Showing papers in "IEEE Power & Energy Magazine in 1996"
TL;DR: In this article, an artificial neural network (ANN) approach to the diagnosis and detection of faults in oil-filled power transformers based on dissolved gas-in-oil analysis is presented.
Abstract: This paper presents an artificial neural network (ANN) approach to the diagnosis and detection of faults in oil-filled power transformers based on dissolved gas-in-oil analysis. A two-step ANN method is used to detect faults with or without cellulose involved. Good diagnosis accuracy is obtained with the proposed approach.
335 citations
TL;DR: In this article, a review of the characteristics of the current solar cycle, the power system reliability threat, geomagnetically induced currents (GIC) as the cause of transformer failures, and magnetic storm forecast improvements is presented.
Abstract: This article examines the lessons learned for solar cycle 22 and the application of these to solar cycle 23. The topics of the article include a review of the characteristics of the current solar cycle, the power system reliability threat, geomagnetically induced currents (GIC) as the cause of transformer failures, and magnetic storm forecast improvements.
154 citations
TL;DR: In this article, a hierarchical Markov model (HMM) is proposed to decompose the reliability model based on power system topology, integrated protection systems and individual protection devices, which easily accommodates the effects of backup protection, fault isolation and load restoration.
Abstract: Distribution system reliability assessment is concerned with power availability and power quality at each customer's service entrance. This paper presents a new method, termed hierarchical Markov modeling (HMM), which can perform predictive distribution system reliability assessment. HMM is unique in that it decomposes the reliability model based on power system topology, integrated protection systems and individual protection devices. This structure, which easily accommodates the effects of backup protection, fault isolation and load restoration, is compared to simpler reliability models. HMM is then used to assess the reliability of an existing utility distribution system and to explore the reliability impact of several design improvement options.
126 citations
TL;DR: In this paper, the authors provide an explanation of the phenomena of very fast transients which can occur in gas-insulated substations (GIS) and the simulation of the GIS for this type of transient should be suitable for frequencies from 100 kHz up to 50 MHz.
Abstract: The objective of this task force report is to provide an explanation of the phenomena of very fast transients which can occur in gas-insulated substations (GIS). The simulation of the GIS for this type of transient should be suitable for frequencies from 100 kHz up to 50 MHz. The corresponding equivalent circuits developed in previous work of CIGRE have been reported. The accuracy of the simulation of this phenomenon and verification with field measurements are given. An example of a GIS calculation with detailed input data is presented which could be used for the recalculation of the results.
106 citations
TL;DR: In this paper, a neural network for controlling shunt capacitor banks and feeder voltage regulators in electric distribution systems is presented, where the objective of the neural controller is to minimize total I/sup 2/R losses and maintain all bus voltages within standard limits.
Abstract: A neural network for controlling shunt capacitor banks and feeder voltage regulators in electric distribution systems is presented. The objective of the neural controller is to minimize total I/sup 2/R losses and maintain all bus voltages within standard limits. The performance of the neural network for different input selections and training data is discussed and compared. Two different input selections are tried, one using the previous control states of the capacitors and regulator along with measured line flows and voltage which is equivalent to having feedback and the other with measured line flows and voltage without previous control settings. The results indicate that the neural net controller with feedback can outperform the one without. Also, proper selection of a training data set that adequately covers the operating space of the distribution system is important for achieving satisfactory performance with the neural controller. The neural controller is tested on a radially configured distribution system with 30 buses, 5 switchable capacitor banks and a nine tap line regulators to demonstrate the performance characteristics associated with these principles. Monte Carlo simulations show that a carefully designed and relatively compact neural network with a small but carefully developed training set can perform quite well under slight and extreme variation of loading conditions.
105 citations
TL;DR: In this article, the feasibility of vibration analysis for the diagnostic testing of high-voltage circuit breakers is assessed, and a comprehensive field test program has been carried out, where the breakers were assumed to be in good condition with no known irregularities at the time of testing, but several serious faults, including an incipient rupture of the contact plug shaft, an incorrectly assembled crank, and major lubrication problems were disclosed.
Abstract: In order to assess the feasibility of vibration analysis for the diagnostic testing of high-voltage circuit breakers, a comprehensive field test program has been carried out. Vibration patterns from 31 breakers (93 identical single-phase units) have been acquired, compared and analyzed. The breakers were assumed to be in good condition with no known irregularities at the time of testing. However, several serious faults, including an incipient rupture of the contact plug shaft, an incorrectly assembled crank, and major lubrication problems were disclosed. Thus, this "blind test" performed under realistic conditions on circuit breakers in normal service demonstrates that vibration analysis can be a reliable and suitable tool for noninvasive diagnostic testing.
81 citations
TL;DR: In this article, a new approach for optimal network routing in distribution system planning is presented, where the main objective is to minimize the total cost which is the summation of reliability costs, feeder resistive loss, investment and maintenance costs.
Abstract: A new approach for optimal network routing in distribution system planning is presented in this paper. The distribution network routing planning problem is formulated as a nonlinear constrained, nondifferentiable optimization problem. The main objective is to minimize the total cost which is the summation of reliability costs, feeder resistive loss, investment and maintenance costs. Simulated annealing, which is a general purpose combinatorial optimization algorithm, is used to obtain a global optimum solution of the problem.
79 citations
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TL;DR: In this article, the electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination (C), ice (I), fog (F) and an ambient temperature that rises through 0 C (T{sub 0{degree}}).
Abstract: The electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination (C), ice (I), fog (F) and an ambient temperature that rises through 0 C (T{sub 0{degree}}). Failures at operating voltage on 115-kV, 230-kV and 500-kV systems occur with increasing probability under these conditions. A new CFT{sub 0{degree}} or cold-fog test method has been developed to reproduce the flashovers at all three voltage levels. Three options are identified for improving CFT{sub 0{degree}} performance: use of semi-conductive glazes, substitution of silicone for porcelain and use of silicone coatings on existing porcelain insulators.
69 citations
TL;DR: In this paper, expanded wholesale and retail competition and the effect that they are likely to have on the electric power industry are examined. But, based on the experience of the natural gas industry and the electrical power industry in California and other parts of the world, the author counsels caution in moving toward expanded retail competition.
Abstract: This article examines expanded wholesale and retail competition and the effect that they are likely to have on the electric power industry. The author believes that expanded wholesale competition is good and will bring immediate benefit to all electric consumers; however, based on the experience of the natural gas industry and the electric power industry in California and other parts of the world, the author counsels caution in moving toward expanded retail competition.
65 citations
TL;DR: A frequency relay capable of under/over frequency and rate of change of frequency measurements has been implemented on a digital signal processor using an instantaneous frequency measuring algorithm.
Abstract: A frequency relay capable of under/over frequency and rate of change of frequency measurements has been implemented on a digital signal processor using an instantaneous frequency measuring algorithm. Careful attention to the filtering aspects of the relay is needed under dynamic conditions due to frequency modulation of the input signal. An algorithm for avoiding unwanted relay operation due to impulsive changes in the input signal is presented. Results are shown for simulated tests using computer based relay testing equipment, and for overloads on a micromachine power system simulator.
63 citations
TL;DR: The proposed expert system has a topology-based simple structure and utilizes basic rules suggested by the Korean electric power company including heuristic rules, topology identification rules and search rules to generate switching sequences for feasible restoration processes.
Abstract: This paper presents a practical restoration aid expert system for 154 kV distribution substations. The proposed expert system has a topology-based simple structure and utilizes basic rules suggested by the Korean electric power company including heuristic rules, topology identification rules and search rules to generate switching sequences for feasible restoration processes. In this paper, the general system structure as well as rules and data representations are discussed. The expert system is realized using an HP9000 workstation. X-window and Motif shells are used for the user-friendly GUI. The system has been tested in a practical sub-control center as a part of an intelligent fault diagnosis and restoration aid system to assist the decision making of SCADA operators.
TL;DR: An artificial contamination method for hydrophobic polymer insulators has been developed which can provide a uniform contaminant layer, similar to that found in nature, without either damaging the polymer surface or by adding any chemical agent to the conventional contamination slurry as mentioned in this paper.
Abstract: An artificial contamination method for hydrophobic polymer insulators has been developed which can provide a uniform contaminant layer, similar to that found in nature, without either damaging the polymer surface or by adding any chemical agent to the conventional contamination slurry. Using this method, the basic contamination withstand voltage characteristics of polymer insulators were investigated compared with those of porcelain insulators. The results show that although hydrophobic polymer insulators generally have excellent contamination withstand voltage characteristics, critical reduction of withstand voltage sometimes occurs under rapid and heavy wetting and contamination conditions.
TL;DR: Alarm processing and fault diagnosis are demonstrated as further requirements of the DSS for protection engineers, within which knowledge- based reasoning and model-based reasoning are combined to provide the overall functionality required.
Abstract: This paper discusses model-based reasoning applied to power network protection system performance analysis. Appropriate modelling and reasoning methodologies are indicated, and their advantages considered. The necessity of incorporating protection system performance analysis within a decision support system (DSS), designed for electric utility protection engineers, is presented. Alarm processing and fault diagnosis are demonstrated as further requirements of the DSS for protection engineers, within which knowledge-based reasoning and model-based reasoning are combined to provide the overall functionality required.
TL;DR: In this article, a new closed loop control method for HVDC transmission networks is presented, which uses information locally available at each power converter station and combines and coordinates control possibilities with the objective of improving the dynamic behaviour of HVDc transmission networks during fault recoveries and disturbances around their operating points.
Abstract: The paper presents a new closed loop control method which uses information locally available at each power converter station and combines and coordinates control possibilities with the objective of improving the dynamic behaviour of HVDC transmission networks during fault recoveries and disturbances around their operating points.
TL;DR: In this article, a planning methodology for distribution system harmonic filtering is proposed, which is intended for use on radial distribution systems with no large harmonic sources, and it is proposed that 60 hertz VAr planning be done first to allocate the VAr resources.
Abstract: A planning methodology for distribution system harmonic filtering is proposed. The method is intended for use on radial distribution systems with no large harmonic sources. It is proposed that 60 hertz VAr planning be done first to allocate the VAr resources. Following this process, the harmonic filter planning can be readily accomplished. Characteristics of the distribution systems and the harmonic sources are exploited to provide a practical filter planning technique which is effective and efficient.
TL;DR: In this paper, two schemes for determining harmonics in power systems that are not limited to stationary waveforms, but can equally estimate harmonic phasors in waveforms with time-varying amplitudes and changing fundamental frequency are presented.
Abstract: This paper applies, to a practical test case, two schemes for determining harmonics in power systems that are not limited to stationary waveforms, but can equally estimate harmonic phasors in waveforms with time-varying amplitudes and changing fundamental frequency. The first scheme relies on the short-time Fourier analysis performed using the fast Fourier transform (FFT) with time-domain windowing and frequency-domain interpolation. Another scheme combines fundamental-frequency tracking with a Kalman filter-based harmonic analyzer, yielding a uniformly sampled, self-synchronizing harmonics tracker. The performance of these advanced measurement schemes for changing harmonics is illustrated convincingly on nonstationary waveforms generated in the EMTP using a realistic series-compensated transmission network.
Journal Article•
TL;DR: In this article, a hybrid method for the design and planning of passive optical networks (PONs) is described, which uses expert system and evolutionary computing techniques to produce "most fit" PON designs taking into account practical planning rules and constraints.
Abstract: A new hybrid method is described for the design and planning of passive optical networks (PONs). The method utilises expert system and evolutionary computing techniques to produce 'most fit' PON designs taking into account practical planning rules and constraints. The implementation of the planning tool is described with reference to the planning process, design factors and optimisation goals. Example results of centralised-split PON designs are shown which demonstrate the optimised placement of network plant such as spur joints, splitters and distribution points.
TL;DR: In this article, the dielectric performance of gas-insulated bus was investigated under conical-and disk-type spacers, and it was found that conical type spacer is better than disk type.
Abstract: In order to discuss the dielectric performance of DC GIS, the flashover characteristics of gas-insulated bus were studied under conical- and disk-type spacers. The test involves the investigation on effect of electrification for charge to be accumulated in spacers and the effect of metallic particles. As the result, it was found that the dielectric characteristics of conical-type spacer are better than disk type. Moreover, the dielectric performance of DC GIS is more affected by the characteristics of coaxial electrode system than spacer surface with regard to metallic particle. On the basis of the results of these tests, this report presents the conception of insulation design for DC GIS.
TL;DR: This paper is written as a tutorial describing the stages of signal processing: modulation, amplification and demodulation, without reference to power electronics since the solid-state switches are modelled as ON-OFF switches.
TL;DR: In this paper, three broad types of post-measurement processing objectives are considered: to enhance accuracy, to estimate data, and to reduce the volume of the collected data.
Abstract: This paper addresses the issues of post-measurement processing of data collected in a power quality assessment study. Three broad types of post-measurement processing objectives are considered: to enhance accuracy; to estimate data; and to reduce the volume of the collected data. The methods used to enhance accuracy are bad data identification and rejection. Averaging is discussed as a method to "filter" measurement error. The methods used for data estimation are state estimation techniques in both the time and frequency domain. The methods used to reduce the volume of the collected data are based on the calculation of marginal and conditional probabilities and expectations. The integrated use of these techniques in an instrumentation system for power quality assessment is discussed. The main suggested application is for the measurement of harmonics.
TL;DR: In this paper, a method that uses uncertain network data, load distribution information and telemetered data for feeder voltage profile calculation is proposed for power system operation planning, and lower and upper bounds can be used to alert dispatchers for possible system deterioration.
Abstract: A method that uses uncertain network data, load distribution information and telemetered data for feeder voltage profile calculation is proposed in this paper In the proposed method, data involved in the calculation are represented by using fuzzy numbers All possible feeder voltage solutions within bounds obtained from fuzzy arithmetic are considered The mean values of the obtained intervals are useful for power system operation planning, and lower and upper bounds can be used to alert dispatchers for possible system deterioration Measurements are included in the calculation to reduce the uncertainty of the obtained results The voltage calculation method is used to evaluate the measurement configuration and a meter placement scheme is proposed to select the locations of new meters from the standpoint of minimizing the uncertainties of the calculated voltage profile
TL;DR: In this paper, the basic elements of transformers, including two independent coils and a closed iron core, are described and compared to the transformer energy distribution networks that are used today, from experimental devices of the 1830s to the first transformer systems of the 1880s.
Abstract: he apparatus Michael Faraday constructed in 1831, by which he invented electromagnetic induction, contained all basic elements of transformers: two independent coils and a closed iron core. Nevertheless, another 54 years passed before the appearance of the transformers and transformer energy distribution networks that are generally used today. From experimental devices of the 1830s to the first transformer systems of the 1880s
TL;DR: The authors argued that if international organizations continue to deny third-world countries the funds they need for development, if developed nations do not improve their trade and investment relationship with them, it will be impossible to create conditions for sustained development.
Abstract: should aim at social justice and respect of nature. It should strive for economic efficiency without, however, letting these concerns be an end to themselves. If international organizations continue to deny third-world countries the funds they need for development, if developed nations do not improve their trade and investment relationship with them, it will be impossible to create conditions for sustained development. Global policies and economic relations must be democratized in order to eradicate poverty on earth with minimal damage to the environment.
TL;DR: In this article, the authors present a tutorial describing the stages of signal processing: modulation, amplification and demodulation, without reference to power electronics since the solid-state switches are modelled as ON-OFF switches.
Abstract: The pulse width modulation (PWM) technique has been proposed for the force-commutated shunt and series VAr controllers and unified power flow controllers in flexible AC transmission systems. The PWM converters can be operated as linear amplifiers of constant gain so that linear control system theory can be brought to bear more easily when applying feedback controls. For example, pole-placement and active filtering have been successfully applied in laboratory models. This paper is written as a tutorial describing the stages of signal processing: modulation, amplification and demodulation, without reference to power electronics since the solid-state switches are modelled as ON-OFF switches.
TL;DR: In this paper, the authors examine the functions performed by the equipment and people that generate, control, transmit, and distribute electricity to support the basic services of generating capacity, energy supply, and power delivery.
Abstract: The US electricity industry, dominated by vertically integrated, retail-monopoly, regulated utilities, is undergoing enormous changes. The industry, within the next few years, will evolve into a deintegrated, competitive-market dominated, less regulated industry. Part of this process involves unbundling electric generation from transmission, which raises the issue of ancillary services. Since the Federal Energy Regulatory Commission (FERC) published its March 1995 proposed rule on open-access transmission, ancillary services have been an important topic. Ancillary services are those functions performed by the equipment and people that generate, control, transmit, and distribute electricity to support the basic services of generating capacity, energy supply, and power delivery. These services cost US electricity consumers about $12 billion a year. This article examines the functions performed by the equipment and people that generate, control, transmit, and distribute electricity to support the basic services of generating capacity, energy supply, and power delivery.
TL;DR: In this article, a light-triggered thyristor with ratings of 8 kV and 3.5 kA was developed for next generation HVDC transmission systems using a six-inch diameter wafer.
Abstract: A high voltage thyristor valve is the basic component of an HVDC transmission system. Development of a 500 kV valve for next generation HVDC transmission systems is described. First, the power loss of the valve is analyzed to decide a reasonable wafer size for the light-triggered thyristor. From these results, a six inch diameter wafer size is selected. A light-triggered thyristor, with ratings of 8 kV and 3.5 kA, is developed using the six inch wafer. The design of the valve employing the thyristor and test results with a prototype valve prove that a 500 kV valve can be realized by this design method.
TL;DR: In this article, the authors investigated a scheme to improve the reach measurement of distance relays and fault locators for series compensated lines, which requires only local voltage and current at the bus.
Abstract: This paper investigates a scheme to improve the reach measurement of distance relays and fault locators for series compensated lines. A deterministic method and a feedforward neural network method have been implemented for on-line calculation of the voltage across a non-linear capacitor installation. These techniques are compared and incorporated into a new relaying scheme which is independent of the series capacitor installation, operation of the capacitor protection, and the surrounding power system elements. The proposed scheme is simple and accurate and requires only local voltage and current at the bus. Detailed testing using EMTP has been done to show the benefits of the new adaptive scheme. The results demonstrate the suitability of the techniques for real world applications.
TL;DR: In this article, the magnetic properties of a steel core were measured on a length of the steel core taken from a 54/3.77 mm+19/2.24 mn (Grackle) ACSR conductor.
Abstract: To calculate the radial current distribution and core loss within a concentric-lay steel-cored conductor, the magnetic properties of the core must be known for any service condition. The paper describes comprehensive measurements on a length of the steel core taken from a 54/3.77 mm+19/2.24 mn (Grackle) ACSR conductor. Curves are given to illustrate the effects of magnetic field strength, tensile stress and temperature on the modulus, real and imaginary parts of the complex relative permeability, the hysteretic angle, the loss tangent, the total core loss and the hysteresis loss.
TL;DR: In this paper, the frequency modulation property of the discrete Fourier transform (DFT) has been used to calculate the periodic steady state of power distribution system loads for electronically switched, time varying cases.
Abstract: The periodic steady state of power distribution system loads is studied for electronically switched, time varying cases. Many loads of this type appear on contemporary power systems as energy saving and controllable demands. Several alternative methods of calculating the periodic steady state are discussed and a new method is proposed based on the frequency modulation property of the discrete Fourier transform. The new method is termed the gain-shift formula (GSF) because the format of the technique entails adding frequency shifted terms which represent the parameter to be calculated. An example of a triac-switched load on the distribution system is given. The main advantages of the GSF are: rapid calculation of the periodic steady state; and efficient calculation of the frequency spectrum of voltages and currents in the periodic steady state.