bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decentralized load frequency control on each power plant
Authors: Tanaka Eiichi , Hasegawa Jun 
Published: July 2007

AbstractThis paper presents a load frequency control system using a refined controller for interconnected power systems. The controller consists of an integral compensator and state feedback. It has been proven that any transfer function between a reference input and a controlled output or between a disturbance and a controlled output is attained by this controller if it is attainable by realizable linear compensation. Parameters of the controller are determined by the optimal regulator theory and additional calculation.The controller can reduce time deviation and inadvertent interchange without information about tie‐lines as well as deviations of frequency and net interchange power. This structural features makes it possible to design the control system for each regulating power plant instead of for the control center. If some state variables are not available, the control system can be designed with the remainder of state variables and a dynamic compensator.Simulation results show that the control system is superior to the TBC system.
Relation between the superstructures and the tree deterioration in polypropylene
Authors: Yamakita Takayuki , Ariyasu Tomio 
Published: July 2007

AbstractThe initiation and growth of the electrical tree in crystalline polymers are influenced by the superstructure. However, there are still many unclear points in the relationship between the tree deterioration and the superstructure (spherulites).To study the relationship between the tree deterioration and the spherulite, we designed the measuring apparatus which allows simultaneous observation of these phenomena. The sample was set on the stage of the polarizing microscope to make observations of the tree initiation and growth in polypropylene.This paper reports the results of some observations concerning the tree initiation and growth in polypropylene with 60‐Hz ac voltage. The results are as follows:Prior to the initiation of trees, a fine deterioration zone is formed on spherulite surfaces. Thereafter, the discharge occurs along the spherulite surface, and the trees occur.Tree shapes change under the influence of the distribution state of spherulite.Tree initiation voltage is 5.8 kV for the spherulite inside and 5.1 kV for the spherulite boundary, respectively.
New balance ground relay for parallel four‐circuit transmission lines
Authors: Kai Takaaki , Nomura Shizuo , Ando Takeshi 
Published: July 2007

AbstractA 66‐kV network generally is grounded through a neutral grounding resistor. In this network a single‐phase ground‐fault current is limited to as small as 100 to 400 A. There are parallel four‐circuit transmission lines mounted on the same tower in the 66‐kV network. In such transmission lines, the load and the fault currents could induce circulating current that flows through the lines. Since the circulating current has zero‐phase‐sequence and negative‐phase‐sequence components, it could cause unwanted operation of a balance ground relay using zero‐phase‐sequence current. However, it is difficult to compensate for the circulating current by the conventional vector compensation scheme.This paper presents a new balance ground relay to deal with the circulating current. In the relay from the ground‐fault inception until first tripping, the difference current Δ3I2d of negative‐phase‐sequence current 3I2d of the differential current between two protected lines is used as an input current. The Δ3I2d is the difference current of 3I2d between, before and during faults. After the first tripping, the difference current of positive‐phase‐sequence load current and zero‐phase‐sequence current of the forementioned differential current are used as an input current. Consequently, a higher sensitivity of the ground‐fault protection for these lines has been achieved. The correct operation of the new balance ground relay was confirmed when a single‐phase‐ground‐fault occurred in the parallel four‐circuit transmission lines, to which the relay is applied.
Development of an on‐line stabilization method for local power systems with large‐capacity generation plants
Authors: Suzuki Mamoru , Yanagihashi Ken , Tomizawa Kazuhiro , Gouda Tadahiro , Oshida Hideharu 
Published: July 2007

AbstractThis paper presents an on‐line stabilization control method developed with the aim of maintaining transient stability in a local power system which includes large‐capacity generation plants. The characteristics of this method are that the power/angle curve is estimated from the on line active and reactive power measured at the generator terminal, and the optimum generation shedding for stabilization is determined by applying the equal area method to this curve.Simulation tests using detailed models of the power system confirmed that the optimum generation shedding for stabilization could be computed for various fault conditions, both symmetrical or asymmetrical.It was also determined that the on‐line data could be sampled for several tens of milliseconds after clearing the fault. Thus, this method provides effective control logic for practical stabilizing systems.
Accuracy of waveform parameters in digital measurement of single‐shot waveforms
Authors: Michishita Koji , Kawamura Tatsuo , Ishii Masaru 
Published: July 2007

AbstractIn high‐voltage measurement, the digital measuring system is used widely because of its attractive features, for example, automatic data acquisition. However, the accuracy in the measurement of both the amplitude and time parameters by the digital measuring system is not known in detail, especially in the measurement of single‐shot waveforms.In this paper, the accuracy of the peak value and the virtual front time of the standard lightning impulse without any signal processing of raw data is shown. From these results, the required characteristics for the digital measuring system to satisfy the IEC Draft on digital recorders for measurement in high‐voltage impulse test techniques are shown. In addition, the accuracy of the peak voltage and the rise time of the Gaussian pulse is shown.
Impulse breakdown voltages of triggered multistage vacuum gap
Authors: Itagaki Koichi , Ali Md. Mortuza , Kitamura Hiroshi , Maruyama Takeo 
Published: July 2007

AbstractSeveral sealed‐off triggered vacuum gaps are connected in series to improve hold‐off voltage. The characteristics of impulse breakdown voltage of these series‐connected gaps are investigated experimentally. The sum hold‐off voltage of series‐connected gaps decreases to a unit hold‐off voltage when the maximum value of voltage division ratio across the gaps increases to unity.Self‐breakdown probability of the series‐connected gaps is always higher than that of a single gap under the same conditions. Hence, stage efficiency of the multistage gap decreases with increasing number of stages. Its value is 90 percent with 2‐stage gap and 75 percent with 5‐stage gap, respectively, under the same voltage division ratio and the same gap length (2.0 mm) in each stage.Triggered breakdown voltage of 2‐ or 3‐ stage gap is several hundred volts when all gaps are triggered simultaneously at the peak of the main impulse wave and a working voltage range is nearly 100 percent in this case. The working voltage range decreases with number of stages. Its value is 45 percent with 3‐stage gap and 15 percent with 5‐stage gap, respectively, when one triggered gap is fired for switching.
Reduction of AC flashover strength by the attachment of insulating strings on the insulator surfaces
Authors: Yamano Yoshiaki , Ishikawa Emi , Takahashi Yuzo , Kobayashi Shigeo 
Published: July 2007

AbstractAC flashover voltage in air (ACFOV) decreases when nylon string is attached on the PMMA insulator surface which has a backside electrode. The decrease in ACFOV by the attachment is explained by the generation and the propagation of the negative surface leader along the string. When the contact angle between the HV electrode and the insulator surface is in a range from 90° to 120°, some of the negative surface leaders generated proceed along the string to the grounded counterelectrode. The magnitude of the negative leader along the string is stronger than that of the leader on the insulator without a string. In the range of the contact angle from 120° to 180°, the negative surface leader which does not appear on the insulator without a string is generated along the string by the attachment. In both ranges of the contact angle, the negative leader along the string promotes the flashover.
A novel technique for a DC brushless motor without position sensors
Authors: Kaku Kazunori , Yamamura Naoki , Tsunehiro Yuzuru 
Published: July 2007

AbstractA dc brushless motor is a kind of synchronous motor driven by an inverter and requires sensors to detect the rotor position. As one of the methods, the induced voltages of a brushless motor have been utilized in practice. However, there are some problems in this method, e.g., the motor can obtain insufficient torque due to the low induced voltages in a low‐speed range.This paper proposes a new method which controls the inverter angular frequency ω1 by using inherent characteristics wherein the torque current ir is almost proportional to the internal phase angle φ where the primary flux of a synchronous motor is controlled to be constant.If the parameters of a motor are given exactly, the speed regulation is quite small and the transient characteristics with high response and high starting torque are obtained. Furthermore, it is possible to operate a synchronous motor in the field‐weakening range.Here, the principle of the control method and the performance characteristics of a dc brushless motor having no position sensors are discussed. The simulation and the experimental results of the tested machine show that the proposed method is very useful for practical applications.
Relationship between the energy distribution of electrostatic field change and lightning activity
Authors: Miyazaki Tadaomi , Nishida Yasushi , Kokubu Satomi , Kawamata Shuichiro 
Published: July 2007

AbstractA lightning strength parameter α (denoted as LSP or LAIDO), which is used for characterizing the phenomena of lightning activity, has been proposed, where α is defined by the characteristic energy obtained from the energy distribution of a radiated field component E in the electrostatic field changes produced by lightning discharge. Here, it is observed that the energy distribution of Eγ components is Maxwellian type.To prove more clearly the forementioned assumption from another viewpoint, changes of the amplitudes of the electrostatic field component ES were measured and their distribution functions constructed.In the cloud‐to‐ground lightning discharges, the ES components have a positive sign in the changes. However, those changes in the intercloud discharges are observed with either a negative or positive change depending on the distance between the striking point and the observation site. Therefore it is necessary to sum the numbers of occurrences of both positive and negative components for constructing an energy distribution of the ES component.A fieldmill and a pair of doughnut‐shaped electrostatic antennas are used in measuring the changes of the ES component. As a result it is found that the changes of the amplitudes of the ES components have a Maxwelliantype energy distribution. A characteristic energy β is defined which is obtained from the component of the electrostatic fields as a measure of LSP.Based on comparison of α and β it is clarified that β has the same characteristic nature with α. The lightning activity could be estimated from β.
Probability evaluation of low‐voltage distribution equipment lightning failures due to AC arc
Authors: Imai Yasutomo , Nagayama Katsuya , Matsuoka Masanori , Sadakata Takashi 
Published: July 2007

AbstractTo construct low‐voltage power distribution systems, it is important to have correct information on the probability of failures by lightning to meet the requirement for high reliability of these systems.The burn‐out of low‐voltage distribution equipment is triggered by flashover due to lightning overvoltage followed by the arc discharge current at the commercial frequency voltage. The arc characteristics were investigated by superimposing the lightning impulse voltage across terminals of the low‐voltage distribution equipment connected to the commercial frequency power supply to reproduce these events on an experimental basis. As a result, it was found that the arc characteristics were affected by a number of factors.The probability of flashover occurrence on low‐voltage distribution equipment is determined based on the frequency distribution data of lightning overvoltage occurrence obtained by monitoring the surge counters on actual distribution lines. Then the probability distribution of arc currents is established by application of the forementioned experimental equation on arc characteristics. Finally, the method for evaluating damages by lightning to low‐voltage distribution equipment on actual lines was investigated with the frequency of lightning strokes and the configuration of low‐voltage distribution systems taken into consideration.
Development of a pumped‐storage power station model for power system stability study
Authors: Taniguchi Haruhito , Nagao Taiji , Higasa Hiromasa 
Published: July 2007

AbstractSince a pumped‐storage power station generally is located far from the load center, it frequently encounters problems of power system stability, especially at the pumping operation mode. Capacity of units constructed in recent years is as large as a few hundred megawatts, and water head is as high as 500 m. The period of water pressure oscillation of such a high head station becomes longer and closer to power system swing.Under such condition the output is affected by the conduit system dynamics and becomes different from analytical results using the classical model which assumes constant torque or output during power system disturbance at the pumping operation mode.This paper describes the newly developed simplified pumped‐storage plant model based on the elastic theory of the conduit system and the complete characteristics of the turbine, which has necessary accuracy to be analyzed because it is connected to bulk power system. Comparison with the real plant test result verifies the validity of the developed model. The interaction with power system is examined by linearized analysis and simulation study.
Development of an expert system for analyzing faults in power systems based on waveform recognition by artificial neural networks
Authors: Fukuyama Yoshikazu , Ueki Yoshiteru , Kaneko Kazuhiro 
Published: July 2007

AbstractIn restoration of a power system, appropriate steps need to be taken in early stages to avoid damage to the public caused by insufficient power supply. The first step in the restoration is the analysis of the fault that has produced the power failure.Today, a large amount of data will be available at the occurrence of a fault due to the use of advanced communication systems using digital relays and optical fibers. Such systems are intended to obtain data from the relays and circuit breakers (CBs) under operation and the voltage and current during operation and the prefault and postfault periods.This paper presents a hybrid fault analyzing expert system using data based on protective devices and phasor measurement. This system is a combination of an artificial neural network (ANN) and an expert system (ES). The ANN is used to simplify the analysis of current and voltage waveforms, which is considered difficult due to the presence of a fault resistance and the line impedance. Since a fault waveforms contains various ambiguous factors depending on the nature of the fault resistance, load current and other system parameters, the use of ANN is effective making such determinations.
Constant frequency and constant voltage control of induction generator
Authors: Kuge Katsutaro 
Published: July 2007

AbstractA doubly fed induction generator is useful for a local‐use water power plant. Setting it in nonconstant water flow, we can use it as a constant‐frequency power generator. This paper shows how to control this generator system.This paper has two important points. One is that this generator system is always excited at primary winding. Another is that the control target in this study is secondary q axis current to obtain a constant voltage of primary generated power.
Thrust control of a linear induction motor using magnetic field detection
Authors: Onoki Takashi , Numata Hiroyuki , Yamamura Tsugio 
Published: July 2007

AbstractA two‐dimensional hybrid finite‐element method is used to analyze the thrust response of a linear motor system in terms of vector control, using the air‐gap flux as the input signal. A novel control scheme is used, in which the supply current leads the flux vector by 45°, obviating the need for circuit analysis that arises in the usual vector control scheme. The flux detection method is compared with the conventional average thrust control method and its effectiveness is evaluated.
A novel control scheme of magnetic lift and guidance
Authors: Kwon Byung Il , Masada Eisuke 
Published: July 2007

AbstractThe electromagnetic suspension system, which is a kind of magnetic levitation, can be divided into two groups: separate lift and guidance system; and combined lift and guidance system. This paper considers the latter system, in which lift and guidance forces are generated by a pair of staggered magnets with the inverted U‐shaped rail. Although the forementioned arrangement provides the lift and the guidance simultaneously, a separate control scheme over them is desirable.In this paper, a quasi‐decoupled control method is presented which reduces the coupling between guidance and lift over a substantially wide range of lateral displacement. Simulation showed that the lift control has a small effect on the guidance but the guidance control has a considerable effect on the lift. Therefore a parallel complimentary controller on the lift controller is proposed to reduce the sensitivity for parameter variation and force disturbance.As a result, the lift system has robustness to parameter variation and force disturbance, while the guidance system is independently controllable with respect to the lift system. Hence it is possible to obtain adequate guidance force and to meet the ride quality standard related to the guidance of levitation vehicles.
Principle and operation of a new type motor consisting of piezoelectric device and strain wave gearing
Authors: Ishida Muneaki , Hori Takamasa , Hamaguchi Junichi 
Published: July 2007

AbstractThe authors have developed a new type of motor consisting of a piezoelectric device and strain wave gearing, and is called a piezoelectric motor. This is a first step in realizing a low‐speed, small‐size and lightweight motor. The principle of the motor is that the traveling wave is produced by piezoelectric devices and displacement conversion devices without mechanical resonance, and the torque to rotate the motor is generated by a mechanism of strain wave gearing (circular spline and flexspline) without using friction. The motor is operated at variable frequency and its rotational position (angle) is controlled in open‐loop because it is basically a synchronous motor.In this paper, the structure and principle of the proposed motor are explained and the driving method and the mechanical characteristics of an experimental motor also are described.The results are as follows:

The realizability of the proposed piezoelectric motor is verified experimentally. The experimental motor operates at 2920 steps per revolution, and its speed range is 0 to 960 pps [or 0 to 20 (rpms)].
The torque characteristics are clarified qualitatively.
The generated torque of the experimental motor is small (less than 0.03 Nm) and therefore the improvement of the torque is an important subject hereafter.
It is possible to construct the motor with nonmetallic material. This fact is considered to facilitate obtaining a means to lighten the weight of the motor in the future.
Finite‐element analysis of electromagnetic force based on permeance
Authors: Kimura Akio , Matsuzaka Tomoyuki , Kagawa Yjkio 
Published: July 2007

AbstractThe permeance coefficient of actuators and motors with permanent magnets depends primarily on the effective magnetic flux density and the magnetomotive force. A finite‐element technique is used to calculate the torque and electromagnetic force from the permeance based on the magnetic flux density distribution. The calculation results are consistent with measurements and with calculated values obtained by other methods. The permeance coefficient at the operating point, which is a performance characteristic of actuators, is estimated.
Investigation of space‐charge effect on the AC treeing mechanism in an LDPE film by tsc and TSSP measurement
Authors: Fukuzawa Masahiro , Iwamoto Mitsumasa 
Published: July 2007

AbstractWhen an ac voltage is applied to a low‐density polyethylene (LDPE) film placed under a needle‐plane electrode system, there is a possibility of the formation of the space‐charge field in the vicinity of the needle electrode by electrons (or holes) injected from the needle electrode. In this paper we investigated the properties of the space charge, e.g., the total amount of trapped charge formed in the vicinity of the needle electrode by using electrical measurements of thermally stimulated current (TSC) and thermally stimulated surface potential (TSSP).From the investigation, it was concluded that a space‐charge field is formed in an LDPE film by the application of the ac voltage, and that the total amount of trapped charge by the application of the ac voltage is less than that by the application of the dc voltage, etc. Finally, on the basis of the present experimental results, we studied the space‐charge effect on the ac treeing mechanism.
Investigation of a new extinguishing principle for a gas circuit breaker
Authors: Hamano Suenobu , Sasao Hiroyuki , Wada Yuuichi , Hasegawa Hiroshi , Kobayashi Noboru 
Published: July 2007

AbstractA self‐extinguishing principle of a gas circuit breaker (GCB) without puffer action (autopuffer GCB) using an external magnetic field was investigated to improve the interrupting capability in the small current region (several kA). Properties of the rotating speed of an arc, the arc voltage, and the gas pressure rise in an expansion space under the external magnetic field were studied experimentally. The relation between the interrupting capability and the radial magnetic flux density in the autopuffer GCB with a permanent magnet (magnet‐assisted autopuffer GCB) was obtained experimentally and also analyzed numerically. The results are summarized as follows.
The arc column is driven in the azimuthal direction by the radial component of the external magnetic field.
The rotating speed of the arc driven by the radial magnetic field of a permanent magnet remains constant in the arc current range below several kA, and it decreases with an increasing current in the current above several kA.
Since the arc rotation raises the arc voltage and gas pressure in the expansion space, the gas flow from the expansion space to the arc increases in the vicinity of current zero. The interrupting capability is then improved in the small current region.
It is confirmed that the magnet‐assisted auto‐puffer GCB has a good interrupting capability not only for the large current region but also for the small current region.