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Power Delivery, IEEE Transactions on

Issue 4 • Date Oct. 1994

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Displaying Results 1 - 25 of 35
  • Bibliography of research on nonstandard lightning voltage waves

    Publication Year: 1994 , Page(s): 1982 - 1990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    Because of the increasing importance of the effects of the nonstandard lightning voltage waves on power apparatus, the Task Force was formed to (1) compile a bibliography of the research on the nonstandard lightning voltages, and (2) review the previous research. The bibliography and the review dealt with: (1) behavior of air gaps under nonstandard lightning voltages, (2) generation of fast-front voltage waves, and (3) measurement of fast-front voltage waves. The bibliography is presented in this paper. The bibliography contains 207 publications, published by IEEE and by other societies, in English and in other languages.<> View full abstract»

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  • Measurement of synchronous machine rotor angle from analysis of zero sequence harmonic components of machine terminal voltage

    Publication Year: 1994 , Page(s): 1770 - 1777
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    Generator rotor angle measurement is useful in identification of electric machine parameters in the d and q axes and as an indicator of stability of the operating condition. Rotor angle measurements with the appropriate bandwidth are also very useful in observation of rotor torsional oscillations both for monitoring and protection against undamped torsional modes, and for use in control schemes designed to damp torsional oscillations. A method of measurement of synchronous machine rotor angle from an analysis of the phase angle of zero sequence harmonic components of terminal voltage is presented View full abstract»

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  • Optical current transducers for power systems: a review

    Publication Year: 1994 , Page(s): 1778 - 1788
    Cited by:  Papers (35)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB)  

    The technology of the optical measurement of current is revived. Several fundamentally different approaches are described. Implementations from a number of manufacturers are examined so as to highlight the similarities and the differences. Experience with optical current transducers is reported. The question of interfacing to an optical current transducer is discussed. The special problems posed by calibration of this kind of instrument are reviewed View full abstract»

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  • A method for modeling nonlinear core characteristics of transformers during transients

    Publication Year: 1994 , Page(s): 1916 - 1925
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    An EHV transformer's insulation system must be designed to withstand stresses generated during transient events. Computer models are employed for predetermination of these stresses. The lack of accurate and consistent computer models for use by both utilities and manufacturers, is felt to contribute to the relatively high failure rate of EHV transformers. This paper develops a detailed nonlinear transformer model and a solution method that improves the accuracy with which the effect of the nonlinear characteristic of the magnetic core during transients can be predicted. This model is based on linearization of the core's saturable characteristic during solution time intervals. This paper describes a nonlinear, single phase, detailed transformer model and its verification against measured data View full abstract»

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  • The electrical breakdown characteristics of oil-paper insulation under steep front impulse voltages

    Publication Year: 1994 , Page(s): 1926 - 1935
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Disconnecting switch operations in gas insulated equipment cause transient voltages with risetimes as steep as 5 to 20 nanoseconds and magnitudes as high as 2.5 pu. There is very little information on the effect of these transients on oil-paper insulated equipment. There have been reports, however of transformer and bushing failures caused by these transients. The electrical breakdown characteristics of oil-paper insulation under steep front impulse were studied in this project, which was co-sponsored by the Canadian Electrical Association and BC Hydro. V 50 (50% breakdown probability voltage) breakdown data was obtained with steep front (10 ns/2500 μs), lightning and switching impulse waveforms. Insulation breakdown voltage vs breakdown time (V-t) data and multiple impulse breakdown data were obtained with the steep front impulse waveform. The V50 results showed that the breakdown strengths were lower for steep front impulses than for lightning impulses. The multiple impulse breakdown results showed that oil-paper insulation breakdown strength can be lower than 100 kV/mm. These results are alarming, since they suggest that oil-paper insulated equipment subjected to steep front transients will fail at voltages below the lightning impulse design level (BIL). The volt-time data had a discontinuity. The breakdown process at risetimes below about 50 ns was different from the breakdown process at risetimes above 50 ns View full abstract»

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  • Water cooling of HVDC thyristor valves

    Publication Year: 1994 , Page(s): 1830 - 1837
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    It is generally accepted that water is a very effective medium to remove heat losses from any type of equipment. When used for HVDC thyristor valves, the fundamentals of electrolyte conduction and water chemistry need to be considered in the design of the cooling circuit. The characteristics of the materials used, in conjunction with high voltage stresses and circuit configuration, play an important role to assure longevity and corrosion-free performance View full abstract»

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  • Damping of power system oscillations by use of controllable components

    Publication Year: 1994 , Page(s): 2046 - 2054
    Cited by:  Papers (49)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    This paper deals with damping of power system electromechanical oscillations using controllable series compensators (series capacitors and phase shifters) and controllable shunt capacitors. The study is based on investigation of the eigenvalues of a simple linearized power system model. The controllable series components are located on the transmission line connecting two areas and the controllable shunt capacitor is located close to a load. It is shown that the level of transmission line loading, load characteristics and inertia of the two areas influence the damping achieved by the controllable components to different degrees. The contributions of the controllable series components to the enhancement of power system damping for the same rating of the controllable components are compared. Numerical examples are provided to verify the theoretical findings. The purpose of this paper is to provide an insight and understandings in the basic characteristics of the damping effects of the studied devices. This insight is obtained by study of a simple power system that exhibits power oscillations. The understandings and findings can facilitate the analysis of realistic, and more complex power systems View full abstract»

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  • Development of 500-kV XLPE cables and accessories for long distance underground transmission line-Part I: insulation design of cables

    Publication Year: 1994 , Page(s): 1741 - 1749
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    This paper discusses the results of a basic study for the development of 500 kV XLPE power cables. The authors have established that the factors that decide the performance of today's XLPE cables are impurities in the insulator and protrusions on the semiconductive layer, and that the insulation performance of XLPE power cables is determined by the size of these defects. In model tests of XLPE power cables, the minimum insulation breakdown stress of cables was determined, to set the design values for 500 kV XLPE cable. As a result, it was found that it is possible to design cables having an insulation thickness of 25 mm View full abstract»

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  • EMTP-based model for grounding system analysis

    Publication Year: 1994 , Page(s): 1838 - 1849
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (916 KB)  

    EMC and lightning protection analyses of large power systems require the knowledge of the dynamic behavior of extended grounding systems. They cannot be regarded as equipotential planes, but must be treated as coupling paths for transient overvoltages. This contribution presents a model for linear earth conductors based on the transmission line approach and outlines its integration in the transients program EMTP. Validation of the presented model is achieved by comparison with field measurements and with a rigorous electromagnetic model. Overvoltages and electrical fields throughout electrical power systems can thus be computed View full abstract»

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  • Directional sensitivity to geomagnetically induced currents of the Hydro-Quebec 735 kV power system

    Publication Year: 1994 , Page(s): 1963 - 1971
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (804 KB)  

    To examine the sensitivity to geomagnetically induced currents (GIC) of the Hydro-Quebec 735 kV power system, model calculations were made of the GIC produced by uniform electric fields directed northwards (azimuth of 0°) and with azimuths increasing in 15° increments. The results show that the maximum GIC was produced in the system for an electric field bearing of 15°. In addition the model results allow the variation of GIC amplitude with electric field direction to be examined for individual substations. Maximum GIC occurred at substations at the ends of a long transmission line when the electric field was aligned with the transmission line View full abstract»

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  • Extensive evaluation of high performance protection relays for the Hydro-Quebec series compensated network

    Publication Year: 1994 , Page(s): 1799 - 1811
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1276 KB)  

    This paper reports on an extensive study to compare the performance of 8 preselected high performance power line protection systems on the Hydro-Quebec series compensated network. The paper first presents an evaluation of the commissioning aspects and manufacturing quality of the tested relays. It then describes the simulated network, the relay testing procedure, and the laboratory test results obtained on a modern real time power system simulator. Published results of relay performance on series compensated lines are scarce and this paper provides valuable information for utility protection engineers. A total of 115,000 network disturbances were simulated and recorded on 20 different 735 kV lines; fractional test results for 84,030 cases are presented in the paper. The approach using real time power system simulation proved to be an efficient technique for evaluating protection relay performance. The laboratory test results demonstrated that the two best protection principles to be applied on the Hydro-Quebec series compensated network are those based on current differential and segregated phase comparison. The analysis does not take into account telecommunication requirements or other external constraints View full abstract»

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  • Rating of composite suspension insulators related to the long term mechanical strength of rods

    Publication Year: 1994 , Page(s): 2055 - 2063
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    The long duration mechanical strength of rods used in composite insulators is a major problem for the line designer. The previous approach to the problem and the requirements of standards give an extrapolation for the long term performance of the rod which is not confirmed by accurate analysis of test results. So, a new model for the load-time curve is determined. Based on the analysis of the behaviour of the rod under tensile stresses with acoustic emission and the determination of the physical “damage limit”, a mathematical model of the breakage process is proposed. This model takes into account two damage mechanisms; at high stresses, the slope of the load-time failure curve is governed by the relaxation of the resin matrix, then the curve tends to a horizontal asymptote corresponding to the intrinsic mechanical strength of the glass fibres. The model can solve any problem related to the ultimate behaviour of the fibreglass rod after various load histories. The conditions required to have no reduction of the ultimate strength of the rod in relation with the SML of composite suspension insulators are established View full abstract»

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  • Development of 500-kV XLPE cables and accessories for long distance underground transmission lines-Part II: jointing techniques

    Publication Year: 1994 , Page(s): 1750 - 1759
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    This paper reports on the results of a basic inquiry for the purpose of developing extrusion-molded joints (EMJ) for use with 500 kV XLPE power cable. The authors have made it clear that the factors that govern EMJ performance, like cable performance, are contaminants in the insulation and protrusions in the semiconductor layer. Through modeling experiments, the authors determine the minimum breakdown strength of EMJ and use this to determine design values for 500 kV EMJ. Finally, they carry out breakdown tests on actual equipment, resulting in the prospect of the actual realization of 500 kV EMJ View full abstract»

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  • A new method and instrument for touch and step voltage measurements

    Publication Year: 1994 , Page(s): 1850 - 1860
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    This paper describes a new method and instrument for measuring touch and step voltages near a grounding system, for example in and around a substation. The hardware, software, and testing procedures are an extension of the smart ground multimeter, developed under EPRI sponsorship. The instrument injects a transient electric current between the ground under testing and an auxiliary ground, and it measures ground potential differences (GPDs) at up to six locations. The GPD measurements are processed with software which rejects external noise using correlation methods. Subsequently, statistical estimation methods are used to extract the touch or step voltages from the thousands of measurement points normalized with the system short circuit capability. Knowledge of the short circuit capability of the substation allows the quick measurement of the touch and step voltages View full abstract»

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  • A new network reconfiguration technique for service restoration in distribution networks

    Publication Year: 1994 , Page(s): 1936 - 1942
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    Whenever a fault occurs in a particular section of a distribution network and on isolation of the fault, some of the loads get disconnected and are left unsupplied. Service should be restored to these affected load points as quickly as possible through a network reconfiguration procedure. A new and efficient technique is presented in this paper for this purpose. Network reduction and determination of the interested trees of the reduced network by a specially developed algorithm for finding the required restorative procedures, are the main contributions of this paper View full abstract»

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  • Transient electromagnetic interference in substations

    Publication Year: 1994 , Page(s): 1869 - 1884
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1464 KB)  

    Electromagnetic interference levels on sensitive electronic equipment are quantified experimentally and theoretically in air and gas insulated substations of different voltages. Measurement techniques for recording interference voltages and currents and electric and magnetic fields are reviewed and actual interference data are summarized. Conducted and radiated interference coupling mechanisms and levels in substation control wiring are described using both measurement results and electromagnetic models validated against measurements. The nominal maximum field and control wire interference levels expected in the switchyard and inside the control house from switching operations, faults, and an average lightning strike are estimated using high frequency transient coupling models. Comparisons with standards are made and recommendations given concerning equipment shielding and surge protection View full abstract»

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  • The effects of nonstandard lightning voltage waveshapes on the impulse strength of short air gaps

    Publication Year: 1994 , Page(s): 1991 - 1999
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    Sphere-sphere, rod-rod and rod-plane air gaps, each 5-cm long, were tested with lightning surges of eight voltage waves of both polarities. The critical breakdown voltage levels of the tested air gaps attained a minimum plateau within a specific range of wavefronts of the lightning surges. Long time delays of breakdown for the fast-front and short time delays for the slow-front waves were observed. These phenomena would significantly affect the insulation coordination of the power apparatus and systems View full abstract»

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  • An adaptive high and low impedance fault detection method

    Publication Year: 1994 , Page(s): 1812 - 1821
    Cited by:  Papers (25)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB)  

    An integrated high impedance fault (HIF) and low impedance fault (LIF) detection method is proposed in his paper. For a HIF detection, the proposed technique is based on a number of characteristics of the HIF current. These characteristics are: fault current magnitude; magnitude of the 3rd harmonic current; magnitude of the 5th harmonic current; the angle of the third harmonic current; the angle difference between the third harmonics current and the fundamental voltage; and the negative sequence current of HIF. These characteristics are identified by modeling the distribution feeders in EMTP. Apart from these characteristics, the above ambient (average) negative sequence current is also considered. An adjustable block out region around the average load current is provided. The average load current is calculated at every 18000 cycles (5 minutes) interval. This adaptive feature will not only make the proposed scheme more sensitive to low fault current, but it will also prevent the relay from tripping during the normal load current. In this paper, the logic circuit required for implementing the proposed HIF detection method is also included. With minimal modifications, the logic developed for the HIF detection can be applied to low impedance fault detection. A complete logic circuit which detects both the HIF and LIF is proposed. Using this combined logic, the need of installing separate devices for HIF and LIF detection can be eliminated View full abstract»

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  • Ampacity of cables in single open-top cable trays

    Publication Year: 1994 , Page(s): 1733 - 1740
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    A mathematical thermal model that can predict the operating temperatures for cables when there is load diversity in single, horizontal, open-top cable trays is presented. The model accommodates two different loading scenarios-one in which the heat load is distributed evenly across the cable tray cross-section and a second one which concentrates the heavily loaded cables along the center-line and surrounds them with more lightly loaded cables. The second model is designed to yield a maximum cable temperature and to account for the load diversity that exists in a realistically operated tray. Temperature predictions provided by the model are compared with previous laboratory cable tray experiments and with data collected during a four year study in which cable temperatures were measured in an operating nuclear plant. Reasons for differences between the field data and the computer results are discussed. The model is used to evaluate the conservatism in the ICEA P54-440 as a result of load diversity View full abstract»

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  • Experimental validation of a computer model simulating an impulse voltage distribution in HV transformer windings

    Publication Year: 1994 , Page(s): 1789 - 1798
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1092 KB)  

    A number of computer models have been recently proposed for simulation of the impulse voltage distribution in the winding of power transformers. Some of these models can predict the winding behavior at high frequencies, some other were developed as a practical tool for designers of lower voltage transformers. The time and expenditure put in development of these models should be balanced by a similar effort to check the model validity. Such checks consist of a comparison of the predicted voltages to the actually measured ones. With the advent of high resolution, fast digital recorders and signal processing techniques, this validation can be performed to a much higher accuracy and completeness than the conventional comparison of analog oscillograms to simulated graphs. The paper presents such a validation technique applied to a computer model of a transformer winding View full abstract»

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  • An efficient EMTP compatible algorithm for modelling switch-controlled drive circuits

    Publication Year: 1994 , Page(s): 2018 - 2025
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The possibility of opposite interactions between the machine systems and the switching circuits of converters has created a need for both better models and more efficient computer programs to conduct detailed simulation studies involving machines and arbitrary drive systems with switching circuits included. This paper presents an efficient and fully Electromagnetic Transients Program (EMTP) compatible numerical algorithm that introduces the resistive representations and the cut-set algorithm into the system formulation stages, such that the possible numerical problems as might occur from using the EMTP can be avoided and the system equations needing to be solved can be minimized. Numerical verifications based on the proposed algorithm and the EMTP are provided for illustrations View full abstract»

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  • Steady-state and transient ampacity of bus bar

    Publication Year: 1994 , Page(s): 1822 - 1829
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    This paper presents a thermal model that can be used to calculate both the steady-state and transient electrical current carrying capacity (ampacity) of a power system busbar. Using a thermal model, a computer program has been formulated that can calculate the ampacity of busbar for any time-varying current and any variation in environmental conditions. Relations for the convection heat transfer coefficient for busbars with circular, rectangular and angular cross-sections are presented. The steady state values for ampacity predicted by the program are compared to accepted values. The transient capabilities of the program are illustrated by calculating the variation in busbar temperature when it is subjected to a step change in current. The predicted temperature histories of typical bus designs are compared to temperatures measured in the laboratory using thermocouples attached to the bus material View full abstract»

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  • Interphase power controller with voltage injection

    Publication Year: 1994 , Page(s): 1956 - 1962
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    This paper introduces a new family of interphase power controllers (IPC) based on the principle of voltage injection commonly used in phase-shifting transformers (PST). The voltage injection IPC exhibits power (active and reactive) control characteristics similar to previously defined IPCs and retains their inherent qualities: passive control, short circuit limitation and voltage decoupling. It also provides more flexibility for the adjustment of the operating point. Two promising topologies are described in more detail. One of them offers the potential of retrofitting existing phase-shifting transformers into full-fledged IPCs. The application of the IPCs is in flexible AC transmission systems View full abstract»

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  • Misinterpretations of some power properties of electric circuits

    Publication Year: 1994 , Page(s): 1760 - 1769
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    It might be expected that the meaning of the apparent power S, a quantity of innumerable everyday applications for almost a century, is well understood. It occurs, however, that this meaning is still a matter of discussion and some interpretations hard to accept are published. Also it is suggested in some papers published recently that only oscillations of the instantaneous power may cause an increase of the apparent power S, which is not true. Misinterpretations that refer to fundamental notions such as powers could be particularly harmful for electrical engineering and should be eliminated as much as possible. Therefore, this paper shows that the apparent power does not have the physical meaning suggested recently. Also it shows that load unbalance in three-phase power systems does not cause any oscillation of the instantaneous power. The conclusion that load unbalance causes oscillations of the instantaneous power is a consequence of a substantial misinterpretation of this quantity in three-phase power systems View full abstract»

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  • Induced transients in substation cables: measurements and models

    Publication Year: 1994 , Page(s): 1861 - 1868
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    An extensive set of switching transient EMI response measurements on several types of substation cables and internal cable wires is described in this paper. Measured and predicted cable/wire current and voltage transients at both air-insulated substations (AIS) and gas-insulated substations (GIS) are presented, for system voltages ranging from 115 kV to 500 kV. The maximum peak-to-peak amplitudes of measured wire transients are found to vary from around 1 A to almost 20 A (current in amperes), and from 0.3 kV to almost 7 kV (voltage in kilovolts). Predictive models for field-driven coupling, as well as for direct-driven coupling via current transformers or capacitively-coupled voltage transformers (CTs/CCVTs), are presented. Model predictions are compared to and validated against measured wire 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.

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