A direct-steam-generation (DSG) collector is expected to make it possible to improve solar thermal collection efficiency and the economics of a solar thermal power generation system. In this paper, characteristics and economics of two kinds of power generation systems using a DSG and a conventional collector are investigated: a CO₂-capturing hybrid-type power generation system (Hybrid system) and a conventional solar thermal power generation system (STPG system). In evaluation, the total area of collector is assumed to be 10 ha and the capacity of each system was determined so as to minimize the unit power generation (UPG) cost. It has been shown through simulation study under assumed premises that for the STPG system the UPG cost is improved from 24.4 to 19.4 yen/kWh and that the net generated power quantity is increased by 30.8% by using a DSG collector. For the Hybrid system the UPG cost is improved from 15.8 to 14.9 yen/kWh and the net generated power quantity is increased by 17.5%. It has also been shown that CO₂ reduction amount is increased from 2, 106 to 2, 759 t-C/y in STPG system and from 6, 282 to 7, 380 t-C/y in Hybrid system. The Hybrid system using a DSG collector is expected to be one of the most desirable power generation systems under the CO₂ emission constraint in the future, since among investigated systems (a) it has the highest fuel-base power-generation-efficiency as high as 67.2%; (b) its UPG cost is the lowest; (c) it emits no CO₂; and (d) its CO₂ reduction effect is the largest.

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In this paper, we present a nonlinear state feedback control using neural networks(NN). Since the NN models the nonlinear excitation controller using only measurable state variables from the synchronous generators, the proposed method can implement in real system easily. The effectiveness of the proposed method is demonstrated by computer simulations for a singe and multi machine power systems. Furthermore, the NN is implemented on the experiment system with a laboratory size 2.2kVA synchronous generator.

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A bstract: This paper presents a consideration on the accuracy of various types of approximate models of synchronous machines for power system transient stability simulations. Synchronous machines are, in general, expressed by the d, q axis Park model in the simulations. However, there are several types of approximate models. In the first half of this paper, accuracy of 4 models is evaluated by performing numerical simulations for three phase short circuit fault in a model system. In the second half of the paper, accuracy of the standard model with one q-axis damper circuit and the detailed model with two q-axis damper circuits is discussed for analyzing the transient stability of turbine generators with solid rotors.

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The electric power industry has been facing deregulation. Many power producers will entry into the power market. So we recognize that the frequency control system is a crusial service for power of good quality. Therefore understanding and evaluating the frequency control systems are becomming more important. Some Control Performance Standards had been proposed. In this report, we will conduct a statistical analysis of control performance standards and confirm that the statistical analysis matches results of power sysytem simulations. And we will verify whether control performance standards can evaluate the frequency control systems.

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The theoretical analysis has already been performed for the cylindrical rod electrode that is driven vertically into the earth with its upper end at earth surface. However, there are almost no reports to describe the grounding resistance when the rod is buried into the multi-layered earth. It is important to understand how various buried depths of the electrode affect the potential distribution and the grounding resistance.
In this paper, the electric potential distribution in the underground and the voltage along the earth surface for the buried rod with buried depth t into the multi-layered earth are analyzed. Based on the results, the authors described a calculating method of the grounding resistance for the rod buried into the multi-layered earth.
The validity of those estimated values for the buried rod is verified with the numerical calculation.

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A 500kV DC extruded cable and a factory joint have been developed. As the first step of this development, space charge accumulation in insulation material is studied. DC high electric field accumulates space charges, and causes local increase of the electric field, which can lead to breakdown. In order to resolve this problem, polyethylene with polarity organic matter is selected as dielectric material for the DC power cable. Model cables, which have 9mm dielectric layer thickness, were made and these DC performances were evaluated. As the result, it is confirmed that these cables have much higher DC breakdown strength and smaller accumulation of space charge than XLPE cables. For the next step, a full-size 500kV DC extruded dielectric submarine cable with a factory joint was designed, and manufactured. The thickness of the insulation is designed as 23mm with consideration of space charge influences. Voltage withstand tests were carried out after mechanical tests which simulate the equivalent damage during cable laying into the sea. As the result, it was confirmed that the developed DC cable has sufficient initial electrical properties as an UHV DC power cable.

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In this paper, we propose a method of analytically calculating an impedance of a thyristor-controlled series capacitor (TCSC). The TCSC consists of a thyristor-controlled reactor (TCR) and a capacitor. If a small voltage component of frequency f superimposes TCSC voltage of frequency f_o, then current components of frequency (nf_o±f) flow through the TCR, where n takes even numbers. We derive theoretical equations for them. In the derivation, we consider an influence of odd harmonics in the TCSC voltage. We also consider deviations in its zero-crossing times due to the superimposed voltage. The current components flow through the capacitor and the transmission line, and produce new voltage components of frequency (nf_o±f). In order to count their influence, we introduce admittance matrices for the TCR, the capacitor, and the transmission line. By solving a network equation consisting of the matrices, we can obtain distribution of the voltage and current components. We define the impedance of TCSC as a ratio of the voltage component of frequency f to the current one of the same frequency. The impedance analytically obtained corresponds well with that obtained by simulations. Its frequency responses vary with the firing method of thyristors.

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Photovoltaic power generation system (PV) and cogeneration system (CGS) are expected to being installed as environmentally benign distributed power sources. Many discussions about PV and CGS have so far focused on the individual performance of the energy saving and/or reduction of CO₂ emission. This paper discusses the ability of PV system and CGS for reducing CO₂ emission of the whole energy system. The results are summarized as follows. 1) When the capacity of the combined-cycle generator is reduced by the introduction of CGS in house, hotel and hospital, the electric power supply of other generators of higher CO₂ emission decreases in addition to that of the combined-cycle generator. As a result, the effectof CO₂ reduction of CGS could be evaluated as high value compared to the individual system point of view. 2) When the annual power supply of coal generator isrestricted considering the reduction of total CO₂ emission of the electric powersystem, the effect of CO₂ reduction of PV and CGS introduced in office and shopisevaluated lower.

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Wire and cable are demanded to have not only high reliability in electrical and mechanical properties, but also low disaster characteristics from the viewpoint of fire safety. For this purpose, Fujikura have supplied low smoke, halogen free and flame retardant cables “Clean Cable” since 1983. From the viewpoint of environmental protection, we have developed a new type of halogen free recyclable cable with low toxic gas emission “Eco-Cable” since 1998. Our new recyclable cable material is low density (d=1.1), halogen free and flame-retardant material. We have examined to separate the cable jacket (new material and PVC) and insulation (XLPE) using density difference. We employed the liquid cyclone method which developed at Hitachi, Ltd.. As a result, XLPE (d=0.9), new material (d=1.1) and PVC (d=1.4) are separated by purity 99.6%, 99.9%, and 99.3% respectively.

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The field observations are conducted during winter thunderstorm. We obtained excellent data sets of positive CG flashe more than ten. Three-dimensional images of UHF radiation sources for positive CG flashes are shown. UHF radiation sources at leader progression stage show the tendency of concentration at constant altitude (2km, -5degrees) without any remarkable progression. On the other hand, after the return strokes the location of radiation sources proceeds very rapidly and penetrates into the thunderclouds horizontally. By applying the “Bi-directional leader concept”, 3D location of positive CG flashes is interpreted. The UHF radiation intensity of the negative leader is about 15 dBm stronger than that of the positive leader. Therefore, in case of 3D location of positive CG flashes, we can see negative leader propagating into thunderclouds, and we do not see positive leader tip coming down to ground.

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VLF (Very Low Frequency) high voltage with frequency of 0.1Hz will be utilized for an on-site test of XLPE underground cables, instead of conventional dc high voltage test. Since XLPE cables are connected to GIS (Gas Insulated Switchgears) in substations, the influence of VLF voltage application to GIS insulation should be investigated. One of the most important characteristics for GIS insulation lies in the metallic particle contamination and its behavior, which may induce breakdown in GIS.
From the above viewpoint, this paper discusses the metallic particle behavior and breakdown characteristics under VLF voltage application in GIS. Experimental results revealed that (1) Particle motion under VLF condition was similar to that under dc condition, while specific in the transient behavior at the polarity reversal. (2) Breakdown was induced by particles located in the vicinity of high voltage conductor at the instance of crossing the gap or in the firefly conditions. (3) Breakdown voltage in positive half cycle was higher than that in negative half cycle at the lower gas pressure, while lower at the higher gas pressure, which was attributed to the particle behavior and the breakdown mechanism of SF₆ gas.
Consequently, metallic particles in GIS under VLF voltage application exhibited the specific behavior associated with the slow change of instantaneous voltage and polarity, and resulted in the complex pressure dependence of breakdown characteristics.

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There are two interfaces, rubber/epoxy and rubber/XLPE, in PJ these interfaces are pressurized by spring. In long term using of PJ, cable insulation of rubber/XLPE interface is shrink with the pressure. Then, at first, we investigate what factors are domestic for the shrink. In our results, domestic factors are cyclic heating, high temperature, high pressure, and thin insulation thickness. On the other hand, we find out that the property of shrink is much depend on the passage of time, and the amount of cable shrink(ΔD) is formulated with the passage of time(t), ΔD=A•t^m_??_ then A is coefficient. With this formulation, we can estimate the amount of cable shrink after 30 years. Secondary, we give the estimated amount and assemble real PJ's. And we estimate the electrical property of the PJ and we can get good result. Finally, we are assured that the PJ has good long-term property.

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In this paper, we evaluate the reduction rate of the current capacity that is used to design the power transmission capacity of the electric power cable constructed in the air and the culvert. In the first, when the distance from the cable, which is adjacent is changed, the behavior in the heat influence receive from the adjacent one is calculated. In the calculation, the radiation and the natural convection generated from the rise of the cable surface temperature are considered. Next, an experiment is done to verify the calculation result with 66kV XLPE Toripurex-type electric power cables, which are constructed in the tent. When the current was made constant in the point where the conductor temperature entered the state of equilibrium at 90° or 105°, the conductor temperature, the surface temperature, and the temperature of the cable of surrounding air are measured with the automatic record meter and evaluated. Finally, it is shown that the reduction rate is nearly 1.00 by the calculation and the experiment.

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We investigated high-field conduction, dc and impulse breakdown strength, space charge distribution, and tree inception voltage for 3 kinds of new low-density polyethylene (LDPE) prepared using metallocene catalyst(mLna, niLao, mLIdao), linear LDPE prepared using Ziegler catalyst (LLao) and LDPE prepared by high-pressure process (LDna). The de and impulse breakdown strengths of LDPE's using metallocene catalyst were higher than those of LLao and LDna. The high-field currents of LDPE's using metallocene catalyst were lower than those of LLao and LDna. Homo space charge was accumulated near the cathod in mLna, The tree inception voltage of mLna was higher than that of LDna. From these results, it is concluded that LDPE using metallocene catalyst has superior electrical insulating properties to the conventional LDPE and that the former has a potential as insulator of power cable.

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This paper describes the development of ±500 kV DC XLPE cable. The purpose of this study is to improve the impulse breakdown strength of XLPE insulation with filler using highly-purified inorganic filler with uniform diameter. It is revealed that the impulse breakdown strength of the improved filler-added XLPE cables increased from the test results of model cables. In the next stage, the ±500 kV DC submarine cable involving factory joint was designed and manufactured using the XLPE insulation with the above improved filler. Both mechanical and electrical tests were then carried out to verify the performance of the DC XLPE cable, which showed that it has sufficient initial performance for practical use of 500kV submarine cable system

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The influence of one-sided anode (asymmetrical electrode configuration) on the performance of an experimental disk-MHD generator with small thermal input was examined experimentally and numerically. In MHD power generation experiments, the performance of a disk MHD generator with one-sided anode is confirmed to be comparable to that of a disk MHD generator with both-sided anode (symmetrical electrode configuration). From the results of r-z numerical simulations, the plasma properties in the disk MHD generator with one-sided anode are asymmetric in the z-direction near the downstream edge of anode. However, the r-z distributions of the fluid properties and performance in the disk MHD generator with one-sided anode are almost the same as those in a disk MHD generator with both-sided anode. These facts indicate that the asymmetrical electrode configuration hardly influences the performance of the disk MHD generator.

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Thermal degradation test of insulating papers was conducted in oil. Time to the degraded Average Degree of Polymerization and the dependence of amount of total Furfural generated from the paper on DP were cleared.

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This paper presents a detection method of poor contacting of low voltage switch in the normal current state under the legal scheduled inspection. This is an unique method using ultrasonic wave and a diode commutation circuit.

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