Today, a more effective power network is a key solution to the right-of-way problem in terms of transmission cost reduction. Various advanced techniques and planning methods are currently adopted in power utilities for this purpose. So far, the authors have presented two approaches for the rational coordination of transfer capability with transmission reliability. One is a method to numerically evaluate the critical transferable power increased by means of lightning countermeasures in a long transmission route. The other is an index of system margin to be uniformly allocated in a power system from the adequacy point of view.
This paper newly proposes a concept of system margin from the dynamic stability point of view and a definition of probabilistic load transfer capability, both aiming for quantitative evaluation of power system alternative plans. Several different fault patterns have been taken into account with their occurrence frequency and critical transferable power. These proposals are applicable to the practices of power utilities in conjunction with the conventional planning methods. This paper also illustrates numerical examples of the proposed methods applied to a 500kV trunk model power system.

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Periodical overhaul planning for boilers and turbines in electric power plants has been done on expert's experience to satisfy various constraints hard to be formalized, for instance, legal regulations, the overhaul interval restriction between units, the adjustment strategy in the case of including special events, the daily electric power requirement and so forth. Although its computer processing using the knowledge base approach has been tried, it does not lead to good results because of exaggerated hardware environment, low performance and no assurance of optimality.
Two step approach is proposed based on the categorization of constraints hard to be formalized into “strong constraints” and “weak constraints” in this paper. It replaces non linear integer programming problem corresponding to “strong constraints” to the iteration problem for the combination of integer programming and combinatorial analysis. Consequently it can lead to optimal solution on the fuzzy satisfaction measures within allowable time with PC.

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Advanced closing switch for three phase short circuit test was developed for very fast current limiter using power electronics devices. The conventional short circuit test method was used for verification of the current interrupting device with longer time duration to interrupt fault current after the separation of contacts. In the conventional short circuit test method, a deviation of the closing time between the each phase closing switch with a mechanical driving was regulated so that the breaking performance of the conventional switching device could be examined. However, in the new current limiter with very short fault current interruption time, the deviation time between each phase must be reduced less than the regulated time by the conventional test method. For this purpose, the advanced closing switch for three phase short circuit test method was developed. In the advanced test method, power electronics devises were used for the initiation of three phase short circuit fault. Results of the short circuit test showed that the advanced circuit had very small deviation time between the initiation of each phase fault. Also, the very fast current limiter with power electronics devices was proved to have an intended interrupting performance.

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Accuracy of an LLP system and a lightning frequency map is evaluated by using transmission line faults in Hokuriku area from November in 1993 to October in 1996. The accuracy and efficiency of the system were calculated by statistical methods. From the above results, the lightning frequency map with 10 minutes meshes was proved capable of replacing the Isokeraunic Level Map with 15 minutes meshes used now for lightning protection design. However, the correlation between the number of detected lightning flashes and transmission line faults in each mesh was found to be week. This result suggests that more detailed analysis taking account of the length of transmission lines in each mesh is necessary. The correlation is stronger in winter than in summer, despite the fact that there is difference in the lightning current distribution in each mesh in winter. This characteristic can be explained if upward flashes from transmission lines are dominant among lightning faults in winter.

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Authors propose a three-dimensional thermal analysis method applying a finite element method with two-order tetrahedral isoparametric elements to calculate the static temperature distribution of terminal section of sheathed heater and ascertain that the method enables the static temperature distribution of the terminal section of sheathed heater to be calculated with a high degree of accuracy according to the measurements made for a long cylindric sheathed heater.
In the thermal analysis methods, the analysis region is made as little as possible to save memory for calculating and to shorten calculating time, a method dividing the region into two-order tetrahedral isoparametric elements is proposed and one example of dividing the region into the elements by which the static temperature distribution is calculated precisely is shown.
Also the least analysis region to enable both temperature distributions of terminal and heating section of sheathed heater to be calculated precisely is given.
It has been obtained by using the thermal analysis method that the static temperature of terminal section varies in the direction of the length of heater and the temperature distribution of the cross-section of heater is almost equal.

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We propose magnetic chromatography (MC) as a new technique for ultra-fine particle separation. We developed an MC simulator, and modeled the transient behavior of 300Å and 500Å particles by taking into account the fluid flow field, magnetic field distribution, and particle diffusion. For the range of flow velocity between 1.0×10^-4 and 1.0×10^-3m/s, the separation efficiency increased with decreasing the flow velocity and increasing the ratio of particle magnetic susceptibility. To improve the separation efficiency, it is also very important to extend the channel length; longer channels (4.0m) completely separated two kinds of ultra-fine particles that can not be separated by shorter channels (i.e., 0.4m). For the smaller particles (300Å), increasing the applied magnetic field strength improves the separation efficiency. We also simulated other types of MC systems, and found that regardless of flow velocity an MC system with a staggered-wire arrangement always has better separation efficiency than an MC system with a face-to-face wire arrangement.

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Faraday current, which flows in a circumferential direction in a disk MHD generator, was successfully measured using a method of Rogowski coil. This fact allowed us to estimate the radial distributions of fluid and elecrical propreties, such as gas flow velocity, Hall parameter, electrical conductivity, from the experimental data.
In the present paper, measuring system of the Faraday current and its calibration method are described in detail. Furthermore, as an example of the experimentally estimated properties, factors governing total pressure reduction along the radial direction are shown.

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This paper describes the mechanical characteristics of a 154 kV line post type polymer insulation arm which has both the functions of a steel arm and a porcelain insulator of a presently used transmission steel tower. The 154 kV line post type polymer insulation arm consists of polymer composite insulators called units which include two horizontal units with an open angle for responding to a longitudinal load of 40 kN and a suspension unit for responding to a vertical load. Its installation length is about 2.3m.
Samples of the insulation arm were installed at different places of an electric wire, to form a truss structure and a lahmen structure, for examining their mechanical characteristics. For the truss structure, it was clarified that neither remarkable bending stress nor torsional stress is generated in the FRP core, and that the mechanical force design of the insulation arm can be evaluated in reference to the axial force of the FRP core only. Furthermore, the buckling coefficient for evaluating the axial force of the insulation arm with the truss structure was experimentally identified. Moreover, it was clarified that a static load test for evaluating the mechanical force performance of the insulation arm against a longitudinal load is more severe than an impact load test at the same longitudinal load.

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Ni/YSZ cermets made from commercial YSZ and pre-calcined YSZ powder were exposed to the reducing atmosphere of 1000°C continuously, in order to clarify the change of physical properties and internal microstructure. Ni particles were sintered between YSZ particles and porosity was changed and conductivity was decreased, regardless the pre-calcination of the YSZ. In the cermets made from pre-calcined YSZ, porosity and pore diameter were increased and higher conductivity was obtained even after the 300hrs reduction. This is thought to be derived from the change of the structure in the cermets. Furthermore, the use of pre-calcined YSZ was revealed to be usefull to maintain the initial generation performance of the cell.

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