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Power Delivery, IEEE Transactions on

Issue 2 • Date Apr 2001

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Displaying Results 1 - 25 of 33
  • Algorithm to predict dry-band arcing in fiber-optic cables

    Publication Year: 2001 , Page(s): 286 - 291
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    Utilities frequently use ADSS (all dielectric self-supporting) fiber-optic cables installed on transmission lines 3-6 m below the high voltage conductors. Dry-band arcing occurs on the fiber-optic cables when the cables are polluted and wet. This has been assumed to cause cable failures. An equivalent circuit has been developed to represent the polluted fiber-optic cable in the high voltage environment. The objective of this paper is to present a novel numerical method that can be used to predict dry-band arcing in fiber-optic cables. KCL (Kirchoff's current law) is used to derive node point equations for the equivalent circuit. Forward elimination and backward substitution of node voltage is used to solve the equations. The effect of pollution, tower arrangement, and conductor sag is analyzed. The numerical method has speed advantages over circuit simulation methods. This method includes conductor sag, nonuniform pollution, and variable capacitance. This algorithm can be used to predict dry band arcing in fiber-optic cables View full abstract»

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  • Communications technology guidelines for EMS/SCADA systems

    Publication Year: 2001 , Page(s): 181 - 188
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    The purpose of this Guideline Technical Paper is to provide a summary of the different communications technologies available for use or application with EMS/SCADA system projects. All of the various communication media are addressed with a brief description along with tables of the advantages and disadvantages of each and recommendations for choosing the most appropriate communication technology. The technologies discussed are: twisted pair metallic cable; coaxial metallic cable; fiber optic cable (either optical power ground wire (OPGW), all dielectric self supporting (ADSS), or wrapped types (WOC)); distribution line carrier (DLC); power line carrier (PLC); satellite (VSAT, LEO, others); leased service; VHF radio (mobile); point-to-point UHF radio; multiple address radio system (MARS) 400/900 MHz UHF radio; trunked mobile UHF radio; spread spectrum UHF radio (monitor frequency for potential interference before installation); and microwave radio (2-40 GHz) View full abstract»

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  • Influence of fault arc characteristics on the accuracy of digital fault locators

    Publication Year: 2001 , Page(s): 195 - 199
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    This paper proposes a time domain model of a fault locator with special reference to fault are nonlinearities by applying the MODELS language of the EMTP. It has been found that an impedance relay type locator is significantly influenced by the fault arc nonlinearities, while the current diversion ratio method is not influenced. This validates the advantage of the current diversion approach over the impedance approach View full abstract»

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  • Optimal trade-offs in distribution protection design

    Publication Year: 2001 , Page(s): 292 - 296
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    The number, type and location of the protective devices on a distribution feeder have a direct effect on the system reliability. In earlier work, a technique was developed to design a protective system in order to minimize the SAIFI index. This paper extends earlier results by using a goal programming approach to achieve compromises among various engineering objectives. The design goals are: (1) to minimize the SAIFI and ASIFI indices by identifying types and locations of protective devices; and (2) to achieve a reasonable trade-off between a decrease in the SAIFI index and an increase in MAIFI index by identifying where a fuse saving scheme should be applied. Numerical examples highlight the approach View full abstract»

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  • Correction of current transformer distorted secondary currents due to saturation using artificial neural networks

    Publication Year: 2001 , Page(s): 189 - 194
    Cited by:  Papers (29)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    Current transformer saturation can cause protective relay misoperation or even prevent tripping. This paper presents the use of artificial neural networks (ANN) to correct current transformer (CT) secondary waveform distortions. The ANN is trained to achieve the inverse transfer function of iron-core toroidal CTs which are widely used in protective systems. The ANN provides a good estimate of the true (primary) current of a saturated transformer. The neural network is developed using MATLAB and trained using data from EMTP simulations and data generated from actual CTs. In order to handle large dynamic ranges of fault currents, a technique of employing two sets of network coefficients is used. Different sets of network coefficients deal with different fault current ranges. The algorithm for running the network was implemented on an Analog Devices ADSP3101 digital signal processor. The calculating speed and accuracy proved to be satisfactory in real-time application View full abstract»

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  • Investigating the impact of embedded generation on relay settings of utilities electrical feeders

    Publication Year: 2001 , Page(s): 246 - 251
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    Since the late 1970s, intensive efforts have been made to utilize renewable energy sources to generate electric power. On the other hand, economical pressure experienced in recent years has led to the development of high efficiency combined heat and power schemes to use the normally wasted heat to generate electric power. Generators used under both schemes can be either synchronous or asynchronous types and when they are integrated into utilities' distribution networks (DNs) they are commonly known as “embedded generators” (EGs). Previous experience has shown that the integration of EGs into DNs could create safety and technical problems. They may contribute to fault currents, cause voltage flicker, interfere with the process of voltage control, etc. This paper reports an investigation to determine the impact of the integration of EGs on the settings of protective devices of electrical feeders emanated from the substation to which EGs are connected. This study also covers the dynamic behavior of EG caused by disturbances on the host network. Results obtained from several case studies presented and discussed View full abstract»

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  • The optimization of spectral analysis for signal harmonics

    Publication Year: 2001 , Page(s): 149 - 153
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    FFT has been applied to technologies of spectrum analysis widely. However, since the signal sampling is at random, and FFT suffers specific restrictions, some defects inevitably occur, which means that harmonic parameters do not show on the spectrum exactly. These defects result from frequency scales not matching signal characteristics. This paper discusses the optimization of spectrum analysis for signal harmonics. By means of scale fine-tuning, the frequency scales will match the signal characteristics. The method eliminates both of the picket-fence effect and the leakage effect; it makes the harmonic parameters show on the spectrum more accurately. This paper takes reasonable and practical evaluations to verify the theory View full abstract»

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  • An optimal and flexible control strategy for active filtering and power factor correction under non-sinusoidal line voltages

    Publication Year: 2001 , Page(s): 297 - 305
    Cited by:  Papers (48)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    This paper gives a new insight into the concept of load compensation under distorted voltages. Achieving both unity power factor (UPF) and perfect compensation of current harmonics are not possible where competition will arise between these two important factors. Through evaluating the present control strategies, a generalized, optimal, and flexible control strategy (OFC) for harmonic compensation of utility lines is proposed. The proposed control strategy, which provides a unified and highly flexible compensation framework has the ability of programming for perfect current harmonics compensation, or (UPF) accomplishment, or other newly defined objectives such as maximizing the power-factor subject to some adjustable constraints on the level of current harmonics and unbalancing via an on-line optimization algorithm. The strategy can fulfill the IEEE-519 standards requirements, while guaranteeing the best achievable power factor and optimum required rating for the compensator. Theoretical concepts and practical features of the proposed control strategy have been shown through extensive simulation studies using MATLAB/SIMULINK programs View full abstract»

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  • A fundamental approach to transformer thermal modeling. I. Theory and equivalent circuit

    Publication Year: 2001 , Page(s): 171 - 175
    Cited by:  Papers (98)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    A simple equivalent circuit to represent the thermal heat flow equations for power transformers is presented. Key features are the use of a current source analogy to represent heat input due to losses, and a nonlinear resistor analogy to represent the effect of air or oil cooling convection currents. The effect was first quantified in 1817. It is shown that the idea of “exponential response” is not the best way to think of the dynamics of the situation. It is also shown that one can consider ambient temperature to be a variable input to the system, and that it is properly represented as an ideal voltage source View full abstract»

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  • Salt fog testing of polymer housed surge arresters

    Publication Year: 2001 , Page(s): 252 - 258
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    This paper deals with the evaluation of the insulation design of polymer housed surge arresters for distribution lines. Five commercial designs were tested in a salt fog chamber for 9 cycles using a cycle consisting of 120 hours of salt fog that was followed by a 48 hour rest period for a total of 1280 hours of salt fog. In these tests, the specification for the 1000-hour salt fog test in IEC 1109 for composite insulators was used as a guide. The results demonstrate that a comprehensive evaluation of the external and internal insulation design of polymer housed surge arresters can be obtained by performing a salt fog test, and as such, the test can be considered as a useful design test. Suggestions for improvements in the insulation design of all polymer housed surge arresters evaluated are given in the paper View full abstract»

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  • Analysis and performance evaluation of a distribution STATCOM for compensating voltage fluctuations

    Publication Year: 2001 , Page(s): 259 - 264
    Cited by:  Papers (71)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    Controller design of a STATCOM-based voltage compensator requires a valid analytical model of the system. If phasor algebra is used for modeling, it is difficult to accurately describe the STATCOM behavior during compensation of subcycle transients in the PCC voltage. In this paper, a small-signal model of the system, with a distribution line, is derived. Predictions based on frequency-domain analysis are made, which are validated by experimental results. This model, therefore, can be used for controller design where subcycle voltage transients are to be compensated. It is shown that the voltage controller, so designed, can accomplish voltage sag mitigation. A discussion on the design of DC bus voltage controller-and experimental results showing its performance-is also included View full abstract»

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  • Development and implementation of an ANN-based fault diagnosis scheme for generator winding protection

    Publication Year: 2001 , Page(s): 208 - 214
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    In this paper, the development and implementation of a new fault diagnosis scheme for generator winding protection using artificial neural networks (ANN) is introduced. The proposed scheme performs internal fault detection, fault type classifications and faulted phases identification. This scheme is characterized with higher sensitivity and stability boundaries as compared with the differential relay. Effect of the presence of nonsynchronous frequencies on the scheme performance is examined. Effect of different values of ground resistance on ground fault detection sensitivity is outlined. The scheme hardware is implemented based on a digital signal processing (DSP) board interfaced with a multi input/output (MIO) board. Test results of the proposed scheme corroborate the scheme stability and sensitivity View full abstract»

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  • Hysteresis and eddy currents compensation in current transformers

    Publication Year: 2001 , Page(s): 154 - 159
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    In the paper a digital technique for improving the accuracy of instrument current transformers is presented. Since the exciting current can be considered as the main error source, its evaluation can allow the compensation of its detrimental effects to be obtained. The exciting current required by the transformer in every kind of steady state operation can be determined by simply acquiring the secondary current, provided that the examined CT has been preliminarily identified. A simple scalar model for the CTs magnetic core, taking into account saturation as well as hysteresis and eddy currents phenomena, has been implemented in a software compensation routine. This allows us to improve the accuracy in the reproduction of the primary current, in the case of both sinusoidal and distorted current waveforms (provided that DC components are not present). Many experimental tests, under different practical situations, have been performed. The results clearly show that the proposed technique is able to significantly reduce, in comparison with traditional methods, the errors introduced by current transformers View full abstract»

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  • Multiple hypotheses and their credibility in on-line fault diagnosis

    Publication Year: 2001 , Page(s): 225 - 230
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (72 KB)  

    In this study, a new method that handles multiple hypotheses is presented for fault diagnosis using sequence of event recorders (SERs). To quantify the certainty of hypotheses, a method to calculate their credibility is provided. The proposed techniques are integrated in a generalized alarm analysis module (GAAM) and have been tested with numerous scenarios from the Italian power system View full abstract»

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  • A fundamental approach to transformer thermal modeling. II. Field verification

    Publication Year: 2001 , Page(s): 176 - 180
    Cited by:  Papers (51)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    For pt.I see ibid., vol.16, no.2, p.171-5 (2001). This paper has two main objectives. One is to show that the top oil rise thermal model proposed in part I is valid, for a large power transformer in service. The second is to show that there is a convenient way of estimating the parameters without removing the transformer from service. A Manitoba Hydro 250 MVA OFAF transformer was chosen and instrumented with data-gathering equipment. Two twenty-four hour test runs were performed, one in February of 1999 and the other in July of 1999. The most basic parameter to be determined was the rated top oil rise but also found were the top oil line constant and the nonlinearity exponent, commonly given the symbol n. The results are very positive View full abstract»

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  • An AC active filter for use at capacitor commutated HVDC converters

    Publication Year: 2001 , Page(s): 335 - 341
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    This paper discusses the application of an AC side active filter in HVDC schemes involving capacitor commutated converters. A suitable topology and control algorithm is selected to achieve the necessary objective of filtering the lower order characteristic harmonics. The dependence of the filter's rating on parameters such as the extent of de-tuning of its passive elements is investigated. The performance of this filter in a capacitor commutated converter application is evaluated using an electromagnetic transient simulation program View full abstract»

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  • ANN-based techniques for estimating fault location on transmission lines using Prony method

    Publication Year: 2001 , Page(s): 219 - 224
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    A system is proposed to locate faults on transmission lines using the traveling wave phenomenon. Prony method is used to analyze the voltage or current signal at the local bus and extract its modal information. This information represents the traveling wave generated by the fault and can be used to estimate its location. Artificial neural networks (ANNs) are used to estimate the fault location based on the modal information. Two schemes are presented: the first with a voltage input signal; and the second with a current input signal. Training and testing data are obtained by ATP-EMTP simulations. Tests were done to study the effect of fault resistance variation and fault incidence angle on both schemes. The system has the advantages of utilizing single-end measurements, using either a voltage or current signal; no pre-fault data is required View full abstract»

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  • A combined uninterruptible power supply and dynamic voltage compensator using a flywheel energy storage system

    Publication Year: 2001 , Page(s): 265 - 270
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    Due to technological advancements, the flywheel energy storage system is becoming a viable alternative to electrochemical batteries. Two potential applications of flywheel systems are for voltage support and as an uninterruptible power supply. The two applications are both useful to protect critical loads on distribution feeders. Therefore, it may be useful to look at the possibility of combining both functions into one system. This paper considers a flywheel energy storage system which performs both functions and presents a novel control scheme using both sinusoidal pulse width modulation as well as a boost converter to regulate the critical load voltage on the feeder. Dynamic voltage compensation is achieved by injecting voltage through series transformers rather than by connecting the system in shunt, to minimize the amount of kVA required by the flywheel system. Simulations are provided using the Electromagnetic Transients Program to validate the concept View full abstract»

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  • Software models for relays

    Publication Year: 2001 , Page(s): 238 - 245
    Cited by:  Papers (15)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    This paper reviews the past and present uses of relay models. It discusses the various types of models, what information is required to build such models and the model validation process. Examples of present and possible future use of software models are given View full abstract»

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  • Numerical electromagnetic field analysis of lightning current in tall structures

    Publication Year: 2001 , Page(s): 324 - 328
    Cited by:  Papers (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    The Numerical Electromagnetic Code (NEC-2) is applied to the electromagnetic analysis of tall structures hit by lightning. The advantage of the analysis using NEC-2 is that it can accurately compute the current distribution along a conductor system by the method of moments. The waveforms of the lightning currents measured on freestanding tall structures are well reproduced, and the computed waveforms of the electric and the magnetic fields at some distance from the structure hit by lightning agree fairly well with the measured waveforms. In the analysis, a lightning channel is represented by a vertical conductor that is loaded by series inductance and resistance so as to simulate the slow propagation velocity of a current wave on the lossy channel. This representation is demonstrated to be quite effective View full abstract»

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  • Distribution of earth leakage currents in railway systems with drain auto-transformers

    Publication Year: 2001 , Page(s): 271 - 275
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    This work presents a novel advanced methodology to accurately predict the earth leakage currents for analyzing the electrification railway systems with drain auto-transformers. The proposed methodology entails applying a decoupled technique to model the equivalent circuit while simultaneously considering the grounding network and the effects on mutual impedance between feeders. Also presented herein are several study cases, particularly with respect to how grounding resistance, span of auto-transformers, turn-ratio of auto-transformers, and location of ground faults influence the leakage currents. These study cases demonstrate that the computer program based on the proposed methodology can effectively analyze the leakage currents in the planning stage for developing railway systems View full abstract»

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  • A FIRANN as a differential relay for three phase power transformer protection

    Publication Year: 2001 , Page(s): 215 - 218
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB)  

    This paper presents an application of a finite impulse response artificial neural network (FIRANN) as differential protection for a real three phase power transformer. Three FIRANNs are designed, trained and tested. The first one has an output which identifies internal faults from any other cases like inrush current and external faults. The two others FIRANNs, each have two outputs that classify between internal and external faults, so that a backup protection is included. These FIRANNs have six inputs, one for each sampled current signal from both transformer sides. The sample rate selected is 2 kHz for a 50 Hz power frequency. All FIRANNs were trained to have a 3.5 ms fault detection time, which is considered as a very fast protection. The test results show very good behavior of the FIRANN as a differential protection and it is planned to build a prototype View full abstract»

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  • The study of inrush current phenomenon using operational matrices

    Publication Year: 2001 , Page(s): 231 - 237
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    The paper presents a new methodology for calculating magnetizing inrush currents. Similarly to the seminal work of Rajakovic and Semlyen, all the calculations are conducted in the frequency domain, hence, circumventing the many problems encountered when time domain simulations are used to solve this problem. Unlike the work of Rajakovic and Semlyen (1989), where a pre-determined sequence of steady-state “images” are obtained for a sufficiently long number of cycles to capture the complete picture of the inrush phenomenon, the authors' method produces the full solution, with no loss of fidelity, of the overall inrush phenomenon. The solution is achieved by resorting to operational matrices and it is fully equivalent to that produced by time domain simulations but carried out entirely in the frequency domain. In principle, any orthogonal series expansion could be used with this method, but in this paper Hartley series have been selected. The usefulness of the methodology is illustrated with simple but practical circuits. Comparisons against time domain simulations are given View full abstract»

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  • Fuzzy-based voltage/reactive power scheduling for voltage security improvement and loss reduction

    Publication Year: 2001 , Page(s): 319 - 323
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    This paper presents a new approach using fuzzy set theory for voltage and reactive power control of power systems. The purpose is to find a solution which takes both voltage security enhancement and loss reduction into account for an electric power system. The approach translates violation level of buses voltage and controlling ability of controlling devices into fuzzy set notations using a linearized model. A feasible solution set which achieves voltage improvement is first attained using the max-min operation of fuzzy sets, the final solution which takes power loss reduction into account is then determined employing the min-operation on the feasible solution set previously obtained. A modified IEEE 30-bus test system is used to demonstrate the application of the proposed approach. Simulation results show that the approach is efficient, simple, and straightforward View full abstract»

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  • Elimination of transformer inrush currents by controlled switching. II. Application and performance considerations

    Publication Year: 2001 , Page(s): 281 - 285
    Cited by:  Papers (41)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (96 KB)  

    For pt. I see ibid., vol.16, no.2, p.276-80 (2001). Transformer inrush currents are high-magnitude, harmonic-rich currents generated when transformer cores are driven into saturation during energization. These currents have undesirable effects, including potential damage or loss-of-life to the transformer, protective relay misoperation, and reduced power quality on the system. Controlled transformer switching can potentially eliminate these transients if residual core and core flux transients are taken into account in the closing algorithm. This paper explores the practical considerations of core flux transients, performance of control strategies, and the application of circuit breakers to control transformer inrush transients 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.

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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