bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of optical ZCT and its application to fault section detection for 66‐kV underground branch transmission lines
Authors: Toya Atsushi , Muraoka Keiichi , Inoue Nobukazu , Ando Kenichi 
Published: July 2007

AbstractThe optical ZCT (Zero‐phase Current Transformer) which combines an optical magnetic field sensor with a magnetic ring core of silicon steel plates has been developed. Bi‐doped YIG [Yttrium Iron Garnet, (BiYbGd)3Fe5o12] having a large Verdet constant is used as a Faraday element. The optical ZCT detects the conductor current of 0 to 2000 A at high resolution and has been applied to the fault section detection system for 66‐kV underground branch transmission lines which monitors a multiterminal line having Y‐branch joint box in on‐line state. Optical ZCTs and a section detector/indicator are connected with optical fibers which are capable of nonrepeatedly transmitting signals over 6 km, and allow monitoring long‐distance underground power transmission lines. A developed system is now operating on the JR Kasai line (Shinkawa pump line) of Tokyo Electric Power Company.
Circuit quality degradation caused by optical fiber cable switching
Authors: Watanabe Ichiro , Kobayashi Hideo 
Published: July 2007

AbstractWith increased demands for optical fiber cable removal, a system which reduces circuit quality degradation due to optical fiber switching has been strongly required. The optical switching elements and optical fiber switching systems were studied aimed at shortening optical switching time, optical loss and other optical specifications. However, the circuit quality degradation cannot be evaluated by these specifications. For this reason, it is important to study the circuit quality degradation due to optical fiber switching, and the study must comprehend the transmission system performance after optical fiber switching.To analyze the circuit quality degradation during optical fiber switching, the standard analysis model and the optimum analysis parameters were defined. Using them, the frame hunting time after optical fiber switching was studied theoretically and its influence on a working transmission system was estimated. The circuit degradation was evaluated experimentally with regard to an actual transmission system, and experimental results agreed with the estimation. Moreover, by utilizing the results of these studies, it was found that the reduction of circuit quality degradation can be realized firmly and the effect of these studies was verified.
Brushless self‐excited three‐phase synchronous generator without exciter
Authors: Inoue Kenji , Yamashita Hideo , Nakamae Eihachiro , Fujikawa Takayuki 
Published: July 2007

AbstractThis paper describes principles together with analytic and experimental studies of an exciterless, brushless, and self‐excited three‐phase synchronous generator which was devised by authors. Since traditional brushless and dc self‐excited three‐phase synchronous generators without exciter did not have the self‐exciting function by series characteristic component proportional to the load current inside the generator, they need auto‐voltage regulating equipment or a transformer with three windings and condensers to obtain constant voltage characteristics. It also has the following problem in the case of two‐pole traditional generator: oscillatory tension is generated at the shaft of the rotor caused by the magnetic force between magnetic poles of stator and rotor windings, and it causes mechanical vibration and noise.This paper proposes a new brushless and self‐excited three‐phase generator solving the aforementioned problems: the ratio of poles of the windings for providing power to load (armature and field windings) to the windings for supplying exciting power (stator and rotor exciting windings) is 1 to 5. Then oscillatory tension does not generate theoretically. Furthermore, a self‐exciting three‐phase generator using the 5th‐harmonic component of armature reaction which makes series characteristic component proportional to the load current, currently is available.In this paper, the winding construction, the electric circuit, and the principle of the aforementioned generator are described, and the experimental results of the trial‐produced generator show that the three‐phase terminal voltage waveforms are almost sinusoidal and also balanced, and the voltage can be kept almost constant for the change of load. This generator has high reliability because of its simple construction.
A parameter design method of pwm voltage‐source rectifier
Authors: Iwaji Yoshitaka , Fukuda Shoji 
Published: July 2007

AbstractThis paper describes a method of determining parameters of PWM rectifiers based on the degrees of total harmonic distortion (THD). The inductance value of ac reactors and the capacitance value of the dc capacitor have a great influence on the amplitude of the harmonics in the ac input currents and dc output voltage, respectively. So far, simulation‐based harmonic analysis is dominant.Here, the harmonic distortion determining factor is proposed that provides a simpler and broader manner of obtaining THD values, that is, it enables approximate THD values to be calculated without conducting any simulations or experiments. Finally, an experiment using a DSP is carried out to confirm the usefulness. An optimal regulator theory is applied to the controller design.
A method of designing ac/dc thyristor converter current control systems by using discrete time MRAC with deterministic disturbances
Authors: Xu Z. , Mochizuki Takuro , Tanaka Yoshiaki , Hanamoto Takahashi 
Published: July 2007

AbstractTwo design methods of ac/dc thyristor converter current control systems with MRAC (Model Reference Adaptive Control) have been designed. To linearize the input/output relation of the systems, the constant term of the model is considered in different ways. In the first method, a linear transformation of the control input is made while in the second method, the constant term and compensated modeling error are neglected by integral adaptation. Computer simulations and experiments have shown that the control performances of the MRAC systems are much better than that of PI controllers. However, in the first method, since the variable vector is not persistently spanning, the convergence rate of estimated parameters is not as high as expected. The second method has better dynamic characteristics but its stability has not been proved in theory.This paper suggests a new design method in which the constant term is considered as a deterministic disturbance. The feature of this method is that by introducing an equality equation which makes the term of disturbances apparently unobservable, the effect of disturbances can be eliminated and the existing adaptive control scheme without disturbances whose stability has been proved theoretically can be used. Computer simulations and experiments show that the new method can obtain better responses than the old ones.
Effect of CaO and SiO2 addition on magnetic properties of anisotropic Ba‐Zn system W‐type hexagonal ferrite magnets
Authors: Yamamoto Hiroshi , Ishii Akinori 
Published: July 2007

AbstractAn experiment was carried out to investigate the effect of CaO and SiO2 addition on the magnetic and physical properties of anisotropic Ba‐Zn W‐type hexagonal ferrite magnets. It was found that magnetic properties of BaO.2ZnO.8Fe2O3 compounds added with CaO and SiO2 were improved. The optimum conditions of typical specimens are as follows: chemical analysis composition‐Ba0.857 Zn1.643 Ca0.150 Si0.266 Fe2+0.030 Fe3+15.857 O27; semisintering condition‐1275°C × 1.0 h in air; sintering condition‐ 1250°C × in air, magnetic and physical properties are Jm = 0.436 T, Jr = 0.393 T. Hcj = 64.4 kA/m, HcB = 64.1 kA/m, (BH)max = 16.1 kJ/m3, Tc = 357°C, HA = 971 kA/m, KA = 2.03 × 105 J/m3 and nB = 33.2 μB.
An efficient method of modifying Z‐matrix elements in short‐circuit capacity calculations
Authors: Tanaka Kazuyuki , Takahashi Kazuhiro 
Published: July 2007

AbstractShort‐circuit study is one of the most fundamental planning analysis procedures for electric power utilities. Measures for increasing transfer capabilities such as installation of additional facilities were originally implemented for the purpose of improving system stability. However, the reinforcement of transmission networks is commonly the major factor in increasing short‐circuit currents. Therefore, short‐circuit studies should be given greater attention in the future, especially with regard to coordination of power system availability and reliability.To effectively solve these problems, it is necessary to develop an advanced algorithm to easily compute short‐circuit currents in one round for a large number of alternative network configurations corresponding to operational changes in bus connections at main substations.This paper proposes a new calculation method to efficiently modify the Z‐bus matrix elements for short‐circuit studies of large power networks, and also demonstrates its practicality by applying the proposed method to the calculation of short‐circuit currents in two model networks.
A fast solution method for multiobjective optimal power flow using an interactive approach
Authors: Kubokawa Junji , Sasaki Hiroshi , Yorino Naoto , Yokoyama Ryuichi , Tanabe Ryuya , Okubo Yoshito 
Published: July 2007

AbstractIn modern industrialized societies, it is mandatory to provide an uninterrupted supply of high‐quality electric energy at modest cost while promoting a better environment. This can only be realized through very sophisticated power system operations that compromise several contradictory factors, namely, economy, security and environment. Since these factors are in trade‐off relationships to each other, they should be analyzed appropriately. One class of problems that simultaneously satisfy several criteria in trade‐off relationships is called “multiobjective optimization problems.” Optimal power flow (OPF) has been regarded as the most powerful means to obtain effective system operation plans since it only optimizes a single objective function.This paper proposes an efficient solution methodology for a class of multiobjective optimal power flow problems which makes use of a heuristic search method. An optimal solution can be found in the proposed heuristic search method based on local information about a preference index, which is chosen arbitrarily from a given set of objectives. This circumvents the exhaustive evaluation of all noninferior solutions needed in the existing multiobjective OPF algorithm proposed by the authors, thus dramatically reducing the solution time. The proposed method has been coded and applied to the IEEE 57 node test system. Simulation results have demonstrated the possibility of utilizing this method in on‐line environments.
New type of Nb3Sn fiber‐reinforced superconductors for high‐field pulsed magnet and effect of thermal stress
Authors: Arai Kazuaki , Tateishi Hiroshi , Umeda Masaichi , Agatsuma Ko 
Published: July 2007

AbstractA new type of superconductor with high elastic modulus fibers is being developed for the application of high‐field pulsed superconducting magnets called Fiber‐Reinforced Superconductors (FRS). FRSs have great potential for the construction of a 15‐T class pulses magnet with its size kept equal to ITER because stainless steels of cable‐in‐conduit‐conductors could be reduced considerably.This paper presents a technique of preparing FRS and measuring its superconducting characteristics including strain‐Ic relation. FRS has a critical current density of 600 (A/mm2/initial niobium) at 15 T, which is almost equal to one of the commercial bronze‐processed wires. The intrinsic strain vs. Ic characteristics are similar to that of bronze‐processed wire. Thermal strain on FRS also is discussed because materials with high elastic modulus tend to have low thermal contraction which leads to degradation of the superconducting characteristics of the Nb3Sn layer. Possibilities of overcoming the degradation while maintaining very high elastic modulus of tungsten fiber for reinforcement are shown.
Magnetic properties of La2Co17‐x‐yFexTiy and La2Co17‐x‐yFexTiyNδ
Authors: Hasebe Akio , Imai Tetsutaro , Otsuki Etsuo 
Published: July 2007

AbstractThe magnetic properties of La2Co17‐x‐yFexTiy and La2Co17‐x‐yFexTiyNδ intermetallic compounds have been investigated. La2Co17‐x‐yFexTiy has the rhombohedral Th2Zn17 structure and exhibits the following magnetic properties: saturation magnetization >1.0 T; Curie temperature >873 K; and easy c‐axis.Nitrogen is introduced into these compounds interstitially through the nitrogenation process. The saturation magnetization and Curie temperature of La2Co17‐x‐yFexTiyNδ is decreased by the introduction of nitrogen, in contrast to Sm2Fe17.
Development of fuzzy excitation control system
Authors: Kitauchi Yoshihiro , Taniguchi Haruhito 
Published: July 2007

AbstractPower system stability is essential to reliable and economical operation of power systems. The quick‐response excitation control with PSS is used as a power system stability improvement measure at the generator. However, this method is not always sufficient to apply in a wide operation range of power system configuration, load flow, and so on.This paper includes results of experiments of fuzzy excitation control system on the ac/dc Power System Simulator of CRIEPI. This control system is verified to improve power system stability and has better performance than the conventional excitation control on a one‐and two‐machine to infinite bus system.
Magnetic properties of iron‐based materials (nitrogen interstitially modified 1:12 compounds and Fe3B‐Nd) for low rare‐earth bonded magnets
Authors: Hirosawa Satoshi , Makita Ken , Kanekiyo Yoshikazu , Umemoto Minoru 
Published: July 2007

AbstractHard magnetic properties of nitrogen interstitially modified NdMxFe12‐xNy compounds and Fe3B‐based ultra‐fine crystalline NdFeCoTB alloys of low Nd content of 3 to 5 at. % are studied. The nitrogen‐modified compounds have been prepared via the rapid solidification route and the mechanical alloying route both followed by gas nitrogenation using N2. The Fe3B‐based materials have been prepared by means of rapid solidification and crystallization treatment. The latter materials appear promising as the base material for high‐remanence, easy‐to‐magnetize bonded magnets with small temperature coefficients of remanence. Typical magnetic properties of compaction isotropic bonded magnets produced from this material are Br = 0.80 T, HcJ = 350 kA/m, and (BH)max = 60.5 kJ/m3.
An efficient algorithm for optimal generation mix taking into account fuzziness of decision making and planning parameters
Authors: Tanabe Ryuya , Yasuda Keiichiro , Yokoyama Ryuichi 
Published: July 2007

AbstractThis paper presents an efficient computational algorithm for selecting the optimal generation mix under uncertain circumstances. Subjective, experiential or linguistic uncertainties are selected from among various uncertainties, i.e., we treat fuzziness in generation expansion planning. The fuzziness can be divided into: (1) the fuzziness of decision making; and (2) the fuzziness of some planning parameters, such as load growth, fuel price, and so on. Both classes of fuzziness are integrated into a fuzzy decision based on fuzzy sets theory, and then the optimal generation mix can be determined by the Fuzzy Dynamic Programming (FDP) technique.The proposed method, which is based on the dynamic programming technique, is extended by using the Bellman‐Zadeh maximizing decision. In the method, each generation technology and generation capacity are selected as a stage and state, respectively. The proposed method can easily accommodate not only the fuzziness but also many constraints of generation expansion planning, such as integer solutions of unit capacities, condition of existing units, and so on. Furthermore, the arbitrary shape of membership function can be used. The effectiveness and feasibility of the proposed method are demonstrated on a typical power system model.
Diamond‐like carbon film produced by vacuum arc deposition technique and its surface appearance
Authors: Takikawa Hirofumi , Taketomi Koichi , Sakakibara Tateki 
Published: July 2007

AbstractDiamond‐like carbon (DLC) films are deposited in a dc vacuum arc plasma with a graphite cathode. The arc current, the flow rate of hydrogen gas and the pressure are 50 A, 10 ml/min and 0.05 Pa, respectively. The substrate materials are Si (111), soda‐glass and Mo. Process parameters are deposition time (3 to 30 min). The films are analyzed by laser Raman spectroscopy and the surface appearance of the films are observed with an optical microscope.The results are as follows: (1) the films deposited under these conditions have diamond‐like carbon structure; (2) the films deposited for 3 min on Si or Mo and for 5 min on glass, wrinkle on the substrates; (3) the films deposited for more than 10 min on Si and for more than 15 min on glass, crack and flake off the substrates; and (4) the films deposited for more than 10 min on Mo, plainly stick on the substrate without any wrinkles or flakes.It is found that plain DLC films are able to be produced by the vacuum arc deposition method if the deposition time is selected appropriately, while never by the conventional plasma CVD method.
High‐precision voltage‐measuring method using fast sampled data for electric power systems
Authors: Chiba Tomio , Kido Mitsuyasu , Kawakami Junzou , Yoneda Katsuhiko , Kawai Tadao , Hirasawa Kotaro 
Published: July 2007

AbstractControl and protection equipment in power systems requires higher sensitivity and operational reliability to meet today's changing power system requirements. The voltage‐measuring deviation requirement for advanced voltage and var control equipment is less than 0.1 percent under conditions of harmonic distortion in the voltage waveform and power‐system frequency variation. Studies on digital signal processing suitable for electric power systems showed that these requirements are satisfied using fast sampling and very fast 32‐bit floating point operations by a Digital Signal Processor (DSP).This paper describes the design philosophy of a high‐precision power system voltage‐measuring method using fast sampled data. In addition, total voltage‐measuring deviation characteristics under a combination of the techniques are described along with digital filter characteristics, frequency‐measuring deviation characteristics, frequency variation versus gain‐compensation characteristics of a digital filter, and peak value operating principles.
Game‐theoretic analysis of a buy‐back system and a cogenerator‐customer wheeling system
Authors: Asano Hiroshi , Kuwahata Akeo 
Published: July 2007

AbstractElectricity markets are experiencing widespread changes that are significantly altering the industry. The purpose of this paper is to analyze the economic consequence of various rules of purchased power pricing and wheeling fees of an electric utility by game theory.A regulator, an electric utility, and a cogenerator are included in this model as players of the game. Consider an extensive game model of an electricity market where a cogenerator sells excess electricity to anelectric utility or an end user. The regulator behaves so as to maximize social welfare. The electric utility and the cogenerator intend to maximize their own profit. The wheeling fee between the electric utility and the cogenerator is adjusted to maximize the sum of incremental profits.We have found that a buy‐back system (the utility purchases cogenerated power) and a cogenerator‐customer wheeling system are equally efficient and are more desirable than a monopoly system. The buy‐back rate should be equal to (in the LP bargaining solution) or less than (in the Nash bargaining solution) the marginal cost of the electric utility. We also conducted an analysis of two‐period electricity market.
Active filter system containing an inverter bypass circuit to suppress harmonic resonance
Authors: Ogihara Yoshiya , Matsukawa Mitsuru , Tada Satoshi , Ikeda Haruo , Kawaguchi Ikuo , Shiraishi Hiroshi 
Published: July 2007

AbstractThe superconducting‐type magnetically levitated railway system (MAGLEV), which is driven directly by variable voltage, variable frequency (VVVF) inverters or cycloconverters, is well known as the new traction system for future super‐rapid mass transportation.Since the frequency converters generate harmonic currents possibly leading to interference problem on utility transmission systems, the conventional ac filter of LC (reactor‐capacitor) branch and/or the active filter is necessary to prevent the harmonic disturbances.The authors have developed a novel harmonic compensation system consisting of shunt LC filters on load side, a step‐down transformer on receiving end, and a small‐capacity active filter with one end connected to the secondary winding of the transformer and the other to the load bus.The active filter is current‐controlled to give adequate damping to the harmonic resonance condition between the power system and the passive filter equipment, especially at lower harmonic frequencies.The principle and the characteristics of the new harmonic compensation system are described, and its laboratory test results which show satisfactory performance are given.
A feasibility study of an 8‐MWh flywheel‐type power storage system using oxide superconductors
Authors: Higasa Hiromasa , Ishikawa Fumihiko , Shibayama Motoaki , Ono Takeshi , Yokoyama Shoichi , Nakamura Shirou , Yamada Tadatoshi , Yoshida Yasuo 
Published: July 2007

AbstractWhen combined with a magnet having a magnetic field gradient (for example, a permanent magnet), a Y‐based oxide superconductor is capable of forming a noncontact bearing with a strong levitational force. Since this bearing exhibits low rotational loss, it is very likely to form a highly efficient power storage system in combination with a flywheel.In this paper, an 8‐MWh power storage system utilizing a flywheel was designed conceptually to examine its applicability and the possible effects of its introduction. It was found that this system was an effective power storage.