We have been investigated the operational feasibility of a future metropolitan electric power system associated with highly densified cryogenic cables. A new conception of power system configuration with cryogenic cables and its operation has been proposed. Three different models of future power transmission systems in large cities of our country have been constructed as the background systems prior to introduction of cryogenic cables at the 21st century. In this paper, we take up one of the three models, which is characterized by its conventional transmission system being constructed mainly by 154 kV transmission lines stepping down directly from the 500kV outer ring without any intermediate voltage class. This paper discusses whether the power system model will be effectively operated or not together with cryogenic cables to supply demands forecasted in the period subsequent to the first decade of the 21st century. The computer simulations are carried out to obtain power flow and bus voltage distributions for a peak load period as well as for an off-peak one in the power system model. These simulations reveal that the conventional background power system should be arranged so carefully ahead of introducing the cryogenic cables to facilitate their operations.
(1) On a contingent trip of a cryogenic cable in the peak load period, all bus voltages are not expected to be kept within a tolerant zone due to high impedance of 154 kV conventional transmission lines in the power system model.
(2) It is thus proposed that the background conventional system prior to introduction of cryogenic cables should be developed not only by extension of 154kV conventional transmission lines but also by introduction of 275 kV ones.
(3) Bus voltage rises induced in the off-peak load period are reduced by effective utilization of 275kV conventional transmission lines.

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Since FY 1981, R and D of solid oxide fuel cell (SOFC) and power generation system have continued in our laboratory as a program of Moon light project of Industrial Science and Technology of MITI. For the interim evaluations of the method of the fabrication and the performance of SOFC, the demonstration of 500W power generation test was executed with the gas conditions of hydrogen and air.
The power generation part was designed only under the rated condition of the operating cell voltage of 0.8V. The cylindrical 15-cell stacks were developed in phase I using the fabrication method with plasma and flame spray coating, and the typical performances were as follows: the output power at rated voltage of 12V was 28W, the maximum output power was 46W at voltage of 7.74V and the specific resistance was 1.2Ω•cm².
The 500W power generation test was executed with 48 stacks, of which specifications were slightly changed for the mass production in phase II. At the test, the output power of 540W was generated at the rated load voltage of 12V, and 1, 200W was obtained as the maximum power. But the DC efficiency was low, because the current efficiency was not able to be increased due to the insufficient impermeability of cell stacks.
The rapid deterioration in the performance was observed due to the increase of the internal resistance coming from the separation of air electrodes from electrolyte because of large expansion coefficient of air electrodes.
Through these experiments, it is concluded that the impermeability of the stacks should be improved and the material of air electrode should be changed.

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Present paper deals with the basic electrical properties of carbon fiber reinforced cement (CFRC) in order to estimate the electrical applications of CFRC. The distribution of carbon fiber (CF) in the cement composite has been estimated from the electrical properties of CFRC. The EMI shielding effect and the ground resistance decrement effect of CFRC electrode are also studied from the stand point of applications.
CFRCs used are the three dimentional randam type, which are prepared by mixing the portland cement and milled PAN-based carbon fibers with about 30μm in length and 7μm in diameter.
It is possible to estimate the distribution of CF in the CFRC from the electrical resistivity or the relative dielectric constant. Their electrical properties give an average length of the electrical current path and the orientation of Us in CFRC from Sillars' model by inhomogeneous dielectric constant based on dispersed spheroidal particles.
CFRCs have an electrical shielding effect up to frequency of around 400 MHz. And also CFRC with a fiber volume content of 30 vol% decreases ground resistance to about 50% against the direct ground of electrodes.

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It is not clear how widely available the tower models which have been derived from the lightning surge response measurements of transmission towers, because those measurements have not been done for so many towers and for so many cases. It could be very useful if the surge response characteristics can be obtained from the tower geometry. In order to do this, the surge response of each tower constructing elements (four main poles, tower arms and lattices) has to be made clear and then the total tower surge response should be derived by combining those responses.
In this paper, firstly the lightning surge responses of vertical cylinders of various radii and heights are measured by the direct method. Then the empirical formula of surge impedance is obtained for the vertical cylinders as a function of time, its radius and height which produces the surge response wave shapes close to the actual measurements. Next, the empirical formula of surge impedance for the multiple vertical cylinder is also obtained from the lightning surge response measurements. Then, the equivalent single cylinder radius for multiple vertical cylinder is derived and is proved to be expressed as a function of the conductor radius, the mutual distance of the conductors and the number of conductors. The above results especially for four vertical cylinder systems would be very useful for the estimation of the total tower surge response characteristics.

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We have carried out experimental study on the recovery characteristics of horizontal rod-rod air gaps after DC arc interruption.
The experimental conditions are listed below.
Gap length: ι₀(m) 0.5 to 5.
Arc current: I_arc(A) 100 to 20, 000.
Arc duration time: T_arc(s) 0.1 to 0.3.
Impulse waveform: Switching impulse (270/2, 500μs, up to 1, 340kV)
Impulse applied time after arc interruption: T_1mp(s) 0.07 to 0.45
The main results are summerized as follows:
(1) In the most severe conditions such as windless, about 4, 000 A in arc current and about 0.1s in arc duration, the switching impulse withstand voltage V_1mp in kV after DC arc interruptions can be discribed as;
V_1mp=α_υ(T_1mp-T₀)
where, α_υ(kV/s) and T₀(s) are experimental constants.
(2) The minimum time T_RCL to be required for restarting after the arc interruption of 4, 000 A on the 500kV DC line can be simulated as;
T_RCL=T_υ-τ{1+l_n(T_υ/τ)}+T₀
wher, T_υ(s) is a constant determined by the line voltage to ground and the gap length and τ (s) is a starting time constant settled in the DC system, for an example T_RCL=0.1s in a 500kV line.

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The alkali metal thermoelectric converter utilizing the sodium ion conducting β''-alumina is a device to convert directly heat energy to electric energy. It is characterized by high conversion efficiencies, high power densities, no moving parts and low maintenance requirements. Because of these merits, AMTEC is one of the most promising candidate for aerospace power systems, remote power station and dispersed small scale power station.
In this paper, the experimental results of the disk type cell and the theoretical considerations about internal resistances have been reported. The film electrode was made with a magnetron sputtering system. The open voltage of 0.98 V and the maximum power density of 0.38W/cm² at the sodium temperature of 1, 073 K have been obtained. It became clear after the theoretical investigation on the internal resistances that the most largest internal resistance was the resistance of β'';-alumina. And so, it is necessary to reduce the thickness of β''-alumina to improve the generating power densities. It was also clarified that the sodium gas flow in the small holes of molybdenum thin film electrode was a free molecular flow and the experimental results became agree well with the theoretical results considering the pressure rise due to this sodium free molecular flow. It was also necessary to develop the more porous and lower resistivity thin film electrodes because this pressure rise were fairly large.

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This paper describes a construction and a characteristics of a coal-gas-burned high efficiency power plant which emits no carbon dioxide (CO₂) into the atmosphere. In a plant, CO₂ gas and superheated steam are used as the main and the sub working fluid, respectively, of a closed dual fluid regenerative gas turbine power plant. Since coal gas composed of CO, H₂, CO₂ and CH₄ is burnt in a combustor using oxygen, the exhaust gas led into a condenser includs only CO₂ and H₂O. Hence, CO₂ gas can be easily separated at the condenser outlet from condensate. In the plant, the combustion gas is first used to generate power by driving a turbine. High-temperature turbine exhaust gas is next utilized at a regenerator to heat the main working fluid of CO₂ gas flowing into the combustor, and then is utilized at a waste heat boiler to produce the superheated steam injected into the combustor. It is estimated that the power can be generated with gross thermal efficiency of 54.4%, and that the power generating efficiency is 46.7% which is calculated by subtracting the power required for producing the high-pressure oxygen used for combustion from the generator output. It is shown that the estimated efficiency is higher by 18.1 percentage points than that of a conventional boiler steam turbine power generating plant into which a process for removing and recovering CO₂ from the stack gas by utilizing alkanolamine-based solvent is integrated.

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