Showing papers in "IEEE Transactions on Power Delivery in 1993"
TL;DR: In this paper, the authors summarize the state of knowledge of the effects of power system harmonics on equipment, including thermal overloading, disruption, and dielectric stressing, and quantitatively describe the effects.
Abstract: The authors summarize the state of knowledge of the effects of power system harmonics on equipment. The general mechanisms presented are thermal overloading, disruption, and dielectric stressing. Quantitative effects are presented or referenced whenever possible. However, many of the effects are can only be qualitatively described. The types of equipment considered are adjustable speed drives, capacitors, circuit breakers, fuses, conductors, electronic equipment, lighting, metering, protective relays, rotating machines, telephones, and transformers. >
441Â citations
TL;DR: In this paper, a modified zero-crossing method using curve fitting of voltage samples is proposed, and polynomial fitting of the discrete Fourier transform (DFT) quasi-stationary phasor data for calculation of the rate of change of the positive sequence phase angle.
Abstract: Three new techniques for frequency measurement are proposed. The first is a modified zero-crossing method using curve fitting of voltage samples. The second method is based on polynomial fitting of the discrete Fourier transform (DFT) quasi-stationary phasor data for calculation of the rate of change of the positive sequence phase angle. The third method operates on a complex signal obtained by the standard technique of quadrature demodulation. All three methods are characterized by immunity to reasonable amounts of noise and harmonics in power systems. The performance of the proposed techniques is illustrated for several scenarios by computer simulation. >
379Â citations
TL;DR: In this paper, the instantaneous power theory was introduced for steady and transient states and for generic voltage and current waveforms, and an example showing how this theory can be used to design and control an active power filter is presented.
Abstract: Conventional active and reactive power theory, valid for the steady-state analysis is reviewed. The instantaneous power theory, introduced by H. Akagi et al. (1983, 1984) is also presented. This instantaneous theory is valid for steady and transient states and for generic voltage and current waveforms. Some examples explaining the physical meaning of the new concepts are presented. By using the concepts of symmetrical components together with the new theory, the powers in an unbalanced system are analyzed, including the zero-sequence instantaneous power. An example showing how this theory can be used to design and control an active power filter is presented. Some simulation results are presented and discussed. >
361Â citations
TL;DR: Strategies are proposed to reconfigure the feeder in distribution systems by using artificial neural networks (ANNs) with mapping ability to reduce the power loss according to the variation of load pattern.
Abstract: Strategies are proposed to reconfigure the feeder in distribution systems by using artificial neural networks (ANNs) with mapping ability. ANNs determine the appropriate system topology that reduces the power loss according to the variation of load pattern. The control strategy can be easily obtained on the basis of the system topology which is provided by ANNs. ANNs are designed in two groups. The first group estimates the proper load level from the load data of each zone. The second determines the appropriate system topology from the input load level. Several programs with the training set builder are developed for the design, the training, and the accuracy test of artificial neural networks. The performance of neural networks designed is evaluated on the test distribution system. Neural networks are implemented in FORTRAN language and trained on a 386 PC. >
286Â citations
TL;DR: In this paper, the requirements of an islanding, or "loss of grid", protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined.
Abstract: The requirements of an islanding, or 'loss of grid', protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions in order to demonstrate the operation of this type of protection. The new protection algorithm is shown to trip for loss of grid and for load fluctuations while the dispersed storage and generation unit is operating independently of the utility supply following a loss of grid, and for an out-of-synchronism reconnection of the utility supply to the dispersed storage and generation unit. It is also shown to remain stable for major load fluctuations while the utility supply remains connected to the dispersed generator system. >
277Â citations
TL;DR: A prototype expert system based on the dissolved gas analysis (DGA) technique for diagnosis of suspected transformer faults and their maintenance actions is developed and a synthetic method is proposed to assist the gas ratio method.
Abstract: A prototype expert system based on the dissolved gas analysis (DGA) technique for diagnosis of suspected transformer faults and their maintenance actions is developed. A synthetic method is proposed to assist the gas ratio method. The uncertainties of key gas analysis, norms threshold, and gas ratio boundaries, are managed by using a fuzzy set concept. The expert system is implemented on a PC-AT using KES with rule-based knowledge representation. The system has been tested to show its effectiveness in transformer diagnosis. >
275Â citations
TL;DR: The impact of electric vehicle charging on the energy and power demand is determined not only by the number of electric vehicles (EVs) in use and their usage pattern, but also by the charging profile of the battery module as discussed by the authors.
Abstract: The impact of electric vehicle charging on the energy and power demand is determined not only by the number of electric vehicles (EVs) in use and their usage pattern, but also by the number of EVs being charged at an instant and the charging profile of the battery module. Case studies that reveal several important issues regarding the impacts EV load may have on utility distribution systems are examined. First, it is not adequate to have only sufficient generation capacity during off-peak hours to assure a system's ability to absorb EV loads without adverse effects. The constraints at the distribution level must be properly studied. Second, a sizable EV load can introduce a new peak in the early off-peak period. This may have scheduling implications and can completely throw any load management programs off balance. Third, at the present state of EV technology, including that of battery modules and chargers, a typical distribution system may not be able to supply EV loads beyond 20% penetration level. This constraint is created by the long (up to 12 hours) charging cycle of batteries. >
254Â citations
TL;DR: In this paper, a model to simulate the high-frequency behavior of a power transformer is presented based on the frequency characteristics of the transformer admittance matrix between its terminals over a given range of frequencies.
Abstract: A model to simulate the high-frequency behavior of a power transformer is presented This model is based on the frequency characteristics of the transformer admittance matrix between its terminals over a given range of frequencies The transformer admittance characteristics can be obtained from measurements or from detailed internal models based on the physical layout of the transformer The elements of the nodal admittance matrix are approximated with rational functions consisting of real as well as complex conjugate poles and zeroes These approximations are realized in the form of an RLC network in a format suitable for direct use with the ElectroMagnetics Transient Program (EMTP) The high-frequency transformer model can be used as a stand-alone linear model or as an add-on module of a more comprehensive model where iron core nonlinearities are represented in detail >
244Â citations
TL;DR: In this paper, the authors proposed a new method for the state estimation of electric power distribution system conditions oriented towards working with minimum number of remote measurements available in the network, which will require information concerning the network reconfiguration, remote measurements of voltages, real and reactive power as well as feeder currents in distribution substations.
Abstract: This paper proposes a new method for the state estimation of electric power distribution system conditions oriented towards working with minimum number of remote measurements available in the network. This approach will require information concerning the network reconfiguration, remote measurements of voltages, real and reactive power as well as feeder currents in distribution substations. All kinds of statistical information pertaining to distribution transformer loads are used together with real-time remote measurements. In the proposed method, the existing scheme configuration is examined by a configuration pre-screening process based on the addressed references in an oriented graph. The permissible intervals for remote measurement errors and the reliability of statistical information are discussed. A practical example is presented and the exploitation of results has proved its accuracy and efficiency. >
219Â citations
TL;DR: In this article, power flow control in electric power systems by use of controllable series power capacitors and phase shifters is discussed and models suitable for incorporation in power flow programs are developed and analyzed.
Abstract: Power flow control in electric power systems by use of controllable series power capacitors and phase shifters is discussed. Models suitable for incorporation in power flow programs are developed and analyzed. The power flow control problem is defined in a stringent way, and a method for solving the power flow control problem is proposed based on decomposition. This method is applied on test systems and the convergence rate of the algorithm is discussed. Simplified models of the components are also derived. These simplified models are shown to be quite accurate in most situations, and are used to construct regions of feasible power flows of the controlled lines. >
187Â citations
Abstract: This paper introduces a decentralized control scheme for the parallel connection of multiple rectifiers feeding a DC network with numerous inverters. The coordination of multiple HVDC power systems without explicit communication is accomplished by the use of DC-side voltages as a "droop" mechanism. The DC side voltage serves the role of frequency in an ordinary AC system. The approach is most suitable to superconducting DC systems and to DC systems that span small distances and where voltage is relatively uniform throughout the DC system. This paper presents the concept in the context of a high capacity superconducting 10 kV urban infeed. >
Abstract: A history of polymeric insulators is given, beginning in the 1940s when organic insulating materials were used to manufacture high-voltage indoor electrical insulators from epoxy resins Their advantages and early experiences with them are given A bibliography covering mainly 1970 to the present is given >
TL;DR: In this paper, an electrical distribution system reconfiguration algorithm for reducing losses is presented, which calculates switching patterns as a function of time and shows that switching at the system peak can reduce losses, but may cause a marginal increase in system peak.
Abstract: An electrical distribution system reconfiguration algorithm for reducing losses is presented. The algorithm calculates switching patterns as a function of time. Either seasonal or daily time studies may be performed. A load estimation algorithm, which provides load information for each time point to be analyzed, can incorporate any or all of the following: spot loads, circuit measurements, and customer time-varying diversified load characteristics. Voltage dependence of loads is considered at the circuit level. It is shown that switching at the system peak can reduce losses, but may cause a marginal increase in system peak. Data structures used to model loads and to store switch configurations as a function of time are described. Example problems are provided to illustrate results. >
TL;DR: In this article, a systematic method to derive an optimal switching plan to achieve energy loss minimization for short-term and long-term operation of distribution systems is presented, which is further divided into several subproblems to find the largest energy loss reduction among all possible switching operations between two feeders.
Abstract: A systematic method to derive an optimal switching plan to achieve energy loss minimization for short term and long term operation of distribution systems is presented. The short term optimal switching criterion is developed by binary integer programming with a branch and bound technique. An overall optimization problem is formulated for the optimal switching operation. It is further divided into several subproblems to find the largest energy loss reduction among all possible switching operations between two feeders. A quick method is applied to estimate the largest loss reduction for each feeder-pair in the distribution system during short term switching operation. The composite load profile of each feeder is derived by field tests over a one year period. After determining the hourly optimal network configuration by taking into the account the typical daily load patterns for all the distributed feeders, the long term optimal criterion for each season is derived and the corresponding critical switches are determined. >
TL;DR: In this paper, the authors analyzed the damping of slow oscillations with active and reactive power modulation of high-voltage direct current (HVDC)-links with the aim of gaining a physical insight into the problem.
Abstract: Damping of slow oscillations with active and reactive power modulation of high-voltage direct current (HVDC)-links is analyzed with the aim of gaining a physical insight into the problem. The analysis shows that active power modulation is efficient when applied a short mass-scaled electrical distance from one of the swinging machines, and reactive power modulation is most efficient when a well-defined power flow direction exists and the modulation is made at a point close to the electrical midpoint between the swinging machines. It is shown that the intuitively appealing feedback signal frequency and derivative of the voltage are appropriate for active and reactive power modulation. The impact of the constraints imposed by the HVDC equations is analyzed, and it is determined when the implicit reactive power modulation resulting from constant gamma control may be detrimental for the damping. >
TL;DR: In this paper, a new type of series power capacitor controlled by thyristor switches is presented, and its major components, basic operating modes, and control/protection system are described.
Abstract: A new type of series power capacitor controlled by thyristor switches, is presented. Its major components, basic operating modes, and control/protection system are described. With respect to the first installation at the Slatt substation, the design, ratings, and test program are summarized. >
TL;DR: In this article, seven daymeasurements of harmonic current and voltage made at the main buses of industrial, commercial, and residential customers are reported, for a large residential load, an accounting operations building, a welded pipes plant, a passing and machining plant, large supermarket, and a retail store.
Abstract: Seven day-measurements of harmonic current and voltage made at the main buses of industrial, commercial, and residential customers are reported. The results are for a large residential load, an accounting operations building, a welded pipes plant, a passing and machining plant, a large supermarket, and a retail store. The results are representative of low-voltage buses in the northeast US. At all the locations it was found that 99% of the time the voltage total harmonic distortion was much smaller than 5% limit recommended by IEEE Std 519. The data provide the initial core of documentation for future reference and follow-up of the trends in harmonic levels at end users. >
TL;DR: In this paper, a simplified network approach to the VAr (volt-ampere reactive) control problem in a distribution system with lateral branches is presented, where the power capacitors are assumed to be located optimally at the feeder branches.
Abstract: A simplified network approach to the VAr (volt-ampere reactive) control problem in a distribution system with lateral branches is presented. According to this method, the power capacitors are assumed to be located optimally at the feeder branches. The optimal compensation levels (capacitor size) are represented by dependent current sources located at the branch connected buses. The solution of the equivalent circuit for the distribution system yields the values of the voltage at any bus. The actual compensation level is then determined by substituting the bus voltage in the dependent current source formula. The method can be used as an online controller and in the planning stage. It can be easily adapted in an expert system configuration. >
TL;DR: In this article, a model of a power transformer for the study of electromagnetic transients is presented, where the effects of eddy current in the damping of transients are evaluated.
Abstract: Eddy current effects are included in a model of a power transformer for the study of electromagnetic transients. Existing analytical formulae for the calculation of losses in the windings are evaluated. Various equivalent circuits are fitted to represent in the time domain the damping produced by eddy currents in the windings. A frequency dependent model is derived for the iron core, based on the physical distribution of losses and magnetization effects. The parameters of this model are obtained by optimal discretization of the laminations. Simulation show the effects of eddy current in the damping of transients. >
Journal Article•
TL;DR: The IEEE Simplified Method for computing lightning performance of overhead transmission lines was first described by Anderson [5] and has been used extensively in the application of the method and in the testing of various component models.
Abstract: The IEEE Simplified Method [33] for computing lightning performance of overhead transmission lines was first described by Anderson [5]. Since its publication, considerable experience has been obtained in the application of the method and in the testing of various component models. This paper describes application experience, sets out the theoretical basis for modifications and provides a framework for future advancements
TL;DR: In this article, the design and application requirements for solid state distribution current limiters and circuit breakers are described and compared to those for the electromechanical switchgear used in present day distribution systems.
Abstract: The design and application requirements for solid state distribution current limiters and circuit breakers are described and compared to those for the electromechanical switchgear used in present day distribution systems. Control strategies are provided for current limiting application in the power transformer main circuit and for current limiting and interruption for the bus tie location. >
TL;DR: A theoretical fuzzy information model is introduced and an inference scheme which yields the most consistent conclusion is proposed that allows various diagnostic methods to be combined in a systematic way.
Abstract: Methods for identifying transformer fault conditions include dissolved gas analysis, liquid chromatography, acoustic analysis, and transfer function techniques. Researchers have applied artificial intelligence concepts in order to encode these diagnostic techniques. These attempts have failed to fully manage the inherent uncertainty in the various methods. A theoretical fuzzy information model is introduced. An inference scheme which yields the most consistent conclusion is proposed. A framework is established that allows various diagnostic methods to be combined in a systematic way. Numerical examples demonstrate the developed system. >
TL;DR: A method is developed to reduce large power systems to single- and multiport frequency-dependent equivalents, which consist of simple RLC modules that faithfully reproduce the frequency characteristics of the network.
Abstract: A method is developed to reduce large power systems to single- and multiport frequency-dependent equivalents. These equivalents consist of simple RLC modules that faithfully reproduce the frequency characteristics of the network. The method is implemented in the EletroMagnetics Transient Program (EMTP) and has been tested at Ontario Hydro. The implementation involves a preprocessor program, the Frequency Dependent Equivalent (FDNE), to generate the model and a EMTP time step loop module to calculate the transient response. The use of the FDNE results in major reductions in computer time and is especially beneficial for multicase statistical EMTP studies. An example showing the accuracy and efficiency of the FDNE when used to reduce a large 500 kV network is presented. >
TL;DR: In this article, an alternative approach for accurately locating faults on teed feeders is described, which uses fault voltages and currents at all three ends of the feeder, independent of fault resistance and largely insensitive to variations in source impedance, teed and line configurations.
Abstract: The basis of an alternative approach for accurately locating faults on teed feeders is described. The technique developed uses fault voltages and currents at all three ends. The method is virtually independent of fault resistance and largely insensitive to variations in source impedance, teed and line configurations, including line untransposition. The basic theory of the technique is presented. It is extensively tested using simulated primary system voltage and current waveforms, which include the transducer/hardware errors encountered in practice. The performance clearly shows a high degree of accuracy. >
TL;DR: In this article, an approach based on fuzzy set theory is developed to estimate the loads in a distribution system and to devise a proper service restoration plan following a fault, which can provide valuable information to distribution system operators.
Abstract: An approach based on fuzzy set theory is developed to estimate the loads in a distribution system and to devise a proper service restoration plan following a fault. To estimate the loads on branching points without real-time meters, typical hourly load patterns for several types of days are established for commercial, industrial, and residential customers. These load patterns are characterized by some linguistic variables using fuzzy set notations. The load of a branching point is estimated through fuzzy set operations. With the estimated loads at hand, a heuristic search method is proposed in order to reach a restoration plan with minimal number of switching operations in a short time. To demonstrate the effectiveness of the proposed fuzzy approach, load estimation and service restoration on a distribution system within the service area of Taipei West District Office of Taiwan Power Company are examined. It is found that, following a fault event, a proper restoration plan can be reached very efficiently. Therefore, the proposed approach can provide valuable information to distribution system operators in reaching a service restoration plan. >
TL;DR: In this article, the results of a computer simulation of three real life 13.8 kV feeders supplying consumers with nonlinear loads which include CFLs (compact fluorescent lights) with electronic ballasts are presented.
Abstract: The results of a computer simulation of three real life 13.8 kV feeders supplying consumers with nonlinear loads which include CFLs (compact fluorescent lights) with electronic ballasts are presented. The computer simulations are supported by laboratory testing and in-the-home installation/monitoring of CFLs. The results are combined with load research information regarding residential load profiles to produce load models for use in computer simulation of the behavior of three distribution feeders. The input current to electronically ballasted CFLs has unusually high distortion, (THD (total harmonic distortion) >100%). The main conclusion is that for a 15 kV class feeder with a maximum 10 MVA load, the total load of electronically ballasted CFLs should not exceed 100 kW if the voltage THD is to be kept >
TL;DR: In this article, the behavior of 138 kV nonceramic line post insulators is investigated by means of clean fog tests conducted before and after aging in a specially designed accelerated aging chamber.
Abstract: The behavior of 138 kV nonceramic line post insulators is investigated by means of clean fog tests conducted before and after aging in a specially designed accelerated aging chamber. The laboratory aging cycles are justified on the basis of actual weather in the coastal regions of Florida. Analytical measurements quantifying the degree of artificial aging are discussed, and artificial aging is compared with service experience. Observations of audible noise and radio influence voltage during the clean fog tests are reported. >
TL;DR: In this article, the apparent power S and the power factor PF in unbalanced polyphase circuits with sinusoidal waveforms are defined and proved to have a definite physical meaning, leading itself to a convenient resolution in positive, negative and zero sequence, nonactive and active power.
Abstract: Definition for the apparent power S and for the power factor PF in unbalanced polyphase circuits with sinusoidal waveforms are presented. It is proved that the definition S/sup 2/=(V/sub a//sup 2/+V/sub b//sup 2/+V/sub c//sup 2/) (I/sub a//sup 2/+I/sub b//sup 2/+I/sub c//sup 2/) has a definite physical meaning, leading itself to a convenient resolution in positive, negative and zero sequence, nonactive and active power. It is suggested that the power factor be represented with the help of the ratio P/sup +//S, where P/sup +/ is the positive sequence active powers. >
TL;DR: In this article, the principle and fundamental characteristics of a solid-state current limiter using GTO thyristors were investigated to prevent voltage decrease of distribution systems, and the results indicated that the solid state current limter was a valuable protecting device for high fault current distribution systems.
Abstract: To prevent voltage decrease of distribution systems, the principle and fundamental characteristics of a solid-state current limiter using GTO thyristors were investigated. Basic components of the apparatus were a fast solid-state switch and a current limiting impedance of low resistance in parallel with the switch. Experimental results of the test current limiter showed the fault current was limited successfully, regardless of DC component size. The time from detection of fault occurrence to interruption of the fault current by the solid-state switch was 40 mu s. This time was very short in comparison with that before the fault current reached a large value. Thermal rise of the solid-state switch for conduction was solved by a self-cooling apparatus using a noncombustible cooling liquid. The results indicated that the solid-state current limiter was a valuable protecting device for high fault current distribution systems. >
TL;DR: In this paper, a study of the conductive materials of the natural contaminants accumulated on insulators in terms of equivalent salt deposit density (ESDD), not much attention has been paid to the basic consideration, such as its solubility in water, correction of its water solution to the standard temperature, etc.
Abstract: In the assessment of the conductive materials of the natural contaminants accumulated on insulators in terms of equivalent salt deposit density (ESDD), not much attention has been paid to the basic consideration, such as its solubility in water, correction of the conductivity of its water solution to the standard temperature, etc. A study was made on these important factors through repeated measurements of the actual contaminants on the insulators. As a result, practical precautions for the measurement of ESDD are indicated. Also, it is pointed out that the difference in the performance of the naturally and artificially contaminated insulators even with the same ESDD may be explained by the solubility of the materials and that the ambient temperature has a significant influence on the contamination flashover voltage. >