Nowadays, conventional energy systems face various kinds of problem, e. g. environmental issues, uncertainties, resource restrictions, etc. The purpose of this study is to develop an energy/economy model to evaluate the security of energy systems in Japan from the macro-social points of view. The term “Environmental Security” conceives the new idea to expand the “Environmental Protection” for positive response to the environmental issues. The effect of cogeneration systems is also taken into account.
This model is a macro-econometric model which involves five primary energy sources, seven secondary energy categories and three final demand sectors. Various scenarios in the future are studied by the cross impact method (X-I method) to evaluate the security through simulations.
In this frameworks, the model calculates the total volume of carbon dioxide emission, including the case of charging carbon emission tax, demand for each primary energy sources, the loss of consumers' surplus, etc. in the case of “oil crisis” (sudden and serious oil supply reduction) and of change in energy supply structure. The contirubion of cogeneration systems are also studied.
The results of the study show the followings: (1) carbon emission tax will stabilize the carbon emission level of 1990, if initial value is set at 4, 000 ¥/C-t in 1993 and then is increased by 1, 000¥/C-t every year, (2) the loss of GDP by the carbon emission tax is calculated ¥450, 000_??_500, 000 per ton of carbon reduced, (3) the loss of consumer's surplus in the case of “oil crisis” is strongly influenced by supply price elasticity and yet it is recovered in a short period of time in the Japanese energy systems.

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This paper presents the application of multi-DSP system, consisting of a personal computer with four DSPs (digital signal processor) for real time reconstruction of lightning discharge channel. Acoustic-based reconstruction of lightning discharge channel has been performed by using three-microphone system while performing the triggered lightning experiment by rocket. Using the DSP system, speedy numerical analysis of the channel including display on CRT was realized within fifteen seconds by parallel processing of the four DSPs. Algorithm of the parallel processing, automatical elimination scheme of erroneous estimated points and the estimation of processing time were discussed.

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An approach to one-day-through seven-day-ahead electrical load forecasting is proposed for the purpose of weekly power station operation. The load is affected by various factors. However, it is impossible to consider all the factors in load forecasting; the relationship between the load and some factors are not clear; and sometimes their own forecasts are required. In our case, information about day of the week and the temperatures obtainable from weekly weather forecasts can be the only reliable input variables to the forecasting model. The other factors which are not included in the model occasionally make the load significantly different from the model output. The data samples measured in such situation reduce the reliability of the model and thus the forecasts. In order to obtain reliable forecasts we need to eliminate these samples out of the estimation procedure of the model, and investigate the reason of such large errors to improve the forecasts. In this paper, an automatic sample selection method is proposed: each measured sample is judged, based on the estimation error, whether it is appropriate for the model estimation or not. With the method we can effectively eliminate harmful samples without loosing useful information contained in the data. The procedure for finding out which factors cause the large errors and how they do is also discussed as well as the method for correcting the forecasts. Some forecasting examples show that we can forecast the load with accuracy of 4 percent average error. Some useful information is also derived from the results which explains large errors and will serve to elaborate the forecasts.

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Transmission line arresters with a series air gap have been installed to protect an overhead power transmission line from a back flashover caused by lightning. It has been required to develop an accurate model of the transmission line arrester together with an arcing horn which can deal with multiple flashovers for an analysis of a transient behavior of the arrester.
The paper proposes a new flashover model of the arcing horn represented by a nonlinear inductance, a nonlinear resistance and two switches. The transmission line arrester with a series air gap is modeled by a composite circuit of the above arcing horn model and a nonlinear resistance. The calculated results of the flashover voltage and predischarge current waveforms by the proposed model are compared with actual measurements, and the accuracy of the model has confirmed to be satisfactory. The model is expected to be useful to analyze multiple flashovers of an arcing horn and an operational characteristic of a transmission line arrester.

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Recently, much attention has been paid to load leveling technology. In Japan, time of use pricing (TOUP) and utilization of non-commercial power plants (NCPs) are widely accepted. This paper presents a linear programming method for the determination of the scale and contract demand of a NCP under changeable fuel prices and TOUP. The method is applied to an existing NCP which burns municipal refuse. It is found that the optimal scale of NCP and reduction of mean operation cost are strongly affected by taking uncertainty in consideration between fuel and electricity energy charge.

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The magnetic field changes due to cloud-to-ground strokes have been measured by loop antennas, which have been installed in the north-south direction and the east-west direction, respectively, in winter and summer seasons during 1982 through 1989. In consequence of the measurements, it is found that there is difference between the magnetic field change due to summer lightning and that due to winter lightning, that is, the magnetic field change measured by the N-S loop antenna is the same as the magnetic field change measured by the E-W loop antenna in summer lightning, but not the same in winter lightning (Winter ligtning in this paper is the triggered lightning initiated at the top of a steel tower of a transmission line.). It is considered that the difference between the magnetic field change measured by the N-S loop antenna and that by the E-W loop antenna in winter lightning is caused by the anomalous shape of the lightning channel, such as the large tortuosity of the channel close to the ground. The effects of the tortuosity of the channel on the magnetic field change is shown by the numerical analysis of magnetic field change due to the lightning stroke current, which propagates along the tortuous channel. When the lightning stroke current is estimated from the magnetic field change, it should be noted that the shape of the channel has an important effect on the magnetic field change.

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The paper presents an application of fuzzy control to enhance power system stability. The proposed control consists of the controller for large disturbance (FU 1), the fuzzy controller for small disturbance (FU 2) and the fuzzy judgement mechanism (FU 3).
FU 1 is determined based on the fuzzy controller _??_FU 1 (F)_??_ or the analog type power system stabilizer _??_FU 1 (P)_??_. The output signal of FU 1 (F) is determined according to the control rules and its input signals, i.e. speed deviation and acceleration at every sampling time of the machine. FU 2 consists of two controllers namely FU 2-ω and FU 2-P. FU 2-ω has the same mechanism as FU 1, while the output signal of FU 2-P is determined according to the rules together with the change of error of electrical power and terminal voltage. To obtain the optimal desired control signal, both during the large and the small disturbances, the operations of FU 1 and FU 2 are judged by FU 3, where the magnitude of speed deviation is chosen as its input signal. The determined control signal is fed to AVR of the machine.
The implementation of the proposed control is simple due to small amount of calculations and required data. The effectiveness of the proposed control is demonstrated by one machine infinite bus system model and very good system performance is obtained throughout all the simulations.

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The economic load dispatching (ELD) among thermal units can be formulated as one of the constrained optimization problems in power system operation. Since an optimization is required under severe constraints, all constraints cannot be taken into account. Therefore, at present stage, an automation is performed considering several constraints and, for the time interval where some constraints are not satisfied, a manual operation is performed for ELD based on the empirical knowledge of operators.
This paper presents an application of artificial neural network to ELD. The method uses one of the probabilistic neuron model, called Gaussian Machine and several constraints are handled by heuristic methods. The method can solve a local minimum problem, initial condition problem of neurons, and parameter tuning problem.
In this paper, parallel processors are used for inplementation of the system. The processors are high performance microprocessors that support parallel processing through on-chip hardware. The number of processors is examined for detecting appropriate parallel computation

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Load flow calculation on electric power systems is one of the most fundamental analysis in system operation and planning. There are many purposes to calculate load flow solutions, and the contingency evaluation is representative one.
In contingency evaluation, it is needed to repeat load flow calculation for tremendous patterns depending on branch or generation outages, then computing efforts are generally very heavy. So, various techniques have been proposed to reduce computing time especially by adopting equivalencing the external network. On the other hand, network equivalents techniques also become important nowadays from the viewpoint of necessity of decentralized monitor and control on bulk power systems.
This report describes newly developed method of load flow equivalents based on Ward equivalent for both direct (DC) solution and precise (AC) solution. Numerical results are also shown to clarify the accuracies and practicality of proposed method through the comparison to representative REI approach.

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Time of Use Pricing of Electricity (TOUP) has improved load factors of power systems in various countries. Theories of TOUP that maximize social welfare have been developed. In Japan, however, there are many non commercial power plants (NCP) that are made and used for the sake of owner's profit, not social welfare. How the optimal TOUP changes when effects of these NCPs exist in power systems is discussed here.
When formulating NCPs parameters, it is necessary to consider the difference of each NCP's cost. Not all NCPs cost equally, because the conditions of plants, such as heat demands, are unique. We first analized how much cost of NCPs differ using the data of prices and NCP ratio in Japanese 9 utilities. We analized next how customers with NCPs make their plants and use them. It is found that NCPs generate the same amount of power throughout the entire period when the difference of peak and offpeak prices are small, and not the same when it is large. Finally we discussed how utilities should set their prices to maximize the social welfare, considering NCPs and their revenue neutral constraints. If there is revenue neutral condition, the difference of prices must be larger when considering NCPs, than without considering NCPs.

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Experimental studies and theoretical considerations are presented on load following characteristics of phosphoric acid fuel cells.
During the transient period in which load increases and required fuel is supplied to cells after a few seconds delay, pressure change, cell voltage, load current and current distribution of the cells are measured using potential lead equipped on large scale cells. As the delay time of the fuel supply increases, generating capability of the cells decreases simultaneously with pressure drop saturation of the stack. These phenomena can be explained by accumulation of inert gas in the cells, which obstructs hydrogen supply to them. Higher hydrogen concentration in the fuel and lower fuel utilization previous to load change are effective measures to allow generation with a longer fuel supply delay, but load ratio previous to load change has no effect.

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