A lightning location system of time-of-arrival type, known by the name of LPATS, was installed in the middle of the Honshu Island of Japan by Tokyo Electric Power Co. in 1990. This system is LPATS version 3 (LPATS III), which is the most widely used version of LPATS in the world, however, there have been few reports on its operating characteristics. In order to utilize the outputs of this system to investigate lightning parameters, it is indispensable to identify the operating characteristics of this system. The system was calibrated, and the observed distributions of the lightning current amplitude were analyzed and compared with previous reports. Resultantly, it is revealed that this system identifies negative return stokes in summer almost correctly, but in summer, it misinterprets many electric field pulses, originating from cloud discharges, as small positive return strokes. This result also suggests the strong dependence of the number of electric field pulses, associated with cloud discharges, on the polarity of the pulses.

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In this paper, a new application of Superconducting Magnetic Energy Storage (SMES) for diagnosis of power systems is proposed. Basic experiments for measurement of damping coefficient of power systems by use of SMES are carried out in an experimental system with a small generator, artificial transmission lines and a small SMES. The SMES gives small power disturbances to the power system without affecting oparating conditions of the power system. The small power oscillations in the power system due to continuous power disturbances generated by SMES are observed. The relations among the damping coefficient, the power disturbances and the power change of SMES are discussed for one-machine infinite-bus system. The damping coefficients of the power system are obtained by investigating the oscillations due to the sinusoidal power change of SMES. The possibility of estimation of the steady state power system stability by monitoring the damping coefficients of the operated power system by use of SMES can be shown experimentally.

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When a fault occurs in a large interconnected power system, several generators may swing coherently and form a group. Loss of synchronism may occur among the groups of these generators. In order to develop a stabilizing control system, two new methods are proposed in this paper. The first method is to select generators which swing coherently.
The method uses a new index that is based on the physical relation : when two generators swing coherently, a phase angle of a generator terminal voltage increases when the angle of the other generator increases and decreases when the other decreases. To detect a loss of synchronism, power P and current I measured on a line with the interval of a certain time period are used. By using this method, the position of an operating point of power system after disturbance on the power angle curve can be estimated. This means that the degree of stability can be observed with a small number of data measured on a line.

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The voltage characteristic parameters of the widely-used static exponential model of a power system load are sometimes esamatea as large as 200 with respect to reactive power loads, even though those of active power loads are usually estimated at most 2 or so. Since most of the components of system loads, i.e. the individual electrical devices, do not have such large characteristic parameter value, this fact is not immediately obvious.
In this paper, the reason of the phenomenon is clarified in terms of the effects of series and parallel impedance existing between loads and an observation point, and the general behavior of the characteristics is analyzed.

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Fuel Cells provide the advantages of high energy conversion efficiency and low emission. Especially, Solid Oxide Fuel Cell has been expected to have higher efficincy, compared to the PAFC etc. and Planer and Tubular type cells have been studied. However, expected high performance has not been attained yet on the SOFC stack composed with these conventional cells. In this paper, new type of SOFC cell is proposed in order to obtain the high per-formance and ease of stacking. This cell uses a tubular, porous flat plate made from electro-de material as cell support, and electrolyte and another electrode are fabricated on one side. This flat plate also provides gas channel, corresponding to the plate material. This cell was fabricated by the application of extrusion and plasma spray technique to the porous support plate and electrolyte layer, respectively. Characteristic tests were carried out on the 40cm² type cells, and the results showed the maximum energy density to reach 0.65W/cm² at 1000°C.

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Design and stability analyses of MHD disk type generators are carried out, which are applied for coal-fired electrical power generation system with CO₂ recovery. Channels designed with sub-sonic flow show rather poor performance compared with supersonic flow channels. Inflow channels show better performance than outflow channels. The inflow channel gives enthalpy extraction ratioes of 20.21% and 21.12% for the thermal input of 1100MW and 2000MW, respectively, while the outflow channel operated with supersonic flow yields the enthalpy extraction ratio of 17.92% and 18.12%, when the magnetic flux density is 8T. The open-cycle disk channels tend to become unstable at the exit region. It seems possible to stabilize the disk channels when operated with 8T but seems difficult to stabilize them when operated with 10T.

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Six typical on-line cable monitoring methods were outlined first. In the field, it has become a problem that in some cases measured insulation resistance values contain much error than expected, especially when the outer sheath resistance is lower. This was recognized as a phenomenon due to intrusion of unpredictable and unstable noise voltage “en” to the measuring system.
The Author presented his extensive investigation results relating to the origins of en, their various aspects, invasion route to the measuring circuit and degrees of influence on the measured resistance values, with the aid of many illustrations and the newly derived numerical formulas which serve as the indexes to tell practicability of each method. Also suggested that all the methods shall be categorized into 3 groups, (A) to (C), according to their extent of measuring error.
Finally, the Author presented and recommended the use of new techniques to reduce en effects, with the adoption of (B) group methods because of their good practicability.

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Surge arresters and overhead ground wires are used to protect equipment and insulation on overhead power distribution lines against lightning. In recent years, surge arresters have been installed on power distribution tines in high density, and number of outages caused by flashover at an insulator has been gradually decreasing. However, failures of surge arresters caused by a large amount of energy more than their withstand capabilities due to lightning still occur.
In this paper, the difference between the energy absorbed by a surge arrester installed at the open-termination of a line and that installed in the midst of a line are studied using the EMTP. In the case of direct lightning hits to an overhead ground wire, the absorption energy of surge arresters installed at the open-termination of a line is about 1.1_??_2.3 times larger than that installed in the midst of a line.

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Creeping impulse discharges occurring at the insulating systems of electric power equipment are significantly af-fected by the presence of a surrounding grounded metal case. Using a standard lightning impulse voltage, the characteristics of creeping streamers were studied over the surface of an oil-immersed polyethylene (PE) insulated wire with a grounded side electrode. The discharge characteristics (discharge aspect, streamer extension length, streamer current and charge, etc. ) were measured as a function of the distance between the PE wire and the grounded side electrode. Streamer polarity and the position of the side electrode significantly affected both streamer generation and propagation. The creepage characteristics were also examined using two methods of voltage application. Differences in the test results of each method were attributed to the position of the side electrode. The potential distribution inside the streamer channel and the streamer propagation velocity were measured by means of a potential probe. Streamer velocity was found to be constant and the streamer channel was not equipotential.

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The photovoltaic module temperature rise is expressed by an approximate equation of solar irradiance, wind direction and velocity.
For this purpose, the experimental data were collected from the 750kW test equipment over 2 years. The data were averaged for 30 minutes periods and divided into monthly groups. Wind directions were classified into 4 categories corresponding to the ranges within ±45 degrees of north, south, east and west, and wind velocities into sections of 1m/s. The correlation between module temperature rise and solar irradiance was used to obtain an approximate equation on wind direction and velocity for the standard solar irradiance(l.0kW/m²). By relating this equation to a linear function regarding solar irradiance, an approximate equation for module temperature rise was derived. The temperature rise calculated by using this approximate equation was compared with measurements. As much as 82 percent of the calculations are within ±2°C of the corresponding measurement, while 96 percent fall within ± 4°C.
This suggests that the approximate equation will be sufficiently accurate to evaluate averages over relatively long periods, such as for calculation of system efficiency and simulation.

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The effect of the ground conductivity on the lightning-induced voltage on an overhead wire, associated with an in-clined return-stroke channel, is studied as well as the effect on the electric field. The induced voltage is calculated by the method where the tangential component of the electric field to the line is looked upon as inducing sources, and the electric field is calculated by decomposing the lightning channel into numerous dipoles. The effect of the ground conductivity on the horizontal electric field is found to be dependent on the direction to the striking point, and the effect on the lightning-induced voltage waveform turned out to be dependent on the three-dimensional configuration of the return-stroke channel relevant to the line.

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The magnetic field waveform over perfectly conducting ground, associated with an inclined return-stroke channel, is studied based on numerical calculations. The magnetic field is calculated by decomposing the lightning channel into numerous dipoles. It turns out that the magnitude of the magnetic field is greatly influenced by the inclination of the lightning channel while the direction is little influenced.
Accuracy of the calculated result is ensured by comparison with the experimental result on the lightning-induced voltage obtained by using a reduced-scale model.

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The lightning-induced voltage on power distribution line having a branch is studied based on numerical calculations. The induced voltage is calculated by the method where the tangential component of the electric field to the line is looked upon as inducing sources, and the electric field is calculated by decomposing the lightning channel into numerous dipoles. Accuracy of the calculated result is ensured with experimental result obtained by using a reduced-scale model. The induced voltage on the distribution line turns out to be influenced by its branch, and is found to be dependent not only on the configuration of a branch line but also on the location of the lightning striking point. In most of the cases, the induced voltage increases when a branch is connected to the distribution line.

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This paper outlines the development of a 500kV DC oil-filled submarine cable capable of transmitting 2800MW with ±500kV 2800A bipole system. Although Polypropylene Laminated Paper (PPLP) has been employed as AC cable insulation material, this is the world first application to DC cables. The conductor size is 3000mm², which would be the largest size for submarine cables. Various fundamental and prototype tests have proved that the cable has excellent characteristics electrically as well as mechani-cally. The cable and accessories are currently undergoing a long-term accelerated aging test as afinal confirmation of their reliability and stability.

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The lightning outages of a power distribusion line are caused by indirect lightning strokes as well as direct lightning strokes. On previous overhead power distribution lines, the lightning protection with surge arresters and an overhead ground wire was directed to induced voltages due to indirect lightning strokes.
On recent power distribution lines which have a larger installation rate of surge arresters and overhead ground wires than previous lines, the outage ratio due to direct lightning strokes might be considered to be much higher than that due to indirect lightning strokes. But there are little simultaneous observations including both lightning discharge channels and manner of outages on power distribution lines. In order to obtain better lightning protection methods, it is important to clarify the cause of the present lightning outages, so the authors have started the obsevation with still cameras.
From July 1993 to July 1995, about 250 lightning discharge channels of ground flashes were recorded. The observed photographs which showed the lightning point clearly were 29 records. From the photographs which showed the lightning point clearly, next results were got. High voltage distribution lines were not suffered from indirect lightning strokes at all, even though those were the nearby lightning strokes. The damages of surge arresters were discovered in case of lightning hit to the building located near the distribution lines. In this case, lightning currents is thought to be injected into the nearby distribution line through damaged surge arresters. Only one record of direct lightning stroke on a power distribution line was obtained, but there were no damages. We have proved the shielding effect of overhead ground wire at the distribution lines against the direct lightning strokes. We have also proved that the high voltage distribution lines with an overhead ground wire and surge arresters could be protected against the direct lightning strokes.

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This paper presents a calculation method for gas flow distribution along a cell stacking direction. Reactant gas lack phenomena at a cell electrode may result in the serious electrode corrosion quite similar to gas crossover phenomena. The method takes into account for the reactant gas density difference between an inlet manifold and an outlet manifold which is caused by hydrogen consumption along gas channels.
The experiments using a 125kW full size stack were conducted to verify the simulation method. These experimental investigations clarified the method could be applied to diagnosis of stack performance with satisfactory accuracy.
The knowledge of the gas lack phenomena acquired in this study is expected to improve cell design and fabrication procedures.

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Analysis of gases dissolved in insulating oil offers the most promising diagnostic method for the faults in oil-filled transformers. This diagnostic method is based on the decomposed gas products for example H₂, CH₄, C₂H₂ etc., from insulating oil due to faults, overheat and discharge, in transformer.
In case of fault in the oil-filled transformer decomposed products are almost generated from insulating solid-materials without insulating oil. Therefore, it is useful for diagnostic of transformer that the decomposed products from insulating sol id-materials in insulating oil are analyzed.
An experimental survey over the decomposed products generated by overheat and discharge in oil-filled transformers was carried out through simplified model tests. Gas chromatography-mass spectrometer and purge/trap extraction were employed in analyses of decomposed products from insulating solid-materials in insulating oil.
Decomposed products characteristic to each solid-materials were identified by the experiment. Above diagnostic method is useful early detection and location of faults in oil-filled transformers.

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