bluuebunny/crossref_metadata_2025 huggingface dataset:
Economic evaluation of a photovoltaic power generation introduced into an electric power system with electricity storage
Authors: Nishikawa Yoshikazu , Tezuka Tetsuo , Kita Hajime , Kang Moon‐Sung
Published: July 2007

Renewable energy utilization and electricity storage will soon be introduced into the conventional electric power system. This study assumes that a photovoltaic (PV) power generation system, a set of the PV units, is installed into the electric power system with electricity storage; moreover, the effects of uncertain variation characteristics of the PV system output on the operations of the conventional power generation system and the storage units are evaluated by simulations, with cost a major consideration. According to the simulation results, it is clearly demonstrated that the costs of the PV system are influence sharply by the prediction accuracy of their output.
A method of large‐scale control system design aided by system visualization technology
Authors: Myoi Takeshi , Amari Haruo , Hayashi Tatuo , Inamura Kouhei , Koike Hideki , Kuzuola Hideaki , Hirose Michitaka , Ishiii Takemochi
Published: July 2007

Progress in computer and communication technology has made it possible to construct a large‐scale control sytem. However, expansion of such a control system will make it more difficult to design control software. In designing a large‐scale control system, it is hard to understand the data flow and synchronization of tasks and messages between computers. To solve this problem, we are developing a system to visualize control software for accessing information about the performance of the entire control system accurately and easily.

This paper describes the characteristics of large‐scale control systems, the method of its visual representation and configuration, the role of the visualization tool, and the efficiency of the visual design method.
Electrical properties of TiO2 thin films prepared by the sol‐gel method
Authors: Yoshimura Noboru , Itoi Masashi , Sato Shigeki , Taguchi Haruo
Published: July 2007

A TiO2 thin film was prepared by the sol‐gel method using a metal alkoxide [Ti(O‐i‐Pr)4 tetrasopropoxy titanium: TIPT]. The crystalline form of the film depends on the preparation conditions and the heat treatment temperature. When the ratio (γ) of H2O to TIPT is 7, the crystalline phase is formed at 400°C; when γ = 2 it is formed at 500°C. The anatase crystal structure was obtained for both γ = 2 and γ = 7. The electrical conductivity of the TiO2 film increased with the heat treatment temperature.
A voltage source PWM rectifier‐inverter with feedforward control of instantaneous power
Authors: Ogasawara Satoshi , Yamagishi Naoyuki , Totuka Hiroyuki , Akagi Hirofumi
Published: July 2007

In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage source inverters. This type of rectifiers, however, causes many problems such as poor power factor and harmonics. Recently, voltage source PWM rectifier‐inverters have been studied to provide the following advantages; (1) harmonic‐free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. It is, however, difficult for a conventional one to regulate the capacitor voltage on transient states because of having only a voltage feed‐back loop.

This paper describes a voltage source PWM rectifier‐inverter with feed‐forward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feed‐forward control of instantaneous power makes a great contribution to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed and some interesting experimental results of a laboratory model are shown.
High‐field dielectric properties of polyethylene in the high‐temperature region
Authors: Tokoro Tetsuroh , Tohyama Kazuyuki , Nagao Masayuki , Kosaki Masamitsu
Published: July 2007

Nonpolar polymers such as polyethylene or polypropylene are widely used as insulation materials, often under conditions involving strong electric fields and high temperatures. Under these conditions, the conduction loss due to DC‐like carrier transport may give rise to a high‐field AC dissipation factor (tan δ).

This paper describes the high‐field dielectric properties of polyethylene films at frequencies from 50 to 400 Hz and temperatures from room temperature to 100°C, as measured with a new type electrode design developed by the authors. In the high‐temperature region, the AC dissipation current waveform at 50 Hz was also measured. At room temperature, the electric‐field dependence of tan δ is almost unaffected by the frequency of the applied field. But at high temperatures and strong electric fields, tan δ tends to have a large field dependence and to be almost inversely proportional to the frequency. Thus the AC conductivity becomes independent of the frequency of the applied field in the region of strong fields and high temperatures. A theoretical analysis shows that the high‐field dielectric loss is governed by two processes, namely, the dielectric relaxation loss inherent to the AC field and the DC‐like carrier transport loss that becomes prominent in the high‐temperature region, where AC dissipation current waveform becomes significantly nonsinusoidal.
Power system stability enhancement by static var system using self‐commutated inverters
Authors: Matsuno Katuhiko , Nagasawa Takashi , Ohtsuki Hiroshi , Ohnishi Shuichi , Ishiguro Fujio , Takeda Masatoshi
Published: July 2007

This paper deals with static var compensators using self‐commutated inverters (which is so‐called SVG) compared with conventional SVC and Rotary Condenser.

Improvement of power system stability is explained by using simple system model and checked by dynamic digital simulation.

In the latter part of this paper, system outline, basic specifications and control diagram of the SVG rated 154 kV, ±80 MVA, which has been installed at INUYAMA Switching Station, are briefly presented.

Field tests at INUYAMA verify that power swing is effectively damped and transmission capacity is increased.
A combined engineering model for the analysis of switching surge flashover characteristics of long air gaps
Authors: Nishijima Kiyoto , Kanekiyo Tadamitsu , Asu Itaru Tsuney
Published: July 2007

The flashover characteristics of long air gaps submitted to switching surge voltages may be predetermined by use of a mathematical model of leader propagation.

The present model is developed from each combination of previous engineering models, and is also applied to positive rod‐to‐plane geometries with gap lengths up to 20 m.

However, four parameters to determine leader propagation with respect to our model are adjusted in the present calculation so as to fit experimental flashover voltages and calculated flashover voltages which depend on waveforms of the applied voltage and gap length. The calculations show that these parameters are only a function of gap length.

Our combined engineering model using parameters that depend on gap length allows the flashover characteristics of long air gaps to be easily determined with a microcomputer.
A solution method using neural networks for the generator commitment problem
Authors: Sasaki Hiroshi , Fujii Yuuji , Watanabe Masahiro , Kubokawa Junji , Yorino Naoto
Published: July 2007

This paper studies the feasibility of applying the Hopfield‐type neural network to unit commitment problems in a large power system. The unit commitment problem is to determine an optimal schedule of what thermal generation units must be started or shut off to meet the anticipated demand; it can be formulated as a complicated mixed integer programming problem with a number of equality and inequality constraints. In our approach, the neural network gives the on/off states of thermal units at each period and then the output power of each unit is adjusted to meet the total demand. Another feature of our approach is that an ad hoc neural network is installed to satisfy inequality constraints which take into account standby reserve constraints and minimum up/down time constraints. The proposed neural network approach has been applied to solve a generator scheduling problem involving 30 units and 24 time periods; results obtained were close to those obtained using the Lagrange relaxation method.
The effect of space charge on the initial growth of electrical trees in polyethylene
Authors: Hozumi Naohiro , Okamoto Tatsuki , Imajo Takahisa
Published: July 2007

This paper describes the influence of space charge on the growth of an electrical tree which is an important factor of the dielectric breakdown in polyethylene‐insulated power cables. Polyethylene and ethylene vinyl‐acetate copolymer with a semi‐conducting needle were used as the treeing specimens. The statistical analysis showed that the growth rate and the unbalance of positive and negative partial discharges increased as the vinyl‐acetate content increased, and that the growth per cycle decreased with the increase in frequency. A model of the tree growth accompanied by the space charge behavior was proposed considering the above experimental results. The tree growth is considered to be caused by the dielectric breakdown due to the field enhancement at the tree tip during the positive half cycle of the applied voltage, the field enhancement being due to residual negative space charge injected during the previous negative half cycle. The negative space charge in polyethylene would be mainly supplied through the partial discharge inside the tree.
Evaluation of lightning fault rate of EHV transmission line based on lightning parameters derived from electromagnetic observation
Authors: Ishii Masaru , Hojo Jun‐Ichi
Published: July 2007

Cloud‐to‐ground lightning flashes in the Niigata area in Japan have been observed for a few years by a magnetic direction‐finder network. Data obtained so far are analyzed carefully taking into account the operating characteristics of the system. As a result, frequency distributions of return‐stroke current for each polarity are produced, and their seasonal variations and the occurrence probabilities of high current exceeding 200 kA are clarified.

Based on the estimated current distributions, back‐flashover rates of 500‐kV 2 cct transmission lines are calculated. It is known that the back‐flashover caused by downward flashes can account for most of the line outages in the summer for both single‐ and multiple‐line faults. However, this mechanism cannot explain the high outage rate in the winter experienced in the winter thunderstorm area in the late 1970s. In spite of the low lightning flash density in the winter, the multiple‐line fault rate in the winter caused by back‐flashovers is predicted to be comparable to that in the summer, because of the seasonal variation of the frequency distributions of return‐stroke current.
An investigation of salt contamination on insulators and the effectiveness of pin‐type insulators with salt‐proof dishes
Authors: Higashimori Yoshio
Published: July 2007

This paper investigates the contamination of the surface of various insulators suspended in the air at a certain altitude and connected in series. It is shown that salt‐proof dishes attached to pin‐type insulators are effective against contamination.

Exposure tests of insulators on Okinawa have been made since 1985 and the results are as follows:

The higher the placement of the insulator, the heavier the contamination.

The amount of contamination on the downward surface of the suspended insulators at the lowest position was considerably smaller than that of the insulators at the other positions.

The extent of contamination of the pin‐type insulators with the salt‐proof dishes was far less in comparison to that of pin‐type insulators without salt‐proof dishes.

The maximum equivalent salt‐deposit density was related closely to the small amount of precipitation during the observation period and the occurrence of high wind speed, which was higher than 10 m/s.
Low‐speed high‐torque drive system applying vernier motor torque
Authors: Ishizaki Akira , Shibata Yukiya , Watanabe Katsuyuki , Saitoh Kazuo
Published: July 2007

The application of the direct drive system is increasing in the field of robot and factory automation because of controllability with high accuracy. However, it requires the motor high torque at low speed.

Although the vernier motor presented by Lee in 1963 could produce the reluctance torque in low speed, it involved many problems to be solved. This paper studies the reluctance torque of the vernier motor using the finite‐element field analysis. Since the increase of rotor slot number is effective in producing high torque, in the model here, there are not only winding slots but also small slots on the stator teeth surfaces. Also, the rotor slots are provided in the periphery of the core more than the total number of stator slots by the pole number. The calculated torques have agreed very well with the experimental results.

A prominent feature of the control scheme is to control the armature current phase based on the detected rotor slot position. Thus there is no problem such as pull‐in or pull‐out in Lee's vernier motor. Then the instantaneous torque is controlled by the amplitude of armature current. The experimental results on both the speed control and the position control also are shown in this paper.
Sputter etching mechanism and changes of surface structure of PTFE
Authors: Yamamoto Suguru , Toyooka Masahide , Kubo Uichi
Published: July 2007

Growth of microscopic cones on PTFE surface by RF sputter etching process are studied. The surface texm changes from initial submicron hillocks to large cones during sputter etching. The height of these cones is 33 to 45 percent of the etching depth calculated from etching rate. The direction of these cones is nearly equal to the ion incident angle. Boundary energy of sputtering and growth of cones are 100 eV and 150 eV, respectively. It is obtained that the redeposition ratio by back diffusion to sputtered molecule is 11 percent from the experiment using collector. It is concluded that redeposition and repolymerization process of sputtered material occurs in parallel with the ion etching process, and cones continue to grow partly during etching.
Improvement of magnetic properties in Fe‐based nanocrystalline alloys by addition of Si, Ge, C, Ga, P, Al elements and their applications
Authors: Yoshizawa Yoshihito , Been Yoshio , Yamauchi Kiyotaka , Sugihara Hosaki
Published: July 2007

Magnetic properties of Fe‐Cu‐Nb‐X‐B (X Si, Ge, C, Ga) and Fe‐Cu‐Nb‐Si‐B‐X (X: Ge, C, P, Ga, Al) nanocrystalline alloys were studied to improve soft magnetic properties and they were evaluated for some applications. Si was the best element for the Fe‐Cu‐Nb‐X‐B system. Substitution of P for B made the coercive force small in the Fe‐Cu‐Nb‐Si‐B‐X system having high saturation flux density. The cores using the Fe‐based nanocrystalline alloys showed low core loss, excellent dc superimposed characteristics and good noise attenuation characteristics. Hence, Fc‐based nanocrystalline alloys have high performance for such magnetic components as transformers and choke coils.
A high‐sensitivity magnetic field sensor shielded from the effect of earth's magnetism
Authors: Sonoda Toshikatsu , Ueda Ryuzo , Ikemoto Hajime
Published: July 2007

To realize a general‐purpose magnetic field sensor having a detection sensitivity of the order of 10−12 T/Hz at room temperature, a problem of removing the effect of the Earth's magnetism from the sensor must be solved because its magnitude is 4.5 × 104 times larger than that in the range to be detectable. For this purpose, a well‐known approach of exciting the sensor in the opposite direction to the Earth's magnetism to cancel out the value has been adopted.

This paper aims at realizing a magnetic field sensor free from the Earth's magnetism by introducing a method called “zero magnetic field.” In practice, such a sensor was developed and the tested results confirmed that the detection performance was maintained without losing the high sensitivity.
Development of a large‐capacity static var generator using self‐cornmutated inverters for improving power transmission system stability
Authors: Hasegawa Taizo , Betsui Takashi , Ohnishi Shuichi , Takeda Masatoshi , Seto Makoto , Murakami Shotaro , Kohan Toyokazu
Published: July 2007

A Static Var Generator (SVG) based on a self‐commutated inverter using GTO thyristors has been newly developed. The size of the SVG used for improving power system stability will be as large as approximately 100 MVA. The technical subjects to be solved for developing such a large SVG are summarized as follows:

compact design;

harmonic elimination by means of multiple transformers; and

large inverter with series connection of GTO thyristors.

This paper describes the solutions to these subjects, especially the application of a large number of multipulse connection and series connection of GTO thyristors, including the analysis of the basic performance of SVG and the multiple transformer. The test results of a 12‐pulse partial model (8 MVA) and a 48‐pulse miniaturized model prove the solutions proposed in this paper to be effective and reasonable.
MRAS‐based speed sensorless control scheme with stator resistance identification function for vector‐controlled induction motor drives
Authors: Yang Geng , Chin Tung‐Hai
Published: July 2007

This paper describes a new scheme for the speed sensorless control of the vector‐controlled induction motor drive.

Based on the model reference adaptive system (MRAS) theory, the rotor speed of the induction machine is estimated with a full‐order adaptive observer. The estimated speed then is used as the signal for the vector control and the speed control. To accurately estimate the speed at the lower speed range, the value of the stator resistance also is identified at the same time and then is used to modify the resistance value set in the observer. The resulting system is verified to be hyperstable with Popov's criterion. As a result, this drive can operate stably in a wide range of speed even at zero speed. Also, it is shown theoretically that neither speed nor resistance of the rotor can be identified at the same time because these two parameters are dependent on each other. Simulation results and experiments also show that the scheme is effective.
Hyperstability of the full‐order observer for vector‐controlled induction motor drive without speed sensor
Authors: Yang Geng , Chin Tung‐Hai
Published: July 2007

Vector‐controlled induction motor drive systems without speed sensors have been widely studied. Speed estimation can be treated as a problem of parameter estimation under the theory of MRAS (model reference adaptive systems). In such cases, the convergence and robustness of the system are major issues. In this paper, we discuss the stability of an MRAS, that includes a full‐order adaptive observer of the induction motor and is used for estimating the rotor speed and identifying the stator resistance. It is verified that, under some conditions, the transfer matrix in the forward path of the MRAS is strictly positive‐real and that the non‐linear block in the feedback path satisfies Popov's criterion. As a result, the system is hyperstable. The influence of the set error of the rotor resistance is discussed and the design criterion for the feedback gain of the observer is presented. Finally, the system is linearized for the parameter design of the speed estimator.
Prospects for the application of superconductivity technology to power systems
Authors: Hashimoto Yasuo , Ito Shunichi , Hasegawa Taizo , Mino Yoshiaki
Published: July 2007

By relying only on the conventional technology, it may be difficult to meet the recent requirements of electric power systems such as further improvement of the quality of electric power supply, environmental compatibility, and so on. Some of the limitations of conventional technology can be eliminated by the application of superconductivity technology. Roughly speaking, superconductivity‐applied components which have relatively high feasibility are the superconducting generator, small‐capacity SMES. and liquid nitrogen‐cooled superconducting cable. To use them practically, reliability, maintainability, controllability and economy must be improved to the level of conventional components.
Contact‐failure phenomena and their development in gas‐insulated switchgear
Authors: Mukaiyama Yoku , Takagi Isao , Izumi Kunikazu , Sekiguchi Terukazu , Kobayashi Akio , Sumikawa Toshio
Published: July 2007

To explain contact failure phenomena and their development in the gas‐insulated switchgear (GIS). tests were conducted by simulating abnormal current‐carrying conditions using an actual 300‐kV, 2000‐A GIS.

This paper describes the process observed. ranging from contact failures to ground faults, deteriorative phenomena and some detection methods for initial contact failure conditions. A summary of this study is as follows:

(1) The contact resistances are greatly dependent on the materials and construction of contacts.

(2) The relation between the initial contact resistance and the carried current resulting in arcing is derived with approximately constant Joule‐heat generation.

(3) Ground faults result from sagging of a shield melted by arcing or a combination of two causes: (i) scattering of molten metal caused by arcing; and (ii) sagging of a conductor caused by bolt melt down.

(4) To detect initial contact failures, it is recommended to observe the contact resistance, the temperature rise on the tank surface, or the electrical partial discharges.
Cooling characteristics of a large‐current capacity AC superconducting cable
Authors: Torii Shinji , Akita Shirabe , Tsukamoto Osami
Published: July 2007

Diameter of the superconducting ac composite strand is small, typically 0.1 mm, because the strand must be twisted in a very short pitch to reduce coupling losses. Therefore, current capacity of the single strand is small and in the range of ∼10 A. In large‐scale electric power apparatus, the conductors must be able to carry large currents and hundreds of these composite strands should be bundled. The composite strand is highly unstable and susceptible to a very small disturbance due to a frictional wire motion because the main matrix of the wire is highly resistive CuNi.

For stable operation of an ac superconducting winding, every strand in the bundle cable should be fixed firmly. An effective technique to fix strands is to impregnate the winding by epoxy. In this case, the ac losses in the winding are to be cooled by heat conduction through the epoxy. Therefore, it is important to estimate the temperature rise of the winding to discuss the fact that the epoxy impregnation technique is applicable to the ac superconducting electric power apparatus.

In this paper, the mechanism of thermal conduction of the epoxy‐impregnated winding at the 4.2 K region is discussed based on experimental data and the temperature rise of a large‐scale cable bundles by 7 × 7 × 7 strands calculated considering thermal resistivity at the interface between the epoxy and the strand. The calculated value agrees well with the measured value.
A new partial discharge detection method for live UHV/EHV cable joints
Authors: Fukunaga Kaori
Published: July 2007

Partial discharge (PD) detection on live UHVEHV power cables and accessories is one of the most important techniques to prevent cable systems from serious difficulties caused by slight errors in joining the cables. A new PD detecting method is proposed in this paper. A resonance‐type partial discharge (REDI) sensor is developed for detecting PD occurring inside the joints of live XLPE insulated cables. This sensor picks up the high‐frequency components of PD current pulses on the surface of live cables, hence the output signals can clearly be observed at the noiseless area (for example, 10‐60 MHZ).

This new method was applied to the initial ac breakdown tests with three different types of joints of UHV/EHV power cables. The PD pulse sequence was detected before their breakdown in all cases. The charge quantity and the number of pulses increased tremendously just before the breakdown. In addition, the phase of PD pulse against the applied voltage (ϕ‐q characteristics) changes with time or with the progress of deterioration. According to these experimental results, the REDI sensor can be applied to the insulation diagnosis of live power cable joints.
Basic characteristics of a self‐excited induction generator under secondary excitation at constant voltage
Authors: Koyakumaru Yoshinori , Miyanaga Hiroaki
Published: July 2007

A self‐excited wound‐rotor induction generator excited with a capacitor can be used as an independent source for small‐capacity wind power generator.

With constant excitation capacitance, the secondary‐circuit power of the induction generator is returned to the primary circuit through a converter, an inverter and a transformer; the power is controlled at the inverter so that the generator voltage is always maintained constant in spite of the changes of generator speed and load. The basic characteristics of the generator under the above conditions are analyzed.

The fundamental waves of both the main circuit and the feedback circuit are determined. Using these results, the equations for various portions of the generator are derived, the performance characteristics of the generator are then analyzed and compared with experimental results.
Quench propagation of forced‐flow‐cooled superconducting coil
Authors: Shimada Mamoru , Hamajima Takataro , Yamaguchi Mitsugi
Published: July 2007

Forced‐flow‐cooled superconducting coil (FCC) has several advantages: large stability margin; high mechanical rigidity; and good electrical insulation. As a result, FCC could provide efficient superconducting magnet systems for such large machines as fusion devices.

Cable‐in‐conduit conductor (CICC) is regarded to be most attractive for FCC because of its good heat transfer characteristics which make the magnet more stable against disturbances. However, there are some problems. One problem is that the coolant pressure will become very high during a quench because its hydraulic diameter is relatively small. Also. the propagation of a normal zone has a close relation with the pressure rise. These characteristics must be considered in designing and protecting FCC.

This paper describes the results of the stability tests of FCC and the analyses of these characteristics. and compares them with the results of numerical simulations.
Measurement of the magnetic characteristics of oriented silicon steel in an arbitrary direction
Authors: Morino Harumi , Ishihara Yoshiyuki , Todaka Toshiyuki
Published: July 2007

The measurement method and the experimental results on the magnetic characteristics of oriented silicon steel in any direction are described in this paper. A single sheet tester of rotational loss has been used in order to simulate conditions existing in real devices. The flux of any direction is induced in the specimen by exciting from X and Y directions in the same phase. The flux density was measured by each search coil. The magnetizing force was measured by the double H‐coil method. The outputs of the B‐coils and the H‐coils were treated by sending the outputs from the wave digitizer to the personal computer.

The components of the magnetic characteristics in the X and Y directions for small values of B are the same. Only the saturation value changes, and it depends on the direction of flux.
Suppressing the effect of lightning‐induced overvoltages by the combined use of surge arresters and overhead ground wires
Authors: Morooka Yasunari , Yokoyama Shigeru , Asakawa Akira
Published: July 2007

Lightning voltage induced by nearby strokes is one of the causes of major overvoltages which threaten the insulation of power distribution lines. Surge arresters as well as an overhead ground wire usually are employed for the protection of equipment and line insulation on overhead power distribution lines.

The fundamental mechanism of suppressing effects of overvoltages induced by nearby strokes has been demonstrated independently by one of the present authors for surge arresters and for an overhead ground wire.

In this paper, the protective effect of the combination of surge arresters and overhead ground wire is analyzed. As a result, it is found that the effect of surge arresters used together with an overhead ground wire is almost the same as that of surge arresters alone.
Optimal pulse patterns of a nine‐phase voltage source PWM inverter for use with a triple three‐phase wound ac motor
Authors: Takami Hiroshi , Matsumoto Hisao
Published: July 2007

The authors have already described the nine‐phase inverter driving system providing both the triple three‐phase voltage source inverter with 180‐deg conducting period and the ac motor windings with triple three‐phase construction. The nine‐pulse inverter driving system used three small‐capacity three‐phase coupling reactors having special windings for current balance and reduction of higher harmonics.

In addition, for voltage control, current balance, and waveform improvement, optimal PWM pulse patterns were applied to the six‐phase inverter driving system using a three‐phase coupling reactor to provide double three‐phase construction.

In the system based on the mode in the title, the PWM control was applied to the nine‐phase inverter driving system described in the foregoing. The coupling reactors in the system balance the fundamental currents of three sets of three‐phase inverters and also absorb higher harmonic voltages other than 18p±1 (p = 1, 2, …) orders. The optimal pulse patterns found by the approach to make the performance index minimum using the Lagrange multiplier method can be applied to the PWM to reduce the higher harmonic currents greater than those calculated by the modulation method comparing the sinusoidal signal wave with triangular carrier signal.

This system can have a larger capacity than the six‐phase PWM inverter driving system in which coupling reactors absorb higher harmonic voltages other than the 12p±1 orders and also improve output current waveforms. In addition, the system includes the capacity of coupling reactors slightly larger than the six‐phase PWM inverter driving system but enables operation with smaller torque ripples and electromagnetic noises in low‐ to high‐frequency ranges.
Static thrust analysis of a cylindrical moving‐core linear oscillatory actuator
Authors: Yamaguchi Masaki , Nagumo Masamichi , Iio Minoru , Yamada Hajime , Mizuno Tsutomu , Suzuki Hiroya
Published: July 2007

This paper considers materials for the movers, the volume ratio of the stator and of the mover, and the structure of the mover in a cylindrical moving iron‐type linear oscillatory actuator (LOA) having a permanent magnet. As a result, we obtain the following:

the static thrust characteristics are evaluated on two movers: movers P and S are made of a permendur and a stainless steel, respectively. It is clarified that the static thrust of the mover P is 30 percent larger than that of the mover S;

it is suggested that the structure of the mover P should be improved to eliminate a “lump” in the static thrust‐displacement curve due to the step on the mover, and which disturbs the smooth motion of the LOA.
An automatic torque ripple compensation system for direct drive motors
Authors: Sato Hirokazu , Makino Tatsuo , Matsui Nobuyuki
Published: July 2007

A serious problem in motion control is the occurrence of torque ripple. Since a direct drive (DD) motor with a magnet rotor uses a rare‐earth magnet, the torque ripple is more serious than that of conventional servomotors.

This paper presents an auto‐compensation of torque ripple using a software‐implemented torque observer. The frequency and amplitude of torque ripple can be obtained in the controller by using the estimated torque from an observer, and the autonomous generation of a compensating current component for a torque ripple is possible. The proposed algorithm has been verified by experiments.
Flashover characteristics of vapor‐mist dielectrics under lightning impulse and means to increase the flashover voltage
Authors: Yashima Masafumi , Fujinami Hideo , Takuma Tadasu
Published: July 2007

It has been reported that the flashover voltage of gaseous dielectrics may increase greatly when they are mixed with carbon‐halide mist. However, the factors which bring about the increase of the flashover voltage still are not clarified fully. Based on the study on the basic flashover characteristics of vapor‐mist dielectrics, the authors have suggested the scarcity of initial electrons as the predominant factor.

This paper investigates further the effect of UV light irradiation, flashover characteristics under forced supply of initial electrons, and for lightning impulse superimposed on dc voltage. These results have verified that the scarcity of initial electrons is the decisive factor in increasing the lightning impulse flashover voltage of vapor‐mist dielectrics. It is clarified also that the scarcity is attributed principally to: (1) the reduction of effective period (lifetime) of initial electrons, and (2) the suppression of photoelectric emission from electrodes.
New digital control and protection equipment using multiprocessor architecture of distributed functions for power system
Authors: Chiba Tomio , Kido Mitsuyasu , Kawakami Junzo , Kudo Hiroyuki , Kawai Tadao
Published: July 2007

Control and protection of equipment in power systems generally require a high‐information processing capability to cope with today's power system requirements. Then, new digital control and protection equipment have been developed using high‐speed and high‐precision processors.

Essential requirements for the new control and protection equipment are a multiprocessor architecture of distributed functions to retain sufficient computing power (fast and high‐precision operations), and flexible and expandable hardware with high reliability. In multiprocessor architecture, it is important to determine how the distributed processors share the functions. By analysis and synthesis of relaying and control processings, we divided them into six processing circuits.

This paper proposes a multiprocessor architecture of distributed functions, using 32‐bit floating‐point and 16‐bit microprocessors depending on the computational requirements. In addition a digital filter for fast sampled data is described along with performance of a digital relay.
Development of the double‐rod‐type jumper horns in strain assemblies with pipe jumpers for 500‐kv transmission lines
Authors: Shibuya Masatoyo , Amakawa Tadashi , Sano Kiyoshi , Kimura Sakae
Published: July 2007

This paper proposes double‐rod‐type jumper horns in strain assemblies with pipe jumpers for 500‐kV transmission lines, the structure of which is very simple. It can be estimated that no corona discharge appears on the horns under the line voltage of 525 kV. The arc behavior on the double‐rod‐type jumper horns is similar to that on the single‐rod‐type horns. The arc can be held stably for 60 ms against strong wind (10 m/s). The stable duration increases more than 300 ms under windless condition, therefore the horns have been adopted for practical use.
Superconducting compact synchrotron light source
Authors: Takada Hiroshi , Tsutsui Yasumitsu , Emura Katsuji , Tomimasu Takio
Published: July 2007

A superconducting compact synchrotron light source, the NIJI‐III, has been completed. The development of the NIJI‐III was assigned to Sumitomo Electric Industries Ltd. by the Research Development Corporation of Japan and was deemed successful in October 1991 with the attainment of the design goal of the stored beam current of 200 mA at the final beam energy of 600 MeV. The lattice has a four‐sector configuration: four superconducting bending magnets and eight quadrupole magnets, achieving the optimum beam characteristics for lithography. The world's first superconducting bending magnet was developed and adapted, and was characterized by a cosθ type without an iron, a large bore of 200 mm, and a strong curvature of 0.5 m. Furthermore, a newly developed vacuum system and an rf system were installed.

The high‐speed electron‐beam wobbling method was investigated at a 20‐Hz triangular wave for the exposure of the vertical field of synchrotron light. It was demonstrated that the expansion of the vertical exposure area agreed with the theoretical calculation, and that there was no effect on the beam lifetime.

The achievement of the NIJI‐III can be expected to contribute much to the development of various research applications of synchrotron light.
Analysis of brushless three‐phase synchronous generator without exciter
Authors: Nonaka Sakutaro , Kesamaru Katsumi , Horita Kazuo
Published: July 2007

Recently, a demand for small‐capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines.

It is desired that the structure of small‐capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled.

This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results.
Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station
Authors: Yamazaki Takashi , Takino Yoichi , Matsuoka Ryosuke , Ito Susumu
Published: July 2007

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large‐magnitude over‐voltages were confirmed to occur under some special system conditions.

Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier.

The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition.

Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.
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

The 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

With 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

This 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

This 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

Two 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

An 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

Short‐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.