In order to establish a method of disposing a trace of PCB contained in reclaimed insulating oil in pole transformers (50 mg PCB/kg or less) in a safe manner, a full-scale insulating oil removal test by means of solvent cleaning was conducted using a real transformer not containing PCB. Test conditions were determined to prepare for the decontamination test for transformers containing PCB, and safety of the facilities was confirmed. Major results obtained are shown as follows:
(1) Satisfactory removal performance was obtained by breaking the transformer with the low-temperature crushing technique and sorting the members for cleaning.
(2) It was estimated that residual PCB in ferrous materials, copper materials and ceramics could be redacted to the level below a preset limit after primary cleaning of five minutes and secondary cleaning of ten minutes, and that inpieces of paper and wooden chips could be reduced to the level of 0.1 mg PCB/kg members or below after primary cleaning of 60 minutes and secondary cleaning of 600 minutes or less.
(3) It was confirmed that the facilities could be operated safely, and enviromental and working safety could be ensured.

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As the necessity of high quality electric power supply is increasing, it has been required to make up sophisticated power system operations in which several requirements stemming from economy, security and environmental aspects should simultaneously be satisfied. In general, a problem of satisfying several noncommensurable criteria is called a multi-objec-tive optimization problem. Although the most powerful means to obtain desirable system operations is optimal power flow (OPF), a straightforward application of the conventional OPF optimize only one objective and the remaining objectives must be treated as constraints. However, since such objectives are in trade-off relationships each other, it is necessary to develop an efficient multi-objective OPF.
In this paper, we shall propose a solution method of multi-objective OPF by means of fuzzy coordination. In the first step, the degree of satisfaction of Decision Maker on each objective would be maximized with a pre-specified member-ship function. The membership function would be updated in accordance with the DM's preference information and target value of the objective function. The degree of satisfaction will be improved step by step by updating the membership functions. Finally, the saticificing solution for the Decision Maker would be obtained. The proposed method has been applied to the IEEE 57 and 118 test system, producing successful results.

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Characteristics and economics of three power generation systems which utilize solar energy were investigated and compared when the systems were located in five different regions. The three systems investigated are as follows: a solar thermal system, a solar photovoltaic system, and a CO₂-capturing hybrid power generation system utilizing solar thermal energy (referred to as the hybrid system) which has been proposed by the authors. The net generated power energy and the net exergetic efficiency of the hybrid system have been estimated to be larger and higher, respectively, than those of the others. It has been shown from economics evaluation results that the unit cost of generated power energy of the solar thermal system changes most widely corresponding to the change in solar radiation condition and that the cost of the hybrid system does the least. In general, the most economical system has been estimated to be the solar thermal system in a location which is superior in solar condition and to be the hybrid system in not so good solar condition. The solar photovoltaic system has the possibility of being the most economical if its construction cost is greatly improved, though the hybrid system is still the most economical in considerably worse solar condition such as in Osaka.

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This paper proposes a new concept of relay agent to realize cooperative protection system, which consists of distributed equipment that are combined with communication network and cooperate to realize adaptive protection functions. Relay agents move between equipment to utilize data and functions installed distributively. The paper classified relay agents by its roles and simulated protection functions under some typical conditions. This indicated that the concept enables the protection system to keep isolated zone minimum against any changes in power system conditions and to secure high reliability of the protection system with less redundant hardware.The concept of relay agent will give a powerful means of advanced protection functions by combination of micro processor technology and information communication techniology.

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A new type of double pulse generator is developed to generate independent two pulses with short interval (T_d). The system utilizes a single, gap switch-free pulse forming line designed to produce output pulse of 600kV, 25Ω, 60ns. The system consists of a step-up transformer circuit and a discharge switch free Blumlein pulse forming line, both of which utilizes amorphous metallic cores. Double pulse operation is realized by using hydrogen gap switches and a high-speed pulsed reset circuits of the amorphous cores. At T_d ≥ 500μs (equivalent rep-rate (f_r)=2kHz), the system was operated with good reproducibility and produces two pulses of 400 kV with efficiency of 65%. To enhance the recovery of hydrogen switch, a magnetic switch is used, which enables the operation at T_d ≥ 39μs (f_r=26kHz).

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We have developed a 200kW multifuel-type phosphoric acid fuel cell (PAFC) power plant for liquefied propane gas (LPG) and for town gas 13A, which is made from natural gas. It was made by partially reconstructing a one-fuel (town gas 13A) type PAFC power plant. LPG and town gas 13A were steamreformed in the same reformer to form hydrogen, which is necessary for the fuel-cell reaction. Double-layer catalyst beds were used in the reformer. These beds consisted of Ru-Al₂O₃ catalyst layers located at low-temperature areas on the gas-inlet sides of the beds and Ni-Al₂O₃ catalyst layers located at high-temperature areas on the gas-outlet sides. Steam-reforming LPG needs more steam than that for town gas 13A, but the new catalyst beds reduced the amount of steam needed for reforming LPG so that it was kept within the maximum steam-supply level of the plant without resulting in carbon deposition.
The developed plant generated a maximum AC 200 kW output power by using either fuel. At AC 200 kW power generation, the steam-to-carbon (S/C) ratio in the feed was 3.40 for steam reforming of LPG and 2.56 for steam reforming of town gas 13A. The S/C ratio for steam reforming of LPG was also decreased to 2.80. Fuel switching from town gas 13A to LPG and vice versa was performed without decreasing the output power by adjusting the fuel and steam supplies to the reformer depending on whether the output power remained constant, changed, or was interrupted. Power generation continued stably and the fuel was switched by stopping the town-gas supply even when the fuel-switching trigger pressure of the town-gas supply was set at 100 mmAq, which is the guaranteed minimum pressure. Sufficient heat for LPG vaporization was obtained from the plant exhaust. The fuel-cell DC output power at the same AC power level generated by LPG and by town gas 13A was, therefore, the same. 8.39kW of the parasitic-power consumption for the heat source of the LPG vaporizer was decreased by using the exhaust heat from the plant to vaporize LPG, when the power was generated at AC 200kW using LPG.

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Partial Discharge (PD) within voids in solid insulating system is a symptom and/or a direct cause of a deterioration of a generator winding. It is reported that PD is a very short duration current and/or voltage pulse, about 1-5 [ns]. Generally PD emits electromagnetic wave which is a broadband range signal (_??_ GHz). Therefore we developed a new system for detecting the electromagnetic wave, especially microwave (GHz) associated with a material defect of the winding. From the point of view of protecting an accident of the insulation breakdown, it is important to assess the condition of the winding. We applied our system to a dielectric breakdown test to know the relation between the characteristics of the microwave and the insulation condition of the winding. The dielectric breakdown test is believed to be useful for estimating the minimum breakdown voltage which is a criterion of the insulation condition of the winding. Experimental results showed that this system was able to assess the insulation condition by measuring the number of the pulse and the amplitude of the microwave per voltage cycle.

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Structure and characteristics of step-up transformers using iron cores are discussed for pulsed power applications. The characteristics are compared with that of air core transformers and it is shown that by using the transformer it is possible to obtain an efficient and fast energy transfer. Four types of low inductance, highly insulated transformers are introduced or proposed, i.e., induction adder type, multi-layered coaxial winding conductor type, strip winding type, and race track type transformers. The characteristics of each transformer are evaluated and suitable applications are described with estimated inductance. Sufficiently low inductance is shown to be realized with high voltage insulation in these transformers.

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It takes so long time to investigate the cause of the fault occurred on power transmission line, because of no method to decide it except the survey of the outage place. Therefore, a tot of studies to predict the cause of fault based on current and voltage waveforms have been carried out. Moreover, it is necessary to measure not only the lightning current waveforms, but also voltage waveforms for minimization of lightning outage on transmission lines.
Whereas various attempts have been made to measure the surge voltage on power lines, no system has been successful in practical applications, because of many problems such as sensor output fluctuation due to the weather or measurement calibration.
From these backgrounds, we have devised a new method based upon electric field measurement in wide band frequency and tried to make the measuring system of surge voltage waveforms on power line. Further, we obtained the waveforms of surge voltage arisen on power system at transmission tower and substation by this system.

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A hydrogen-oxygen-burning CO₂-free gas turbine power generation system has been proposed as one of future high efficiency energy systems, in which the steam produced by utilizing waste heat from factories is used as the working fluid of gas turbine. A simulation model is constructed in this study to estimate power generation characteristics of the proposed system by adopting C + + language. It has been shown from simulation results that the proposed system has high exergetic efficiency, that is, the total exergetic efficiency is 66.2% and fuel-based one is 88.2% for a system utilizing steam with 200°C. Sensitivity analysis has also been carried out when usable steam temperature is changed, together with the case when condenser outlet pressure is changed. A modified system is proposed in this study to make it possible to utilize lower temperature waste heat; that is, a system incorporated a waste heat recovery boiler (WHB). It has been shown that the modified system can make use lower temperature steam than the original proposed system, although its efficiency is deteriorated than the one of the system without a WHB. The characteristics of the system when methane gas is usedinstead of hydrogen have also been investigated in this study.

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Voltage - current characteristics of a subsonic disk CCMHD generator are examined with time-dependent quasi-one-dimensional numerical simulations. The output voltage is found to be almost constant for load resistances higher than the designed value, whereas the output current is kept almost constant for lower load resistances. It is confirmed that for the high load resistances the subsonic flow is maintained in the whole generator, and steady and uniform nonequilibrium plasma is realized. The connection of the low load resistances makes the flow choked at the generator inlet, leading to the supersonic flow. Then the shock wave and the ionization instability take place in the generator.

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The relationship between the amount of Sr substitution (x) and the physical properties of La₁-_xSr_xMnO₃, usually used for Solid Oxide Fuel Cell cathodes, was studied. Conductivity increased with an increase in the amount of Sr, and was almost constant in the range of x≥0.4. Bending strength increased in proportion to the density of the body in the range of 0.1≤x≤0.3, and decreased above that range. Thermal expansion was influenced not only by x but also by the sintering temperature. Samples sintered at 1200°C with x≤0.2 show a point of inflection caused by the phase transition at around 800°C, while samples with x≥0.3 have linear characteristics in the temperature range under 1000°C, when the sintering temperature was over 1300°C. XRD analysis showed orthorhombic structure material in the samples with 0.1≤x≤0.3 sintered at 1500°C, which have high bending strength. This material is thought to have some relationship to the increase in the bending strength of La₁-_xSr_xMnO₃. As a result, it was indicated that Sr substitution x=0.2_??_0.3 is adequate for cathode material in Solid Oxide Fuel Cells.

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The lightning damage on low-voltage power distribution systems is almost burning of low-voltage distribution equipment due to flashover and arc dynamic current.
The lightning overvoltage causes flashover of low-voltage distribution equipments. After that, the flashover causes burning, because of impressing the commercial frequency voltage.
Two kinds of experiments were conducted by the authors. The first was using real scale low-voltage distribution line model. The second was using a low-voltage distribution equipment. According to the first experiment, a lightning overvoltage causes burning at an equipment or two equipments on a low-voltage power distribution system. In the second experiment, the authors suggested that flashover current due to lightning overvoltage become 0 ampere at once when flashover current switches to arc dynamic current.
As a result, it became possible to know which equipment would be burnt on a low-voltage distribution systems. By using this mechanism and calculation by EMTP, it is possible to simulete lightning damege on low-voltage distribution lines

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Concentration in population and business activities results in high energy demand in urban areas. This requires the construction of underground substations. Oil-less, non-flammable and non-explosive equipment is recommended for underground substations. Therefore, gas-insulated transformers have been developed. Development of the method for diagnosis of gas-insulated transformers is required.
In this paper experimental survey over the main components of decomposes generated by various faults in gas-insulated transformers is described that is carried out through simplified model tests. The phenomena of overheat and partial discharge are modeled, taking the actual materials related to each fault into account. For example, CO, CO₂, and aldehydes are produced by an overheat from pressboards and PET-films. The amount of gas production increases with temperature rise. While various types of gases are produced from the partial discharge, principal components are SO₂ and SOF₂. These results will be used to develop the diagnostics method for gas-insulated transformers.

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Validity of improvement in performance of a nonequilibrium disk type MHD generator by applying an additional radio-frequency (rf) electromagnetic field is investigated with r-θtwo-dimensional numerical simulation. In particular, the structure of the plasma is examined in relation to the generator performance. The inductively coupled pre-ionization at an upper region of the channel results in the increase of the electron temperature of the plasma. Thus, the nonuniformity of the plasma caused by the ionization instability developing in a weakly ionized seed plasma can be relieved and the fluctuation of the electron temperature and the ionization degree of the seed atoms are also suppressed. As the coil current is increased, the plasma behavior changes from the nonuniform state to the uniform stable state through the unstable transient state. As a result, the enthalpy extraction of the generator is improved. The ratio of the required Joule heating by the rf electric field for the sufficient improvement in the performance to the thermal input of generator is estimated to be about 0.35%.

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The decision making of waste water discharge timing has been done by the planning experts for an appropriate usage the storage water in connected dams. Based on an accurate prediction of the storage water in connected dams, more effective decision making of waste water discharge timing is required to be developed revolutionary.
This paper discusses a method for decision making of waste water discharge timing based on the prediction of storage water in dams of hydro system using the hazard rate of dam overflow. The proposed decision making criteria was evaluated using some actual data of Kawakami hydro system in Saga, Japan and gave a satisfactory accuracy in decision making of waste water discharge timing by predicting the storage water in connected dams. The proposed decision making was compared with the conventional decision making by the planning experts. The proposed decision making was proved to be widely effective for decision making of waste water discharge timing in connected dams of actual fields.

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