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Showing papers in "IEEE Transactions on Power Delivery in 1995"


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a unified power flow controller (UPFC) that is able to control both the transmitted real power and, independently, the reactive power flows at the sending-and the receiving-end of the transmission line.
Abstract: This paper shows that the unified power flow controller (UPFC) is able to control both the transmitted real power and, independently, the reactive power flows at the sending- and the receiving-end of the transmission line. The unique capabilities of the UPFC in multiple line compensation are integrated into a generalized power flow controller that is able to maintain prescribed, and independently controllable, real power and reactive power flow in the line. The paper describes the basic concepts of the proposed generalized P and Q controller and compares it to the more conventional, but related power flow controllers, such as the thyristor-controlled series capacitor and thyristor-controlled phase angle regulator. The paper also presents results of computer simulations showing the performance of the UPFC under different system conditions. >

997 citations


Journal ArticleDOI
TL;DR: The Static Condenser (STATCON) as discussed by the authors is a static condenser that is similar to the rotating synchronous condenser (SVC) and has similar output characteristics to those of the SVC.
Abstract: The availability of high power gate-turn-off (GTO) thyristors has led to the development of controllable reactive power sources, using electronic switching power converters, for use in power transmission systems This new technology has resulted in equipment that is fundamentally different from the conventional thyristor-controlled static VAr compensator (SVC) The new equipment is called a static condenser (STATCON) because its steady state output characteristics are similar to those of the rotating synchronous condenser The paper describes the fundamental operating principles, functional characteristics and basic control approach of the STATCON, with particular reference to a /spl plusmn/100 MVAr prototype planned to be installed at the Tennessee Valley Authority (TVA) Sullivan substation, USA This installation will be the first demonstration of a STATCON under the EPRI flexible AC transmission systems (FACTS) program, and will be the largest installation of its type in the world >

380 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the theoretical foundation and prototype implementation of a power system transient event detector for use in a nonintrusive load monitor (NILM), which determines the operating schedule of the major electrical loads in a building from measurements made at the electric utility service entry.
Abstract: This paper describes the theoretical foundation and prototype implementation of a power system transient event detector for use in a nonintrusive load monitor (NILM). The NILM determines the operating schedule of the major electrical loads in a building from measurements made at the electric utility service entry. The transient event detector extends the applicability of the NILM to challenging commercial and industrial sites. A spectral preprocessor for use in the transient event detector is introduced first. Then, the transient event detection algorithm is developed. The performance of the algorithm is illustrated with results from a prototype event detector. >

337 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented the general equations that relate the new concepts of instantaneous active and reactive power theory and the well known theory of symmetrical components for the case of 3-phase 4-wire systems, where zero sequence components and harmonics may be present in both voltages and currents.
Abstract: This paper presents the general equations that relate the new concepts of instantaneous active and reactive power theory and the well known theory of Symmetrical Components, for the case of 3-phase 4-wire systems, where zero sequence components and harmonics may be present in both voltages and currents. Based on these equations, new control algorithms for 3-phase 4-wire shunt and series active filters for unbalanced power systems are proposed and validated through simulations. The control algorithms presented here are very important for active power filter design and also for FACTS technology reactive power compensators. >

328 citations


Journal ArticleDOI
G. Benmouyal1
TL;DR: In this paper, the capability of popular digital filters used in relaying applications to suppress DC offset in current waveforms over a broad range of time constants as encountered on real power systems was investigated.
Abstract: This paper presents a theoretical investigation of the capability of popular digital filters used in relaying applications to suppress DC offset in current waveforms over a broad range of time constants as encountered on real power systems. First, three mathematical performance indices are introduced to be able to compare filters on the same basis. Then the concept of the FIR type of digital mimic filter is described. It is shown that, for filters exhibiting a null response at frequency zero on their frequency response, the addition of a digital mimic circuit, tuned to the middle of the range of time constants to be suppressed, will almost completely eliminate the effect of an exponentially decaying component. Moreover, this is possible without sacrificing the original response speed, although it increases susceptibility to noisy components. >

296 citations


Journal ArticleDOI
TL;DR: A new approach to fault classification for high speed protective relaying based on the use of neural network architecture and implementation of digital signal processing concepts is presented and its effectiveness in computer simulations on parallel transmission lines is shown.
Abstract: This paper presents a new approach to fault classification for high speed protective relaying and show its effectiveness in computer simulations on parallel transmission lines. The scheme is based on the use of neural network architecture and implementation of digital signal processing concepts. We begin by classifying several fault types like 1-phase-to-ground, 2-phase-to-ground and 3-phase-to-ground faults. We proceed with classification of arcing and nonarcing faults in order to obtain a successful automatic reclosing. Encouraging results are shown and indicate that this approach can be used for supporting a new generation of very high speed protective relaying systems. >

286 citations


Journal ArticleDOI
TL;DR: In this paper, a power line conditioner consisting of two small rating series active filters and a shunt passive filter is proposed to reduce voltage distortion at the connection point, and eliminate harmonic currents escaping into the system upstream of the connection points.
Abstract: This paper proposes a new power line conditioner consisting of two small rating series active filters and a shunt passive filter. The power line conditioner aims at a general filtering system which will be installed at the point of common coupling in a power system feeding harmonic-sensitive loads and unidentified harmonic-producing loads. One of the two active filters is connected in series with the supply, while another is in series with the shunt passive filter. The purpose of the power line conditioner is to reduce voltage distortion at the connection point, and is to eliminate harmonic currents escaping into the system upstream of the connection point. A control scheme of the two series active filters which play an important role is described in this paper. Its filtering characteristics are discussed with the focus on voltage and current distortion. A prototype model of 20 kVA is constructed to verify the functionality and performance of the power line conditioner. >

209 citations


Journal ArticleDOI
TL;DR: A fault direction discriminator that uses an artificial neural network (ANN) for protecting transmission lines and is suitable for realizing an ultrafast directional comparison protection of transmission lines is described.
Abstract: This paper describes a fault direction discriminator that uses an artificial neural network (ANN) for protecting transmission lines. The discriminator uses various attributes to reach a decision and tends to emulate the conventional pattern classification problem. An equation of the boundary describing the classification is embedded in the multilayer feedforward neural network (MFNN) by training through the use of an appropriate learning algorithm and suitable training data. The discriminator uses instantaneous values of the line voltages and line currents to make decisions. Results showing the performance of the ANN-based discriminator are presented in the paper and indicate that it is fast, robust and accurate. It is suitable for realizing an ultrafast directional comparison protection of transmission lines. >

198 citations


Journal ArticleDOI
TL;DR: In this article, the authors present preliminary results from a national monitoring program designed to characterize power quality levels on electric distribution systems, which is being sponsored by the Electric Power Research Institute.
Abstract: This paper presents preliminary results from a national monitoring program designed to characterize power quality levels on electric distribution systems. The monitoring program is being sponsored by the Electric Power Research Institute. Initial stages of the project resulted in the development of a new power quality monitoring instrument (designated the PQNode). This instrument permits simultaneous monitoring of steady state quantities (RMS voltage and current, harmonic distortion levels, power factor, etc.) and disturbances (voltage sags, overvoltages, transients, etc.). Approximately 200 PQNodes have been installed on distribution systems of 24 different utility companies. Monitoring data is being compiled by Electrotek Concepts in Knoxville, TN. The paper describes the monitoring system and presents preliminary results of the monitoring effort. >

183 citations


Journal ArticleDOI
TL;DR: In this article, a hybrid filter topology and its control to prevent harmonic currents from entering the power system is presented, and the proposed topology enables practical implementation of active harmonic current filters.
Abstract: Use of nonlinear loads and devices in power systems is expected to grow rapidly. Examples are thyristor-controlled inductors for FACTS, converters for HVDC transmission and large adjustable speed drives. All of these loads inject harmonic currents into the power system. A novel hybrid filter topology and its control, to prevent such harmonic currents from entering the power system, are presented in this paper. Analysis shows that in the proposed filter, the power electronic converter, required to generate harmonic currents for compensation, has a rating of only 9% when compared to the converter rating in an active filter and approximately one-half of that in a series-hybrid filter discussed in the literature. The proposed topology enables practical implementation of active harmonic current filters. The control of this filter under transient conditions such as start-up and during steady state is demonstrated by means of simulations. Results from a scaled-down hardware prototype are presented to verify the simulations. >

165 citations


Journal ArticleDOI
TL;DR: In this paper, the results of simulations were used to predict the net harmonic currents produced by large numbers of single-phase desktop computers in a facility, such as a commercial office building.
Abstract: In this paper we use the results of simulations to predict the net harmonic currents produced by large numbers of single-phase desktop computers in a facility, such as a commercial office building. We take into account attenuation due to system impedance and voltage distortion, as well as diversity in harmonic current phase angles due to variations in power and circuit parameters. Using experimental and published data we establish ranges of circuit parameters for an equivalent 120 V, 100 W "base computer unit" and branch circuit, update our computer modeling code (described in previous papers) to iteratively handle the interaction between current and voltage harmonics, and use the code to predict the net harmonic injection currents at the point of common coupling (PCC) represented by a shared transformer connected to a stiff power system. The key contributions of this paper are: providing estimates of the net harmonic current injection due to distributed single-phase computer loads in Amps/kW, as well as in percent of fundamental current, for a wide range of system loading and voltage distortion conditions; and illustrating that the reduction in harmonic currents due to phase angle diversity (expressed in Amps/kW) is relatively independent of system loading, whereas the reduction due to attenuation increases significantly with system loading. >

Journal ArticleDOI
TL;DR: In this paper, an experimental investigation was performed on a UHV tower model for the EMTP multiconductor calculation of lightning overvoltage at substations associated with back-flashover at an adjacent transmission tower.
Abstract: An experimental investigation was performed on a UHV tower model for the EMTP multiconductor calculation of lightning overvoltage at substations associated with back-flashover at an adjacent transmission tower. The various lightning surge response characteristics were measured on an actual UHV tower, and parameters of a multistory transmission tower model that can reproduce voltages across the insulator strings, voltages of the crossarms, and voltages of the power lines were determined. A value of 120 /spl Omega/ was determined as the surge impedance at each section of the multistory tower model, which closely agreed with the tower surge impedance measured for the UHV tower alone. >

Journal ArticleDOI
TL;DR: In this article, the authors present a model for TCSC which is applicable for typical transient and oscillatory stability studies and discuss relevant information to extend the modeling detail of the TCSC for use with long-term stability analysis.
Abstract: Thyristor-controlled series compensation (TCSC) is expected to be applied in transmission systems to achieve a number of benefits. To ensure best use of this new controller, planning engineers require analysis capability tailored to the specific performance characteristics of the TCSC. This paper presents a model for TCSC which is applicable for typical transient and oscillatory stability studies. Also included is a discussion on relevant information to extend the modeling detail of the TCSC for use with long-term stability analysis. >

Journal ArticleDOI
TL;DR: In this paper, the interactions between the incremental changes of current harmonic phasors injected by a power system NL (nonlinear load) and the resulting variations of harmonic voltages and powers are analyzed.
Abstract: This paper analyses the interactions between the incremental changes of current harmonic phasors injected by a power system NL (nonlinear load) and the resulting variations of harmonic voltages and powers. It proves that it is not always possible, following simple measurements of individual harmonic powers, to decide if a certain harmonic current is harmful or useful. It is suggested that the NL "distortion" be evaluated with the help of a quantity called non60 Hz (nonfundamental) apparent power. >

Journal ArticleDOI
TL;DR: In this article, the authors investigated the possibility of using the multilevel gate turn-off (GTO) thyristor inverter as an advanced static VAr compensator (STATCON).
Abstract: This paper investigates the possibility of using the multilevel gate turn-off (GTO) thyristor inverter as an advanced static VAr compensator (STATCON). The studies have indicated that the design shows promise and that the fundamental frequency switching of the GTO thyristors is superior to various forms of pulse-width modulation. The main advantages of the multilevel STATCON over other types of STATCON is that each individual GTO thyristor is clamped to a DC voltage and can be switched independently. Hence a staircase type of output voltage can be used to reduce the harmonics, the filtering requirements and the switching losses. >

Journal ArticleDOI
TL;DR: A multi-criteria algorithm is developed based on fuzzy sets for the decision making part of the scheme and can enhance the sensitivity and selectivity of the digital relay and mitigate problems associated with conventional relay schemes.
Abstract: This paper presents a digital relay scheme for the primary protection of power transformers. A multi-criteria algorithm is developed based on fuzzy sets for the decision making part of the scheme. The cost of wrong decision-making and the amount of information inflow are used along with several standard criteria to improve the reliability of the protection. It is shown that the proposed scheme, if properly tuned, can enhance the sensitivity and selectivity of the digital relay and mitigate problems associated with conventional relay schemes. >

Journal ArticleDOI
TL;DR: In this article, a numerical algorithm for power transmission network arcing faults detection has been developed, where important features of a long arc in air are investigated and used as a basis in the algorithm design.
Abstract: To avoid automatic reclosing on permanent faults, a new numerical algorithm for power transmission network arcing faults detection has been developed. Some important features of a long arc in air are investigated and used as a basis in the algorithm design. The fact that the nonlinear arc behavior influences other voltages and currents distorting them, offered an opportunity to detect the arc by measuring and processing the transmission line terminal voltage and current. A series of simulation studies have shown that the algorithm can be used as an effective tool for arcing faults detection. >

Journal ArticleDOI
TL;DR: In this paper, the effect of supply voltage harmonics on the response of single-phase capacitor-filtered diode bridge rectifier loads was investigated, and a complete analytical model for calculating the current harmonics of these loads, when energized by nonsinusoidal supply voltages, was presented.
Abstract: This paper describes the effect of supply voltage harmonics on the response of single-phase capacitor-filtered diode bridge rectifier loads. A complete analytical model for calculating the current harmonics of these loads, when energized by nonsinusoidal supply voltages, is presented. The model is then used to investigate the effect of supply voltage harmonics on current harmonics. The key findings of the paper are as follows: (1) the phase angles of supply voltage harmonics determine whether or not these harmonics increase or decrease current distortion. In general, a peaked voltage wave increases input current distortion, whereas a flattened wave has the opposite effect. Because of this complex relationship, voltage crest factor is a much better predictor of total harmonic current distortion than is total harmonic voltage distortion. (2) The current harmonics created by these loads produce voltage harmonics that tend to have a partial self-compensating effect on the current harmonics. >

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the flashover mechanism of silicone rubber composite insulators and found that it is attributed to the hydrophobicity of the silicone rubber and the diffusion of low molecular weight (LMW) polymer chains.
Abstract: Experimental results show that the contamination performance of silicone rubber composite insulators is better than porcelain insulators. This is attributed to the hydrophobicity of the silicone rubber. This suggests that the flashover mechanism of these insulators is different. This paper experimentally investigates contamination build-up, diffusion of low molecular weight (LMW) polymer chains, surface wetting, electrical field caused interaction between droplets, generation of conductive regions and filaments, field intensification caused spot discharge and the ultimate flashover of silicone rubber along wetted filaments. The studies resulted in a new flashover mechanism, which provides a better understanding of the superior performance of silicone rubber outdoor insulators. The results will be useful for the development of improved laboratory test procedures and to evaluate composite insulators' performance in contaminated conditions. The part of the paper describes an overview of the flashover mechanism and the diffusion of LMW polymer chains and wetting of the silicone rubber surface in detail. >

Journal ArticleDOI
TL;DR: In this paper, a field observation of ice accretion on Hydro-Quebec HV insulators was carried out, as well as a laboratory investigation of the AC flashover performance of various types of insulators covered with artificial ice.
Abstract: A field observation of ice accretion on Hydro-Quebec HV insulators was carried out, as well as a laboratory investigation of the AC flashover performance of various types of insulators covered with artificial ice. The field observations made it possible to identify the type and physical aspect of naturally occurring ice accretions produced during freezing rain precipitation. The laboratory investigation was conducted in a 4.8/spl times/2.8 m/spl times/3.8 m climate room using a HV transformer of 120 kV, 240 kVA with a short-circuit impedance of 5%. A method based on the standard IEC 507 method was developed for measuring the maximum withstand voltage (V/sub WS/) of ice-covered insulators. Various factors were investigated, including the effects on the insulator V/sub WS/ of such particulars as type, thickness, and uniformity of the ice, as well as the arcing distance of the insulators and the conductivity of freezing water. The effects of uniform ice, 2 cm thick, on 5 IEEE insulator units was thus considered to be equivalent to the effect of an ESDD of about 0.13 mg/cm/sup 2/ on the same insulators. >

Journal ArticleDOI
TL;DR: The Harmonic-Adjusted Power Factor (HAPF) as mentioned in this paper is a power factor based approach to encourage both the utility and the consumer to remain within the limits described in IEEE 519.
Abstract: IEEE Recommended Practice 519 sets specific limits on harmonic voltages and currents at the "point of common coupling", which is usually interpreted as the revenue meter. Although most electric utilities will employ these limits simply to persuade and encourage their customers to reduce harmonics (and vice versa), it is also possible to construct economic incentives to encourage both the utility and the consumer to remain within the limits described in IEEE 519. This paper discusses seven approaches to this challenge, and discusses the advantages disadvantages of each. It appears that "harmonic-adjusted power factor" approach is practical, justifiable, compatible with existing rate structures, and relatively easy to implement. >

Journal ArticleDOI
TL;DR: In this paper, a new islanding protection algorithm described in the paper has been developed to be part of an integrated protection package to cover all the protection requirements of a DSG.
Abstract: The ability to detect when dispersed storage and generation (DSG) units become islanded from the main source of generation enables the DSG to be quickly disconnected from the utility network and for that network to be rebuilt in a safe and orderly manner. The new islanding protection algorithm described in the paper has been developed to be part of an integrated protection package to cover all the protection requirements of a DSG. A selection of the results obtained from extensive laboratory and field tests are presented and show that the algorithm reliably trips for islanding conditions within 120 milliseconds, trips for load fluctuations should the DSG be operating independent of the main source of supply and restrains for single phase faults close to the DSG. >

Journal ArticleDOI
TL;DR: An algorithm, which is based on Kalman filter estimation, can be used to predict the instantaneous flicker level and is developed to estimate the instantaneous magnitude and frequency of the voltage flicker.
Abstract: Voltage flicker refers to a slow-0.5 to 30 Hz-modulation of the power system voltage magnitude. This periodic fluctuation can be modelled as an amplitude modulated signal, where the fundamental power frequency represents the carrier signal and the voltage flicker represents the modulating signal. An algorithm based on this premise is developed to estimate the instantaneous magnitude and frequency of the voltage flicker. The algorithm, which is based on Kalman filter estimation, can also be used to predict the instantaneous flicker level. >

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a new method of harmonic power detection based on the instantaneous active power in three-phase circuits, and its applications to search for dominant harmonic sources in power systems.
Abstract: This paper presents a new method of harmonic power detection based on the instantaneous active power in three-phase circuits, and its applications to search for dominant harmonic sources in power systems. The proposed method requires only band elimination filters and a three-phase active power meter to detect the harmonic active power, and it is able to deal with harmonic power flow more easily and precisely than a conventional meter which is based on Fourier series of single-phase circuits. In addition, measurement errors of the harmonic power are discussed theoretically. The validity of the proposed method is demonstrated by digital simulation. >

Journal ArticleDOI
TL;DR: In this paper, the variations of Prony's parameters in terms of some of the power systems characteristics (distance between the busbar and the fault, fault resistance and capacitive current of the whole network) are presented.
Abstract: Prony's method is a technique for estimating the modal components present in a signal. Every modal component is defined by four parameters frequency, magnitude, phase, and damping. This method is used to analyse earth fault currents in Petersen-coil-protected 20 kV networks. The variations of Prony's parameters in terms of some of the power systems characteristics (distance between the busbar and the fault, fault resistance and capacitive current of the whole network) are presented. It is shown that some of the Prony's parameters relating to the fault current transient may be useful to determine what kind of fault occurred, and where it occurred. >

Journal ArticleDOI
TL;DR: In this article, the authors present a power swing blocking principle that has the ability to immediately clear the block when a fault occurs within the relay trip zone, which is demonstrated for extremely fast power swings.
Abstract: Any sudden change in the configuration or the loading of an electrical network causes power swings between the load concentrations of that network. In order to prevent the distance protection from tripping during such conditions, a power swing blocking device is often utilized. Conventional power swing blocking devices cannot cope with very fast power swings of up to 5 Hz/sec. This paper presents a new power swing blocking principle that has the ability to immediately clear the block when a fault occurs within the relay trip zone. This is demonstrated for extremely fast swings (greater than 5 Hz/sec) and even for two phase operation (during single pole tripping). This new principle is in a form which can be implemented on an existing digital distance protection relay. Results are presented based on extensive simulation studies carried out on a typical 400 kV system, using the Electromagnetic Transient Program (EMTP) software. >

Journal ArticleDOI
TL;DR: In this article, the performance of a new transformer diagnosis method is tested experimentally and two test series are carried out to evaluate the method on transformers, a sensitivity test series and an ageing test series.
Abstract: In this paper the performance of a new transformer diagnosis method is tested experimentally. The method is called model-based diagnosis because the diagnosis is based on an identified model of the component-the transfer function. Two test series are carried out to evaluate the method on transformers, a sensitivity test series and an ageing test series. The purpose of the sensitivity test series is to determine how close the identified transformer model is connected to the physical condition of the modelled transformer. The purpose of the ageing test series is to determine if it is possible to identify a development in the transfer function of the transformer towards breakdown. Based on the two test series it is concluded that the detection of failures and ageing phenomena in transformers by transfer functions is dependent on detectable changes in relatively few characteristic transformer parameters-basically lumped winding capacitances, total losses and core reluctance. >

Journal ArticleDOI
TL;DR: In this article, the authors compared the two coupling models most frequently used in the power-lightning literature for the calculation of lightning-induced overvoltages, namely, Chowdhuri and Gross (1967) and the model by Agrawal, Price and Gurbaxani (1980).
Abstract: The two coupling models most frequently used in the power-lightning literature for the calculation of lightning-induced overvoltages, namely the model by Chowdhuri and Gross (1967) and the model by Agrawal, Price and Gurbaxani (1980), are compared and discussed. It is shown that the Chowdhuri-Gross model is incomplete: the source term due to the contribution of the magnetic induction is missing. The authors investigate how much the lack of the source term affects the accuracy of the calculated overvoltages. Experimental tests of the two models using a short line illuminated by a NEMP simulator support the theoretical conclusion. >

Journal ArticleDOI
TL;DR: In this article, a simplified high-frequency model for three-phase, two-and three-winding transformers is presented, based on the classical 60 Hz equivalent circuit, extended to high frequencies by the addition of the winding capacitances and the synthesis of the frequency-dependent short-circuit branch by an RLC equivalent network.
Abstract: This paper presents a simplified high-frequency model for three-phase, twoand three-winding transformers. The model is based on the classical 60 Hz equivalent circuit, extended to high frequencies by the addition of the winding capacitances and the synthesis of the frequency-dependent short-circuit branch by an RLC equivalent network. By retaining the T-form of the classical model, it is possible to separate the frequency-dependent series branch from the constant-valued shunt capacitances. Since the short-circuit branch can be synthesized by a minimum-phase-shift rational approximation, the mathematical complications of fitting mutual impedance or admittance functions are avoided and the model is guaranteed to be numerically absolutely stable. Experimental tests were performed on actual power transformers to determine the parameters of the model. EMTP simulation results are also presented. >

Journal ArticleDOI
TL;DR: In this article, a frequency scanning method is introduced to obtain a more accurate frequency characteristic for identifying harmonic instability in HVDC power systems, and an example of the application is used to identify the resonance frequencies in the CIGRE benchmark model.
Abstract: A frequency scanning method is introduced in the paper to obtain a more accurate frequency characteristic for identifying harmonic instability in HVDC power systems. An example of the application is used to identify the resonance frequencies in the CIGRE benchmark model. The paper shows that the benchmark model is not tuned to the resonance frequency that it was designed for. Using the scanning method, the resonance frequency of the benchmark model maybe shifted to demonstrate a simulation of core-saturation type instability. >