bluuebunny/crossref_metadata_2025_split huggingface dataset:
Operation of power distribution systems by using a section management method
Authors: Sano Tsuneyo , Tatsumi Mitsunobu 
Published: July 2007

AbstractHigh‐voltage power distribution systems are connected in a branch configuration so as to meet the need for highly reliable power service. When service is interrupted the faulty section is automatically isolated and the power supply is rerouted from an adjacent power distribution system thereby minimizing the service interruption area. The faulty section in the power distribution system is quickly located by means of time relays installed in the switchgears. The settings of those time relays, however, must be monitored constantly.For this reason, we have proposed a “section management method” which can supervise each section of the power distribution system. From this method, we developed a prototype automated distribution system for overall management of time relays through the use of internal software, facilities and customer feedback.This paper describes the section management of power distribution systems.
Estimation of breakdown voltages of surface flashovers initiated from triple junction in SF6 gas
Authors: Hama Hiroyuki , Inami Kiyoshi , Yoshimura Manabu , Nakanishi Koichiro 
Published: July 2007

AbstractIn this paper, a method is proposed to estimate the minimum breakdown voltages of surface flashovers initiated from the triple junction at which a solid insulator, SF6 gas, and a metal electrode come in contact.Using four kinds of test samples, the flashover voltages Vf are measured. The voltages Vf become lower than the theoretical voltages Vs of streamer inception in the case of the test sample with the large electrode area at the triple junction. To understand the phenomena quantitatively, we estimated the real partial discharge voltages Vc from the voltages Vf, and investigated the relationship between the voltages Vc and the theoretical values Vs. The values of Vs/Vc, which characterize the properties of the partial discharges, can be shown by the product λS90%Eav P of the following parameters: (1) coefficient λ representing the surface roughness of electrode at the triple junction; (2) effective area S90% of the electrode; (3) average field Eav at the area S90%; and (4) gas pressure p. The minimum surface flashover voltages in the insulators for coaxial electrode systems can be estimated precisely, considering the properties of Vs/Vc.
Daily peak electric load forecasting using an artificial neural network and an improvement method for reducing the forecasting errors
Authors: Makino Kyoko , Shimada Tsuyoshi , Ichikawa Ryoichi , Ono Masaya , Endo Tsunekazu 
Published: July 2007

AbstractThis paper proposes a forecasting method for shortterm peak electric loads using a 3‐layer neural network of locally active units. Each unit in the hidden layer of the neural network is activated only by input vectors in a bounded domain of vector space. This characteristic enables additional learning. Furthermore, it is supposed to provide the network structure with information that helps to improve forecasting accuracy. The neural network is applied to daily peak load forecasting simulations in summer. The results show that the proposed method is superior to a conventional neural network with the backpropagation algorithm. To make the best use of the neural network, an error‐oriented method of parameter modification is also examined.
Proposal and characteristics evaluation of a CO2‐recovering hybrid power generation system utilizing solar thermal energy
Authors: Pak Pyong Sik , Hachikawa Takeshi , Suzuki Yutaka 
Published: July 2007

AbstractA CO2‐recovering hybrid power generation system utilizing solar thermal energy is proposed. In the system, relatively low temperature saturated steam around 220°C is produced by using solar thermal energy and is utilized as the working fluid of a gas turbine in which generated CO2 is recovered based on the oxygen combustion method. Hence, solar thermal utilization efficiency is considerably higher as compared with that of conventional solar thermal power plants in which superheated steam near 400°C must be produced for use as the working fluid of steam turbines; the requirement for solar radiation in the location in which the system is constructed can be significantly relaxed. The proposed system is a hybrid energy system using both the fossil fuel and solar thermal energy, thus the capacity factor of the system becomes very high. The fuel can be used exergetically in the system; i.e., it can be utilized for raising the temperature of the steam heated by utilizing the turbine exhaust gas more than 1000°C. The generated CO2 can be recovered by using an oxygen combustion method, so that a high CO2 capturing ratio of near 100 percent as well as no thermal NOx emission characteristics can be attained. It has been shown through simulation study that the proposed system has a net power generation efficiency of 63.4 percent, which is higher than 45.7 percent as compared with that of the conventional power plant with 43.5 percent efficiency, when the amount of utilized solar energy is neglected and the temperature of the saturated steam is 220°C.
Theory and characteristics of novel variable reluctance 1X resolver
Authors: Ishizaki Akira , Takasaki Kazuhiko , Shimomura Shoji , Masaki Kouichi , Kitazawa Kanji 
Published: July 2007

AbstractAlthough brushless resolvers have been used widely as angular position transducers, they are expensive due to their intricate construction, involving a rotary transformer to supply the exciting coils wound on the rotor poles with the current.It is shown theoretically in this paper that the resolver without rotary transformer or brushes can be realized by simple construction, which consists of the stator core with both 4‐poles exciting windings and 2‐poles output ones and the rotor core carrying no windings. In this resolver the rotor core has minimum gap at one side and a maximum gap at another side of the diameter. It is characterized by an outer surface form that makes the fluctuation part of gap permeance very in proportion to cos θ, where θ represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. The method determining the rotor form to embody the aforementioned gap permeance variation is also shown.It has been confirmed not only by simulation but also experiment that the 2‐phase output voltages of a model designed based on the theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through the conventional resolver/digital converter was within acceptable engineering accuracy.
A three‐degrees‐of‐freedom Maglev system with actuators and permanent magnets
Authors: Oka Koichi , Higuchi Toshiro 
Published: July 2007

AbstractA magnetic suspension system with linear actuators and permanent magnets (instead of electromagnets) has been developed. In this system the bearing forces are controlled by adjusting the air gaps between permanent magnets and the levitated object (a circular disk). This system uses less energy and exhibits none of the overheating of coils typical of systems employing electromagnets. This paper describes a disk suspension system with three degrees of freedom. The system can operate either with a decentralized (distributed) feedback control system or with a centralized (lumped) one. Feedback gain matrices are calculated for each type of control system. The performances of the two types of control systems are compared by numerical simulations and experiment. This work is part of an effort to develop a magnetic levitation conveyer system.
Experimental studies on a structure of eddy current probe for detection of magnetic flux distorted by a flaw
Authors: Ebine Noriya , Takeuchi Shinjiro , Ara Katsuyuki 
Published: July 2007

AbstractBobbin‐coil‐type eddy current probes, which are conventionally used for nondestructive inspection of steam generator tubes in pressurized‐water‐type nuclear power plants, have poor detection sensitivity to circumferential flaws. Hence a new type of eddy current probe was proposed to effectively detect the magnetic flux component that is indicative of a flaw and thus to eliminate the dependency on sensitivity in flaw detection. In the course of development of the proposed method, probe structures were investigated based on the measurement of magnetic fields induced by variously‐shaped excitation flat coils. The new type of probe proposed here consists of differential pick‐up coils detecting magnetic flux and excitation coils having a parallelogrammic shape. The structure of the coils was fabricated in order to detect flaws independently of their directions in trial. Nondestructive flaw detection tests were then conducted with the probe. The results obtained concrete evidence showing that both the horizontal, the vertical slit‐flaws and even the small hole of 0.5 mm in diameter can be detected successfully.
Switching characteristics of a triggered vacuum gap employing a trigger electrode in the respective main electrodes
Authors: Sugawara Akira , Samaulah Hazairin , Itagaki Kouichi , Kitamura Hiroshi 
Published: July 2007

AbstractBoth switching time and minimum firing voltage of a triggered vacuum gap employing a trigger electrode in the cathode and anode (double triggered vacuum gap) were measured. The double triggered vacuum gap was operated below 100 V independent of the high voltage main electrode polarity (positive or negative). This minimum firing voltage was lower than that of the conventional triggered vacuum gap. The switching time is approximately 0.5 μs in the range 3 to 18 kV.The conventional triggered vacuum gap has a trigger electrode that is placed at the center of the grounded main electrode. The polarity of the main electrode affected switching time characteristics. A trigger electrode was added to the high voltage main electrode. The double triggered vacuum gap was only slightly influenced by the polarity of the high voltage main electrode when both main electrodes were triggered at the same time.
On‐line identification of continuous time‐delay systems using the genetic algorithm
Authors: Hachino Tomohiro , Yang Zi‐Jiang , Tsuji Teruo 
Published: July 2007

AbstractThis paper proposes a new kind of on‐line identification method of continuous time‐delay systems from sampled input‐output data. In order to track the time‐varying system parameters as well as time‐delay, the recursive linear least squares (RLS) method is combined in a bootstrap manner with the genetic algorithm (GA) which has a high potential for global optimization. The time‐delay is coded into binary bit strings and searched by the GA, while the system parameters are updated by the RLS method. Furthermore, this method (GALS method) is hybridized with the sequential nonlinear least squares method to improve the speed of convergence. Simulation results show that both the GALS and hybrid methods are efficient in the case that the system changes abruptly, and among them the hybrid method has superior convergence property to the GALs method and yields excellent estimation results in the case that the system changes with time continuously.
Stabilization of temperature dependence of verdet constant of bi‐doped garnet and development of high sensitive optical fiber magnetic field sensor
Authors: Inoue Nobukazu , Yamasawa Kazuhito 
Published: July 2007

AbstractBi‐doped garnet is a rare metal iron garnet made up of a ferrimagnetic substance, of which some portion of the rare metal element is replaced with bismuth. It illustrates a strong Faraday effect and has been applied to optical isolators. In magnetic field sensing applications, however, a shortcoming is apparent: Faraday rotation of Bi‐doped garnet reveals temperature dependencies when the garnet is not magnetically saturated. Close attention has been paid to the magnetization of each rare earth element's different temperature characteristics; garnet compositions have been investigated by calculations and experiments in order to find a garnet that shows flat temperature characteristics between −10 and 80°C. The liquid phase epitaxy (LPE) method was established to obtain a single crystal of the garnet [Bi13(Y, La)0.9Ho0.8Fe4.5Ga0.5O12]. A magnetic field sensor of fiber optic based on the Faraday effect of this single crystal is highly accurate in detecting conductor currents of power cables. The developed sensor is small and lightweight compared to conventional current transformers; additionally, optical fiber transmission of detected current signals is free from both electric and magnetic noise.
A new electric power network for effective transportation of small power of dispersed generation plants
Authors: Saitoh Hiroumi , Toyoda Jun'Ichi 
Published: July 2007

AbstractThis paper proposes a new electric power network that makes it possible for many types of dispersed generation plants owned by nonutility organizations to participate in an electric power market without the disadvantages of existing power utility and customers. This power network is called an open electric energy network (OEEN) because the network is open to the many types of plants for the participation. For achieving such openness, electric power storage devices, load controller at each customer and data communication network are installed in OEEN; the flow of excess electric power generated by each plant is controlled autonomously and in a distributed way. That is, the control is done by transmitting the data on excess electric power such as generation and demand point, power quality, price, etc., from each dispersed generation plant to the power storage devices and the load controllers through the communication network. Since this data‐driven power flow control is similar to the mail system for a packet with the addresses of sender and receiver, it is called packet electric power transportation.In OEEN the storage device plays a different role from load leveling. Therefore, the way to determine the storage capacity differs from the conventional approach. In this paper, the applicability of queuing theory for determining the capacity is also discussed.
An approach to fault point identification using neocognitron and BP neural network
Authors: Zhou Diwei , Yasuda Keichiro , Yokoyama Ryuichi 
Published: July 2007

AbstractThis paper presents a new approach to identify a fault point in a power system on real time. Based on the topology theory, the characteristics of a fault in the power system are treated as a pattern of the fault. Therefore, the calculation complexity of traditional approaches can be avoided. The aim of the proposed method is to identify fault points through directly analyzing the type of fault. Since each type of fault has each characteristic pattern of power flow, fault points can be identified by abstracting characteristics of power flow at each node of the power system. In order to abstract fault characteristics, neocognitron in which symmetrical three phase decomposition and data normalization are calculated using power flow at each node is introduced. Thus, the impacts of voltage grade and unbalanced load can be removed. Since each neocognitron corresponds to one node of the power system, hierarchical autonomous decentralization can be realized. Therefore, the proposed approach can be applied to a large power system. Fault point location is done by BP network. Since the neuro of BP network only corresponds to the nodes of the topologized power system, the training of the neural network can be performed independently. From this point of view, the applicability and flexibility of proposed approach are high. The effectiveness and applicability of the proposed approach are demonstrated on a simple power system model.
First trial of the electric power transmission of 3.8 kV–460 kVA through the prospective power transmission model system integrated under superconducting environment (PROMISE)
Authors: Kato Takeyoshi , Tang Yue‐Jin , Shimizu Hirotaka , Hayakawa Naoki , Yokomizu Yasunobu , Matsumura Toshiro , Okubo Hitoshi , Kito Yukio , Nagafusa Toshiaki , Miyake Seiichi , Kumano Tomoyuki , Hatano Masayuki , Sato Kazuhiko , Sato Wataru 
Published: July 2007

AbstractSuperconducting technology is regarded as a breakthrough to future electric power transmission because of its highly densified and large transmission capability. This paper proposes a concept of the future power system composed of various superconducting apparatuses. A prototype model system called “PROMISE (PROspective power transmission Model system Integrated under Superconducting Environment)” is constructed to prove the realization of the above concept. PROMISE is composed of a superconducting transformer (60 Hz, 6/3 kV, 1000 kVA class), superconducting fault current limiter (6 kV, 200 A class), and superconducting power cable (5 m, 6 kV, 650 A class). This paper also shows that PROMISE realized the transmission of the electric power of 3.8 kV–460 kVA (50 Hz). This is the first achievement in the world. The voltage‐current synthetic test verified that PROMISE can withstand ac voltage of 6 kV while carrying ac current of 170 A (60 Hz). The ac loss of superconducting cables, the heat leak of cryostat and the core loss of the superconducting transformer are measured to estimate the transmission loss of PROMISE. These fundamental performances of PROMISE may indicate the feasibility of the future introduction of superconducting technology for electric power systems.
Two‐degrees‐of‐freedom speed control of resonant mechanical system based on H∞control theory
Authors: Morimoto Shigeo , Takeda Yoji 
Published: July 2007

AbstractIn industrial motor drive systems such as those used in industrial plants and robots, a torsional vibration is often generated as a result of the elastic elements present in the torque transmission systems. This vibration makes it difficult to achieve quick speed responses and may result in plant damage. Such systems are simply modeled as two‐mass mechanical systems.The H∞control theory is applied herein to design a speed controller for the two‐mass system. This controller determines closed‐loop characteristics, including suppression of torsional vibration, rejection of torque disturbance and robust stability. Moreover, two types of two‐degrees‐of‐freedom control systems, which includes the H∞controller, are proposed to improve command response. One is based on the TDOF PI control, in which the PI controller included in the H∞controller is rearranged for the TDOF system. Another is based on the model matching feedforward control, in which the prefilter and the feedforward compensator are added to the H∞controller. The proposed control system is applied to two types of resonant mechanical systems having different inertia ratio. Several examinations demonstrate that the proposed speed control system is useful for a resonant mechanical system.
A design study of a superconductive magnet made of Bi/Ag oxide superconductors
Authors: Umeda Masaichi 
Published: July 2007

AbstractA medium‐sized, high magnetic field magnet was designed using data on the mechanical properties of Bi/Ag oxide tape superconductors. Due to the poor mechanical properties of tape superconductors, the size of a superconductive magnet is limited to a narrow region of radius and magnetic field. In order to build a large superconductive magnet, key mechanical properties of the Bi/Ag oxide tape superconductors, such as irreversible strain and matrix yield strength, have to be improved significantly.
Self‐regulated self‐excited brushless three‐phase synchronous generator
Authors: Fukami Tadashi , Kawai Takahiro , Miyamoto Toshio 
Published: July 2007

AbstractFor lightweight and compact implementation of a generation set, many attempts have been made by some researchers to develop a brushless self‐excited synchronous generator without an ac exciter. A previous paper proposed a novel self‐excitation scheme by which the second‐space harmonic component of armature mmf is used for exciting the rotor field system. In this excitation scheme the effect of the series excitation characteristic, as well as a self‐excited and brushless implementation without an ac exciter is automatically obtained. However, in the case of system configuration of the generator already reported, voltage regulation in the inductive load condition was very large. To remove this problem, this paper presents a new system configuration of the generator with a self‐regulating feature that can compensate voltage regulation automatically. The new generator consists of a stator installing two three‐phase windings, externally connected to a load and a capacitor bank, respectively, and a rotor with field and harmonic windings.In this paper the system configuration and theoretical concepts of the presented generator are described and detailed experimental investigations with a laboratory machine are also shown.
Test run of combined propulsion, levitation and guidance system at Miyazaki test track
Authors: Murai Toshiaki , Fujimoto Tsuyoshi , Fujiwara Shunsuke 
Published: July 2007

AbstractIn commercializing the superconducting Maglev system it is important to reduce the cost, especially that of ground coils constructed along the whole length of the guideway. For this purpose we have examined the combined propulsion, levitation and guidance system (PLG system) which can generate levitation, guidance and propulsion forces by the same coil. This paper describes the test run of the PLG system, whose ground coils (PLG coil) are constructed in one part of the Miyazaki test track. In designing the PLG coil, we make clear the magnitudes of the force acting both under normal and unusual conditions because the electromagnetic force, which levitates, guides, and propels the vehicle, directly acts on the magnet winding of the PLG coil. In the experiment, we examine both the performance of the vehicle and the force of a PLG coil. The measurement of the force at the PLG coil gives not only propulsion force and levitation force directly, but also guidance stiffness by sifting the measured coil. Good correlation recognized between the calculation and the experiment in the propulsion force, levitation force, and guidance stiffness proves that the required characteristics can be expected from the PLG system even under combination of propulsion, levitation and guidance.
Wavelet transform‐based signal waveform discrimination for inspection of rotating machinery
Authors: Tamaki Kenji , Matsuoka Yasuhiro , Uno Masato , Kawano Takeshi 
Published: July 2007

AbstractThis paper presents a new discrimination procedure of signal waveforms based on wavelet theory for the inspection of rotating machinery. The wavelet transform decomposes signals into time‐frequency space, rather than mere frequency space, limited by the uncertainty principle. This decomposition permits time‐frequency analyses and provides a more flexible means of signal processing than before.To examine a rotary compressor pump, particular waves in the rotational load torque signals that correlate with failure modes are discriminated from one another and evaluated. To extract the focal waves, the signal is decomposed with wavelets and then only particular waves, such as impulses, are reconstructed from a selected set of wavelet coefficients. This is called time‐frequency space filtering. The wavelet local modulus maxima are used to pen a time‐frequency window through which only the focal waves can pass with high fidelity. The maxima have information of the inflection points of the wave at each resolution that represent its waveform.The experimental results show the effectiveness of the procedure.