bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of lead‐plastic laminate tape for water‐impervious XLPE cable
Authors: Fukuda Teruo , Uematsu Tadayuki 
Published: July 2007

AbstractTo take full advantage of combined effects of metal and plastic materials, a composite tape combining lead foil which lacks mechanical strength with plastic film which imparts strength has been developed. This composite tape is designed to serve the purpose of a water‐impervious layer in an XLPE cable. Evaluation of its properties such as corrosion resistance, fatigue, expansion and shrinkage was made. The results of tests indicate that the combination of lead foil with plastic film is more effective in several ways than either alone. As one of its applications, the lead laminate tape was used as a water‐impervious layer in an XLPE cable. This composite material may be used not only in XLPE cable applications but also in many other various fields of industry.
Dynamic preventive control for power system using transient stability assessment based on pattern recognition
Authors: Kita Hiroyuki , Nishiya Ken‐Ichi , Hasegawa Jun , Mizuno Takahiro 
Published: July 2007

AbstractTo maintain power system security, the authors are developing an integrated security monitoring and control (ISMAC) system which consists of the three main functions: security monitoring, preventive control and emergency control. This paper focuses on the dynamic preventive control which deals with the transient stability immediately after the contingency has occurred. The proposed method is based on the transient stability assessment using the pattern recognition with two‐dimensional feature space. Therefore, a preventive control strategy can be obtained rapidly. An index which represents the severity of the contingency quantitatively (security index) is defined by the distance from a linear decision surface which divides a feature plane into a stable and an unstable region. Further, this method has also the advantage that it is possible to consider the effect of the control devices or damping to some extent and specify the operator demand for stabilization flexibly.The effectiveness of the proposed method is ascertained through numerical examples for model power systems.
A method of fault diagnosis in adaptive control systems by using fuzzy inference
Authors: Kumararu Kousuke 
Published: July 2007

AbstractAn on‐line fault diagnosis scheme for adaptive controlled systems designed by a self‐tuning approach is proposed. A physical parameter change in the controlled system can effectively be detected by using Kullback Discrimination Information (KDI) as an index for model discrimination. In the adaptive controlled system, parameter changes may occur under the normal operation, as well as under a failed situation. In order to decide whether the detected system parameter change really means a fault occurrence or not, a fuzzy inference approach to fault diagnosis is considered. Some appropriate membership functions which describe fuzzy events of the fault are constructed to implement the fuzzy inference. In this way, useful knowledge about fault modes obtained from, e.g., experts, can be introduced into the model‐based diagnosis technique. Simulation studies on a second order damped oscillator have been carried out to demonstrate the effectiveness of the method.
Magnetic properties of melt‐spun Nd‐Pr‐Fe‐Co‐B‐V system alloys and their bonded magnets
Authors: Yamamoto Hiroshi , Kodama Iwao 
Published: July 2007

AbstractMelt‐spun ribbons of Nd‐Pr‐Fe‐Co‐B‐V system alloys were prepared by the single‐roller rapidquenching method. The effects of composition, wheel velocity and heat treatment on the magnetic properties were investigated. The magnetic properties of their isotropic compression bonded magnets prepared from optimally annealed ribbons also were measured. Remanence (Br) was found to increase with decreasing rare‐earth content, and a maximum value of more than 1.0 T was obtained. A maximum energy product of 164.0 kJ/m3 was obtained for (Nd0.5 Pr0.5)9Fe4Co8B7.5 V1.5 alloy ribbon prepared at a wheel velocity of 17.1 m/s.From TEM observation, the particle size of these ribbons was determined to be between 20 to 30 nm. It is conjectured that the high remanence is obtained by the interaction of these fine particles. The amorphous (Nd0.5Pr0.5)9Fe74Co8 B7.5V1.5 ribbons prepared at a wheel velocity of 20.7 m/s were crystallized by heat treatment, and the optimum annealing condition was found to be at 650°C for 20 min. Its corresponding value of (BH)max was 146.2 kJ/m3. A maximum energy product of 86.4 kJ/m3 was achieved with (Nd0.5Pr0.5)9Fe74Co8 B7.5V1.5 bonded magnets made from the optimally prepared ribbons.
Separately frequency modulated single‐ended type quasi‐current resonant DC/DC converter with high‐frequency‐link incorporating forward and flyback hybrid transformer
Authors: Lu Ding , Nakaoka Mutsuo 
Published: July 2007

AbstractThis paper considers an improved bidirectional zero‐current switching (ZCS) quasi‐resonant‐type single‐ended soft‐switching mode dc/dc converter with an HF center‐tapped transformer link and ZCS commutated diode rectifier which is capable of minimizing switching losses of a power device, its electrical stresses and electromagnetic interference (EMI/RFI) noises. This converter topology can operate efficiently under a simple frequency‐regulation strategy in the ultrasonic frequency ranges.The advanced exact computer‐aided simulating analysis of the new converter circuit is presented introducing the normalized frequency variable and circuit system parameters. The open‐loop/closed‐loop steady‐state voltage regulation characteristics in a variable frequency‐modulation mode are illustrated and discussed in the normalized general‐purpose expressions in addition to the load variation performance.The feasible high‐power density SMPS breadboard with a full‐wave quasi‐current resonant switch assembly using a single MOS‐gate switching power semiconductor device is originally developed and investigated, and is optimally designed for a distributed low‐voltage large‐current power supply system. Its experimental results in the PFM control implementation are demonstrated compared with the exact simulation ones from a practical viewpoint.
Characteristics of a brushless and exciterless three‐phase synchronous generator with DC exciting system
Authors: Shibata Fukuo , Naoe Nobuyuki 
Published: July 2007

AbstractFrom the viewpoint of maintenances and constructions, it is desirable that brushless and exciterless type three‐phase synchronous generators be made.To meet this requirement, one of the authors devised a brushless and exciterless synchronous generator in which exciting currents flow simultaneously with load currents in armature windings. Thus, generators can be used both as the generators themselves and as the exciters. A generator system has already been reported by one of the authors. In it, the dc stator exciting current flows between the middle points per phase of the double‐star armature winding through the rectifiers. However, the winding connection between the armature winding and the rectifiers are complicated. Three sets of rectifiers are needed by the stator excitation.The authors present a generator system by which the electric connection of between the stator armature winding and the rectifier can be simplified, and the number of the rectifiers can be reduced. In this system, the stator is provided with a double‐star armature winding having two neutral points.In this paper, first, a circuit constitution and the principle for the brushless and exciterless three‐phase synchronous generator are described, and second, the characteristics are elucidated by means of characteristic analysis. Further, the results of the experiments for the generator conducted on the test machine of 2.0 kW are shown.
Fundamental electromagnetic characteristics of magnetically anisotropic damper‐wedges
Authors: Takahashi Miyoshi , Watanabe Masatoshi , Arai Keizi , Takahashi Noriyoshi 
Published: July 2007

AbstractA magnetically anisotropic conductor was applied to the damper‐wedge which acts as a slot wedge and damper bar in electrical rotating machinery. This conductor is composed of copper‐clad steel wires of 1.6 mm diameter aligned in the same radial direction. This means permeability in the direction of the wires, i.e., the thickness direction of the damper‐wedge, is larger than the permeability perpendicular to this direction, and electrical conductivity is good.To evaluate the electromagnetic characteristics, a trial damper‐wedge, 1.2 m in length and with a steel space factor of 40 percent to total volume, was manufactured and maintained in a standstill model iron core. Test results were as follows when the magnetically anisotropic damper‐wedge was employed.(1) As the magnetic flux flowed well in the radial direction, the flux distribution at the core slot portion was flattened. Consequently, the ripple amplitude became small and the average flux density increased compared with cases when the nonmagnetic or magnetic isotropic conductor is used.(2) The damper‐wedge had a smaller skin effect for ac current than a conventional copper damper bar. The losses concentration for the damper system was relieved so that better machine performance under heavy load condition would be obtained.
Fast parallel algorithm on sparse matrix for power system analysis
Authors: Oyama Tsutomu , Karube Takafumi 
Published: July 2007

AbstractPower system analysis is the basis of operation and planning. Since power systems are very large and complex, however, it takes a long computation time for the analysis. It is desired to develop a fast method especially for transient stability analysis. In this paper, a parallel algorithm for sparse matrix factorization, forward substitution, and backward substitution is discussed. The algorithm is made operational on the actual transputer network. The computation time using the algorithm is measured and compared with that of the ordinary (single processor) algorithm. Finally, the parallel transient stability program is developed and evaluated.
Compensation for parameter variation of induction motor improved torque control characteristics in low‐ and high‐speed regions
Authors: Yamada Tetsuo , Yamamoto Yasuhiro , Ichioka Tadashi , Niwa Tohru 
Published: July 2007

AbstractIn the vector control system using the slip frequency control method, the rotor resistance of an induction motor is used to calculate a slip frequency. Thus the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic.This paper presents a new method of compensating for the rotor resistance change which is robust for the stator resistance change. A current control loop is composed of the λ‐δ axes in which the λ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved, particularly in the low‐speed region. The experimental results of the current response and the compensation for the rotor resistance deviation also are shown.Moreover, although the mutual inductance has been treated as an invariable value, the value does change by a frequency and an exciting command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no‐load running condition. Furthermore, in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance are shown.
Novel control strategies for HVDC system with self‐contained converter
Authors: Tokiwa Yukio , Ichikawa Fumitoshi , Suzuki Kenichi , Inokuchi Haruhisa , Hirose Syunichi , Kimura Kazuaki 
Published: July 2007

AbstractThis paper discusses newly developed control strategies of a self‐commutated converter applied to the HVDC system. An upper and lower power‐limited dc voltage control establishes high performance in a two‐terminal HVDC system. A voltage margin method to reverse dc transmission power also is introduced. Even when the communication system is shut down, if required, dc transmission power can be changed with the authors' proposed controls applied to the terminal control. Furthermore, the dc voltage control scheme with two‐stage voltage control characteristic is presented for multiterminal HVDC system use. When one terminal is collapsed, the multiterminal HVDC system can be operated because of the proposed control characteristics.Simulator studies were carried out to verify the proposed control performance in the two‐terminal HVDC system and successful test results such as power reversal and a terminal start‐up during other terminal operations are shown.
A vector control system using a neutral‐point‐clamped voltage‐source pwm inverter
Authors: Ogasawara Satoshi , Sawada Tadashi , Abe Keiichi , Akagi Hirofumi 
Published: July 2007

AbstractThis paper describes a vector control system of an induction machine using a neutral‐point‐clamped voltage‐source inverter (NPC‐VSI) that is one of the double series‐connected inverters.The NPC‐VSI is able to output five‐level step‐shaped line‐to‐line voltage without output transformers or reactors, and it may reduce harmonic currents corresponding to torque ripples. However, the NPC‐VSI has a problem in that excessive high voltage is applied to switching devices when a neutral point of two dc capacitors of the NPC‐VSI varies from the center of the dc link voltage, because the neutral point is floating.This paper proposes also a current controller to which the space vector theory is applied. This can reduce harmonic currents to one‐fourth those of a conventional voltage‐source inverter using six switching devices, and regulate the neutral point potential within a preset range. To simplify the current controller, information about voltage space vectors is given from the vector controller to the current controller. The validity of the current controller is confirmed by a prototype using an induction machine of 2.2 kW.
Magnetic noise caused by output waveform harmonics of voltage‐source inverters
Authors: Iida Shoji , Okuma Yasuhiro , Masukawa Shigeo 
Published: July 2007

AbstractHarmonic components included in the output waveforms of inverter circuits cause magnetic noise, that is, audio noise, from the output transformers or load motors. To estimate the magnetic noise due to the harmonic components, we have already proposed the equivalent noise voltage Es and current Is.In this paper, by applying the aforementioned Es, we compare quantitatively the magnetic noise in the various ordinary voltage‐source inverters, both PWM inverters with multipulse waveforms and PAM inverters with multistep waveforms. Then, to reduce the magnetic noise, the output waveforms of the PWM inverters are improved by applying Es into the idea of harmonic elimination. Moreover, by employing PAM system as voltage regulation in the aforementioned method, the more improved output waveforms can be obtained with lower noise and also lower distortion.
The vector potential revisited
Authors: Adachi Toshimi , Sasabe Shigeru , Inagaki Toshio , Ozaki Masao 
Published: July 2007

AbstractThe vector potential in electrodynamics is investigated through the decomposition of its form to the following two parts: 1) the so‐called transverse part represented by a divergenceless vector; and 2) the longitudinal part represented by an irrotational vector. The decomposition can be done by the Helmholtz theorem in the vector analysis because the conditions which should be required when the Helmholtz theorem is used are satisfied for the almost vector potentials of physically interesting problems.As an example of such interesting problems, the Aharonov‐Bohm effect is chosen here. As for the Aharonov‐Bohm effect, the vector potential given in the original paper of Aharonov and Bohm has the singularities along the z‐axis. It is shown that even for such a singular potential the Helmholtz theorem is held provided that the concept of the distribution is introduced in it. Generally, the transverse part of the vector potential obtained through such a decomposition is determined uniquely by the magnetic field and does not alter by a gauge transformation. On the other hand, the longitudinal part depends on the choice of special gauge. It is shown that the Aharonov‐Bohm effect is due to the contribution of the transverse part of the vector potential and therefore should not be influenced by any gauge transformations.
Mechanical characteristics related to fault currents in bundle conductors
Authors: Hanamura Makoto , Kobayashi Takayuki , Yoshida Kouji , Serizawa Yasuo 
Published: July 2007

AbstractThe flow of fault currents in bundled conductors induces an electromagnetic attraction between subconductors and thereby the bus conductor system to an extremely high level of tension. This tension, which is the most important factor in designing the mechanical strength of the system, is determined by a large number of parameters—the magnitude of the fault current, the size and number of the subconductors, spacer interval, the spring of the structure, and so on.Full‐scale 63‐kA class fault current tests were carried out on eight types of bus conductors used in 275‐and 500‐kV subconductors, and measurements of fluctuation in tension were used to clarify the relationship between the various parameters and maximum tension at fault time.A method also was devised for calculating maximum tension at fault time on the basis of the various parameters, and it has been applied in the mechanical strength design of the bus conductor system.
Verification and expansion of a method of transient analysis of voltage collapse based on the induction motor load model
Authors: Ohtsuki Hiroshi , Yokoyama Akihiko , Sekine Yasuji 
Published: July 2007

AbstractVoltage instability is now under intensive study in Japan, and some dynamic methods for analyzing voltage collapse have already been presented. However, the suitability of load models used in the methods and the generality of the results have not been verified.In this paper, useful voltage collapse data acquired in real power systems are presented. The measured data are compared with the result of dynamic digital simulation to verify the suitability of an induction motor load model.In the latter half of this paper, dynamic simulations of voltage collapse with consideration of generator dynamics are carried out. An interconnected power model system with 10 nodes is analyzed. The generality of basic characteristics concerning voltage collapse which have already been obtained without considering generator dynamics is verified by such simulations.
Soft switching based on analysis of transient and steady‐state characteristics: Application to a single‐ended high‐frequency inverter
Authors: Hatanaka Yoshihiro , Mutsuo Nakaoka 
Published: July 2007

AbstractA single‐ended resonant‐type high‐frequency inverter using a static induction transistor (SIT) described in this paper can be performed as a zero current switching (ZCS) operation without dc reactor.The SIT high‐frequency inverter is a low‐cost one which has no transformer and it would be developed for a high‐intensity ultrasonic power supply and dc‐dc converter. The circuit operation regions, not only ZCS but also ZCS‐ZVS (zero current switching and zero voltage switching), were elucidated in the normalized plane. The characteristics of the inverter including the power control by frequency regulation were discussed. Furthermore, the switching characteristics in the transient‐state were investigated. These characteristics were substantiated on the basis of the numerical analysis and experimental results.
Disturbance suppression control with preview action for a linear dc brushless motor
Authors: Egami Tadashi , Okabayashi Senri 
Published: July 2007

AbstractThis paper proposes a disturbance suppression control with preview action for a brushless and coreless‐type linear dc motor. The brushless and coreless‐type linear dc motor is coggingless and has long life. It is suitable for high speed and precise positioning control. Parameter variation and load change are regarded as an equivalent disturbance signal and the compensation action is applied by utilizing the estimated value of the equivalent disturbance inside the inner loop. Next, an optimal preview control system is synthesized including the disturbance suppression control system mentioned in the foregoing. Disturbance suppression, improving phase delay and lowering the input peak value are attained in this control system. These effects are confirmed by applying the linear dc motor.
Development of a partial discharge location method for power cables
Authors: Ohno Hironobu , Katsuta Ginzou , Sakaguchi Ryuji , Ebinuma Yasumitsu , Sakai Nobuhiro , Nagaoka Akira 
Published: July 2007

AbstractInsulation deterioration of power cables can be measured by the method of partial discharge. If a large partial discharge is detected in a cable, the cable is considered to be defective and a partial discharge is located to find the position of the defect. However, partial discharge location methods are generally disadvantageous in that they require much skill for operation and have inferior sensitivity and accuracy.To solve these problems, the authors developed a locating method using two‐phase cable and an automatic partial discharge locator which automatically localizes the generating site of discharge immediately after making partial discharge measurement by simple operations. Field measurements are made on SL (separately lead‐covered) cables and other cables with the locator to test its accuracy and reliability, and it was found that the device is effective and useful.
Development of a live‐line partial‐discharge detection method for XLPE‐insulated copper wire‐shielded cable using a “yoke coil”
Authors: Nakanishi Yutaka , Nakatani Youichi , Suzuki Hiroshi , Endoh Takeshi 
Published: July 2007

AbstractThis paper describes a new partial‐discharge detection method for an XLPE‐insulated copper wire‐shielded cable line using a “yoke coil.” Partial discharges are measured with the yoke coil which detects the azimuthal component of the current flowing through the copper wires wound on an outer semiconducting layer with a given angle against the axial direction of the cable.The highest detection sensitivity of 2 pC has been achieved at a frequency range of 5 to 20 MHz using a 77‐kV 100‐mm2 model cable line (200 m in length). It was confirmed that the partial discharge caused by an artificial defect has successfully been detected using the proposed method.In the PD measurement for an actual 77‐kV XLPE‐insulated live line, the detection sensitivity was 10 pC.
Partial discharge detection by AE sensors for prefabricated joints for xlpe cables
Authors: Nakanishi Yutaka , Nakatani Youichi , Iizumi Masahiro , Kasuya Masaharu 
Published: July 2007

AbstractThis paper describes detection by the AE (acoustic emission) sensor of partial discharge in a prefabricated joint, one of the accessories for XLPE cables which is composed of factory‐formed parts. Since the prefabricated joints can be installed in a short time, an increasing number of such joints has been used on power transmission lines. However, the interface between the parts of prefabricated joints tends to exhibit weak points because of a structure peculiar to this type of joint.The AE sensor is provided for practicability in comparison with conventional electrical defect detection methods. In the course of the present study, a method for locating a defect using multiple signals from the AE sensors was developed and its validity was evaluated by the dielectric breakdown test.