This paper presents a new approach to optimal voltage and reactive power control based on a geneticalgorithm. The process and the number of control are hardly considered in the voltage and reactive power control by the genetic algorithm. The proposed method switches one of control devices by the generation of the genetic algorithm and considers the number of control to the fitness. The proposed nethod can give the control process and improve the fitness with the practical number of control. Therefore, the technique to cancel the limited deviation as early as possible is implemented. Moreover, the technique to reduce the number of control to the fitness as much as possible is proposed. The effectiveness of the proposed method is demonstrated by practical 15-bus and 118-bus systems.

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This paper describes a new practical methodology for studies on required generating capacity in powergeneration planning. In the process of evaluating electricity supply reliability, actual data of various changingfactors, such as demand variation due to the daily ambient temperature changes, reduction in capacity due to the forced outage of generating units and load forecast errors, are statistically treated and represented as probability distribution. In addition, this methodology takes into consideration other factors like the maintenance schedule of generating units and emergency operating measures in case of capacity shortage. They are practically important but they have rarely been handled so far. Examples of study results using the proposed methodology in the power system of Tokyo Electric Power Company are also presented.

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Adjustable-speed pumped storage generating systems with large capacity have been newly installed in power systems with recent progress in technologies of power electronics as its setting. Many papers have been published in which the enhancement of power system stability by fast control ability of power and voltage of these new generating systems has been described. However, studies have not been reported until now about the dynamic stability of separated power system that consists of a load and an adjustable-speed pumped storage generating system.
New analytical models were developed in order to analyze and understand dynamic stability of a separated power system that consists of a load and an adjustable-speed pumped storage generating system. Results of studies on dynamic characteristics of the control systems, especially voltage control system, applied in the new generating system are shown with numerical examples.

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A flexible power resource planning is to construct an adequate power generation system in order to cope with future power demand. However, it is difficult to estimate “flexibility” of each power resource planning proposal considering various aspects (reliability, installation and operation cost, economy environmental impact, etc.) and uncertainties.
This paper aims at developing a method which can evaluate flexibility of power resource planning under the uncertain conditions. Namely results from scenario analysis for each planning proposal are plotted on the Euclidean space where the multiple evaluation criteria of power resource planning, i. e., construction cost, fuel cost, reliability, etc., are taken as each axis. The planning proposal is evaluated as flexible when the plot of each scenario analysis in this space is concentrated on the knee part of trade-off curve.

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A combined cycle plant model for power system dynamic simulation studies has been developed. The major results of the research are as follows:
(1) Scope of the model: The unit plant in the large-capacity power station, which consists of the generator, the gas turbine and the steam turbine, is modeled. The unit plant is assumed to be operated in normal high output power (at least 60% of rated power). In the model, behavior of the output power, exhaust gas temperature, the fuel flow rate, and the air flow rate of the gas turbine, as well as the output power of the steam turbine are represented.
(2) Accuracy of the model: The results obtained by applying the developed model to dynamic simulations of an actual plant reveal that the model is in reasonable agreement with the static and dynamic behavior of the plant.
(3) Basic behavior of the plant under powersystem disturbances: Using the developed model, the basic behavior of the plant dynamics under power system disturbances such as system frequency change is demonstrated.

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Doubly-fed (adjustable-speed) pumped storage generating systems of large capacity have been installed in power systems with recent progress of power electronics technologies as its setting. Many papers have been published in which the enhancement of power system stability by application of doubly-fed machines has been described.
We propose in this paper new rotary equipment for power system operations. That is doubly-fed rotary frequency converter, which consists of 2 machines that are directly connected each other with shaft, and they are a set of doubly-fed machine and synchronous machine or a couple of doubly-fed machines.
Analytical models were newly developed in order to analyze and understand the behavior of the proposed doubly-fedrotary frequency converter. Basic control scheme for the doubly-fed rotary frequency converters is proposed. Results of studies on dynamic characteristics of the control systems applied in the converters are shown. Moreover, merits and demerits were discussed in comparison with static DC converter with thyristor valves from the practical point of view.

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The location of lightning radiation sources observed by our narrow band interferometer and the lightning channel image by an all sky camera are compared with that of our broad band interferometer. The broad band interferometer system is described by Ushio and Kawasaki et al. [1997] and measures the two dimen-sional direction of the radiation sources from 25 to 250 MHz with sub-microsecond time resolution, using 500 MHz digitizer which has 8 Megabyte memory. These three observations show the excellent correspondence, and we can conclude the potential capability of the newly designed wide band interferometer. By analyzing simultaneously observed data by narrow band and wide band interferometers for of one flash, the advantages and disadvantages of the both type of interferometers are discussed. The analysis shows that the broad band system can also locate two radiation sources, which propagate simultaneously like branching, in time and space. And we conclude this is a new technology.

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As a transformer fault diagnostic method at impulse voltage test, directly comparing possible variance in impulse voltage wave form and current wave form under two different conditions, namely at reduced voltage and predetermined voltage has long been and, still is, commonly practiced.
With the recent improvement in digital measuring techniques, a new diagnosis method by comparing resonance frequencies is also expected. The new method is based on comparing resonance frequencies which are derived from frequency transfer function which in turn is calculated from voltage and current wave forms converted to frequency ranges. In the event that the specimen transformer has failed in the impulse voltage test, the impulse voltage wave form should show rapid voltage drop and the current wave form should show increase in direct current component. In the frequency range, on the other hand, resonant frequency of frequency transfer function should change.
In this paper, we have attempted to compare these two fault diagnosis methods, namely direct wave form comparison method and frequency transfer function method, based on the results of wave form simulation and simulated fault test using transformer model. As a result, it has been confirmed that both of the method can diagnose not only whether or not fault has occurred but also the magnitude of the fault.

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Two-dimensional (r-θ) numerical simulations to our disk MHD power generation experiments with Ar/Cs were carried out considering the transient lomzation process in the nozzle. The objectives of this study were to explain several kinds of electrical discharge structures observed in the experiment and to predict the disk MHD generator performance more precisely. The calculated contours of ionization degree were compared with high-speed photographs of the discharge taken in the experiment. The following four kinds of discharge structures were successfully simulated; (1) unsteady periodic luminous ring-type discharges caused by the partial ionization of argon when seed fraction of cesium was much lower than the optimum value, (2) a steady single luminous ring-type discharge caused by the partial ionization of argon when the seed fraction of cesium was lower than the optimum value, (3) an almost uniform discharge when the seed fraction was near the optimum value and (4) a spiral or nonuniform rotating unsteady discharge caused by ionization instabilities when the seed fraction was higher than the optimum value. It was also verified that plasma and fluid properties in the generator and the performances of it could be predicted well with this simulation code.

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Structures of plasma and fluid flow in a nonequilibrium disk MHD generator with inlet swirl have been examined with three dimensional numerical simulations, which will comprehend one and two dimensional simulations. It is confirmed that the inlet swirl reduces the Faraday current density and the steep increase in static pressure near the inlet region of generator channel, which arise in a radial flow generator without inlet swirl under the same operating conditions. The optimum load resistance giving the highest enthalpy extraction ratio shifts to the high value owing to inlet swirl, while structures of plasma and fluid flow are almost the same as those in a radial flow generator except for azumithal velocity. It is found for a low load resistance that nonuniform and unsteady plasma structure with low and high electron temperature regions appears in the r-θ plane, in contrast to streamer structure which appears without inlet swirl.

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Experimental investigation on short-circuit phenomenon through ejected hot gas between source-side terminals in molded case circuit breakers (MCCB's) was performed. The occurrence rate of short-circuit phenomenon proved to increase with the peak value of breaking current and with the order of breaking test. The conductance of the ejected hot gas was also found to rise with the peak value of the breaking current and with the order of the breaking test. These results indicate that the hot gas with high conductance causes the short-circuit phenomenon to happen. Then some effective means were taken in the MCCB to reduce the conductance of the hot gas. Decreasing in the conductance of the hot gas successfully prevented the short-circuit phenomenon from occurring.

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The Gas Insulated Switchgear (GIS) is intended to be both maintenance free and inspection free, inhibiting the affects of the external environment by sealing the main circuit equipment with SF₆ gas in a tank. Once an abnormality occurs inside it, however, it may develop into a major malfunction. Therefore, it is necessary to develop the fault locating technique.
In this paper, we present the fluorescent plastic optical fiber system for a way to detect a fault location in the GIS, and we examined the system reliability using a full scale GIS.
The sensitivity of the fluorescent plastic optical fiber is considered to be influenced by structure of the GIS, decomposed material of SF6 gas deposited on the fiber surface, and other environmental conditions. We conducted reliability tests against these factors. We conclude that under the normal field condition, we can practically locate 100A fault current, if faults occur somewhere in the units of GIS, even inside the current breaker units.

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A new prediction method called an event matching prediction (EMP) for a purpose of predicting pollution deposits of insulators located in coastal substations had been proposed by the authors in a previous study. Performance of the EMP was strongly related to selection of database of events and a closeness function. This paper aims at improving a performance of the EMP by introducing conditional probability. By use of the prediction of the insulator pollution based on the conditional EMP, reliable decision making for the washing timing of the polluted insulators was developed and evaluated successfully based on actual data in Karatsu substation, Japan.

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When the space charge distribution in coaxial cable insulator is measured using pulsed electric-acoustic (PEA) method, it is necessary to consider the cable geometry such as inner and outer radii. In PEA method, amplitude of acoustic waves generated by applied pulse voltage depends on the pulse electric field distribution which is not constant in the cable insulator. Furtheremore, since the generated acoustic waves radiate from the generated positions, the amplitude of the signal acoustic wave depends on the propagation distance to the detecting piezo sensor. Therefore, the effect of electric field distribution in cable insulator and distance of propagation must be considerd. However, the signal obtained from the cable insulator measurement is usually processed as same as the signal of plate sample. In this paper, difference between the space charge distribution obtained with and without considering a cylindrical function are simulated in the various geometry of cable insulator.

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Power apparatus in overhead distribution lines is set up on a concrete pole, and the impedance of a grounding lead wire can not be ignored. Therefore, it is important to know the surge impedances of the concrete pole and the grounding lead wire in the distribution lines for accurate lightning surge analyses. A scale model technique is very convenient to carry out an experimental study. Thus, the surge impedances are measured by an experiment on a reduced scale-model. Measured results lead to the following conclusions.
(1) The surge impedance of the concrete pole alone and the grounding lead wire alone are 244 and 477 ohms, respectively.
(2) The surge characteristic of the concrete pole is equivalent to that of a metallic pipe.
(3) The surge impedance of the grounding lead wire to be along the concrete pole is significantly reduced as the location of the grounding lead wire becomes closer to the concrete pole.
Moreover, this paper describes the reduction effect of a distribution surge arrester voltage by using the concrete pole as a grounding lead wire.

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