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Power Delivery, IEEE Transactions on

Issue 1 • Date Jan. 2003

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Displaying Results 1 - 25 of 53
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  • Closure to "Evaluation of the potential for power-line noise to degrade real-time differential GPS messages broadcast at 283.5-325 kHz"

    Page(s): 343 - 344
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (158 KB)  

    The author replies to the comments made on the original paper ("Evaluation of the potential for power-line noise to degrade real-time differential GPS messages broadcast at 283.5-325 kHz", J.M. Silva, see ibid., vol.17, p.326-33, 2002) by V.L. Chartier (see ibid., vol.18, no.1, p.343, Jan. 2003). View full abstract»

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  • Condition monitoring techniques for electrical equipment-a literature survey

    Page(s): 4 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (547 KB) |  | HTML iconHTML  

    Increasing interest has been seen in condition monitoring (CM) techniques for electrical equipment, mainly including transformer, generator, and induction motor in power plants, because CM has the potential to reduce operating costs, enhance the reliability of operation, and improve power supply and service to customers. Literatures are accumulated on developing intelligent CM systems with advanced practicability, sensitivity, reliability and automation. A literature survey is felt necessary with an aim to reflect the state of the art development in this important area. After introducing the concepts and functions of CM, this paper describes the popular monitoring methods for and research status of CM on transformer, generator, and induction motor, respectively. The paper also points out the potential benefits through the utilization of advanced signal processing and artificial intelligence techniques in developing novel CM schemes. View full abstract»

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  • Condition assessment of power transformer onload tap changers using wavelet analysis and self-organizing map: field evaluation

    Page(s): 78 - 84
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    An onload tap changer (OLTC) is the most maintenance intensive subassembly on a power transformer. Vibration monitoring is an effective technique that can be used to assess the condition of an OLTC nonintrusively. The authors have developed a condition monitoring system for common types of OLTCs that enables the condition of tap changer contacts and associated drive system to be inferred from vibration signals. A number of prototype systems have been installed onto OLTCs in distribution zone substations for field trials. Particular emphasis has been given to the detection of faults in a particular type of older tap changer that had been prone to a range of faults associated with the switching contacts and drive mechanism. For this type of tap changer, it has been shown to be possible to determine not only that the tap changer is aging but also to identify the particular part that is degrading. View full abstract»

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  • Estimating overpressures in pole-type distribution transformers. II. Prediction tools

    Page(s): 120 - 127
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (909 KB) |  | HTML iconHTML  

    Low-impedance faults are difficult to contain from the point of view of cover retention and tank rupture in pole-type distribution transformers. When evaluating a transformer's containment capabilities, one needs to consider two aspects: the overpressure caused by an arc of given parameters and the pressure withstand of the tank. This paper presents two methods to calculate overpressures as a function of the arc and all of the relevant geometrical parameters: tank diameter, air-space height, and the depth of the arc below the oil. Both methods have been validated with experiments. Results of tests to determine the pressure withstand of typical tanks are presented. It was found that an average value of the overpressure withstand capability is approximately 100 kPa. For a given tank geometry and fault parameters, a current-limiting fuse would be required if the methods proposed here predict an overpressure of more than 100 kPa. View full abstract»

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  • A case of abnormal overvoltages in a Petersen grounded 132-kV system caused by broken conductor

    Page(s): 195 - 200
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    This paper analyzes a case where a broken phase conductor in a Petersen grounded system caused extensive damage and outages due to excessive stationary overvoltages. It is shown that the high overvoltages resulted from a combination of the following: (1) the fault occurred on a radial connection, (2) the total compensation was close to 100%, and (3) the compensation of the two subnetworks defined by the fault was far from 100% (one subnetwork was undercompensated and the other overcompensated). Overvoltages calculated by a simple model compare favorably with recorded results. The overvoltages are shown to be strongly dependent on the compensation level, the compensation distribution, the shunt conductance to ground, and the load. A least squares method is used for estimating the shunt conductance based on a measured resonance curve. View full abstract»

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  • Application studies of line arresters in partially shielded 138-kV transmission lines

    Page(s): 95 - 100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB) |  | HTML iconHTML  

    The application of arresters on transmission lines has been one of the most effective alternatives for the reduction of lightning flashover rates. This paper reviews previous methods for evaluating lightning performance of lines with arresters. Improved calculations of line outage rates are developed to include power frequency voltage and arrester failure-rate evaluations, based on field experience. The transmission lines are modeled in detail in the electromagnetic transients program (EMTP)/(ATP) and the outage rates are calculated with the Monte Carlo method. Probability energy stresses on arresters are evaluated for strokes on conductors and shield wires as a function of tower footing resistance (TFR). View full abstract»

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  • Signatures of voltage dips: transformer saturation and multistage dips

    Page(s): 265 - 270
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB)  

    Obtaining information on the voltage dips that occur in a network is one of the most important tasks of a power quality monitoring program. This paper focuses on two types of voltage dips that although mentioned in the literature, their characteristics have not been presented before. These types are: voltage dips due to transformer saturation and multistage voltage dips due to faults (dips that present more than one stages of voltage magnitude before the fault clearing operation). Simulations and real measurements are used to show the features of these types of phenomena. Overall, the paper offers the means for a systematic processing of the measurements obtained by power quality monitors. View full abstract»

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  • Comparison of field results and digital simulation results of voltage-sourced converter-based FACTS controllers

    Page(s): 300 - 306
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (793 KB) |  | HTML iconHTML  

    This paper compares the field results of voltage-sourced converter (VSC)-based flexible alternating current transmission system (FACTS) controllers, such as static synchronous compensator (STATCOM), static synchronous series compensator (SSSC), and unified power flow controller (UPFC) with that obtained from the computer models of the FACTS controllers using an Electro Magnetic Transients Program (EMTP) simulation package. The operational results of the actual equipment include the control of the line voltage and the control of the real and reactive power flow in the line. The correlation of the results establishes the validity of the models. The protection scheme of the FACTS controllers during faults and contingencies is also described. The simulation results can be used to accurately predict the behavior of an actual controller. View full abstract»

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  • Optimal acquisition and aggregation of offshore wind power by multiterminal voltage-source HVDC

    Page(s): 201 - 206
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    This paper addresses the exploitation of the offshore wind energy. A good example is in the shallow coastal waters around the Baltic Sea where there is high potential for wind turbines, located 10-30 km from the shore. The underwater transmission of power to shore has to be by cables. Therefore, DC transmission is required to avoid the large capacitive reactance currents of AC cables. This paper describes the optimal acquisition and aggregation of wind power by multiterminal high-voltage direct current based on sinusoidal pulse-width-modulated, three-phase voltage-source converters connected at their AC terminals to the wind turbine generators. View full abstract»

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  • Dependence of arc interrupting capability on spatial distribution of airflow velocity in air-blast flat-type quenching chamber

    Page(s): 101 - 106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    The dependence of an interrupting capability on the spatial distribution of airflow velocity was investigated in an air-blast flat-type quenching chamber. To obtain a various distribution of airflow velocity, the axial position of a nozzle and the inlet width of the nozzle were varied. For each of the axial positions and each of the inlet widths, arc interruption tests for AC currents were performed to measure the interrupting capability. Furthermore, the distribution of airflow velocity in the quenching chamber was calculated intentionally in the absence of the arc. From the test and calculation results, we found out a definite relationship between the velocity distribution and the interrupting capability. View full abstract»

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  • Charge-Voltage curves of surge corona on transmission lines: two measurement methods

    Page(s): 307 - 314
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (425 KB) |  | HTML iconHTML  

    This paper investigates the charge versus voltage (q-v) curves of surge corona on transmission lines. Two measurement methods of the q-v curves are proposed, and field test results are shown to validate the methods. Since the new methods do not require a charge-measuring conductor, such as a corona cage, the q-v curves are measured in the real electric-field distribution. One of the methods obtains the amount of charges q by numerically integrating the digitally stored waveform of injected current, assuming that the line is short in length and open ended. Thus, it is suitable for measurement using an experimental setup. The other calculates q from voltage and current waveforms based on the traveling-wave theory, assuming that the line is long enough to expect no reflected waves, and it is applicable to existing "real" transmission lines. Measured q-v curves are compared with simulated ones, and their physical properties are discussed in the paper. View full abstract»

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  • Mechanical deterioration of ACSR conductors due to forest fires

    Page(s): 271 - 276
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1463 KB) |  | HTML iconHTML  

    Considerations for the remaining life of the aluminum stranded conductors steel reinforced (ACSR) in transmission lines have become gradually important to hold the reliability and the stability of the electric power supply. The useful life of the ACSR exposed to the atmosphere for a long period may be dependent on deterioration caused by such factors as atmospheric corrosion, galvanic corrosion, crevice corrosion, or fatigue corrosion. Forest fires for any overhead transmission lines built nearly on the ridge of the mountains may significantly reduce to the mechanical strength of the ACSR and lead to failure or accident. In this paper, material and mechanical deterioration performances of ACSR due to forest fires are presented through several sample tests. Data analysis for tension load and extension of ACSR after blazed are reported. View full abstract»

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  • Real-time digital processing of GPS measurements for transmission engineering

    Page(s): 177 - 182
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (373 KB) |  | HTML iconHTML  

    The Global Positioning System (GPS) is a state-of-the-art timing and positioning system based on 24 or more satellites launched and maintained by the US government. Power engineering applications based on GPS include phasor measurement, positioning applications, such as surveying and mapping, and potentially in deriving real-time data on transmission lines that will allow them to be loaded to a dynamic (thermal or security) limit. Inherent errors in GPS technologies are discussed, and the differential GPS method is described for accuracy enhancement. Further digital-processing needs are necessary for meeting the accuracy requirements of certain specific applications. The focus of this paper is on the digital signal processing (DSP) of differential-GPS (DGPS) measurements. The paper describes a methodology for further improving DGPS altitude measurements for the purpose of accurate determination of high-voltage overhead conductor sag. The Haar wavelet transforms (HWT) and least-squares parameter estimation (LSPE) techniques are considered. View full abstract»

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  • Some frequency domain aspects of wave propagation on nonuniform lines

    Page(s): 315 - 322
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (510 KB) |  | HTML iconHTML  

    Nonuniform line (NL) is the designation of a transmission line segment where the conductors are not parallel or where the sag is significant. In addition, transformers and also parts of metallic towers can be viewed as NLs. In this paper, the propagation characteristics of NLs are examined. They appear as generalizations of concepts from uniform transmission lines (ULs). It was found that an n-conductor NL has n pairs of modes and the forward and backward waves of a mode have the same propagation constants. However, the modeshapes defined by the voltages and currents of a given mode are different. For illustration, the variation with frequency of these propagation characteristics has been presented for the wide-span river crossing of an overhead transmission line. View full abstract»

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  • An investigation on the validity of power-direction method for harmonic source determination

    Page(s): 214 - 219
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (321 KB) |  | HTML iconHTML  

    The power-direction method has been used widely to identify the locations of harmonic sources in a power system. A number of utility-customer disputes over who is responsible for harmonic distortions have been settled with the help of the method. A closer examination of the method, however, reveals that it is unable to fulfil the task of harmonic source detection. Case studies can easily show that the method yields incorrect results. In this paper, problems associated with the method are investigated using case studies and mathematical analysis. The results show that the power direction method is theoretically incorrect and should not be used to determine harmonic source locations. The main cause of the problem is that the direction of active power flow is a function of the phase-angle difference between the two sources. The direction of reactive power flow, on the other hand, has a better correlation with the source magnitudes. View full abstract»

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  • Measurements of small diametral vibrations in metallized polypropylene capacitors subjected to current pulses, by means of laser vibrometry

    Page(s): 277 - 282
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (924 KB) |  | HTML iconHTML  

    One of the main factors limiting the reliability of metallized polypropylene capacitors is degradation of the electrode/sprayed end contacts, a process known to be caused by thermal effects and the effects of electrical discharges. It has also been suggested that electrodynamic effects could contribute to the phenomenon; an experiment was performed to investigate the possibility and the findings confirm that this is indeed the case. View full abstract»

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  • New solid-state onload tap-changers topology for distribution transformers

    Page(s): 136 - 141
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (290 KB) |  | HTML iconHTML  

    High controllability advantages of power electronic switches lead to their application in the tap-changer of distribution transformers. Using such switches leads to quick operation of the tap-changer and, thus, improved performance. Moreover, their application reduces maintenance and repair costs of tap-changers. This paper introduces a new solid-state onload tap-changer topology that has many steps with fewer power electronic switches compared with those reported in the literature. This tap-changer is designed for an 800-kVA, 20-kV/400-V distribution transformer, and the results are discussed. View full abstract»

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  • Surge protection for interface circuits of communication system

    Page(s): 85 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    Microelectronic circuits are often damaged by surges. Surge protection for microelectronic circuits has some special requirements that are different than those for electrical equipment. The approach that the surge invades microelectronic circuits is studied in this paper. The surge withstand capability of some typical serial communication integrated chips, the behaviors of voltage-limiting components, and the influence of the connecting capacitance of a voltage-clamping device on digital signals are studied. Then, a design method of surge suppressor for communication systems is proposed. View full abstract»

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  • An analysis of the five-wire distribution system

    Page(s): 295 - 299
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    Most power distribution systems in North America employ a four-wire multi-grounded neutral design. A five-wire distribution design has been proposed and studied in a project cosponsored by EPRI, the Empire State Electric Energy Research Corporation, the New York State Electric and Gas Corporation, and the New York State Energy Research and Development Authority. While summary information on the project claims five-wire distribution is a viable means of dealing with stray voltage, magnetic fields and high impedance faults, it does not appear that a balanced assessment has been presented. The purpose of this paper is to summarize the significant differences between the five-wire distribution system and the conventional four-wire multigrounded neutral system. Both four-wire and five-wire distribution are assumed to be multigrounded systems. View full abstract»

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  • Estimating overpressures in pole-type distribution transformers. I. Tank withstand evaluation

    Page(s): 113 - 119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    When an electric arc is generated in transformer oil, a strong overpressure may rapidly develop in the tank, especially for low-impedance faults. This paper presents the test method and results obtained in a project aimed at assessing the human and environmental risks associated with this type of fault. Limit energy and pressure values were defined in terms of different safety levels. The best method of limiting the energy and pressure at a safety level in the transformer tank during internal faults of greater than 1.7 kA is to protect the transformer with a current limiting fuse. Other ways to increase the mechanical withstand of transformer tanks under such faults are also discussed. View full abstract»

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  • A wideband lumped circuit model of eddy current losses in a coil with a coaxial insulation system and a stranded conductor

    Page(s): 50 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (778 KB) |  | HTML iconHTML  

    This paper presents a wideband lumped circuit model of eddy current losses in a coaxially insulated coil. The wide frequency range of the model is achieved by means of dual and extended Cauer circuits, which are equivalent circuits used for eddy current modeling. The complete lumped circuit reproduces the expected response well. However, because of resonances in the coil, the model cannot be experimentally verified for higher frequencies than 5 kHz. The parameters of the lumped circuit are mainly acquired from field calculations and aggregate the eddy current losses in the stranded conductor of each turn. The aggregate considers the contact resistance between the strands. The eddy current model can be used as a part of a complete model of the coil intended for, e.g., lightning impulse simulations, as the winding is discretised into short pieces. The results of the paper are of special interest for coaxially insulated electric machines, such as the commercially available Powerformer™ and Dryformer™. View full abstract»

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  • Impact of TCSC control methodologies on subsynchronous oscillations

    Page(s): 243 - 252
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (686 KB) |  | HTML iconHTML  

    This paper presents a detailed analysis of the impact of different TCSC control methodologies on subsynchronous oscillations problem of series capacitive compensated transmission systems. The first IEEE benchmark model for the analysis of SSR phenomena is adopted. The system was evaluated for several different compensation levels. Three different control methodologies were checked, namely: constant current, constant power, and constant impedance control. The influence of ratings and the impact of different firing control methodologies are also evaluated. View full abstract»

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  • A new protection scheme for fault detection, direction discrimination, classification, and location in transmission lines

    Page(s): 34 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB) |  | HTML iconHTML  

    This paper presents a new adaptive fault protection scheme for transmission lines using synchronized phasor measurements. The work includes fault detection, direction discrimination, classification, and location. Both fault-detection and fault-location indices are derived by using two-terminal synchronized measurements incorporated with distributed line model and modal transformation theory. The fault-detection index is composed of two complex phasors and the angle difference between the two phasors determines whether the fault is internal or external to the protected zone. The fault types can be classified by the modal fault-detection index. The proposed scheme also combines online parameter estimation to ensure protection scheme performance and achieve adaptive protection. Extensive simulation studies show that the proposed scheme provides a fast relay response and high accuracy in fault location under various system and fault conditions. The proposed method responds very well with regards to dependability, security, and sensitivity (high-resistance fault coverage). View full abstract»

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  • Phase-time analysis of the leakage impulse current of faulty line-post pin insulators

    Page(s): 323 - 328
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (243 KB) |  | HTML iconHTML  

    Leakage impulse current of the faulty insulators was experimentally studied. The leakage impulse current was characterized in terms of the phase-time base of the applied voltage. The study showed that the leakage impulse is observed only in a distinct location in phase-time space. Based on the findings, prioritized maintenance scheduling was proposed, which could be used for status monitoring of insulators and distribution feeders. 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