bluuebunny/crossref_metadata_2025 huggingface dataset:
A fast solution method for multiobjective optimal power flow using an interactive approach
Authors: Kubokawa Junji , Sasaki Hiroshi , Yorino Naoto , Yokoyama Ryuichi , Tanabe Ryuya , Okubo Yoshito
Published: July 2007

In modern industrialized societies, it is mandatory to provide an uninterrupted supply of high‐quality electric energy at modest cost while promoting a better environment. This can only be realized through very sophisticated power system operations that compromise several contradictory factors, namely, economy, security and environment. Since these factors are in trade‐off relationships to each other, they should be analyzed appropriately. One class of problems that simultaneously satisfy several criteria in trade‐off relationships is called “multiobjective optimization problems.” Optimal power flow (OPF) has been regarded as the most powerful means to obtain effective system operation plans since it only optimizes a single objective function.

This paper proposes an efficient solution methodology for a class of multiobjective optimal power flow problems which makes use of a heuristic search method. An optimal solution can be found in the proposed heuristic search method based on local information about a preference index, which is chosen arbitrarily from a given set of objectives. This circumvents the exhaustive evaluation of all noninferior solutions needed in the existing multiobjective OPF algorithm proposed by the authors, thus dramatically reducing the solution time. The proposed method has been coded and applied to the IEEE 57 node test system. Simulation results have demonstrated the possibility of utilizing this method in on‐line environments.
New type of Nb3Sn fiber‐reinforced superconductors for high‐field pulsed magnet and effect of thermal stress
Authors: Arai Kazuaki , Tateishi Hiroshi , Umeda Masaichi , Agatsuma Ko
Published: July 2007

A new type of superconductor with high elastic modulus fibers is being developed for the application of high‐field pulsed superconducting magnets called Fiber‐Reinforced Superconductors (FRS). FRSs have great potential for the construction of a 15‐T class pulses magnet with its size kept equal to ITER because stainless steels of cable‐in‐conduit‐conductors could be reduced considerably.

This paper presents a technique of preparing FRS and measuring its superconducting characteristics including strain‐Ic relation. FRS has a critical current density of 600 (A/mm2/initial niobium) at 15 T, which is almost equal to one of the commercial bronze‐processed wires. The intrinsic strain vs. Ic characteristics are similar to that of bronze‐processed wire. Thermal strain on FRS also is discussed because materials with high elastic modulus tend to have low thermal contraction which leads to degradation of the superconducting characteristics of the Nb3Sn layer. Possibilities of overcoming the degradation while maintaining very high elastic modulus of tungsten fiber for reinforcement are shown.
Magnetic properties of La2Co17‐x‐yFexTiy and La2Co17‐x‐yFexTiyNδ
Authors: Hasebe Akio , Imai Tetsutaro , Otsuki Etsuo
Published: July 2007

The magnetic properties of La2Co17‐x‐yFexTiy and La2Co17‐x‐yFexTiyNδ intermetallic compounds have been investigated. La2Co17‐x‐yFexTiy has the rhombohedral Th2Zn17 structure and exhibits the following magnetic properties: saturation magnetization >1.0 T; Curie temperature >873 K; and easy c‐axis.

Nitrogen is introduced into these compounds interstitially through the nitrogenation process. The saturation magnetization and Curie temperature of La2Co17‐x‐yFexTiyNδ is decreased by the introduction of nitrogen, in contrast to Sm2Fe17.
Development of fuzzy excitation control system
Authors: Kitauchi Yoshihiro , Taniguchi Haruhito
Published: July 2007

Power system stability is essential to reliable and economical operation of power systems. The quick‐response excitation control with PSS is used as a power system stability improvement measure at the generator. However, this method is not always sufficient to apply in a wide operation range of power system configuration, load flow, and so on.

This paper includes results of experiments of fuzzy excitation control system on the ac/dc Power System Simulator of CRIEPI. This control system is verified to improve power system stability and has better performance than the conventional excitation control on a one‐and two‐machine to infinite bus system.
Magnetic properties of iron‐based materials (nitrogen interstitially modified 1:12 compounds and Fe3B‐Nd) for low rare‐earth bonded magnets
Authors: Hirosawa Satoshi , Makita Ken , Kanekiyo Yoshikazu , Umemoto Minoru
Published: July 2007

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

This paper presents an efficient computational algorithm for selecting the optimal generation mix under uncertain circumstances. Subjective, experiential or linguistic uncertainties are selected from among various uncertainties, i.e., we treat fuzziness in generation expansion planning. The fuzziness can be divided into: (1) the fuzziness of decision making; and (2) the fuzziness of some planning parameters, such as load growth, fuel price, and so on. Both classes of fuzziness are integrated into a fuzzy decision based on fuzzy sets theory, and then the optimal generation mix can be determined by the Fuzzy Dynamic Programming (FDP) technique.

The proposed method, which is based on the dynamic programming technique, is extended by using the Bellman‐Zadeh maximizing decision. In the method, each generation technology and generation capacity are selected as a stage and state, respectively. The proposed method can easily accommodate not only the fuzziness but also many constraints of generation expansion planning, such as integer solutions of unit capacities, condition of existing units, and so on. Furthermore, the arbitrary shape of membership function can be used. The effectiveness and feasibility of the proposed method are demonstrated on a typical power system model.
Diamond‐like carbon film produced by vacuum arc deposition technique and its surface appearance
Authors: Takikawa Hirofumi , Taketomi Koichi , Sakakibara Tateki
Published: July 2007

Diamond‐like carbon (DLC) films are deposited in a dc vacuum arc plasma with a graphite cathode. The arc current, the flow rate of hydrogen gas and the pressure are 50 A, 10 ml/min and 0.05 Pa, respectively. The substrate materials are Si (111), soda‐glass and Mo. Process parameters are deposition time (3 to 30 min). The films are analyzed by laser Raman spectroscopy and the surface appearance of the films are observed with an optical microscope.

The results are as follows: (1) the films deposited under these conditions have diamond‐like carbon structure; (2) the films deposited for 3 min on Si or Mo and for 5 min on glass, wrinkle on the substrates; (3) the films deposited for more than 10 min on Si and for more than 15 min on glass, crack and flake off the substrates; and (4) the films deposited for more than 10 min on Mo, plainly stick on the substrate without any wrinkles or flakes.

It is found that plain DLC films are able to be produced by the vacuum arc deposition method if the deposition time is selected appropriately, while never by the conventional plasma CVD method.
High‐precision voltage‐measuring method using fast sampled data for electric power systems
Authors: Chiba Tomio , Kido Mitsuyasu , Kawakami Junzou , Yoneda Katsuhiko , Kawai Tadao , Hirasawa Kotaro
Published: July 2007

Control and protection equipment in power systems requires higher sensitivity and operational reliability to meet today's changing power system requirements. The voltage‐measuring deviation requirement for advanced voltage and var control equipment is less than 0.1 percent under conditions of harmonic distortion in the voltage waveform and power‐system frequency variation. Studies on digital signal processing suitable for electric power systems showed that these requirements are satisfied using fast sampling and very fast 32‐bit floating point operations by a Digital Signal Processor (DSP).

This paper describes the design philosophy of a high‐precision power system voltage‐measuring method using fast sampled data. In addition, total voltage‐measuring deviation characteristics under a combination of the techniques are described along with digital filter characteristics, frequency‐measuring deviation characteristics, frequency variation versus gain‐compensation characteristics of a digital filter, and peak value operating principles.
Game‐theoretic analysis of a buy‐back system and a cogenerator‐customer wheeling system
Authors: Asano Hiroshi , Kuwahata Akeo
Published: July 2007

Electricity markets are experiencing widespread changes that are significantly altering the industry. The purpose of this paper is to analyze the economic consequence of various rules of purchased power pricing and wheeling fees of an electric utility by game theory.

A regulator, an electric utility, and a cogenerator are included in this model as players of the game. Consider an extensive game model of an electricity market where a cogenerator sells excess electricity to anelectric utility or an end user. The regulator behaves so as to maximize social welfare. The electric utility and the cogenerator intend to maximize their own profit. The wheeling fee between the electric utility and the cogenerator is adjusted to maximize the sum of incremental profits.

We have found that a buy‐back system (the utility purchases cogenerated power) and a cogenerator‐customer wheeling system are equally efficient and are more desirable than a monopoly system. The buy‐back rate should be equal to (in the LP bargaining solution) or less than (in the Nash bargaining solution) the marginal cost of the electric utility. We also conducted an analysis of two‐period electricity market.
Active filter system containing an inverter bypass circuit to suppress harmonic resonance
Authors: Ogihara Yoshiya , Matsukawa Mitsuru , Tada Satoshi , Ikeda Haruo , Kawaguchi Ikuo , Shiraishi Hiroshi
Published: July 2007

The superconducting‐type magnetically levitated railway system (MAGLEV), which is driven directly by variable voltage, variable frequency (VVVF) inverters or cycloconverters, is well known as the new traction system for future super‐rapid mass transportation.

Since the frequency converters generate harmonic currents possibly leading to interference problem on utility transmission systems, the conventional ac filter of LC (reactor‐capacitor) branch and/or the active filter is necessary to prevent the harmonic disturbances.

The authors have developed a novel harmonic compensation system consisting of shunt LC filters on load side, a step‐down transformer on receiving end, and a small‐capacity active filter with one end connected to the secondary winding of the transformer and the other to the load bus.

The active filter is current‐controlled to give adequate damping to the harmonic resonance condition between the power system and the passive filter equipment, especially at lower harmonic frequencies.

The principle and the characteristics of the new harmonic compensation system are described, and its laboratory test results which show satisfactory performance are given.
A feasibility study of an 8‐MWh flywheel‐type power storage system using oxide superconductors
Authors: Higasa Hiromasa , Ishikawa Fumihiko , Shibayama Motoaki , Ono Takeshi , Yokoyama Shoichi , Nakamura Shirou , Yamada Tadatoshi , Yoshida Yasuo
Published: July 2007

When combined with a magnet having a magnetic field gradient (for example, a permanent magnet), a Y‐based oxide superconductor is capable of forming a noncontact bearing with a strong levitational force. Since this bearing exhibits low rotational loss, it is very likely to form a highly efficient power storage system in combination with a flywheel.

In this paper, an 8‐MWh power storage system utilizing a flywheel was designed conceptually to examine its applicability and the possible effects of its introduction. It was found that this system was an effective power storage.
Development of an advanced voltage control technique to improve voltage and reactive power characteristics of a large‐scale power cable system
Authors: Michigami Tsutomu , Nakamura Keiji , Suzuki Takamitsu , Yamabe Chobei , Horii Kenji
Published: July 2007

The power supply system for a metropolitan area consists of multiple 275‐kV power cable systems to supply power to a large number of consumers. Each system has a large charging capacity (capacitive reactive power). When 275‐kV power cable systems experience a voltage drop, their charging capacity decreases. However, the reactive power losses increase in the 275‐kV overhead transmission lines, which supply large power to power cable systems, thus causing the performance of the power supply system to deteriorate.

In this paper, the following three points are reported:

When the secondary power system of the trunk substation is a large‐scale power cable system, new techniques can greatly improve the voltage and reactive power characteristics by controlling the rise of the sending‐end voltage at the secondary side of the trunk substations and maintaining the voltage of power cable systems at a constant level.

In the use of this control technique, it has been demonstrated that controlling by the direct‐detecting method of a voltage drop in the primary power system is superior to one that controls by the indirect‐detecting method, which increases load power in the cable system.

The results of simulations obtained by using a 275‐kV cable system model and a performance power system model show that the use of this control technique can produce a good effect despite the allowances made for the opposite effect, i.e., a decrease in the capacity of power capacitors resulting from voltage drop at the tertiary voltage of a 500‐kV transformer.

This study is carried out to examine the possibility of lightning control using a photoionized plasma produced by a UV laser without an optical air breakdown. As the fundamental experiment, the characteristics of a laser‐triggered spark gap (LTSG) are examined, where a laser beam is not irradiated on the surface of the electrodes. In this experiment, the KrF excimer laser is very effective in increasing the plasma density ne and the reduction ratio p of 50 percent breakdown voltage against the self‐breakdown voltage. The relation between ne and p is increased by generating a long and high‐density plasma parallel to the discharge axis.

On the other hand, the abnormal discharge process in triggered lightning using a rocket is examined, and it is indicated that the most important condition to trigger a lightning discharge is the production of a plasma channel of length 200 m and density about 1019 m−3. It is suggested that such a plasma channel could be produced by a KrF excimer laser with an energy of only about 3.67 J.
Evaluation of photovoltaic modules considering spectral solar radiation
Authors: Hirata Youichi , Tani Tatsuo
Published: July 2007

For the optimum design of photovoltaic power systems, it is very important to estimate their annual maximum amount of output. In general, the annual maximum amount of output has been calculated by using photovoltaic module efficiency under irradiance of 1 kW/m2 at AM 1.5 with solar cell temperature of 25°C. Since the spectral distribution of solar radiation changes with weather, season and time, the efficiency of solar cells is not always constant.

This paper describes a method evaluating the maximum amount of output in photovoltaic modules, ‘the spectral method,’ by using the measured annual spectral solar radiation and the spectral response of various photovoltaic modules.

The calculated values using the spectral method agreed well with the measured values for amorphous silicon photovoltaic modules from March 1991 to February 1992. The spectral method proved most effective for optimum design of amorphous silicon photovoltaic power systems.
An algorithm for linguistic risk assessment of uncertain factors in generation planning
Authors: Tanabe Ryuya , Yasuda Keiichiro , Yokoyama Ryuichi
Published: July 2007

This paper presents an efficient computational algorithm for evaluating the risks of uncertain factors in generation planning. Uncertainty in a multiobjective risk assessment problem can be divided into (a) uncertainty of the possible conditions to be evaluated; (b) uncertainty in multiobjective decision making; and (c) uncertainty in risk which is obtained using imprecise information.

The proposed method basically consists of two phases: (1) the aggregation of risks with respect to all of the objectives for each uncertain factor; and (2) the linguistic expression of the aggregated risk of each uncertain factor. In the first phase, uncertainty in possible conditions is treated as fuzziness in planning parameters, and uncertainty in multiobjective decision making is also treated as fuzziness in decision making.

Furthermore, the statistical trend of risk with respect to an objective for each uncertain factor can be extracted from uncertain risks obtained using imprecise information. In this method, both classes of fuzziness and the statistical trend of risk for each uncertain factor can be integrated into the risk of each uncertain factor, and then the risks of each uncertain factor with respect to all the objectives can be aggregated by extension principle in fuzzy sets theory. In the second phase based on the linguistic approximation technique, the aggregated risk of each uncertain factor can be represented by natural language. The proposed method can realize an effective and flexible decision support for evaluating the risks of uncertain factors in generation planning. The effectiveness and feasibility of the proposed method are demonstrated on a typical power system model.
Nb3Sn single‐phase targets for fiber‐reinforced‐superconductors and technique of preparing superconducting films without post annealing
Authors: Arai Kazuaki , Tateishi Hiroshi , Agatsuma Ko , Saito Takashi , Sadakata Nobuyuki , Nakagawa Mikio
Published: July 2007

A new type of superconductor is being developed for the application of high‐field pulsed superconducting magnets, which are called fiber‐reinforced‐superconductors (FRS). A filament of FRS consists of a reinforcement fiber with high elastic modulus and a superconducting layer around it. The strain can be reduced against electromagnetic force because of highelastic modulus fibers. If Nb3Sn target is utilized, the preparation process of FRSs is shortened and there is the possibility to produce Nb3Sn layer which leads to high current density because of its uniform stoichiometric Nb3Sn layer.

This paper presents first a technique of preparing a single‐phase target of Nb3Sn to produce superconducting layers on reinforcement fibers of FRSs.

Mixture of niobium and tin powder was reacted in a furnace filled with argon gas to be Nb3Sn, and then it was broken and cast into a stoichiometric target with a diameter of 77 mm. The critical temperature of the target itself was 17.5 K. The thin film deposited with the target showed no superconductivity without post annealing, but it had critical temperature from 14.5 K to 12.5 K after heat treatment. Second, a new target containing rich tin was prepared and the film deposited with it had superconductivity without post annealing.
Development of fault detector for 33‐kV ungrounded power line
Authors: Yamamoto Minoru , Ifukube Atsuchi , Murata Yoshikazu , Hashimoto Makoto
Published: July 2007

A fault section detection system is being developed for 33‐kV ungrounded power line. The fault section is obtained from the relation of two point zero‐phase currents on power line. This fault detector is composed of optical current sensors and the processing unit and solar battery system. The optical current sensor consists of a Faraday cell and a porcelain bushing. Zero phase current on the processing unit is obtained through a three‐phase composer with auto gain control and residual current eliminator.

This fault detector has the ability of 0.15 A zero‐phase current detection fault factory test; in field tests, this fault detector detects ground fault.
Accurate measurement method of the position of a buried line
Authors: Takao Toshiharu , Hara Kazuhiro
Published: July 2007

A conventional method to measure the position of a buried line has been used. This method is based on the measurements of magnetic field around a line which conducts a current. However, the pitfall is that the magnetic field generated by an induced current in a secondary line allows considerable measurement errors.

This paper describes a novel method to exclude such errors caused by the induced current. While the magnetic field generated by the current in the primary line is in phase with the current, that generated by the induced current delays more than 90° compared to that of the current in the primary line because of a reluctance component of the secondary line. Hence, the 90° component of the magnetic field results from the induced current. This component is measured by a solenoid coil and a lock‐in amplifier; the 0° component is measured also and corrected by using the 90° component. Thus, the net magnetic field generated by the current in the primary line is calculated. It is used to determine the correct position of the primary line. The new method is tested by using two buriéd lines and is proved to be useful.
Daily electric load forecasting using artificial neural network
Authors: Ishida Takaharu , Tamura Shigeru
Published: July 2007

A multilayered‐type neural network is attractive for daily electric load forecasting because the neural network can acquire a nonlinear relationship among the electric load data and their factors (weather, temperature, etc.) automatically. This paper discusses first some essential issues to be considered in neural network applications. One is difficulty of obtaining sufficient effective training data, another is the influence of abnormal learning data, and one more is the inevitable outerpolation. For these issues, the following three methods are developed in order to forecast more accurately: (1) a structure of the neural networks for insufficient training data; (2) detection and diminishing the influence of abnormal data; (3) employment of interpolation network and outerpolation network with additional data for outerpolation. Furthermore, to increase the sensitivity between electric loads and factors, (4) removal of base load is developed. Those methods work effectively to decrease the average absolute errors of peak‐load forecasting and 24‐hour load forecasting to 1.78 percent and 2.73 percent, respectively.
Transient stability limit issues at three‐phase short‐circuit in parallel running of both a superconducting generator and a conventional one
Authors: Nitta Tanzo , Shirai Yasuyuki , Kawauchi Toshikazu , Okada Takao , Ogawa Yoshihiro
Published: July 2007

Experimental studies using20‐kVA superconducting generators (SCG) have been performed in an attempt to understand some of the characteristics of SCG in power systems. It is necessary to investigate the characteristics for the parallel operations of both an SCG and a conventional generator (CG) when an SCG is installed in a present power station. Some of the results of the authors' studies on parallel running of the 20‐kVA SCG and the 20‐kVA CG are described in this paper. In the experimental system, the SCG is connected to a regional power system (infinite bus) through reactors (artificial transmission lines) and the CG is connected to the terminal of the SCG. Using experiments and computer simulations, the transient characteristics at three‐phase short‐circuit faults are investigated: 1) when the CG is not disconnected; and 2) when the CG is disconnected after reclosing the line with the fault cleared. Two kinds of stable limit curves are obtained for output power at three‐phase short‐circuit fault for the aforementioned two cases.
Diagnosis method for live‐wire insulation of high‐voltage XLPE cables by DC superimposition
Authors: Shinmoto Takashi , Kimura Chiaki , Yamamoto Ken , Ninomiya Nobuo , Umeda Susumu
Published: July 2007

Recent preventive maintenance for equipment has grown to include diagnosis of the insulation of cables under hot‐line conduction. Much of the equipment constructed during the high‐growth period in the 1960s has become obsolete. Recent circumstances make it difficult to obtain a longer service interruption time.

Results of a study of the method that measures the live‐wire insulation resistance by superimposing dc 50 V to a high‐voltage busbar through GPT and forms a bridge with the resistance of a cable insulation are discussed. It is clarified that this live‐wire insulation diagnostic method is highly effective at detecting degradation of a cable insulation resistance and is, therefore, suitable for so‐called trend monitoring as well.
Fundamental characteristics of overhead transmission line galloping determined by simulating calculation using equivalent single‐conductor method
Authors: Yamaoka Masaru , Hasegawa Jun
Published: July 2007

Theoretical study and phenomenal examination have been ongoing for many years; however, some electric power companies still have instantaneous power failure due to galloping. This study differs from others in that nonlinear three‐dimensional simultaneous equations of conductor movement can be solved directly using numerical calculation. Fundamental characteristics of galloping can be ascertained by changing calculation parameters variously. This time, a method is used in which bundle conductors are changed equivalently to single conductor. It is also clarified that unstable domain becomes wider when rotational movement of conductor occurs.
Development of a new two‐input PSS to control low‐frequency oscillation in interconnecting power systems and the study of a low‐frequency oscillation model
Authors: Michigami Tsutomu
Published: July 2007

In Japan, large and small power systems were interconnected over time and thus ultimately grew into a large‐scale national power system. A highly important stability problem arising from large‐scale power system interconnections is low‐frequency oscillation (about 0.3 Hz to 0.5 Hz) of interconnected systems. The ΔP‐type PSS has been applied to all generators in trunk power systems as a measure to improve the damping of local mode oscillation (about 1 Hz). However, it is difficult for this PSS to improve the damping of low‐frequency oscillation because of the hardware and the design of PSS control constants. Therefore it has become necessary to develop a new two‐input PSS.

This paper explains the development of this two‐input PSS and the study of a low‐frequency oscillation model. This paper can be summarized as follows:

(1) The effect of control over low‐frequency oscillation is affected by the kinds of PSS detecting signals. The Δω‐type or Δf‐type detecting signals used for lead‐phase compensation are suitable for this purpose.

(2) It is possible to cause low‐frequency oscillation studies in a one‐machine infinite‐bus power system model with medium loads.

(3) According to the simulation of a three‐machine and actual large‐power system models, dynamic stability was largely increased by this two‐input PSS used for generators.
Influence of charged droplet cloud on flashover of air gaps for lightning impulse voltage
Authors: Sugimoto Toshiyuki , Higashiyama Yoshio , Asano Kazutoshi
Published: July 2007

Transmission lines passing through a mountainous region often are struck by winter lightning. As a result, numerous double‐circuit faults occur. Space charge might be responsible for this phenomena. Several investigations on flashover characteristics have been performed focusing on reduction of flashover voltage due to ionic space charge formed by corona discharge.

In this paper, flashover characteristics of an air gap within a charged droplet cloud ejected from an airless nozzle using an induction charging method are discussed. The droplets are charged in the range ‐200 to 200 μC/kg, forming the space‐charge density of approximately 13 μC/m3. The flashover voltage and the time lag to flashover were measured when 1.2 × 50 μs lightning impulse voltage applied to a rod‐sphere gap is placed within the charged cloud. Flashover voltage for a positive rod increased markedly within a positive charged cloud by increasing the charge‐to‐mass ratio. The increase of flashover voltage was up to 80 percent in comparison with uncharged droplets. Flashover voltage for the negative rod decreased about 20 percent in the cloud of either polarity. The results show that the presence of charged droplets in the air gaps affects the discharge process significantly.
Fast‐switching‐speed, low‐forward‐voltage‐drop static induction (SI) thyristor
Authors: Maeda Mitsuhide , Keno Takuji , Suzuki Yuji , Abe Toshiro
Published: July 2007

A static induction (SI) thyristor using a normally‐off planar‐gate structure in a low power class has been developed to be used as a power switching device in a three‐phase inverter circuit. A 600 V‐15 A class SI thyristor with very fast switching time (tgt, tgq) and low forward voltage drop (VTM) was designed and created. This design was performed with a reasonable wafer structure (n−/n/p+), an n− base carrier concentration and thickness, and a gate structure (gate diffusion length and gate‐gate pitch). Microscopic processing was used to obtain this SI thyristor. The performance trade‐off between turn‐off time and forward voltage drop is controlled by a lifetime control process using proton irradiation that results in a very fast switching time with tgt of 500 ns and tgq of 500 ns with VTM of 1.5 V (at IT= 18 A). At a current level of IT = 18 A, the current density in the active area becomes 200 A/cm2, which indicates that the performance of the SI thyristor is superior to that of conventional IGBTs and MOSFETs.
Suspension of soft magnetic materials using high Tc superconductors
Authors: Tsutsui Yukio , Higuchi Toshiro
Published: July 2007

This paper describes a novel suspension technique using high Tc superconductors and magnetic materials. It was found for a field‐cooled superconductor and an adjacent magnetic material that the usual inverse relationship between the attractive magnetic force and gap distance reverts to a direct relationship for small gap length. Thus, stable, noncontact suspension is possible within a certain gap range. This phenomenon was found for even a soft magnetic material possessing minimal coercive force. Since remarkable reversals were observed for magnetic materials with diameters much smaller than that of the pinned area, it is considered that some of the pinned flux is subject to a gathering effect in the magnetic material. Stable, contactless suspension of a 180 g carbon steel weight under a high Tc superconductor was achieved using this technique.
Change of characteristics of desulfurization and denitrification by combustion flue gas composition and electrode configuration under pulsed corona discharge
Authors: Kato Ken , Kasuga Yasuhiro , Fujiwara Masanori , Onda Kazuo
Published: July 2007

Laboratory‐scale and parametric experiments of SO2 and NOx removal from the simulated combustion gas by pulsed corona discharge have been performed by changing the combustion gas composition and temperature, the electrode configuration of plasma reactor, and the polarity of high‐voltage electrode. The following results are obtained: 1) the higher the concentration of H2O and O2, the higher the efficiency of desulfurization and denitrification at the same specific input; 2) the pulsed corona discharge with a voltage pulsewidth as short as 200 ns of negative polarity shows the possibility to attain almost 90 percent deSOx and deNOx efficiency at the specific discharge input of 20 J/g, which is almost the same as the specific input in the electron‐beam process; 3) the deNOx characteristics show a little temperature dependence in the range of 70 to 130°C, but the deSOx efficiency increases rapidly in the temperature region below 100°C suggesting the thermochemical dependence of deSOx reaction; 4) when desulfurization and denitrification proceed, the white dendritic powder deposits on the plasma reactor whose composition is identified to be 49 mol% (NH4)2SO4 and 47 mol% of 2NH4NO3 · (NH4)2SO4, and the ratio of SO2, NO and NH3 of the deposit is almost equal to that of supplied gas.
Development of the DC superimposition bridge method for the measurement of high insulation resistance of medium voltage XLPE cables in operations
Authors: Shinmoto Takashi , Kimura Chiaki , Yamamoto Ken , Umeda Susumu
Published: July 2007

The method for measuring insulation resistance by superimposing the dc voltage has potential for detecting the deterioration of cable insulations. The deterioration of cable insulations can be detected by measuring current which flows through a grounded shielding wire. However, the earth current also flows from the cable sheath into the grounding wire as noise. Thus, to assess the deterioration properly, it is necessary to separate the earth current from the total current. On the other hand, to improve detection sensitivity, it is desirable to superimpose the highest possible dc voltage. In this case, provision must be made so that there are no adverse effects on the GPT.

The authors, placing special emphasis on the method of measuring high insulation resistance by configuring the bridge, have conducted an investigation on how to detect the insulation deterioration with high accuracy and sensitivity without impairing the functions of the GPT. The following issues were investigated and the results are reported in this paper:

(1) It is possible to measure insulation resistance as high as 100,000 MΩ by superimposing 50‐V dc through the GPT after cancelling the earth‐current and by configuring a bridge for determining insulation resistance from voltage ratio.

(2) Even if 50‐V dc is superimposed through the GPT, it is possible to prevent the magnetic saturation of GPT if the current injected by such superimposition is limited (i.e., below max. 5 mA).

(3) In lieu of a variable resistor, a variable dc voltage supply is employed in the bridge. The variable dc voltage supply requires no mechanically driven part, thus making it possible to realize a fully automatic monitoring system.
Selection of the best siting of static var compensators for effective damping
Authors: Okamoto Hiroshi , Kurita Atsushi , Kobayashi Naoki , Sekine Yasuji
Published: July 2007

A static Var compensator (SVC) can improve the steady‐state stability (or the small signal stability), if it is located appropriately. The present paper proposes a method for selecting the best siting of SVC in large‐scale power systems for damping effectively.

Conventionally, it is thought that SVC improves steady‐state stability by its voltage regulating ability. From this point of view, the stability can be improved significantly if SVC is located at the bus which has a large voltage fluctuation due to the lightly damped power swing mode. In contrast to the conventional viewpoint, the present paper makes it clear that the steady‐state stability deteriorates by the conventional voltage regulating control of SVC in some cases. Therefore, the voltage fluctuation is not an appropriate index for effective damping.

This paper explains the mechanism of improvement of steady‐state stability by SVC in terms of modal analysis. On the basis of modal analysis, an index for determining the location of SVC is derived. The index is called LIED (Location Index for Effective Damping) by the authors. Digital simulations are conducted for an 8‐machine longitudinal system and a 29‐machine looped system to demonstrate the validity of the proposed index.
Load levelling by control of air conditioner operation
Authors: Sasaki Hiroshi , Sadakuni Seiji
Published: July 2007

The recent drastic increase in the number of air conditioners has caused sharp and narrow peaks in summer seasons due to the inherent temperature‐sensitive characteristics. The authors propose a method to reduce the peak power demand by controlling air conditioner operations, and verify its effectiveness on clipping peak demand. However, former study has shortcomings in that no qualitative treatment of room temperature or comfort was attempted, and it did not provide a way of assessing peak demand clipping in a power system as a whole.

In this paper, the authors propose a new control method that can deal with the maintaining of comfort and the reduction in power demand. Although air conditioners are used for “comfort,” this contradicts the reduction of power consumption and furthermore the concept of “comfort” is very vague. Hence, Weber‐Fechner's law is utilized to quantify the pleasant feeling which is treated as a fuzzy quantity. A fuzzy coordination method is used to resolve this difference between power demand curtailment and comfort.

The second part of this paper prepares an approach for assessing the amount of peak load clipping when the newly proposed control strategy is adopted in a real‐size power system. A decrease in the required generation capacity is estimated provided that the loss of load probability (LOLP) is maintained at the same level before and after the application of the new control strategy. The reduction can be regarded as a dividend of load management.
Theory of fault characterization on power system
Authors: Tsuji Kouichi , Bandou Matsuo
Published: July 2007

In the field of protective relay, a dream which is unable to be realized by analogue technology has come true with the advance of computer technology. However, there is still room for the development of a high functional protective system, which makes the most of a merit of digital processing because the present digital relay uses the same principle as an analogous one. The points of proposed theory are that first it uses a lot of data of fault, second uses the first and second Kirchoff laws at the same time which are the starting point of electric circuit theory, and third calculates both fault location and resistance by solving nonlinear simultaneous equations.

In this paper high speed calculation for protective relays is achieved by solving a compact matrix using the Newton‐Raphson method.

The matrix consists of two sorts of variables (fault location, fault resistance), and the nonlinear simultaneous equation is reduced by definition of new variables.

As a result of applying this theory to some real faults, we testified that the fault location error was within 0.1 percent, and the calculation time was less than 5 ms. Therefore we think that this theory has already been in a practical stage.

The ultimate goal of this theory is the integration of various algorithms of protective relay, fault locator, and fault restoration operation.
Optimal power system expansion planning under uncertain CO2 emissions control policies
Authors: Fujii Yasumasa , Akimoto Keigo
Published: July 2007

Many efforts towards a settlement of the CO2 problem have already been made through internationally organized meetings. It is not unlikely that some targets will be set for the reduction of CO2 emissions. If a stringent reduction target should be imposed on CO2 emitted from a national energy system, this can possibly have as severe an impact upon electric power sectors as the oil price crises experienced in the seventies. It is, however, quite uncertain whether or not political muscles will be used specifically for tackling the CO2 problem in the near future.

In such a context, this paper presents a new method for optimal power system planning under uncertain CO2 emissions control policies. The derived optimal expansion plan gives us the minimum expected value of the sum of the total system cost and the total amount of carbon taxes levied on net CO2 emissions from fossil fuel‐fired power plants. The stochastic dynamic optimization problem discussed here is formulated as a linear programming problem decomposable into several small subproblems. The proposed method can take into account a specific future scenario of the magnitude of control policy uncertainties, which can be presumably resolved in the first half of the next century due to the increase in scientific wisdom.

In order to evaluate the usefulness of the method proposed here, the authors also present a simple case study with the Japanese national power system up to the year 2050.
Development of kA‐class alternating current superconducting conductors and fabrication of a prototype coreless superconducting autotransformer
Authors: Kajikawa Kazuhiro , Kaiho Katsuyuki , Yamamoto Mitsuyoshi , Fuji Hiroshi , Sadakata Nobuyuki , Saito Takashi , Kohno Osamu
Published: July 2007

Recently, multifilamentary superconducting wires with very low ac losses have been produced and practical applications will now be considered. To realize actualsize power machines and apparatuses, it is necessary to develop 1 ‐ 10 kA ac conductors. However, the critical currents of multifilamentary wires at 1 T are several tens of A, and therefore it is necessary to use multistrand conductors consisting of several tens or several hundreds of strands. Such conductors sometimes show ac current degradation because of such factors as (1) nonuniform current distribution, (2) wire motion, (3) temperature increase, (4) longitudinal magnetic field effect, etc.

Formerly, a coreless transformer was considered unpractical because of its large exciting current. However, Yamamoto and others proposed that a coreless superconducting transformer could be used as a stepdown autotransformer at the receiving side, utilizing its large exciting current as the reactive power source to cancel the charging current of an underground transmission line or UHV line, and therefore the shunt reactors could be eliminated.

In this paper, development of ac‐superconducting conductors aimed at prevention of current degradation are discussed, as well as quench test results of two small coils made with these conductors. In these conductors, low ac low strands with ultrafine NbTi filaments are twisted around a central bundle of stainless steel wires. One of the coils has been designed as a model coreless autotransformer, and its test result is also described.
Basic principles and characteristics of hybrid excitation synchronous machine
Authors: Mizuno Takayuki , Nagayama Kazutoshi , Ashikaga Tadashi , Kobayashi Tadao
Published: July 2007

Permanent magnet type synchronous machines have been widely used for industrial applications. It is commonly known that they are operated at high efficiency since no excitation input is required. However, it is difficult to control the air‐gap magnetic flux, because the magnetic flux is determined by the property of the permanent magnet and approximately kept constant.

On the other hand, synchronous machines with the field winding make it easy to control the air‐gap magnetic flux. But the copper loss of the field winding becomes large at the rated load.

In order to realize the magnetic flux control easily and improve the performance of the conventional synchronous machine, we propose a hybrid excitation type synchronous machine (HSY) with the permanent magnets and the field winding. Advantages of HSY are (1) it has no brushes (maintenance free), (2) required excitation input is small (high efficiency), (3) it is easy to get a sufficient magnetic flux control, and others. Therefore, HSY has a great possibility of use for various applications.

In this paper, basic principles and characteristics of HSY are mainly discussed and made clear.
The Fluorescence Labelling of Primary Amines with Perylenetetracarboxdiimides
Authors: Langhals Heinz , Becherer Thomas , Lindner Jörg , Obermeier Andreas
Published: July 2007

The synthesis of perylenetetracarboxdiimide‐labelled aldehydes is described as well as their condensation with primary amines. Thus, a highly fluorescent and light‐fast fluorescence labelling process has been demonstrated. Application of this method to biological targets is also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Thermokinetic Analysis Reveals the Complex Growth and Haloadaptation Pattern of the Non‐Conventional Yeast Debaryomyces hansenii
Authors: Schumer D. , Breuer U. , Harms H. , Maskow T.
Published: July 2007

The high halotolerance, simple cultivation, potentially easy downstream processing together with a broad substrate spectrum raises growing interest in the non‐conventional oleaginous yeast Debaryomyces hansenii as a cell factory for the chemical and food industry. Moreover, the potential of non‐conventional yeasts for the decontamination of the environment and as possible hosts for biosensor developments are still unexplored. However, non‐conventional yeasts often respond in a highly complex manner to unfavorable conditions. Exploiting the potential of these yeasts on a technical scale requires the development and testing of robust monitoring tools providing deeper and real‐time insight into metabolism. Calorimetry is ideal for this particular process since it measures the entirety of metabolic processes, while indicating changes immediately and allowing the quantitative description of regulatory processes when combined with further online and offline analytics. Furthermore, recent calorimetric developments promise applicability under technical “dirty” conditions and suitability for high‐throughput measurements. To demonstrate the analytical potential of calorimetry for the characterization of the highly complex yeast metabolism, the heat production rate and the dynamics of key metabolites were assayed at different salinities. Strong correlations between these features were observed, and the complex heat pattern reflected the dynamics of key metabolites quantitatively.
Insider trading in futures markets: A discussion
Authors: Dinehart Stephen J.
Published: July 2007

“…Every man in the War Department, and the Executive Mansion, who was so situated as to be able to communicate valuable information in advance of the newspaper dispatches was approached by the gold operators, and in most instances an arrangement existed between the former and the latter, for mutual profit.…”
Optimal bank asset and liability management with financial futures
Authors: Brodt Abraham I.
Published: July 2007

This paper presents a model for optimal bank asset and liability management with financial futures. This model is a multiperiod linear programming model based on Markowitz portfolio theory. Given the bank's initial position, its economic forecasts, and the constraints under which it operates, the model can help a bank's senior executives determine the current and expected future balance sheet composition and financial futures position which will minimize the bank's operating risks and which will meet the bank's expected profits goal with the minimum possible profits risk. By parametrically varying the expected profits goal, the model will generate the set of risk‐return efficient decisions. Bankers need then examine only the set of efficient decisions to choose their optimal solution.

A simplified example is used to illustrate the application of our model and to demonstrate that banks that use financial futures in asset and liability management can obtain better results than banks that do not use financial futures.