Nowadays, the electric power industry is in transition to a deregulated market. Under this circumstance, the power system control such as frequency control will be served as an ancillary service, as well as the configuration of power system will be changed by the proliferation of the Independent Power Producers (IPPs). In this paper a control method using a solid-state phase shifter to provide an active control facility of system frequency, is proposed. In the Load Frequency Control (LFC), the interconnections among some areas are the inputs of disturbances, therefore, it is important to suppress the disturbances by the coordination of governor systems so far. On the contrary, the power flow control by the phase shifter located between two areas makes it possible to stabilize the system frequency positively through the interconnection, which is also expected as a facility to provide a new ancillary service for the power systems. This paper proposes a method to design the frequency stabilization by the phase shifter based on an elementary two area system and an elementary three area loop system, which is extended to the design of general multi-area system by applying a system reduction method. A frequency stabilization controller of phase shifter is designed based on stabilization of an inter-area oscillation mode between interconnected areas. Numerical results demonstrate the significant effect of the proposed control on the frequency stabilization of interconnected power systems.

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Photovoltaic power generation systems are expected to be widely used because of their cleanness in the environment. One of their disadvantages is the unexpected fluctuation of generated output caused by the weather conditions. This paper proposes to forecast the power fluctuation of the photovoltaic power generation by analyzing clouds in the sky through the image processing technique. First, the velocity of the cloud in the image is calculated by the comparison between two sequential images of the cloud, and then, the weather conditions are forecasted by examining the color values of the image along the direction of the cloud movement. Experimental results, the weather forecast 60, 90 and 120 seconds ahead and the estimation of the time required for the solar radiation to fluctuate on a large scale, show the possibility of the forecast of the power fluctuation of the photovoltaic power generation.

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A practical method for constructing a microprocessor-based wide-area protection system which operates in the current differential scheme is proposed for achieving better selectivity, smaller outage areas and faster operation times than conventional distance backup protection as well as for obtaining coordinated and/or integrated operations of primary and backup protections. The system consists of central equipment (CE), terminal equipment (TE) installed at every circuit breaker, time transfer system such as OPS for providing precise timing signals for the simultaneous sampling of currents throughout the power system, and broadband backbone networks and standardized LAN interfaces with measures for logically dedicated communications channels implemented for signal transmissions between CE and TE. A simplified and effective scheme for expanding protection zones after its primary protection operation by manipulating the current data from CTs in the faulty zone is employed for the backup protection. An experimental system employ ing a 155-Mbps ATM (Asynchronous Transfer Mode)-backbone network and Ethernet interfaces is examined using a power system simulator configuring a busbar and a power line, and operates satisfactorily with respect to both primary and backup protection functions in various states of power system faults and telecommunication failures.

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We proposed a circuit model of oil-immersed transformer for surge analyses in high frequency regions and evaluated its effectiveness by referring to measurement, results of a model winding. We also carried out lightning surge analyses in a 500kV substation with the new transformer model and investigated effects of transformer modeling on the lightning surge voltage at the transformer terminal. In the case of applying the new model for transformer modeling, the peak value of the surge voltage decreases but the rate of the voltage rise increases compared with the conventional transformer modeling by a concentrated capacitance element. This difference can be explained considering the charging process of capacitors in the transformer model.

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Fluid flow and performance of a nonequilibrium disk MHD generator with subsonic flow are examined with time-dependent r-z two dimensional numerical simulations. It is found that the development of boundary layer is enhanced with the increase in the load resistance, which is also observed in a supersonic generator. The development of boundary layer affects not only the generator performance but also thermal input to the generator in contrast with a supersonic generator. These facts leads to considerable departure from the performance predicted by quasi-one dimensional simulation, and suggests that the two-dimensional design of generator channel with the consideration of the development of boundary layler should be required to realize a high parformance subsonic generator.

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A feasibility of improvement in performance of a disk CCMHD generator with electromagnetic diffuser is investigated with two-dimensional numerical simulation where the development of boundary layer can be clarified. Mach number at the exit of electromagnetic diffuser can be controlled by the load resistance connected between the electrodes equipped in the electromagnetic diffuser. By optimizing the load resistance, the total enthalpy extraction ratio and adiabatic efficiency can be improved. This is ascribed to the fact that the additional power output can be obtained in the electromagnetic diffuser without a change in the total pressure at the exit.

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DC reactors in HVDC transmission line are used to smooth the current containing many harmonics. They are also expected to suppress the large fault current to protect converter electronic devices such as thyrister valves. The inductance of air-core type DC reactors with magnetic shields has to be linear up to the large current region to perform its role. But the inductance decreases as the current increases because of the magnetic saturation phenomena of magnetic shields. The inductance of DC reactors is defined as the incremental value of the magnetic flux to the current and could be measured by applying small a. c. current superimposed on large d. c. current. Such a measurement is usually very difficult on account of testing facilities. This paper shows the non-linear characteristic of the inductance of DC reactors through the numerical analysis by three and two dimensional Finite Element Methods.

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It is possible to operate the fuel cell for a long time by supplying the phosphoric acid to the cell under the phosphoric acid loss condition after detecting the phosphoric acid loss cell. To establish the method of detecting the phosphoric acid loss cell, short stack test was conducted using the practical size cell including the phosphoric acid loss cell. The cell voltage and temperature behavior of phosphoric acid loss cell were investigated comparing with normal cell behavior and analysis of cell voltage and temperature was conducted using the short stack and small size cell test data. The method of detecting the phosphoric acid loss cell in the practical fuel cell plant are proposed based on the test and analysis results.

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A mesh grounding electrode is, in many cases, enclosed with iron fence. When fault current flows into the grounding electrode, a person touching the fence is subjected to the touch voltage. If the touch voltage level is hazardous, an additional construction work is needed for reduction of the touch voltage. For this purpose metallic rods may be struck into the earth at the fence corner and electrically connected to the fence.
In this paper, simulation of the touch voltages for a square mesh grounding electrode is executed by the current sources superposition method and the method of images. First, for homogeneous earth, the touch voltages to the iron fence from the outside are estimated and it is found that the maximum touch voltage appears at each fence corner. Then the touch voltages to the fence, in addition of one or three longer rods than buried length of the fence foot at each fence coroner, are estimated and it is found that the maximum touch voltage is reduced to about half of the touch voltage without the rods.
Second, for two-layer earth structures, the touch voltages are estimated without and with one or three rods at each fence corner. If the upper layer resistivity ρ₁, is much smaller than the lower layer resistivity ρ₂, one or three rods of the same length as the upper layer width H are struck into the earth. If ρ₁, is much greater than ρ₂, one longer rod than H is struck into the earth. In this case, the rod has the optimum length for the touch voltage reduction, and it is noted that the lower layer part length of the optimum length is very short in some cases.

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The electric self-potential (SP) induced in the ground at lightning has been reported by several authors, however the data were recorded by a slow sampling interval. To better understand the details of SP induced at lightning, it is necessary to record at a higher frequency sampling.
In this study, we analyzed the high frequency change of SP induced at rocket triggered lightning and natural lightning. The extinct SP change correlating with the lightning flash was identified. The SP change appeared few to ten ms before the flash. The induced SP appeared before the first flash is composed of many changes with short period, which is to be caused by the stepped leader stroke. The induced SP lies in the characteristic direction, which proves the anisotropic SP formerly suggested at lightning with low frequency recorders. The FPT spectrum indicates that the characteristic SP change may be caused by an anisotropy in capacitive property in addition to the resistivity of the ground.
The SP observation is a means to study lightning from the ground. The study combined with the magnetization survey of the soil (Sakai et al., 1997) may be available such as to elucidate the propagation of lightning current. This study also indicates that the SP change induced at lighting is to be duly considered in the recent topic to use SP observation for the seismo-electromagnetic research.

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Recently, due to a rapid increase of demand for air-conditioning in summer, peak power demand is becoming acute increasingly. Therefore, load factor has a tendency to drop every year. The drop of load factor is leading to a drop in utilization factor of the power facilities and an increase in cost of installation.
In this paper, we proposed an energy storage system for peak-cut of power demand, to which is applied large capacity electric double-layer capacitors. Then, we studied the circuit arrangement and the control method of the proposed energy storage system, produced an 1kW mini model system, and tested the fundamental operation characteristics of this system. Finally, the application effects of this system to distribution system were evaluated by the tests with an artificial power system.

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Hydrogen production of petroleum technology was applied to reforming technology on PAFC. Pressure of the petroleum plants were not atmospheric but high. So petroleum technologies could not applied directly PAFC reforming condition. For this reason, we observed behavoir of catalyst which is most influenced on reforming ability. Generally, decline of catalytic ability was caused by three phenomenons: sulfur poisoning, carbon deposition and sintering. Sulfur poisoning was well known to decrease catalytic activity, but regeneration methods did not be reported in detail under PAFC reforming condition yet. And other phenomenons, carbon deposition and sintering, were prevented by best choise of catalyst on the market to be suitable for operating conditions. But to be compared these catalysts with the same condition did not be reported yet, too. For pressed comercialization of PAFC, we experimented with micro reactor to observe regeneration of sulufur poisoned catalysts and to compare of carbon deposition and sintering with two type Ni catalysts under PAFC conditions. And we could observed that best condition of regeneration and influence of catalytic support's compound on carbon deposition and sintering.

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The correlation between an arc interrupting capability and a spatial distribution of the airflow velocity was investigated in a flat-type air-blast quenching chamber. Five orifice-nozzles with different inlet widths were used to obtain various distributions of the flow velocities. For each of the nozzles, a number of arc interruption tests were performed to measure the failure rate of the arc interruption. Furthermore, the velocity distribution of the airflow for each of the nozzles was calculated in the absence of the arc. From this calculation and the interruption test results, we found out correlation between the velocity distribution of the airflow and the interrupting capability.

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Charge-voltage (q-v) curves of a transmission line have to be measured accurately in order to identify the influence of corona discharge on surge propagation, because the corona effects are important to determine the insulation level of transmission lines and substations. Conventional q-v curve measurement techniques use a charge measuring conductor such as corona cage placed nearby the specimen conductor for measuring the amount of charges q. Other conventional techniques integrate injected current using a capacitor or by a numerical method also for obtaining q. All those conventional techniques require that the specimen transmission line has to be short in length and open-ended so that the line impedance is seen as a capacitance, and thus the measurement of q-v curves of an existing transmission line has been impossible. In order to measure the q-v curves of existing transmission lines, a new technique has been developed and described in this paper. The method calculates the amount of charges from the applied voltage and injected current waveforms of the specimen conductor based on a traveling-wave theory. The technique has been validated using a test transmission line of CRIEPI, and the obtained q-v curves are discussed.

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Recently the transfer function method, which computes a frequency characteristic from input voltage and response waveforms, has become a subject of attention in insulation level designs and performence tests of transformers. Its computation principle is based on deconvolution operation between the two waveforms and many application softwares are being developed by using FFT algorithms. However, in this process they have some numerical difficulties which are experienced by most of users and developers. First this paper proposes a numerical recipe of a developed program for the method which almost eliminate such difficulties. Furthermore it is necessary to develop a checking method for their accuracies and reliabilities. In this paper analytical test data are generated for full and chopped wave tests accurately by simulating a transformer circuit from a fractional polynorninal model based on its transfer function characteristic. Test data are estimated for signal-to-noise ratio by so-called coherence function. Finally experimental data are also analyzed for transfer and coherence functions and the results are investigated.

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