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Power Engineering Review, IEEE

Issue 5 • Date May 2000

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Displaying Results 1 - 17 of 17
  • Superconducting magnetic energy storage

    Page(s): 16 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (571 KB)  

    Superconducting magnetic energy storage (SMES) is an energy storage technology that stores energy in the form of DC electricity that is the source of a DC magnetic field. The conductor for carrying the current operates at cryogenic temperatures where it is a superconductor and thus has virtually no resistive losses as it produces the magnetic field. The overall technology of cryogenics and superconductivity today is such that the components of a SMES device are defined and can be constructed. The integrated unit appears to be feasible for some utility applications at a cost that is competitive with other technologies. SMES is the only technology based on superconductivity that is applicable to the electric utilities and is commercially available today. In addition to today's power quality application, the historical development of SMES starting with the concept of very large plants that would store hundreds of megawatt hours of energy and were intended for diurnal load leveling are described. View full abstract»

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  • 2000 summer meeting preview

    Page(s): 28 - 34
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    Freely Available from IEEE
  • Optimal active OPF with FACTS devices by an innovative load-equivalent approach

    Page(s): 63 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    In this letter, a load-equivalent model suitable for FACTS devices is proposed for use in optimal active power flow computations. Specified power value or voltage-dependent loads can represent a FACTS device. The power flow of the power system including FACTS devices can be solved with slight modification of the conventional power flow program to include the effects of the introduced equivalent loads View full abstract»

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  • Applications of superconductivity to electric power systems

    Page(s): 4 - 7
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    The interest in superconducting systems stems from their promise to be more efficient, smaller, and lighter than those made from conventional conductors. The types of applications in which superconductivity has the potential to be effective in an electric power system can be separated into two general classes. The first type includes those technologies in which superconductivity is simply a replacement of existing resistive materials, for example, cables, motors, generators, and transformers. The second type includes technologies that will be enabled by superconductivity and that have little or, at most, limited capability if conventional resistive or other materials are used. Examples are superconducting magnetic energy storage (SMES) and large fault current limiters (FCL). Before looking at the applications under development the article discusses the discovery and development of superconductivity View full abstract»

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  • Identifying a vanishing eigenvalue in voltage collapse analysis with limits consideration

    Page(s): 76 - 77
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    Modal analysis has been widely employed in voltage stability studies. The literature shows that monitoring the least eigenvalue/singular value as a function of load increase may drive one to draw the wrong conclusions, since these indices present a sharp variation at the bifurcation point. This letter shows that a “well-behaved” eigenvalue may be identified, even when reactive power limits are considered. For this purpose, the center manifold theorem is employed View full abstract»

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  • Development status of superconducting motors

    Page(s): 12 - 15
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    The article gives a brief history of the development of superconducting motors with emphasis on the use of high temperature superconductors. At present, effort is directed toward the demonstration of a 1000 hp HTS motor, the test of which will mark another significant milestone in HTS motor development. For the first time, a closed-loop refrigeration system will be used to maintain an operating temperature near 30 K for the HTS field winding. Following the conclusion of the 1000 hp HTS motor project, a 5000 hp HTS motor will be constructed and tested to demonstrate its economical viability. The progress in developing HTS motors to date is shown. The rotor for the 1000 hp motor was designed to accommodate other coils and can provide a test bed for wire developed in the future View full abstract»

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  • Triangular distribution load flow

    Page(s): 60 - 62
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    This letter presents the results of an investigation concerning the load-flow solution of radial distribution networks. The special topology (i.e., the triangular structure) of distribution load-flow equations is investigated and exploited to develop a simple and direct solution technique View full abstract»

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  • A novel technique for measuring grounding capacitance and grounding fault resistance in ineffectively grounded systems

    Page(s): 72 - 73
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    A principle for resonance measurement based on injecting a resonant frequency signal is presented in this letter. Using this principle, the grounding capacitance of lines and equipment and the grounding fault resistance can be measured on-line in ineffectively grounded systems. Based on this, Petersen-coil automatic tuning is implemented and 100% stator grounding fault protection for generator stator windings is also proposed. The prototype for Petersen coil tuning has been tested on networks for many years. The new method for generator stator grounding fault protection is verified by simulation View full abstract»

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  • Nonlinear optimal power flow with intertemporal constraints

    Page(s): 74 - 75
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    This letter describes an interior point dynamic optimal power flow (OPF) algorithm and illustrates its application to a model network that includes large energy-intensive consumers such as metal smelters that are able to reschedule demand to reduce electricity cost subject to meeting the day's production quota. Although the behavior predicted by the algorithm is no surprise (those consumers whose demand is price sensitive reschedule their power purchases to periods of lower energy cost), its efficiency demonstrates the power of the approach. Relaxation of intertemporal and operational constraints leads to an algorithm in which an inner loop rapidly solves a series of relatively small quadratic programming problems via an interior point method while an outer loop is performing computations analogous to an iterative load flow calculation View full abstract»

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  • Power systems of the future. 3

    Page(s): 21 - 24
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    For pt.2 see ibid., vol.20, no.3, p.10-29 (2000). The assets and working philosophy of individual electric utilities will in large measure be reflected by the modernization of their power systems during the next 20 years. This part looks at the potential for fault current limiters, lightning and restoration preparedness, and advanced delivery technologies (compressed-gas-insulated delivery, evaporative cooling delivery, conducting polymers, electron beam delivery, microwave delivery, and laser beam delivery) View full abstract»

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  • Superconducting power generation

    Page(s): 8 - 11
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    With respect to the electric power industry, the superconducting AC generator has the greatest potential for large-scale commercial application of superconductivity. Such a machine should be able to convert mechanical energy to electric energy more efficiently and with greater economy of weight and volume than any other method. These advantages can be accrued at a scale of 1200 MVA output, with the added potential of operation at transmission line voltage and greater system stability. In the past, a great deal of R&D was done in this area, but the present industry trend to smaller machines has decreased this effort. Though the advantages diminish at the much smaller scale of 250 MVA, such machines still offer interesting possibilities. Superconducting synchronous generators with a superconducting adjustable field rotor keep power losses to a minimum since the field in the stator is phase-locked in synchronism with the rotating rotor field. The high magnetic flux density produced by a superconducting rotor field winding permits a great reduction in the amount of iron required in both the rotor and stator. This reduction introduces degrees of freedom not previously possible in generator or motor design. This article is written to help better perceive the technological potential of new developments View full abstract»

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  • Frequency-dependent simple harmonic model of synchronous machines

    Page(s): 58 - 60
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    In this letter, a detailed harmonic model of synchronous machines is established based on previous work by X.P. Yhang (1995) and X.P. Yhang et al. (1999). Then a frequency-dependent simple harmonic model (FSHM) of synchronous machines is derived directly from this detailed Park equation-based synchronous machine model. Finally the connections and differences between this FSHM and widely used simple harmonic model (SHM) are given through theoretical analysis View full abstract»

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  • Effect of distribution system protection on voltage sags

    Page(s): 66 - 68
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    The general relationship between distribution system protection schemes and voltage sags is presented. The definition, characteristics, and sources of sags are given. The probability of sag occurrence is studied from the three points of view: reliability assessment, historic reliability, and general tendency. General values for the reliability assessment uncertainties and facts related to the historic reliability are proposed. The general tendency is analyzed in normalized form. The reliability index appropriate for the study of the protection scheme interaction with voltage sag are described View full abstract»

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  • Method of reducing the effect of supply unbalance on induction motors

    Page(s): 70 - 71
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    The operation of induction motors under unbalanced supply conditions is well documented. Because of the resulting unbalanced currents, there is an increase in losses and consequent overheating of the windings. IEC Standard 34-1-1996 and NEMA Standard MG-1-1993 stipulate that a motor should be able to withstand continuous operation with 1% negative sequence voltage without derating. Where motors are continuously subjected to unbalance beyond this, the effects become significant and derating the motor becomes essential. Where an unbalance in the supply cannot be easily corrected, the general method adopted is to use a motor of larger rating. Although this solves the problem of the motor getting overheated, the performance parameters of the motor (viz., power factor, efficiency, starting current, etc.) deteriorate. In fact, the negative sequence currents in the supply lines increase, causing additional losses and requiring larger capacity supply cables. Thus, although simpler to implement, use of a larger size motor does not lead to the desirable solution (viz., reduction of unbalance in the motor winding currents). This letter studies the feasibility of modifying the machine in order to minimize the unbalance in the currents of a motor subjected to unbalanced supply voltages View full abstract»

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  • Novel energy-based Lyapunov function for controlled power systems

    Page(s): 55 - 57
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    This letter first derives the Hamiltonian equation for a power system with excitation control. A modified energy-based Lyapunov function is then presented for fast transient stability analysis of the controlled power systems View full abstract»

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  • Calculation of optimum directional overcurrent relays settings: the parallel lines case

    Page(s): 68 - 69
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    A simple and practical criterion is proposed to consider the transient changes due to nonsimultaneous operation of directional overcurrent relays in parallel lines. The criterion consists of using two different time coordination intervals: one for relay coordination pairs that do not belong to parallel lines and another for pairs belonging to parallel lines. The method can be implemented in programs that use the optimization technique for the calculation of relay settings. Numerical results showing the performance of the method are also presented View full abstract»

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  • On a hysteresis model for transient analysis

    Page(s): 53 - 55
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    The letter describes an approach to a representation of transient behavior due to switching off complex nonlinear circuits. For this purpose the widely known Jiles model (JM) was implemented into the Alternative-Transient-Program (ATP). Calculations have been made on simplified transformer single-phase and three-phase circuits View full abstract»

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