ground design problems. In particular, earth parameters for a multilayer structure obtained through the proposed method can be used for calculating the ground resistance required by deep-driven rods in a particular geologic formation. >
TL;DR: In this article, a predictive out-of-step protection system is proposed to prevent total system collapse caused by step-out between large-capacity generator groups due to a serious fault in the trunk transmission line.
Abstract: A recently developed predictive out-of-step protection system is described. The purpose of this protection system is to prevent total system collapse caused by step-out between large-capacity generator groups due to a serious fault in the trunk transmission line. This is accomplished by using online data collected during the incubation phase to predict a step-out and then issuing a system-seperation command. The system has the following characteristics: (1) the phase difference between several large generator groups is measured from online voltage data collected from substation busbars in the vicinity of the generators at a sampling rate of 600 Hz: (2) the phase difference at 200 ms in the future is predicted from the measured phase-difference data; and (3) if the predicted phase difference exceeds the instability threshold value, system separation if performed taking into account the power supply and demand balance after tripping. >
TL;DR: In this paper, a measuring instrument named ALPS (Automatic Lightning Discharge Progressing Feature Observation System) was developed to determine the progress of lightning flashes in the coastal area of the Japan Sea.
Abstract: With the aid of recent optoelectronic techniques, the authors have developed a measuring instrument named ALPS (Automatic Lightning Discharge Progressing Feature Observation System) to determine the progress of lightning flashes The progress velocities of stepped leaders for lightning in winter seasons were observed using the ALPS in the coastal area of the Japan Sea The progress velocity of an individual step of a stepped leader can be expressed by a lognormal distribution and its mean value is 16*10/sup 6/ m/s for upward leaders and 40*10/sup 6/ m/s for downward leaders The mean progress velocity of a total leader process is given as 08 approximately 27*10/sup 5/ m/s for upward leaders and 29*10/sup 5/ m/s for downward leaders >
TL;DR: In this article, a magneto-optic current transducer (MOCT) is used to measure the rotation of the plane of polarization by a magnetic field exhibited in certain glasses.
Abstract: A current measurement technique using the magneto-optic or Faraday effect, has been developed, tested, and demonstrated. The device developed is a magneto-optic current transducer (MOCT). It uses the rotation of the plane of polarization by a magnetic field exhibited in certain glasses (Faraday effect). Test data obtained in an extensive field evaluation of the MOCT were compared with the design qualification data gathered during the development phase of this project. The analysis indicates that operation of the MOCT-based metering system under field conditions compares favorably with performance predicted during design qualification. >
TL;DR: In this paper, the effects of the many sources of harmonics which occur on distribution systems are discussed and contrasted with the single source from a high-impedance ground fault.
Abstract: The effects of the many sources of harmonics which occur on distribution systems are discussed and contrasted with the single source of harmonics from a high-impedance ground fault. Field data are presented which show the complexity of modeling the ambient harmonics and the simplicity of the change in the phasor value of the third harmonic which occurs due to a high-impedance ground fault. This phasor change is shown to be unique and predictable and hence suitable for use in detecting these faults. It is shown that variations in ambient harmonics may be greater than the change due to a high-impedance ground fault and must be considered in the fault detection system. Calculations of fault current harmonics are simpler than those for the ambient harmonics. >
TL;DR: In this article, the authors present power line data and dynamic line rating statistics obtained during a one-year study in New York State and propose a forecast rating algorithm for calculating power line ratings intended to remain valid over a defined period of time with minimal risk.
Abstract: The authors present power line data and dynamic line rating statistics obtained during a one-year study in new York State. Conclusions from the study apply specifically to the Porter/Rotterdam line Hash 30. Dynamic line ratings, defined as the minimum dynamic rating for the power line, were 20% lower than the average or single-station ratings. The greatest gains to dynamic line rating come from the limited time or transient rating. Limited time dynamic ratings derive their added benefit from the use of actual preload conductor temperatures in the rating calculation rather than the 95 degrees C conductor temperature assumed by many utilities. A forecast rating algorithm is proposed for calculating power line ratings intended to remain valid over a defined period of time in the future with minimal risk. Based on the algorithm, the 4-h forecast ratings were found to be 12% lower on the average than dynamic line ratings. >