IEEJ Transactions on Power and Energy
Online ISSN : 1348-8147
Print ISSN : 0385-4213
ISSN-L : 0385-4213
Volume 115 , Issue 12
Showing 1-17 articles out of 17 articles from the selected issue
  • Kazuyoshi Nagai, Hideo Kitagawa, Hiroyuki Hirayama
    1995 Volume 115 Issue 12 Pages 1401-1405
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
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  • Tadshiro Yanagisawa, Tadashi Taguchi, Michiyuki Abe, Hirokazu Kaneko, ...
    1995 Volume 115 Issue 12 Pages 1406-1411
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    A converter-fed variable-speed generator-motor for a pumped storage power plant has been developed in order to contribute to the automatic frequency control on an electric power system during pumping operations, as well as to improve the efficiency of turbines during generating operation together with electric power stability. This system consists of a reversible pump-turbine, generator-motor, cycloconverter and control units. The rotor of the generator-motor, which is coupled directly with the turbine runner, is normally operated at a rotating speed equal to the difference between the frequency of the electric power system and that of the rotor current. In the state that a fault has occurred in the primary circuit of the generator-motor, the variable-speed rotating speed varies and the generator-motor fault current differs from that of a conventional synchronous generator-motor.
    We have previously reported the fault current analysis results on the assumption that the rotating-speed of the generator-motor does not vary during the fault. However the rotating-speed of the generator-motor does vary during the fault, therefore this paper describes the fault current analysis results without this assumption for the condition when a sudden short-circuit is made on the primary side or secondary side of the generator-motor, and collates the analysis results with the EMTP simulation results.
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  • Takeshi Takashima, Handong Wang, Takahiro Sakuta, Tosio Satoh
    1995 Volume 115 Issue 12 Pages 1412-1418
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    For the design of a grounding electrode, the ground configuration at an intended site for the electrode needs to be clear. For this purpose, in many cases, ρ-a curves from the measured results with Wenner's four electrodes arrangement are analysed by Sundberg's standard curves. But analysed results for ρ2 have not been sufficient especially when thicknesses of the second ground layers are small.
    In this paper, new standard curves are proposed for analysis of ρ-a curves. Sundberg's curves have one parameter of ρ2/ρ1. However, the new standard curves have two other parameters of ρ3/ρ2 and h2/h1, in addition to ρ2/ρl. Accordingly the new standard curves resemble ρ-a curves for three-layer grounds in shape.
    First constitutions of the new standard curves are described. Then many model ρ-a curves are analysed for ρ1, h1 and ρ2 by the new standard curves and also by Sundberg's curves. It is found that the new curves are better than or as good as Sundberg's curves, and the errors of the results for ρ2 analysed by the new curves are less than 12%.
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  • Yasuyuki Tsutsumi, Sachio Yamada, Motoaki Komata
    1995 Volume 115 Issue 12 Pages 1419-1425
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    It is well known that previous penetration of phosphoric acid into wet proofed catalyst layer of phosphoric acid fuel cells is necessary for initial stable operation at high current density.
    In order to accelerate the penetration and improve the electrode performance, five methods are tested such as ultrasonic vibration, vacuum impregnation, alcohol addition, acid concentration and electric capillarity. External pushing forces such as ultrasonic vibration or vacuum impregnation are not so effective for accelarating the penetration, whereas interfacial forces affected by alcohol addition, acid concentration or electric capillarity are much effective.
    Though electrode performance increases with increasing penetrated acid volume, performance of acid penetrated electrode by alcohol addition is low compared with that by acid concentration or electric capillarity at same penetrated acid volume.
    Acid penetrating mechanism, mechanism of unstable phenomena on initial operation at high current density, a diagnostic method for insufficient acid penetrated cells and accelerating methods for acid penetration into catalyst layer are proposed.
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  • Susumu Yamashiro, Hisashi Kinoshita, Kouichi Nakamura, Mitugu Kimura, ...
    1995 Volume 115 Issue 12 Pages 1426-1431
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Under the current deregulation of electric utility industry, power system planning has become more complex. System planners are required to study how to use the available resources to meet customer's demand economically with an acceptable reliability and quality. The integrated resource planning is emerged as one of the effective approach for this problem recently and the approach has been expanded to include the value of reliability, that is, power interruption cost.
    This paper is aimed to develop a flexible decision method to select a favorable plan among various transmission system expansion alternatives, not only from power supplier's view point, but also from customer's perspective including cost of interruption.
    Bellman-Zadeh's maximizing decision using fuzzy decision set is applied as an flexible decision method which is able to reflect the planner's intensions. Numerical examples are shown to ascertain the effectiveness of the proposed method.
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  • K. Honda, H. Sasaki, M. Osada, S. Maebara, H. Yokose
    1995 Volume 115 Issue 12 Pages 1432-1437
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The demand-supply imbalance on electric power system is absorbed by system frequency variations, before the LFC controls. Since frequency fluctuations are common in all linked blocks, demand-supply imbalance of one block is absorbed by another block too. Demand-supply imbalance arises in another block simultaneously, and is absorbed by the former block. These mutual supports have a direct effect on linkage power fluctuations. The size of this self-regulation is regarded as proportional to the size of frequency fluctuation and the ratio of the former to the latter is nearly proportional to the block capacity. But, at a short period variation range, there is a fear that such a proportional relation will be biased by linkage position. We analyze this point, and reached the following conclusions. First, we can prove the existence of self-regulation bias theoretically and point out that the bias has some effect on linkage power fluctuations at short period variation range. Second, we apply this analytical method to 4 blocks-linked system of Japan, and compare the theoretical value with measured one. The result indicates no correlation among demand fluctuations of those blocks which are presupposed for calculation of the theoretical values; among several blocks is found some ununiformity of the smallest unit size of demand power variations.
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  • Kazuo Gotoh, Yutaka Nagata, Yoji Uchiyama, Yasuhiko Fujii
    1995 Volume 115 Issue 12 Pages 1438-1446
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    To find the economical merit of Photovoltaic Power Plant (PV) introduced into the electric generation mix as one of the alternative power source, the generation planning simulation analysis including PV up to fiscal year 2030 has been made with use of a probabirity model of PV output. In the probabirity model, it has been taken into account that there is an advantage for the correlation between PV output and the electric load over the considering electric power system, and then the value of capacity for PV as an index about confidence on operating power source (what we call kW effect of PV) has been estimated.
    The economic analysis has been extended to the installation of battery, which is expected to raise the kW effect of PV.
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  • Hiroyuki Fudou, Yukio Kawasaki, Susumu Egawa, Kouichi Shinozaki, Norio ...
    1995 Volume 115 Issue 12 Pages 1447-1454
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    In order to improve the reliability of electricity service, a distribution line state monitoring system has been developed, which is composed of the central control unit, the remote control switches, the slave unit and the monitoring sensors. The first system employed fiber-optic voltage and current sensor. The latest system employs a unique form of cost reduction, with no voltage sensors incorporated. This system can detect the grounding direction by the information of the phase difference between the line-to-line voltage and lo provided by the monitoring sensor, and grounded line information (64 ø) from the substation. The installation of the system has been proceeding since 1992, at present, displays its performance.
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  • Hideo Tanaka, Takao Ueda, Shogo Nishida
    1995 Volume 115 Issue 12 Pages 1455-1461
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    This paper proposes a computer-supported collaborative learning environment to enhance knowledge creation, store and transfer in power system education. Recently power systems have become more complex than before. This situation has become more noticeable year by year, and there is a strong need to develop an educational system which is useful for novice engineers. A number of research on CAI (Computer-Assisted Instruction system) has been done to overcome the problem. A central concern of the research is to make computer more intelligent by applying Artificial Intelligence technology, such as knowledge representation, student modeling, etc. On the other hand our research focuses on collaboration of engineers as an important activity in learning process, and provides a collaborative learning environment to enhance knowledge creation, store and transfer in cooperation with other engineers. In terms of computer system the proposed system is a learning environment based on a personal visual simulator which has a function to support collaborative work with other engineers through computer network.
    In this paper, first the significance of this research is made clear in comparison with research on CAI and CSCW (Computer-Supported Cooperative Work). Secondly, the features of the system, basic function, architecture of window sharing and data structures are explained in detail. Finally, the effectiveness of the system is discussed by using an example of power system, and results of simple evaluation are shown.
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  • Hui Chen, Osami Tsukamoto
    1995 Volume 115 Issue 12 Pages 1462-1470
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    A fully superconducting generator, which possesses both superconducting armature windings and superconducting field windings, has great potential merits to increase efficiency and decrease size and weight, compared with a partially superconducting generator that has normal armature windings and superconducting field windings. To obtain these merits, the warm and cold dampers should be omitted. However, a fully superconducting and damperless generator (FSDG) has following problems when it is operated being connected to a power line system: (1) The dynamic stability of the generator operation is deteriorated because the FSDG has no damping elements. (2) When the power system is subject to a fault, big transient currents and electric torque are induced in the superconducting armature and field windings, which may cause quenches in the windings. As to the problem (1), we have shown that the generator could be stabilized in wide range of the operation by controlling the excitation voltage of the field winding in our previous work.
    In this paper, the problem (2) is addressed. We investigate methods, adjusting electric parameters of the generator and introducing superconducting current limiters (the inductance type and the resistance type), to suppress the peak values of the transient currents in the armature and field windings and the transient torque. Characteristics of these methods are studied by numerical simulation and it is shown that the introducing of the resistance type current limiter is the most effective.
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  • Kazuhiro Kajikawa, Katsuyuki Kaiho, Mitsuyoshi Yamamoto, Hiroshi Fuji, ...
    1995 Volume 115 Issue 12 Pages 1471-1479
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Recently, multifilamentary superconducting wires with very low AC losses have been produced and those practical applications are going to be realized. To realize the actual-size power machines and apparatuses, it is necessary to develop 1_??_10 kA AC conductors. However, the critical currents of multifilamentary wires at I T are several-tens A, and therefore it is necessary to use the multistrand conductors consisting of several-tens or -hundreds of strands. Such conductors sometimes show AC current degradations because of some sources as (1) imperfect transposition, (2) wire motion, (3) temperature increase, (4) longitudinal magnetic field component effect and so on.
    Formerly, a coreless transformer had been considered to be unpractical because of its large exciting current. However, Yamamoto et al. proposed that a coreless superconducting transformer should be possible as a step-down autotransformer at the receiving side utilizing its large exciting current as the reactive power source to cancel the charging current of an underground transmission line or UHV line, and therefore the shunt reactors could be eliminated.
    In this paper, about the configurations and characteristics of AC conductors which are removed of some causes of AC degradations are mentioned, and then the quench test results of two small coils made with these conductors are reported. In these conductors, low AC loss strands with ultra-fine NbTi filaments are twisted around central bundle of stainless steel wires. One of the coils has been designed as a model coreless autotransformer, and its test result is also described.
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  • Maki Ishizawa, Shigemi Iida, Isao Abe
    1995 Volume 115 Issue 12 Pages 1480-1486
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    We have developed a new heat recovery method that uses a heat exchanger in which there is direct contact between the fuel cell exhaust gas and the heat recovery water. Estimates of the heat recovered from the exhaust gas of a 50-kW fuel cell show that the amount of the recovered heat decreased due to the decrease in latent heat when the temperature of the heat recovery water increased. Futhermore, more heat was recovered from the reformer exhaust gas than from the cathode exhaust gas. The amount of recovered heat was confirmed to be hardly influenced by the diameter and the mass of the packed column, and the angle of the perforated plate in the direct contact heat exchanger, nevertheless the pressure drop was influenced remarkably. The amount of recovered heat agreed well with the estimated value, and the maximum temperature of the heat recovery was 78°C. The efficiency of heat recovery from the reformer exhaust gas was 9% at the heat recovery temperature of 65°C, so it can supply an absorption refrigerator with steam and hot water.
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  • Kunio Yokokura, Junichi Arai, Eiji Kaneko, Toshihiko Komukai, Takashi ...
    1995 Volume 115 Issue 12 Pages 1487-1493
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    We analized the switching duties for circuit breakers which are applied to 13.8kV system in the Uruguaiana static frequency converter station interconnected the Brazillian 60Hz and Argentine 50Hz electrical power systems. We usually select the ratings of the circuit breakers for medium voltage system according to the system voltage, normal current and short circuit current without the system analysis; however, by present analysis we found out the severe recovery voltage could be able to appear in the 13.8kV system when circuit breakers interrupted the short circuit current and the capacitor cur-rent. On the basis of these analysis results, we applied higher rated voltage circuit breakers to the frequency converter station.
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  • Toshiaki Ueda, Sadanori Neo, Toshirou Sugimoto, Toshihisa Funabashi, N ...
    1995 Volume 115 Issue 12 Pages 1494-1500
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    This paper proposed an improved model to simulate the transfer voltage of a power transformer. This model consists of the EMTP TRANSFORMER model with some capacitances, and is used as a component of EMTP. Conventionally, the power frequency EMTP TRANSFORMER model can not be used for high frequency transfer voltage study. In high frequency transfer voltage study, transformers are simulated as capacitances only. This representation is very simple and less accurate. Recently, the high frequency transformer models have been reported. these models are based on the numerical calculations for a wide range of frequency response of the transformer. However, the users have to deal with the model as a black box, the physical meaning of which is unknown.
    In this paper, the measurement of transfer voltages for an actual transformer(11/154kV, 68.3MVA) was performed in various conditions. The value of various parameters of the proposed model are calculated from the actual measurements entailing no numerical calculations and help in understanding their physical relevance. The accuracy of the proposed model is confirmed by comparing the simulated results with the actual measurements.
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  • Masamitsu Kosaki, Masayuki Nagao, Yukio Mizuno, Atsushi Minoda, Noriyu ...
    1995 Volume 115 Issue 12 Pages 1501-1507
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The extensive use of an extruded crosslinked polyethylene insulation for the power transmission cables and the excellent insulation capabilities of polymeric materials at cryogenic temperatures allure a challenging trial of applying them to the electrical insulation of superconducting cables. Through a long and systematic survey and research on material properties, authors came to the conclusion that ethylene-propylene rubber (EPR) is highly suited for this purpose. Thus efforts were made toward the development and testing of the extruded EPR insulated superconducting cables. The superconductor is a niobium layer clad on a copper pipe. The main insulation design consists of EPR simulatneously extruded with semiconducting electrostatic shielding layers. Helium is the coolant for the superconductor and solely plays a role of cooling the cable. The complete exclusion of the vulnerable cryogenic helium from the electrical insulation structure is the specific feature of this cable. The cable is cooled down to the boiling helium temperature (4.2K) inside the copper pipe and subsequently the voltage (20kVrms) and current (2kArms) tests were carried out successfully. Ethylene-propylene rubber has proved to be the distinguished material for cryogenic electrical insulation.
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  • Yosuke Hashimoto, Shigeru Yokoyama, Tsutomu Yokota, Akira Asakawa
    1995 Volume 115 Issue 12 Pages 1508-1514
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    To clarify characteristics of lightning stroke distance to power distribution lines, experimental studies were done on discharge characteristics of a rod-ground wire (open wire) and a rod-conductor (insulated wire). The experiments were done by using the 12MV impulse generator at Shiobara testing yard of CRIEPI.
    50% flashover voltage of a rod-insulated wire gap is higher than that of a rod-open wire gap under negative impulse voltages (2/50_??_250/1700μs) and a positive lightning impulse voltage (2/50μs). These effects become so notable as an insulated part of the insulated wire is thicker. Measurements by using ALPS (Automatic Lightning-Discharge Progressing-Feature Observation System) show that development of an upward leader from an insulated wire is suppressed by the insulated part of the wire. Therefore it is clarified that an insulated wire is more unlikely to attract lightning hits than an open wire.
    From these experimental results, characteristics of lightning stroke distance to power distribution lines were studied in the case that a ground wire is removed. Attractive area of direct lightning hit to a conductor (insulated wire) becomes narrower as the peak value of lightning stroke current becomes higher.
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  • Yoshio Maehana, Takao Ino, Shuichi Nitta
    1995 Volume 115 Issue 12 Pages 1515-1522
    Published: November 20, 1995
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    It is well-known that a twisted-pair wire (TPW) is very effective for reduction of the inductive coupling noise. The model of reduction of the coupling noise on TPW has been studied by C. R. Paul. In this model, he describes on an effect of reducing the inductive and capacitive coupling noise, and carries out examination on TPW on the premise that the coupling noise has been induced on TPW. He also says that TPW has no effect for reducing the capacitive coupling noise in case that one side of TPW is grounded, and as a result, unbalanced, and that TPW has a great effect of reducing the capacitive coupling noise if TPW is balanced against ground.
    However, in practical cases, TPW is not used under balanced condition. And he does not quantitatively verify an effect of reducing the capacitive coupling noise, including a mechanism of the capacitive coupling.
    In this paper, we propose a simple capacitive coupling model and the equivalent circuit that are valid for low frequency area. And we study theoretically an effect of reducing the capacitive coupling noise and clarify experimentally its effect, in every case that TPW is balanced, unbalanced and grounded against ground.
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