Various energy conservation practices and DSM programs are in effect in the Japanese electric utility industry at this time. These include tariff driven conservation, electric hot water storage and thermal storage air-conditioning. It is expected that these activities have the potential of significantly altering the load shape of these electric utilities, and thus improve their load factors. However, since many of these programs are very new, there are no long-term historical data to carry out statistical predictions. A methodology is presented which can be used to estimate the impact of energy conservation and demand side management (DSM) activities on the system load shape. The load shape impact can then be analyzed for capactiy savings. This methodology is based on Analytic Hierarchy Process (AHP) which relies on expert opinions and mathematical analyses. The AHP technique is discussed in this paper. Then a conceptual framework is provided showing how the available data at Tokyo Electric Power Company (TEPCO), for example, can be used to estimate the long term load shape impact. The load shape impact can then be studied to determine their influence on future capacity needs.

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This paper proposes arcing horn flashover models for a multi-phase flashover analysis and a lightning surge analysis by the ATP (EMTP). One is the leader development model which consists of nonlinear resistances. Another is the integration method which is not considered a predischarge current, but it is convenient to calculate. The calculated results by the proposed models agree well with experimental results. It is effective to simulate electrical power networks with various parameters (gap lengths, lightning currents, circuit models, and so on).

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Currently, IEC publications 60-3, 4 are being revised. In the revised draft of the International Standard, a new calibration method will be introduced. It was summarized as follows; The accuracy of most industrial measuring systems is maintained by means of comparison test against “Reference Measuring Systems”.
This paper describes an excellent reference divider for switching impulse voltage measurements. Switching impulse voltages are measured generally with capacitance voltage dividers. However, in this study, a shielded resistance divider with a very high resistance value (200kΩ) was developed as a prototype reference divider. The high voltage arm of the divider is a wire-wound resistor with very low temperature-resistance coefficient. In order to improve the response characteristics, a suitable shielding electrode was attached to the high voltage arm. The shielding electrode makes the potential distribution near the high voltage arm uniform and the capacitance of the high voltage arm to earth much decreases. Therefore, the response characteristics of the divider were improved drastically regardless of the very high resistance value. The measured response time of this divider was about 14 ns.
An excellent shielded high resistance reference divider with rated voltage of 500kV for switching impulse voltages has been developed.

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Optimal switching pattern planning is the main subject of distribution network reconfiguration to restore from blackout or to avoid blackout from maintenance and construction. This is a combinatorial optimization problem, and enumerative check of the every pattern is necessary to get the optimal solution.
Practically, successive heuristic search methods are adopted to get the quasi-optimal solution within a limited computation time. But a very long computing time is still required, when the problem size gets slightly larger. Step by step nature of the methods brings many iterations, though it assures satisfaction of the constraints. Reduction of the iterations is regarded to be necessary for the enhancement of processing speed.
In this paper, ‘supply adequacy’, is introduced as a new criteria index to guess the solution, which is obtained by fuzzy inference for each possible pair of source and load zone. The reconfiguration pattern is obtained at once or in a few processing steps, by assigning the each zone the source with the highest adequacy. Numerical examples show that the proposed method can get the solution faster than the ordinary method, more remarkably with the increase of problem size.

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The Telegraphers' Equations for multiconductor lines are solved taking account of the vertical and the horizontal electric fields due to a nearby return stroke. Based on the Telegraphers' Equations, the correct equivalent circuits for calculation of overvoltages induced by the nearby return stroke are presented. The vertical and horizontal electric fields are calculated by decomposing the return stroke channel into numerous dipoles.
By means of this method, lightning-induced voltage waveforms on multiconductor power distribution lines over lossy ground are calculated with respect to the conductivity of ground. As a result, these calculated waveshapes are found to be in reasonably good agreement with the experiments over both perfectly and imperfectly conducting ground. It is concluded that the ground conductivity plays an important role on the lightning-induced voltages over poorly conductive ground.

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When electricity supply is interrupted due to a fault, it is of primary importance to restore the power system promptly according to an adequately planned restoration procedure. Recently, power system restoration problems have received much attention in the literatures.
This paper proposes an efficient restoration procedure by making use of the linear programming. in which a restoration problem is formulated as a minimum cost flow problem and solved by the LP algorithm. Assumptions postulated in this approach are: (1) the priorities in restorative operations have been mapped on to the costs of branches, (2) available power sources are allocated to source nodes, and pre-falut loads to sink nodes, and (3) the optimal restorative plan is decided from a solution of the optimal flow.
The proposed approach has been applied to the practical power system restoration problem, resulting appropriate solutions.

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In this paper, in order to determine the optimal radial power system structure rapidly we propose a constrained noise approach with the Hopfield model, which can avoid local minima. When a radial power system has a number of connected feeders, the combinational number for possible system structures become too many. Determination of the optimal system composition from a great number of combinations is a combinational optimization problem, and it has ever been difficult to solve this type of problem quickly with the conventional digital computer techniques so far. However, because of the modelling of excellent parallel processing ability of neurons, it has become possible to carry out the optimization with the Hopfield neural network model. The constrained noise we propose has an ability of satisfying constraints. In addition, we compare the poposed method with a conventional branch-and-bound method which exists in a field of mathematical programming area. Simulations have been carried out for 10 and 21 substation systems successfully.

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In this paper, we propose a practical method of solving a reliability objective maintenance scheduling problem based on neurocomputing approach. The objective of this problem is to levelize reserve over planning periods. In the proposed method, the Dynamical Canonical Network for nonlinear programming, which developed by Kennedy and Chua, is modified to apply the neural network to 0-1 integer programming.
However, it is difficult to obtain good solutions using neurocomputing. Therefore, we observe the effectiveness of ‘excess-bias method’ called and apply it to neural network for 0-1 integer programming so that we get good solutions. Nevertheless, its algorithm needs considerable time, and so we don't think it is an efficient algorithm. An efficient algorithm is desirable to rapidly obtain good solutions because we put neurocomputing as fast-approximation method. Hence, we propose to improve the algorithm of the excess-bias method to rapidly find good solutions.
The proposed algorithm is examined on three types of model system, small scale, medium scale, and real scale. In consequence of the computation, the effectiveness of the neurocomputing has been verified. And, the proposed algorithm has been found to be in a middle situation between normal and excess-bias method for the accuracy and the speed of the computation.

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When ground-fault trouble occurs on a cable line, immediate fault location and restoration are required. Therefore, various new methods to locate the fault point instantaneously, have been investigated to take over the conventional methods such as Murray loop method and pulse radar method⁽¹⁾, which require a long time to locate the fault point. One of the possible fault location methods, is to sense the temperature rise following a ground fault, using a fiber optic distributed temperature sensor. Application of this method was found feasible, through sensing the temperature rise at a ground-fault test, using a thermocouple as a temperature sensor with test cables⁽⁴⁾.
A power/optical composite cable was experimentally prepared and after verifying its thermal mechanical performance, the temperature rise at an incidence of a fault was determined and anticipated performance was demonstrated in a ground-fault test. This article describes the outline of the test.

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Power systems are becoming larger and larger for meeting electric power demand. Then it is becoming more difficult and more complex to design the stable systems where fault currents have to be less than breaking capacity of circuit breakers. For handling the increasing fault current due to expansion of power networks, superconducting fault current limiters, which are now being developed, are expected as one of the effective apparatuses to solve the above problem.
This paper describes a method of fault analyses of power systems with superconducting Fault Current Limiters. The method by use of symmetrical co-ordinates can analyse the asymmetrical fault condition where the line impedances are unbalanced when a fault occurs and Fault Current Limiters are operated.

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Control and protection equipment in power systems needs higher sensitivity and operational reliability to meet doday's changing power system requirements. The voltage measuring deviation requirement for advanced voltage and var control equipment is less than 0.1% 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 these requirements are satisfied using fast sampling and very fast 32-bit floating point operations by a DSP (Digital Signal Processor).
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.

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In the case of arc burning in narrow channel made from organic materials, the inner surface of a channel is heated, melted, liquefied, evaporated and consumed by arc. This phenomenon is ablation. Some of the high voltage switching devices use the decomposed gas by ablation in order to arc extinction or current interruption.
The before paper reported the relations dielectric recovery characteristic after current zero made measurement on many different dimensions of kraft tubes, various values of arc ignition current and arc energy. Then in the last paper, the relation between decomposed gas generating from inner surface of kraft tube and the pressure in the exhausting pipe channel was investigated. The experimental apparatus was consisted of the test set with a kraft tube, an enclosed chamber which was cylindrical and closed at one end and an exhausting pipe channel to connected at the other end of the test set eject decomposed gas. The paper reported the relation between pressure waveform in the enclosed chamber and in the exhausting pipe channel caused by arc ignition current and arc energy.
The aim of this investigaion is to clarify the electrical characteristic of the arc, the structure of arc column and surrounding gas flow, the gas evaporation mechanism of tube inner surface in the case of ablation controled arc. This paper shows pressure characteristics in the enclosed chamber in relation to arc ignition current, arc energy on the various different dimensions of kraft tubes and shows that the pressure waveform in enclosed chamber is well explained by models including pressure distribution, gas evaporation, gas flow in the tube during arc period and gas flow after current zero.

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Two-dimensional time-dependent MHD equations representing the flow in a closed cycle MHD (CCMHD) disk generator have been solved numerically by finite difference method or finite element method in the r-z plane of the cylindrical polar coordinate system. Boundary layer phenomena in the Disk F 3 a channel of FUJI-1 facility are investigated. The current and velocity distributions in the boundary layer can be obtained, and the results suggest the boundary layer separation and eddy current occurs in the MHD channel. The dependence of these boundary layer phenomena on load resistance is investigated. Finally, the results are compared with those of quasi-one dimensional analyses and experiments.

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The objective of the present paper is to analyze a supersonic Faraday channel which is suffered from short faults of many loads, and to reveal shock-boundary layer interaction caused by the short faults. The Galerkin finite element method and the TVD method are combined to calculate coupled Maxwell and Navier-Stokes equations. The following results are obtained: (1) The short faults induce a standing shock-wave far upstream from the region with the short faults. (2) There is no boundary layer separation in the analyzed channel. Asymmetry of flow is induced by the MHD interaction.

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