Power transfer between systems is getting an important mean due to uneven distribution of generating plants. This paper investigates relation between transfer capacity of a longitudinal power system and voltage control of static var compensators. The transfer capacity is basically limited by thermal capacity of transmis-sion lines. However, in practical systems, it is much restricted by stabilities, and power transfer level is considerably lower than the thermal capacity. In this paper, we consider a basic case where SVCs are set to all buses except generator terminals. In this case, it is possible to transfer power up to a reciprocal of transmission reactance value. Two modifications are applied next to the basic case. One is removal of SVCs at high voltage sides of generator transformers. In this case, generator damping torques deteriorate, and a local oscillation mode gets unstable. The other is removal of SVCs at intermediate buses on the trunk system. In this case, shapes of oscillation modes change much, and a global mode gets unstable. The voltage control of SVCs maintains generator damping torques, and prevents deformation of mode shapes. By investigating with different system sizes and transmission circuits, we show that the system transfer capacity is determined by those of individual transmission lines.

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In this paper, a mathematical simulation of the temperature distribution of a tubular solid oxide electrolysis cell (SOEC) is presented. In the method, the effects of joule heating, heat-transfer, radiation and heat convection are taken into consideration. As examples, the temperature distributions in the SOEC with an internal high temperature heat-exchanger and with an external high temperature heat-exchanger are calculated. As a result, the temperature distribution with an external high temperature heat-exchanger is smoother, but the current density is kept lower because of the limit of a working temperature. It is also estimated that a lower electrolysis rate contributes to decrease the maximum temperature and to smooth the temperature distribution.

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This paper describes an optimal load-shedding method which can be applied to local buses to suppress voltage deviations based on local information obtained at each bus. When a generation outage occurs, adequate amounts of loads must be shed within a few seconds to keep the balance between supply and demand. This method is able to decide the optimal amounts of loads to be shed after the accident quickly.
The proposed method is based on the fact that the location of the accident can be estimated from only power flow deviations at local buses which are measured after the generation outage. Because the amounts of loads to be shed have constraints, it is necessary to find the optimal factors which decide the amounts of load-shedding at each bus by quadratic programming. To solve this problem easily, in this paper, firstly the linearization of the study system is performed. Secondary, in order to relate power flows to voltage deviations at each bus, the voltage sensitivity factors using AC power flow calculation are evaluated.
The numerical simulations with 4-machine and 9-machine power system models show the effectiveness. The proposed method distributes adequate amounts of loads which are almost the same to those of a complete optimized one, and it indicates small voltage deviations compared with conventional method. Improved transient characteristics of voltage deviations are also shown in the paper.

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Two general approaches are feasible to reduce the computation time of network equation described as Y. V=I. The first method is based on the sparsity of admittance matrix and injection current vector. This method is widely spread in power system analysis. Recently, sparse vector method is one of the most remarkable methods. The other hand, second one is based on reduced matrix method. But the bottlenecks of this method are the fact that reducing the dimension of admittance matrix. it becomes dense. Consequently due to a number of generations of fill-in elements, operations of the reduced matrix are rather increasing.
This paper presents a new technique of the reduced admittance matrix method minimizing the number of operations. The proposed algorithm was tested using three model systems. The result shows that the proposed method performs much better than sparse vector methods using MD-ML.

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We have already reported about the case-based fault restoration support system in erectrical power systems. Case-based reasoning systems can improve the performance of problem solving by storing all new cases into the case-base. However, the performance of retrieval declines because of the expansion of the case-base. Generalizing cases and merging similar cases prevent from declining the retrieval performance. Besides, it is easy for users to understand the applicable scope of the cases. Cases also need to be specialized to adapt their applicable scope to the environment. This means that cases which were useful for solving problems in the past often become unsuitable since environmental conditions would change as time passes. For example, after new substations or electric power facilities have been built, some cases may become unable to be applied to current failures. This paper describes refinement methods of case-base by generalizing and specializing cases. The experimental results through computer simulations demonstrated that both the number of cases and the time for problem solving decreased to around 5%, and the percentage of getting optimum solutions using a case with the highest priority increased, compared to a case where all new cases are added to the case base.

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For the multi-media era, the authors planned to use optical fiber cables as the transmission media for integrated automatic distribution system. This system provides a variety advanced customer service functions and power distribution reliability such as remote metering load control and information service including power consumption notification. The authors studied the optical fiber multi-drop network whose transmission path comprised no active device, using only optical fibers and optical couplers. The development of these passive optical networks must be developed useful components, maintenance methods and operation procedure. The authors developed ABF(Air Blown Fiber) composite power cables optical branch boxes and studied new optical network control procedure. Also the authors studied maintenance methods for optical multi-drop network, such as localization methodsof obstacle point and chargeover switch for transmission path.

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In this paper, a method of reactive power compensation to prevent voltage instability is proposed. The proposed method of reactive power compensation maximizes the static power transfer capability under given short circuit current constraints. The concept of voltage-ideal power system (ideally voltage regulated system) is first introduced in which all node voltages are kept constant by powerful voltage regulators such as SVCs and synchronous condensers. This system is absolutely free from voltage instability, but its short circuit capacity becomes very large and a large amount of reactive power has to be supplied in order to keep all node voltages constant.
To meet the practically levels of the reactive power requirement and short circuit current capacity, the quasi voltage-ideal regulated system is next discussed. This system is obtained by carefully choosing a limited number of nodes to be kept voltage constant in order to maximize the active power transmission capacity with a reasonable reactive power requirement without exceeding specified short circuit capacity level.

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The distribution power line carrier system has been used for an automatic distribution control, in order to advance the highly reliable operation and labor saving on electric power supply in suburban districts. The most serious problem is that load current originated by fluctuation of voltage at the upper level of the power line system degrades the error rate performance in the answer-back-current signal receiver.
This paper proposes a method to get the clear answer-back-current signal by eliminating the fluctuating load current from the received current signal with ADF (Adaptive Digital Filter). First, we evaluated the algorithm in the proposed method by many simulations by using real data. Next, in the field experiments, we could confirm that the successive ratio of transmission was more improved by employing the proposed method.

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The present paper treats stability of a diagonal type MHD generator of commercial scale by examining two types of growth rate of disturbances along the MHD channel. A sensitivity analysis evaluates the spatial growth rate of disturbances in the channel flow, while a linear stability analysis examines the time growth of disturbances through the load current. The MHD generator analyzed here is-a coal-fired diagonal type MHD generator with thermal input of 1300MW. The sensitivity analysis shows that the MHD channel operated with constant current loads is so sensitive that it is apt to be unstable, while the growth rate of low frequency disturbances is not very high when the channel is operated with constant voltage loads. The linear stability analysis shows that subdivision of load sections is effective for suppressing the instability led by the growth of load current disturbances. The sensitivity analysis and time-dependent analyses also show that the diagonal connection with inductors can suppress the growth of high frequency disturbances.

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We propose a new technique that uses magnetic chromatography for continuous separation of ultrafine particles (i. e. <1, 000Å diameter) from mixed colloids. The separation is done using field flow fractionation, and the separation results from differences in the magnetic susceptibility and volume of the ultrafine particles. Our theoretical analysis shows that high-gradient magnetic fields generate very steep distributions of the concentration of a Nd fine particles that have a susceptibility 3.5×10^-3 and a diameter of about 100 to 150Å. Our magnetic chromatography can be done by applying flow fractionation to the concentration distribution in a channel from 5 to 50μm thick and using embedded ferromagnetic wires from 2 to 20μm in diameter. A simplified numerical simulation of our magnetic chromatography technique suggests the potential of separating very weak paramagnetic materials (e. g., a nuclear fuel element and Nd) which we have not been able to deal with through the conventional high-gradient magnetic separation techniques.

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Electron temperatures of non-equilibrium cesium seeded argon plasmas in a disk MHD generator installed in a blow-down facility are measured spectroscopically, and the generator performance is discussed in relation to the electron temperature. The temperature is decreased from_??_9000K to_??_3000K when the seed fraction is increased from l×10^-4 to 3×10^-4. For the seed fraction of about 2×10^-4 giving the maximum power output, the temperature is found to be 4000_??_5000K and the temperature fluctuation becomes minimal. For the seed fraction around 2×10^-4, the electrical conductivity evaluated from the temperature is almost independent of the temperature. These facts suggest that the plasma is almost under the regime of full seed ionization. Argon and cesium partially ionized plasmas are dominant under the seed fraction below 1.3×10^-4 and over 2.3×10^-4, respectively, which reduce the generator performance.

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When a stand-alone photovoltaic/wind generating system is equipped in an electric power system, it is favorable that an auxiliary diesel generator is so controlled that a storage battery is maintained as long as possible and solar/wind energies are acquired as large as possible. In this paper, an adaptive fuzzy control method is proposed in which the control rule is optimized with time in accordance with the state of the battery.
An estimation equation which is a function of the state of charge of the battery and its changing rate is adopted as an adapting algorithm. The algorithm is also accompanied by appropriate fuzzy variables and parameters. A smoothing procedure is applied to get final control rules.
The system is operated by a simulation for one year. The results show that the adaptive fuzzy control more suppresses the time variation of the state of charge of the battery and takes more widely fluctuation suppression region in relation to the proportional gain and the battery capacity than the constant fuzzy control.

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Leakage current of distribution line insulators under various environments were examined in labo-ratory. A neural network simulation system was constructed for the electrical insulation diagnosis of distribution line insulators referring to waveforms of the leakage current. It is found that the sys-tem constructed can distinguish cracked insulators from sound ones.

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Recently, the FACTS (2)(3)(4) is actively researched and developed. A Solid State Phase Shifter is one of the FACTS equipments, and has become of major interest to control power flow with its phase-shift finction. (10)(11)(12)
This paper describes voltage compensations by a Variable Reactor (VR) using a Solid State Phase Shifter. The VR is connected in series with a power system, and control the line voltage by a compensation of the line impedance. In this paper, characteristics of voltage compensations with the series compensators are compared with those of the parallel compensators such as Static Var Compensators in a power system. Then, a power circuit configuration and a control system of the VR are presented in practically. We have examined performances of the VR through digital simulations and experiments using mini-model and obtained satisfied characteristics. Voltage fluctuation caused by reactive loads was completely compensated, and voltage unbalance ratio was improved from 7.4% to 1.7%. These results are presented.

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The lightning-induced voltage has been an important factor for the insulation design of power distribution lines. Recently, the effect of the ground conductivity on the induced voltage has drawn attention.
In this paper, the distribution of the lightning-induced voltage on an overhead wire, associated with a vertical return-stroke channel, is studied based on numerical calculation. The induced voltage is calculated by the method where the tangential component of the electric field to the wire is looked upon as inducing sources. It turns out that the distribution of the induced voltage along the overhead wire is greatly influenced by the ground conductivity and/or the velocity of the return-stroke current.
The validity of the calculated result is verified by comparing the experimental result obtained outdoors by using a 1/20 scale model.

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