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Power Delivery, IEEE Transactions on

Issue 2 • Date Apr 1999

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Displaying Results 1 - 25 of 48
  • Numerical electromagnetic field analysis on measuring methods of tower surge impedance

    Page(s): 630 - 635
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    The dependence of the tower surge impedance on the measuring methods is studied with the help of NEC-2. The tower surge impedance measured by the direct method varies dependent on the arrangement of the current lead wire. The arrangement of a vertical current lead wire and a horizontal voltage measuring wire gives about 20% higher value than that measured with a horizontal current lead wire in extension to a voltage measuring wire. The former gives about 150 Ω for a typical double-circuit transmission tower and it is almost equal to the value given by the estimating method recommended by the IEEE Working Group. The tower surge impedance evaluated from the current splitting ratio at the tower top is more than 20% higher than that characterized by the direct method when the current is injected into the connecting point from a simulated vertical lightning stroke. On the other hand, the tower surge impedance evaluated by the refraction method is about 10% lower than that characterized by the direct method View full abstract»

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  • Calculation of lightning current parameters

    Page(s): 399 - 404
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    The new expression of the lightning current at the striking point is analyzed. The basic four channel-base lightning current quantities are assumed to be known: current peak value, current rise-time, maximum of the current steepness and the charge transfer at the striking point. The algorithm for a fast calculation of the channel-base current parameters is proposed. The numerical example of the current parameters determination is given. The proposed algorithm can be successfully used for the lightning current modelling in power engineering as well as in the research of the radiated lightning electromagnetic pulse and its coupling with the overhead lines and other metallic structures View full abstract»

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  • New signal processing tools applied to power quality analysis

    Page(s): 561 - 566
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    This paper deals with the comparison of new signal processing tools for power quality analysis. Three new signal processing techniques are considered: the continuous wavelet transform, the multiresolution analysis and the quadratic transform. Their theoretical behaviours are investigated using the basic theory of the Fourier transform. Then, examples of the four most frequent disturbances met in the power system are chosen. Finally, each kind of electrical disturbance is analyzed with example representing each tool. A qualitative comparison of results shows the advantages and drawbacks of each new signal processing technique applied to voltage disturbance analysis. The continuous wavelet transform appears to be a reliable method for detecting and measuring voltage sags, flicker and transients in power quality analysis View full abstract»

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  • Modelling of adjustable speed drives for power system harmonic analysis

    Page(s): 595 - 601
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    A three-phase equivalent circuit model is developed to model adjustable speed drives (ASD) for power system harmonic analysis. The validity and accuracy of the model were verified by comparing simulation results with lab test results. Sensitivity studies are then conducted to determine the key factors affecting the harmonic characteristics of ASDs. Guidelines on modelling ASDs for harmonic distortion assessment are developed based on the results View full abstract»

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  • A study on the characterization of the incipient failure behavior of insulators in power distribution line

    Page(s): 519 - 524
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    A feasibility study on the characterization of incipient insulator failure for distribution fault prediction is presented. In this study, real distribution data was collected and analyzed to isolate incipient failure signatures or parameters which were expected to show distinct behaviors before and after failure incident. Several signal analysis methods were applied to isolate the parameters and a new strategy of analysis, the event-date concept, was also applied to find a relationship between nonharmonic and high frequency signal activities and imminent insulator failures View full abstract»

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  • Nonlinear deterministic modeling of highly varying loads

    Page(s): 537 - 542
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    Typically, the modeling of highly varying, nonlinear loads such as electric arc furnaces has involved stochastic techniques. This paper presents the use of chaotic dynamics to describe the operation of nonlinear loads. Included is a discussion of the Lyapunov exponents, a measure of chaotic behavior. The alternate approach is applied to electric arc furnaces. A tuning mode is described to develop the parameters of a chaotic model. This model is trained to have time and frequency responses that are tuned to match the current from the arc furnace under study. The simulated data are compared to actual arc furnace data to validate the model. This model is used to assess the impact of various highly varying nonlinear loads that exhibit chaos in power systems View full abstract»

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  • Calculation of pressure rise due to arcing faults

    Page(s): 365 - 370
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    Calculation methods are an important tool for the determination of pressure effects due to high current area in electrical installations. In this contribution an improved standard calculation method and a new CFD-(computational fluid-dynamics) based method are introduced and compared with two other existing methods. The fundamental physical phenomena are mentioned and their importance for the process of pressure rise is explained. The calculation methods are discussed and it is shown that the relevant parameter for the application of one of the calculation methods is the geometrical size. The application of the different calculation methods is demonstrated with three typical examples. The CFD-based method is applicable for all typical applications whereas the improved standard calculation method is limited to small size applications View full abstract»

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  • Test systems for harmonics modeling and simulation

    Page(s): 579 - 587
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    This paper presents three harmonic simulation test systems. The purpose is to demonstrate guidelines for the preparation and analysis of harmonic problems through case studies and simulation examples. The systems can also be used as benchmark systems for the development of new harmonic simulation methods and for the evaluation of existing harmonic analysis software View full abstract»

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  • An assessment of conductor temperature rises of cables, caused by a sudden application of short pulse in a daily cyclic load

    Page(s): 307 - 313
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    The method for calculating cyclic and emergency current power cable ratings has been elaborated for many years and has been standardized in form of IEC standards based on the application of a step function. To achieve a better accuracy, a computer method has been developed, based on finite difference approaches. With the propose procedures, this paper provides a sound basis for the accurate evaluation of temperature rises of conductor in cyclic load calculations. In addition, it proposes a compression-decompression approach for evaluating the temperature rise of the conductor, caused by the application of rectangular current pulses in daily cyclic load View full abstract»

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  • Application of high voltage gradient zinc oxide elements to SF6 gas insulated surge arresters for 22 kV-765 kV power systems

    Page(s): 419 - 424
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    Zinc oxide elements have been developed for the surge arrester elements. Basically, these zinc oxide elements are evaluated by the reference voltage VNmA. Newly developed high voltage gradient zinc oxide elements have about twice value VNmA/mm of normal zinc oxide elements. This paper describes the application of the high voltage gradient zinc oxide elements to SF6 gas insulated tank type surge arresters for 22 kV-765 kV power systems View full abstract»

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  • Development and calibration of a network-based streaming electrification model for core-form transformer structures

    Page(s): 431 - 436
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    Streaming electrification occurs in large power transformers when oil circulated for cooling purposes acts to separate charges from the Debye layer on the cellulose insulation surfaces. This phenomenon is believed to have caused several catastrophic transformer failures and remains to be satisfactorily understood in realistic geometries. A network-based streaming electrification model is presented which utilizes single winding ducts as the basic element to investigate a core-form structure. The network is first analyzed using hydraulic duct parameters to calculate the oil flow distributions within the structure. This data is then provided to the electrification solver which predicts the charge densities at each duct outlet. The charge density results are ultimately used to determine the streaming potentials at each node based on an a suitable matrix of leakage resistances. Development of the network model is presented along with empirically-based calibration data for a realistic section of core-form transformer geometry View full abstract»

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  • Performance of MOV arresters during very close, direct lightning strikes to a power distribution system

    Page(s): 411 - 418
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    In 1996, at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida, the responses of MOV arresters in an unenergized test distribution system, composed of an overhead line, underground cable, and padmount transformer with a resistive load, were measured during very close, direct lightning strikes to the overhead line. Arresters were installed on the overhead line at two locations 50 m apart (on either side of the strike point) and at the primary of the padmount transformer which was connected to the line via the underground cable. We obtained arrester data for this test configuration from two lightning flashes (containing a total of five strokes) which were artificially initiated from a natural thunderstorm, using the rocket-and-wire technique. We present the simultaneously-recorded arrester discharge current and voltage waveforms from one lightning stroke for one of the two arresters on the line and for the arrester at the transformer primary. Additionally, we estimate the energy absorbed by the arrester on the line as a function of time for the first 4 ms of the lightning event. The records presented are representative of those for all five strokes View full abstract»

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  • Novel current controller design for elimination of dominant oscillatory mode on an HVDC line

    Page(s): 543 - 548
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    A procedure for designing a novel HVDC current controller is presented. The proposed controller makes HVDC system performance less prone to fundamental frequency oscillations on a DC line, and thus less susceptible to the second harmonic instability. The design is based on a linearised AC/DC system model and on the pole-placement technique. Controller performance is tested against the CIGRE HVDC Benchmark model using the EMTDC/PSCAD simulation package. It is demonstrated that this controller eliminates the dominant oscillatory mode on the DC side, and that it gives a significant improvement in system response even for low SCR AC systems View full abstract»

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  • Long-term reliability testing of 500 kV DC PPLP-insulated oil-filled cable and accessories

    Page(s): 319 - 326
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    This paper describes the results of a long-term reliability test of a newly developed 500 kV DC oil-filled cable and accessories that transmit up to 2800 MW. This is the largest capacity ever used for submarine cables. The test line was 500 m and consist of submarine cables, land cables and several kinds of accessories. An optical fiber sensor was first installed in the oil duct of the cable to measure the conductor temperature directly under application of DC voltage. From 1994 to 1996, the authors carried out an accelerated electrical and thermal aging test equivalent to 40 years, a load cycle test, a polarity reversal test and a transient overloading current test. Satisfactory breakdown strength was confirmed in the residual test which followed the long-term test. These results have been instrumental to the decision to construct 500 kV DC commercial submarine cable lines View full abstract»

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  • Development of GIS fault location system using pressure wave sensors

    Page(s): 371 - 377
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    This paper describes a series of development tests carried out when developing a GIS (gas insulated substation) fault location system using pressure wave sensors for a GIS with a main bus in which each gas section per bay is connected by gas piping. This paper also refers to the basic construction of the software of the fault location system actually applied to a GIS with a rated voltage of less than 168 kV View full abstract»

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  • Unified power flow controller (UPFC): modeling and analysis

    Page(s): 648 - 654
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    The unified power flow controller (UPFC) is a novel power transmission controller. The UPFC provides a full dynamic control of transmission parameters, voltage, line impedance and phase angle. This paper presents a useful tool for power utilities engineers to evaluate the application of the UPFC, its impact on their power system and what would be the shunt and series ratings. This paper gives sets of equations for a system including the UPFC and an equivalent two bus power network. A numerical method tested with Matlab has been successfully validated with an analog model and EMTP. The Matlab code given in the paper allows fast parametric studies to be performed for the application of the UPFC View full abstract»

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  • Selection of passive elements for a three-level inverter based static synchronous compensator

    Page(s): 655 - 661
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    Mathematical models for a three phase three-level static synchronous compensator (STATCOM) working with both fundamental frequency modulation and selective harmonic elimination modulation are described. The mathematical models were obtained by assuming that the power system and the operation of the STATCOM are on a balanced three-phase basis. The mathematical models were simplified to obtain the STATCOM AC side current, the DC capacitor voltage and the ripple for both switching strategies. These simplified design tools were validated using the exact model. The resonance between the DC side capacitance and the coupling reactance was studied using the mathematical model and the resonance frequency for the three-level STATCOM was obtained. The resonance frequency was validated against results of electromagnetic computer simulations. Using the design tools developed and considering the resonance studies, the process for selection of the size of DC side capacitors for a small STATCOM was demonstrated View full abstract»

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  • Radial temperature distribution in ACSR conductors applying finite elements

    Page(s): 472 - 480
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    One of the most interesting aspects in the thermal analysis of an ACSR (aluminium conductors steel reinforced) conductor is the knowledge of the temperature distribution in its interior. These conductors have the problem of heterogeneous characteristics in their interior. This paper proposes a model, based on the finite-element technique, that considers temperature distribution in the interior of the conductor. The model relates the current distribution through the layers with the transmission of heat between them and with the exterior, both in steady state and in transient conditions View full abstract»

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  • Some effects of mill practice on the stress strain behavior of ACSR

    Page(s): 602 - 629
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    Operating temperatures of overhead lines have risen. Tests have indicated that conventional sag tension calculations may underestimate sags that occur at the higher temperatures in ACSR (aluminum conductor steel reinforced) spans. Search for the source of the disparities has identified two effects associated with the manner in which conductors are manufactured. One effect involves residual stresses, resulting from stranding practice, in the finished conductor. The other is caused by the ability of the aluminum part of ACSR to bear axial compression. Analysis of these effects appears to explain the disparity in at least one of the test programs that revealed it View full abstract»

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  • Modeling and simulation, and their validation of three-phase transformers with three legs under DC bias

    Page(s): 443 - 449
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    This paper proposes a new model for three-phase transformers with three legs with and without task under DC bias based on electric and magnetic circuit theory. For the calculation of the nonsinusoidal no-load currents, a combination of time and frequency domains is used. The analysis shows that (1) asymmetric three-phase transformers with three legs generate magnetizing currents with triplen harmonics not being of the zero-sequence type. (2) The wave shapes of the three magnetizing currents of (asymmetric) transformers are dependent on the phase sequence. (3) The magnetic history of transformer magnetization-due to residual magnetization and hysteresis of the tank-cannot be ignored if a DC bias is present and the magnetic influence of the tank is relatively strong, e.g., for oil-cooled transformers. (4) Symmetric three-phase transformers with three legs generate no-load currents without triplen harmonics. (5) The effects of DC bias currents (e.g., reactive power demand, harmonic distortion) can be suppressed employing symmetric three-phase transformers with three legs including tank. Measurements corroborate computational results; thus this nonlinear model is valid and accurate View full abstract»

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  • Insulation of HVDC converter stations

    Page(s): 387 - 392
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    The results of an earlier survey on creepages and clearances in HVDC converter stations are expanded with data from a new survey and on-site interviews at several operating terminals. The changes which have accompanied the development of several additional HVDC transmission systems at higher voltages are illustrated with specific details on external insulation design. A summary of insulation performance and the effectiveness of different maintenance procedures are discussed View full abstract»

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  • Novel medium voltage fault current limiter based on polymer PTC resistors

    Page(s): 425 - 430
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    For limitation and interruption of short circuit currents in medium voltage (MV) applications, fuses and circuit breakers are widely used today. Fuses exhibit excellent current limitation, but work only for a single shot. Circuit breakers are multi-operation devices, but allow several periods of the short circuit current to pass. Based on new PTC materials (positive temperature coefficient of resistance), we propose a new current limiting device for MV applications, which offers the chance to combine the advantages of fuses with the advantages of circuit breakers: a fast current limitation with a repetitive operation. The active material consists of conducting particles in a polymeric matrix. Its challenging property is a change on resistivity by eight to ten orders of magnitude upon temperature increase. This allows the limitation of available short circuit currents in a stable insulating state for a long period of time. The device consists of a series connection of PTC resistors with varistor elements connected in parallel, which serve for a perfect voltage distribution. Using this principle, repetitive current limitation of prospective currents of 4 to 14 kA within about 1 ms could be demonstrated at circuit voltages up to 12 kV View full abstract»

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  • ATM transmissions of microprocessor-based current differential teleprotection signals

    Page(s): 335 - 341
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    This paper describes prudent considerations for applying asynchronous transfer mode (ATM) transmissions, which can provide broadband and multimedia communications as well as flexible, efficient and wide-area networks, to microprocessor-based current differential teleprotection systems. As both functions of current data transmission and simultaneous sampling among remote terminals are required for the telecommunication systems, measures against cell losses and cell delay variations in ATM network elements such as terminal adapters and switches are proposed for the present delay-sensitive teleprotection systems. Allowable system configurations are examined under severe delay constraints in Japan. A new concept of an ATM-native teleprotection system employing time synchronous systems such as GPS is also proposed View full abstract»

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  • An investigation of the harmonic characteristics of transformer excitation current under nonsinusoidal supply voltage

    Page(s): 450 - 458
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    This paper investigates the effect of supply voltage harmonics on the excitation current of a typical 25 kVA single-phase distribution transformer. A complete analytical model is developed to calculate the time domain waveform and the harmonic components of the excitation current. The key findings are: the phase angles of the supply voltage harmonics determine whether or not those voltage harmonics increase or decrease the distortion of the input current (with respect to the sinusoidal supply voltage case). A peaked input voltage wave distorted by 3rd, 7th, 11th, etc. harmonic components, or a flattened input voltage wave distorted by 5th, 9th, 13th, etc. harmonics, creates a flattened current (i.e., decreases the current harmonics and distortion). A flattened input voltage wave distorted by 3rd, 7th, 11th, etc. harmonic components, or a peaked input voltage wave distorted by 5th, 9th, 13th, etc. harmonics, creates a peaked current (i.e., increases the current harmonics and distortion): The 3rd harmonic component in the supply voltage has the highest effect on the current harmonics and distortion. The effect of higher voltage harmonics gradually diminishes with frequency. The magnitudes of the individual current harmonics follow the same decreasing/increasing pattern of changes as does current distortion variation. The corresponding variations in harmonic current phase angles is negligible View full abstract»

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  • Modeling, control and stability analysis of a PEBB based DC DPS

    Page(s): 497 - 505
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    The Power Electronic Building Block (PEBB) concept is to provide generic building blocks for power conversion, regulation and distribution with control intelligence and autonomy. A comprehensive modeling and analysis of a PEBB based DC distribution power system (DPS), comprising of a front end power factor correction (PFC) boost rectifier, a DC-DC converter and a three phase four leg inverter, is performed. All the subsystems of the DC DPS are modeled and analyzed for stability and good transient performance. The effect of impedance overlap on the system and individual subsystems is examined. Ability of a PEBB based converter to stabilize the integrated system by actively changing the system bandwidth is presented 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