IEEJ Transactions on Power and Energy
Online ISSN : 1348-8147
Print ISSN : 0385-4213
ISSN-L : 0385-4213
Volume 118 , Issue 12
Showing 1-17 articles out of 17 articles from the selected issue
  • Ichiro Gessei, Sadao Fukunage
    1998 Volume 118 Issue 12 Pages 1343-1346
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
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  • Chung-Neng Huang, Hiroumi Saitoh, Junichi Toyoda
    1998 Volume 118 Issue 12 Pages 1347-1356
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    This paper proposes a novel method to identify the area where the power flow can be controlled by phase shifters. In the proposed method, first, the minimum number of phase shifters necessary for the control of power flow in an entire network is determined as the number of co-trees. Since the set of co-trees is not unique, there exists several allocations of phase shifters. Next, the features of controllable area with respect to each allocation are extracted as the eigenvalues and eigenvectors of the matrix, which represents sensitivities of power flows to control angles of phase shifters. The extracted features are applicable to the determination of phase shifter allocation from the viewpoint of flexible power flow control in network open access environments. The effectiveness of the proposed method is confirmed through the simulation studies of two model systems.
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  • Masaru Iguchi, Takao Ueda, Susumu Yamashiro
    1998 Volume 118 Issue 12 Pages 1357-1362
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The maintenance schedule of thermal units is indispensable to prevent a power outage and also has a severe effect on not only reliability, but also stability and economy of power system operations. Under the current deregulation of power industry, the latter aspect of economy is becoming more important recently.
    This paper proposes a new objective function by which an economic maintenance schedule is expected to be realized while satisfying reserve margin constraints. Furthermore, to evaluate the economic aspect of an obtained maintenance schedule more precisely, thermal unit commitment scheduling is carried out over two year scheduling period, where the load pattern is represented by the daily load characteristics.
    The effectiveness of the proposed objective function is ascertained by comparison with the previously reported objective functions in terms of reliability, economy and the adaptability of application of solution methods, and the superiority of the proposed objective function is shown through various numerical examples.
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  • Masahiro Takasaki, Naoki Gibo, Kiyoshi Takenaka, Toshiyuki Hayashi, Hi ...
    1998 Volume 118 Issue 12 Pages 1363-1373
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    For extending self-commutated converter application to future trunk power system, it is important to develop stable operation scheme as well as to realize substantial cost reduction through coordinated system and control design. Suppression controls of converter overcurrent and dc overvoltage in various system fault conditions are essentially needed to ensure stable operation and cost reduction of HVDC system with voltage source type self-commutated converter. Converter control and protection schemes which include such suppression controls have been developed employing CRIEPI's AC•DC Power System Simulator test and EMTP analysis.
    This paper first discusses the cause of converter overcurrent at ac system fault considering the effect of PWM pulse number and converter control speed. Continued operation has been achieved by adding a new overcurrent suppression scheme into the converter control. In a condition of dc line grounding fault, the selection of grounding circuit constant and the adoption of high speed converter control practically ensure the reduction of dc overvoltage while suppressing converter overcurrent. Converter block and restart sequence after de fault, which is coordinated with dc circuit breaker operation, enables stable recovery of HVDC transmission as fast as the usual line-commutated HVDC system.
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  • Hiroyuki Sugita, Tetsuji Matsuo, Yoshitaka Inui, Motoo Ishikawa
    1998 Volume 118 Issue 12 Pages 1374-1379
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Performance characteristics of self-excited pulsed MHD power systems are investigated with one-dimensional time-dependent calculations using a gas-liquid two-fluid model. At first, Russian pulsed MHD power system 'Pamir-3U' is analyzed. The result of numerical simulations of hot-fire tests shows good agreement with the experimental data, confirming the validity of the mathematical model. Performance analysis of Pamir-3U reveals that the power output is approximately constant with the variation of load resistance, while the ballast resistor consumes large electric power. It is also shown that the system has been optimally designed to supply large load current. Next, a new system yielding larger power output is proposed and analyzed. The obtained characteristics show that the new system can provide the maximum power output of 25MW, which is larger than 15MW of Pamir-3U.
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  • Masanori Matsuoka, Satoaki Arai
    1998 Volume 118 Issue 12 Pages 1380-1385
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    In expulsion fuses, load break switches, the electrical arc is formed in a wall made of organic materials during the switching period and the electrical arc induces ablation of these materials. Ablated mass of the organic material is entrained into the gas and arc flow. The estimate of ablated mass is important factor in the design of these devices, therefore, a number of theoretical and experimental investigations have been studied on high current arc in a narrow channel.
    Ablation arcs in a cylindrical tube which has a pressure chamber at its one end have been investigated experimentally and theoretically. The ablation arc phenomena obtained experimentally are interpreted by the model consisting of four processes which are described by the relationship among the pressure distribu-tion, gas flow in the tube and the pressure in the pressure chamber . The estimate of ablated mass inside the tube under arc heating is essential for the theoretical construction of the ablation arc model. The data of ablated mass has been obtained by the experiment.
    This paper describes the experiment and theoretical calculation about ablated mass of plastic tubes. Test samples are selected from the materials used for the arc chamber of switching devices such as load break switches for 6. 6kV distribution line and circuit breakers . The experimental data of ablated mass is obtained about three kinds of plastic tubes. The selected materials are OF (urea formaldehyde resin), POM (polyace-tal), PTFE (polytetrafluoroethylene). Theoretical calculation is made by means of an ablation model consid-ering absorption of thermal energy due to phase-change and heat conduction in the thin layer inside the tube wall. Theoretical calculation and measurement of ablated mass are in good agreement under the heat efficiency of 0.04_??_0.07 for the plastic tubes.
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  • Ohkuma Takeshi, Kagami Jun, Nakauti Hitosi, Kikuchi Takehiko, Takeda K ...
    1998 Volume 118 Issue 12 Pages 1386-1397
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    This study aims at clarifying the factors that cause transmission line galloping and the conditions influencing it, and at determining response evaluation indices of gallopings in turbulent flows. This is done using a three dimensional analytical method considering a large deformation. The analysis is based on 4-bundled transmission lines. Obtained results are as follows;
    1) The occurrence of galloping in the smooth flow is limited by the combination of the following parameters: the initial angle of wind attack, the initial icing angle and the wind speed. The galloping predominates mainly with one or two of the lowest in-plane, out-of-plane and torsional modes for the free vibration under the conditions that the transmission line is subject to dead load as well as static wind force. However, the galloping always occurs with torsional vibration.
    2) The shape of Lissajotis's figure for displacement depends on the initial angle of wind attack and the initial icing angle, as well as wind speed. The main shapes are vertically elliptic, horizontally elliptic and a configuration having the shape of a horizontally rotated figure of eight.
    3) The predominant frequency components of gallopings in turbulent flows are amplified and controlled by the turbulence intensity. Vibration frequency components unrelated to galloping increase linearly with rise in turbulence intensity.
    4) There is a 30sec time lag between galloping vibration and the fluctuating wind speed. The relationships between mean wind speeds and both trend components and standard deviations of galloping in turbulent flows closely correspond to those relationships during the smooth flow, and they can be obtained using the average time of 10 times the shortest vibration period of the transmission line. That is, the response values of transmission lines in the smooth flow can be utilized to estimate gallopings in turbulent flows. To estimate the maximum amplitude of a galloping, a peak factor of approximately 2.5 can be used.
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  • Shinya Ohtsuka, Hidekazu Ohtsubo, Takashi Nakamura, Daisuke Tsuji, Jun ...
    1998 Volume 118 Issue 12 Pages 1398-1405
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    A persistent current switch (PCS) in the GWh class SMES system for load leveling needs to have high OFF resistance as well as zero ON resistance for high efficient SMES operations. So far, the authors have successfully developed NbTi mechanical PCS which has zero ON resistance, i. e. zero contact resistance, and can flow the current up to 200A without quench. The PCS should break current of a few tens amperes even with the counter pulsed technique to reduce the breaking current. The current breaking generates arc discharge which alters the contact condition. Since the superconducting connection strongly depends on conditions of contact surfaces, it is necessary to clarify the influence of the arc discharge on the PCS performance. In this study, arc discharge characteristics of NbTi mechanical PCS and influence of arc on superconducting connection at contact are experimentally investigated using a circuit including a superconducting coil of 1 H and a damping resistance in liquid helium. Arc discharge characteristics are almost similar although arc maintain voltage of 12 V is smaller than that observed with copper contact. Arc discharge does not degrade but rather improves the PCS performance as long as the breaking current is smaller than 50 A. The improvement is attributed to enhanced bridge formation on the contact surfaces and removal effect of the surface oxide film by arc discharge.
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  • Hirotaka Muto, Masashi Doi, Haruhisa Fujii, Mitsuhito Kamei
    1998 Volume 118 Issue 12 Pages 1406-1414
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Electromagnetic wave is used for detectin of partial discharges(PD) in GIS(Gas Insulated Substation). Very wide frequency band up to 1. 5GHz is utilized for the detection. There are three categories of electromagnetic wave which can be excited and propagate in coaxial cylindrical structure like GIS: TEM, TE, TM modes. The characterization and identification of each mode are indispensable to understand the partial discharge phenomena in GIS. In this paper, peaks in frequency spectrum excited by PD are identified in its mode and the resonant characteristics of each mode are studied. The followings are the major results: (1) The resonant peaks appear at the frequencies defined by the spacer distance. (2)The intensity of each mode depends on the position of discharge source along the radial direction. The lower order modes including TEM are excited when a discharge source is located near the center conductor. On the other hand, higer order modes are excited being the discharge source at the enclosure surface. (3) The experimental profile of each mode excited by PD along radial direction approximately agrees with the general theory of electromagnetic wave propagation in coaxial cylindrical cavity.
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  • Hitoshi Kijima, Masahiro Zaima, Kazuo Murakawa, Chikashi Okabayashi, T ...
    1998 Volume 118 Issue 12 Pages 1415-1423
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Insulating transformers in a light, compact unit were developed for providing the best connection to a newly configured grounding system in a telecommunications center building. In the conventional grounding system, telecommunications equipment was tripped by stray DC current and lightning. To solve this problem, a new grounding system was designed with use of insulating transformers. As the specifications of conventional insulating transformers are not sufficient, small-sized insulating transformers were developed. The insulating transformers offer high dielectric strength (more than 50 kV) with low insertion loss (less than 0. 5 dB) in the transmission frequency of 64 kHz to 8 MHz. A dedicated distribution frame was also developed to install the insulating transformers with necessary functions for both jumpering and terminating cables.
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  • Kensaku Miyazaki, Nobuyuki Miyake, Shigeru Kawaguchi, Katsumi Suzuki, ...
    1998 Volume 118 Issue 12 Pages 1424-1430
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The synthetic test is a method to evaluate the interrupting capability of a gas circuit breaker (GCB) used for power system. Because the quality of equivalent circuit will be decided by the starting control of the voltage source, the starting control system with highly stabilized operational characteristics becomes necessary. Recently, because the rated voltage of the testing GCB becomes high and the interrupting capacity becomes large, the voltage of the electrical source becomes high and the current becomes large also. For this reason the starting characteristic of the old starting system became unstable. To solve this problem, a new starting system, using SF6 gas gap switch and laser triggering system, has been developed. In this paper, the development and the test result of the new starting system will be reported.
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  • Isao Inoue, Motoo Ishikawa, Juro Umoto
    1998 Volume 118 Issue 12 Pages 1431-1436
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Characteristics of leakage current in a coal-fired MI-ID generator are studied by a two-dimensional time dependent numerical modeling, the method of which is based on a Finite Element Mathematics formulation for the generator electrodynamics. The analysis is directed at the study of electrical behavior near electrodes influenced by the slag coverage. The simulations have produced solutions which can explained the experimental results of the electric field and the current density for Component Development and Integration Facility 1A4 generator. The following observations are drawn from the analyses. High electrical conductivity of the slag and the Hall effect are the main factors to generate the leakage current and the arc current through the slag layers. It is clarified that the leakage current increases exponentially in the slag conductivity. The leakage current is one of the principal factors of the observed damages to both edges of the cathodes. A local blowout of the slag can be supported by the Fuse Theory where the slag is locally dissipated by leakage currents like a fuse.
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  • Yasunari Morooka, Keiji Maeda, Kuniyoshi Ishii, Hiroshi Nakamoto, Shig ...
    1998 Volume 118 Issue 12 Pages 1437-1443
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Although zinc oxide arresters are generally used on poles of distribution lines to prevent line breakage and minimize temporary failures caused by lightning strokes in Japan, installation cost has become a problem requiring solution with the increasing number of arresters.
    A new line breakage prevention measure has been proposed which capitalizes on the characteristics of creeping discharge along overhead insulated power wires in order to promote cost reduction in lightning protection measures.
    The results of a superimposition test with lightning impulse voltage and AC voltage indicate that if the puncture site on an insulation cover is at least at a critical distance from the line post insulator, line breakage may not arise because the creeping discharge between the puncture site and insulator would not result in an AC follow current which could vaporize the power wires.
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  • Yerzan Eshaf, Satoaki Arai
    1998 Volume 118 Issue 12 Pages 1444-1449
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Three-phase simultaneous interruption will occurs in breaking low current by vacuum switch in a cable circuit. High surge voltages caused by multiple-reignition following three-phase simultaneous interruption will appear between the contacts and the terminals of the source transformer.
    This paper presents the investigation on three-phase simultaneous interruption phenomena in breaking low capacitive current by vacuum switch in a cable circuit. Voltages across the contacts and the terminals of the source transformer, and the currents flowing through the gaps are measured experimentally and calculated by the electromagnetic transients program (EMTP). As a arc model, Mayr type arc equation is used to calculate the high frequency arc currents and arc voltages of the vacuum switches, and good agreement between the calculation and the experimental results have been achieved. The domain of the occurrence of the three-phase simultaneous interruption concerning with current chopping, load current, cable length and insulation characteristic of the gaps is investigated by analysis.
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  • Katsunori Sakai, Takashi Kitai, Tadanori Maoka, Tsutomu Aoki, Mitsushi ...
    1998 Volume 118 Issue 12 Pages 1450-1456
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    It is well known that the voltage of phosphoric acid fuel cell drops due to its on-off operation. The experimental results show that the magnitude of voltage drop depends on the operating cell voltage, the amount of O2 residue in the cathode electrode and start-stop operating duration. The results of half cell and small sized cell test show that the catalyst sintering and flooding of catalyst layer have been promoted by on-off operation with high electrode potential and high temperature, result-ing the voltage drop of fuel cell. To suppress the voltage drop due to its on-off operation, it is necessary to insert the dumy resistance, to operate N2 purge and avoid air intrusion from exterior of the fuel cell. It is also effective to suppress the wetting speed of the catalyst layer with electrolyte by increasing its hydrophobicity.
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  • Yoshihiro Okuno, Kunio Yoshikawa, Tetsuji Okamura, Hiroyuki Yamasaki, ...
    1998 Volume 118 Issue 12 Pages 1457-1462
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    A closed cycle MHD (CCMHD) single power generation system without any conventional gas turbine and steam turbine power generation systems is proposed as one possibility of highly efficient power plant. On the basis of preliminary calculations, the total plant efficiency of the CCMHD single system can reach 60%, which is comparable to that of the CCMHD system combined with conventional bottoming power generation systems. The exclusion of the bottoming systems requires a high performance heat recovery system working for relatively high temperature. The CCMHD single system proposed here is worth examining in more detail.
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  • Yoshitaka Inui, Motoo Ishikawa
    1998 Volume 118 Issue 12 Pages 1463-1470
    Published: December 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    At first, the authors investigate in detail the performance of an impurity-contaminated nonequilibrium disk MHD generator using cesium seeded argon plasma through the quasi-one-dimensional time-dependent numerical analyses and, using the obtained information, propose a new control method for performance improvement of impurity-contaminated generator. The method is applicable even in the case the impurity concentration varies in time, and it is expected that the performance is perfectly recovered from the deterioration and the electrical output power of the generator is always regulated at its nominal value. Next, a time-dependent numerical simulation is carried out for the generator controlled by the proposed method in the case the impurity concentration varies in time, and it is confirmed that the proposed control method has excellent effects as expected on the performance improvement of impurity-contaminated generator.
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