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Power Delivery, IEEE Transactions on

Issue 3 • Date July 2008

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Displaying Results 1 - 25 of 68
  • Table of contents

    Page(s): C1 - 1270
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    Freely Available from IEEE
  • IEEE Transactions on Power Delivery publication information

    Page(s): C2
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    Freely Available from IEEE
  • Fiber-Optics-Based Fault Detection in Power Systems

    Page(s): 1271 - 1279
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    A fiber-optics-based sensing network applicable for fault detection in power system is presented. The proposed scheme is secure and immune from interferences. At each monitoring location, passive rugged fiber-Bragg-grating-based sensors are deployed. They use fast and compact magnetostrictive transducers instead of current or potential transformers to translate current-induced magnetic field into optical signal. These sensors can be compensated for temperature drift and easily be integrated into an optical sensing network. A broadband light source at a substation scans the change in reflected optical power at a unique frequency band that corresponds to the surge in magnetic field associated with an increased fault current at a certain location. A unique feature of this real-time scheme is that it only requires current information for fault detections in both radial and networked systems with various pole structures and line configurations. It can easily coordinate with other protective devices and is free from any time-current coordination curves. The proposed scheme has been extensively tested by simulations. They confirm that the proposed scheme is able to detect the faults irrespective of the type and location. It also performs well in presence of harmonics, high impedance, and sensors malfunctions, as well as sensor noise. View full abstract»

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  • Fundamental Phasor Calculation With Short Delay

    Page(s): 1280 - 1287
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (362 KB) |  | HTML iconHTML  

    Fundamental phasors are used to monitor and control power systems. The conventional method of calculating the phasors is using a Fourier transform, which introduces a delay of at least one fundamental cycle. This paper examines the feasibility of exploiting an alternative using a direct-quadrature (DQ) transformation to calculate the phasors by extracting the fundamental component from a three-phase voltage or current in the DQ reference frame, which may be distorted by unbalanced components and harmonics. The proposed method allows obtaining a clean fundamental component of three-phase quantity with a minor delay less than one third of a fundamental cycle. View full abstract»

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  • New Method of Live Line Measuring the Inductance Parameters of Transmission Lines Based on GPS Technology

    Page(s): 1288 - 1295
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    Based on global positioning system (GPS) technology and differential equation algorithms, a new approach to live line measuring of the inductance parameters of transmission lines with mutual inductance is proposed. The principles and mathematical model of the new method are explained in detail. Data processing by least square algorithm is introduced. To take into account the influence of distributed capacitance of transmission lines, a modified mathematical model is introduced. The hardware structure of the measuring system is given and real-time digital simulator (RTDS) experimental results validate the accuracy of the test system. Finally, an example of live line measuring two 220-kV transmission lines with mutual inductances is given. A comparison of measurement results between the differential equation method and the conventional method is also shown. View full abstract»

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  • The Measurement of Reactive Energy in Polluted Distribution Power Systems: An Analysis of the Performance of Commercial Static Meters

    Page(s): 1296 - 1301
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    This paper presents a comparative analysis of the performances of both a traditional induction meter and various types of commercial static meters for reactive energy in the presence of harmonic distortion. This is a topical issue, since there are several types of static meters on the market, based on different principles of construction. In accordance with current standards, these meters are designed to operate in sinusoidal conditions and their performance is not tested in the presence of harmonic distortion. However, with the increase of pollution levels in power systems, the meters may be used even in the presence of distorted voltages and/or currents; in such cases, their accuracy may be very different from the nominal conditions, and the various meters may lead to different measurements of energy for the same load conditions. In this paper, the analysis is supported by several experimental tests, performed by means of a power calibrator. View full abstract»

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  • Development and Investigation of a New High-Speed Directional Relay Using Field Data

    Page(s): 1302 - 1309
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (659 KB) |  | HTML iconHTML  

    In this paper, a new high-speed directional relay is proposed. The relay is based on the current and voltage signals before and after fault occurrence. The voltage signal is compensated and then used as a reference. The relay is used for the directional comparison protection of extremely high voltage transmission lines. An evaluation of the suggested directional relay is investigated using recorded fault data from the Alberta power transmission system. The real effects of the power system elements, which might have not been completely considered in the mathematical model of the power system, have been included in the recorded real fault data. In this case, the performance of the new directional relay can be verified in a more realistic environment than simulation. View full abstract»

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  • Impact of Waveform Distorting Fault Current Limiters on Previously Installed Overcurrent Relays

    Page(s): 1310 - 1318
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (963 KB) |  | HTML iconHTML  

    This paper investigates in detail the impacts of distorted current waveforms, produced by certain types of fault current limiters on time-overcurrent protection relays. A thyristor-based solid-state fault current limiter is chosen as representative of such a device for a case study which investigates its effects on two coordinated protection relays. A detailed software model of the current limiter has been developed and implemented on the real-time digital simulator platform, modeling a typical distribution system. Relay models are used to obtain initial results, which are later validated by an actual protective relay connected in a hardware-in-the-loop simulation setup. The results illustrate the increase of relay tripping times due to severe current limitation caused by the fixed firing angle control of the current limiter. It is revealed that different current measurement principles employed by the relays, such as fundamental, peak, or true rms, can lead to miscoordination due to the distorted fault current waveform. It is demonstrated that these undesirable effects can be mitigated by employing appropriate control strategies for the firing angle in the current limiter. View full abstract»

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  • Ground Distance Relaying With Fault-Resistance Compensation for Unbalanced Systems

    Page(s): 1319 - 1326
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    Fault resistance is a critical variable in distance relaying. If not considered due to underreaching phenomenon, it may cause the misoperation of ground distance relays for internal faults. Still, as a consequence of the overreaching phenomenon, the unbalanced nature of loads and asymmetry of lines can affect the distance protection operation efficiency. Mainly due to these aspects, there is low precision in protection zone limits of ground distance relays. In this paper, a new algorithm is proposed to increase the precision of these limits, improving efficiency in the distance protection process. The proposed method is based in phase coordinates and uses a fault resistance estimate to develop the trip decision procedure. The results show that the algorithm is suitable for online applications, and that it has an independent performance from the fault resistance magnitude, the fault location, and the line asymmetry. View full abstract»

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  • Ultrasaturation Phenomenon in Power Transformers—Myths and Reality

    Page(s): 1327 - 1334
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB) |  | HTML iconHTML  

    In this paper, the ultrasaturation phenomenon of power transformers during their energization is studied. It is shown that under special conditions, the currents observed after transformer switching on do not contain enough restraining information (e.g., second harmonic), which may lead to protection maloperation. This paper concentrates on a thorough explanation of the problem and possible causes of ultrasaturation. Theoretical investigations are supported and illustrated with simulation studies performed both with MATLAB and electromagnetic transients program-alternative transients program. The outcomes of this research can further be used as hints for substation operation personnel as well as for the development of new protection stabilization criteria, which is not discussed further in this paper. View full abstract»

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  • Identifying the Primary Fault Section After Contingencies in Bulk Power Systems

    Page(s): 1335 - 1342
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (426 KB) |  | HTML iconHTML  

    This paper deals with the problem of fault section estimation in electric power systems, undertaken at a control center level and using information about the operation of protection relays and circuit breakers. The developed methodology should be used after the occurrence of contingencies with definitive disconnections, and before beginning the process of network restoration. Due to the absence of an analytic formulation, the problem calls for the use of artificial-intelligence techniques, such as neural networks and expert systems. Neural networks are employed to model the protection systems, dealing with the uncertainties involved with relay and circuit-breaker operation messages. An expert system is used to complement the results provided by the neural networks, considering the network topology. The results show that the developed methodology is applicable to real large-scale power systems. In addition, it is capable of noise suppression in relay and circuit-breaker trip messages, treats multiple faults naturally, and infers a solution even in cases when remote backup protection action occurs. View full abstract»

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  • Modeling and Protection of Hexagonal Phase-Shifting Transformers—Part I: Short-Circuit Model

    Page(s): 1343 - 1350
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (889 KB) |  | HTML iconHTML  

    Owing to several advantages over traditional phase shifters, applications of hexagonal phase-shifting transformers (PSTs) keep expanding. These transformers are built with unique connections of their windings, neither delta nor wye. Short-circuit modeling and analysis methods are not yet fully established for hexagonal phase shifters. This work is divided into two parts. In this part, a digital model of a hexagonal PST is developed and validated. This original material is of assistance when performing short-circuit system studies, relay setting calculations, as well as when modeling internal faults and developing protection techniques for the transformer itself. This paper explains construction of hexagonal PSTs, deriving their sequence impedances under varying taps and compares the model with manufacturer test data and a physical made-to-scale model developed specifically for this study. The transient model introduced in this paper can easily be integrated into the commonly used Alternate Transients Program and real-time digital simulator modeling environments. Part II of this work presents original protection methods for hexagonal PSTs. View full abstract»

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  • Modeling and Protection of Hexagonal Phase-Shifting Transformers—Part II: Protection

    Page(s): 1351 - 1358
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (206 KB) |  | HTML iconHTML  

    Owing to several advantages over traditional phase shifters, applications of hexagonal phase-shifting transformers (PSTs) keep expanding. These transformers are built with unique connections of their windings, neither delta nor wye. Modeling and protection methods are not yet fully established for hexagonal phase shifters. This work is divided in two parts. In Part I, a digital model of a hexagonal PST has been developed and validated. This part presents protection techniques for hexagonal PSTs. Several novel protection schemes have been developed based on ampere-turn balance equations of a hexagonal PST. These schemes include linear and nonlinear current-based protection methods, a power-based technique, and a phase comparison method. Protection schemes that require position of the tap changer for maximum sensitivity as well as a method to work without this extra information are presented. The developed techniques have been validated with digital and physical made-to-scale transformer models, and implemented on a general-purpose microprocessor-based relay platform. This material is of value to protection engineers facing the problem of protecting hexagonal PSTs. View full abstract»

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  • Under-Reach Correction in Twin Circuits Without Residual Current Input From the Parallel Line

    Page(s): 1359 - 1365
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB) |  | HTML iconHTML  

    Mutual coupling poses difficult problems witnessed during single phase to earth fault, in transmission line protection. In parallel lines on the same right of way, mutually coupled zero-sequence circuits cause error in the apparent impedance seen by the relay. This causes the distance relay at one end of the faulty line to over-reach while the one at the other end to under-reach. Incorrect sensing of the ground fault due to zero-sequence voltage inversion caused by mutually coupled zero-sequence network may lead to false trip of the neighbouring healthy line. The paper develops characteristic expressions for effective sequence impedances of twin circuit lines and presents a non-iterative microprocessor based algorithm for fault distance and under-reach estimation in real time, for under-reach correction in basic distance relaying scheme. The residual current measurement from the parallel circuit is not required for this purpose. View full abstract»

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  • A Universal Fault Location Technique for N-Terminal ({N}\geq q 3) Transmission Lines

    Page(s): 1366 - 1373
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB) |  | HTML iconHTML  

    This paper presents a universal fault location technique for N-terminal transmission lines based on synchronized phasor measurement units. The development of the technique is based on two-terminal fault location technique. The proposed algorithm is different from traditional multiterminal fault location techniques. We apply two-terminal fault location technique to N-terminal transmission lines and propose a novel fault section selector/fault locator. The proposed method has a very good tolerance. The proposed approach provides an analytical solution and its computational burden is very low since it does not require iterative operations. An extensive series of simulations were conducted to verify the accuracy of the proposed algorithm. The average fault location error under various fault conditions is well below 1%. View full abstract»

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  • Analysis of a Sort of Unusual Mal-Operation of Transformer Differential Protection Due to Removal of External Fault

    Page(s): 1374 - 1379
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB) |  | HTML iconHTML  

    Several cases of mal-operation of transformer differential protection with second-harmonic blocking after clearance of external fault are reported. These mal-operations all occurred at the nonrestraint region of percentage restraint plane. The previous theory cannot be utilized directly to analyze this phenomenon. Therefore, a mathematical model for analyzing the transient course of external fault inception and removal, together with the CT model involving the magnetic hysteresis effect, is proposed in this paper. It is proved that the magnetic linkage of one CT core can be pushed into the region nearby the saturation point by the high fault current with aperiodic component. As soon as the external fault is removed, the magnetic linkage formed by the primary current with low amplitude is not high enough to pull the operating point of the magnetic linkage back to the linear region. This phenomenon is named as CT local transient saturation, which results in the big measuring angle error and relative smooth waveform. In this case, the transformer differential protection using second harmonic blocking inevitably mal-operates. This point of view is verified with the simulation tests. View full abstract»

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  • An Experimental Validation for Broadband Power-Line Communication (BPLC) Model

    Page(s): 1380 - 1383
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    Recently, different models have been proposed for analyzing the broadband power-line communication (BPLC) systems based on transmission-line (TL) theory. In this paper, we make an attempt to validate one such BPLC model with laboratory experiments by comparing the channel transfer functions. A good agreement between the BPLC model based on TL theory and experiments are found for channel frequencies up to about 100 MHz. This work with controlled experiments for appropriate validation could motivate the application and extension of TL theory-based BPLC models for the analysis of either indoor or low-voltage or medium-voltage channels. View full abstract»

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  • Assessment of Information Security Levels in Power Communication Systems Using Evidential Reasoning

    Page(s): 1384 - 1391
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (546 KB) |  | HTML iconHTML  

    The purpose of this paper is to present a framework for assessing information security in power communication systems. The framework consists of dividing the communication system to be analyzed into its subcomponents and linking these to relevant evaluation criteria. In this study, the information security standard ISO 17799 has been used as a point of reference to define such evaluation criteria. The framework involves collecting data to evaluate each individual criterion and aggregating these evaluations using a robust algorithm. To cater for the many uncertainties in evaluating information security, the evaluation of the individual subcomponents is aggregated using a Dempster-Shafer based algorithm for evidential reasoning. This algorithm incorporates the many insecure facts and incomplete data that are inherent in large scale systems. The overall result is a set of indicators which highlight the level of information security within a studied communication system. The paper is concluded with a description of a case study in which the framework was applied to a communication system used for automatic meter reading (AMR). Experiences from this application are described in the paper. View full abstract»

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  • Indoor Power-Line Communications Channel Characterization Up to 100 MHz—Part I: One-Parameter Deterministic Model

    Page(s): 1392 - 1401
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2274 KB) |  | HTML iconHTML  

    Advanced communication technologies have allowed the power-line-communication (PLC) channel to be a transmission medium that enables the transfer of high-speed digital data over the classical indoor electrical wires. The development of PLC systems for Internet, voice, and data services requires measurement-based models of the transfer characteristics of the mains network suitable for performance analysis by simulation. This paper presents a deterministic model describing the magnitude and phase of complex transfer functions of power-line networks using only one parameter. First, a PLC channel classification is realized, and an average magnitude and phase channel model by class is proposed. Second, the multipath characteristic of PLC channels is introduced. A statistical-based channel magnitude generator is built, and a group delay-based phase model is suggested. View full abstract»

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  • Indoor Power-Line Communications Channel Characterization up to 100 MHz—Part II: Time-Frequency Analysis

    Page(s): 1402 - 1409
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    Estimations of coherence bandwidth and time-delay parameters from wideband channel sounding measurements made in the 30 kHz-100 MHz band in several indoor environments are described in and taken back in this paper. Powerline communications (PLC) modems rather see a channel which starts almost from 2 MHz . A comparison between coherence bandwidth and time-delay parameters estimated in both frequency bands 30 kHz-100 MHz and 2 MHz-100 MHz is elaborated in this paper. Results are intended for applications in high-capacity indoor power-line networks. The investigation is aimed to show that the PLC channel studies in a band starting from a frequency lower than 2 MHz distorts the real values that an implementer should take, as the PLC modem see only the frequencies from 2 MHz. The coherence bandwidth and the time delay parameters are estimated from measurements of the complex transfer functions of the PLC channels. For the 30 kHz-100 MHz frequency band, the 90 th percentile of the estimated coherence bandwidth at 0.9 correlation level stay above 65.5 kHz and below 691.5 kHz. It was observed to have a minimum value of 32.5 kHz. The maximum excess delay spread results show that 80% of the channels exhibit values between 0.6 s and 6.45 s. And a mean rms delay spread of 0.413 s is obtained. The passage to the 2 MHz-100 MHz frequency band induced an increase of the coherence bandwidth, whose min value is brought back to 43.5 kHz, and an important reduction of the time delay parameters: The min, max, mean, and standard deviation values of the maximum excess delay are almost divided by 2. For the twice frequency bands, this paper studies, also, the variability of the coherence bandwidth and time-delay spread parameters with the channel class , and thus with the location of the receiver with respect to the transmitter, and finally relates the rms delay spread to the coherence bandwidth. View full abstract»

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  • Closed-Form Expression of Nakagami-Like Background Noise in Power-Line Channel

    Page(s): 1410 - 1412
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    A closed-form expression for the real part of background noise is derived for the power-line channel modeled by Nakagami probability density function. Simulation with various parameters shows the derived expression's validity. The closed-form expression can be of benefit to communication system designers in that it facilitates the design of optimum receiver and its performance evaluation. View full abstract»

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  • A Simple Method for Evaluating Ground-Fault Current Transfer at the Transition Station of a Combined Overhead-Cable Line

    Page(s): 1413 - 1418
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    When a substation is fed by a combined overhead-cable transmission line, a significant part of the ground fault current flows through cable sheaths and is discharged into the soil at the transition station where cables are connected to the overhead line. Such a phenomenon, known as ldquofault application transfer,rdquo may result in high ground potentials at the transition station which may cause shocks and equipment damage. The scope of this paper is to present new analytic formulas which can be used for the direct calculation of the fault current transferred at the transition station and its ground potential rise as well as the substation earth current. The proposed formulas allow evaluating the influence of the main factors to the fault application transfer phenomenon and can be employed, at the preliminary design stage, to easily assess the most appropriate safety conditions to avoid dangerous effects. View full abstract»

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  • Impact of Energy End Use and Customer Interruption Cost on Optimal Allocation of Switchgear in Constrained Distribution Networks

    Page(s): 1419 - 1425
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    The introduction of new energy carriers, such as natural gas and district heating, to energy systems dominated by electrical power will certainly relieve stress on the power system. Some of the end uses initially served by the power system will be gradually decoupled and served by alternative energy carriers. As a result, the specific customer interruption costs and load profiles will change. In this paper, we analyze how the optimal level of switchgear in electric power distribution systems is affected by such changes. The proposed optimization method is based on a genetic algorithm and takes into account the constrained network capacity. View full abstract»

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  • A New Converter Transformer and a Corresponding Inductive Filtering Method for HVDC Transmission System

    Page(s): 1426 - 1431
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    A new converter transformer and an inductive filtering method are presented to solve the existing problems of the traditional converter transformer and the passive filtering method of the high-voltage direct current (HVDC) system. It adopts the ampere-turn balance of the transformer as the filtering mechanism. A tap at the linking point of the prolonged winding and the common winding of the secondary windings is connected with the LC resonance circuit. It can realize the goal that once theharmonic current flowsinto the prolonged winding, the common winding will induct the opposite harmonic current to balance it by the zero impedance design of the common winding and the proper configuration of LC parameters, so there will be no inductive harmonic current in the primary winding. Moreover, the reactive power that the converter needs can be partly compensated in the secondary winding. Simulation results have verified the correctness of the theoretical analysis. The new converter transformer can greatly reduce the harmonic content in the primary winding, loss, and noise generated by harmonics in the transformer, and the difficulty of the transformer's insulation design. View full abstract»

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  • Effect of Core Magnetization on Frequency Response Analysis (FRA) of Power Transformers

    Page(s): 1432 - 1438
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    This paper presents how the frequency response analysis (FRA) measurements on a transformer can be influenced by magnetization condition of the core. Measurements were performed on two transformers at different magnetization levels to show effects of remanent magnetization in the core due to removal of 3-supply, of relaxation demagnetization and of dc flux on the frequency response of winding impedance. The most important observations were that any sudden change of excitation field (applying or removing magnetization current) yields a slowly varying magnetic relaxation, which causes the impedance to change with time due to magnetic viscosity. Results of diagnostic measurements of transformer winding impedance can therefore depend on the level of remanent magnetic flux appearing in the core limbs after switching-off a transformer. These observations lead to a conclusion that, for avoiding the effects of core magnetization, diagnostic FRA measurements on power transformers should not be performed directly after disconnection from network. View full abstract»

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Aims & Scope

Installation and operation of apparatus, equipment, structures, materials and systems for the safe, reliable and economic generation, transmission, distribution, conversion, measurement and control of electric energy.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Wilsun Xu
Ph.D., P.Eng.
Dept. Electrical and Computer Eng.
University of Alberta
(9107 - 116 Street)
Edmonton, Alberta T6G 2V4 Canada
wxu@ualberta.ca
Phone:780-492-5965
Fax:780-492-1811