Minami-Fukumitsu BTB (Back-To-Back) Converter Station is the first nonsynchronous link facility within the Japanese 60Hz system and it connects the system of Chubu Electric Power and Hokuriku Electric Power. An Automatic Frequency Controller (AFC) is installed in this facility to stabilize the frequency of the power system after a large disturbance (like one part of power system is divided from the other part) and to enhance suppression of frequency fluctuation.
This paper describes individual problems and countermeasures to install optimal multi-variable control AFC and introduces a part of test results using actual power system to verify performance of control systems. This paper also shows effectiveness of analysis using digital simulation tools.

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This paper proposes a comprehensive model to examine potential energy saving and CO₂ emission reduction in residential sector through architectural enhancements and facility improvements. First, hourly cooling and heating demand in accordance with the insulation level is calculated using SMASH software. Next, thermal energy and electricity supply system model is used to estimate the electricity, gas and kerosene requirements by various systems in residential buildings to cover the air conditioning demand and other demands depending upon the type of household. Finally CO₂ emission reduction by the energy saving technologies is calculated using the estimated energy consumption and the CO₂ emission intensity of electricity obtained using the power generation best mix model. The economic efficiency and potential CO₂ emission reduction by energy saving technologies in the residential sector of Tokyo are evaluated with this approach.

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Discrete Fourier Transform (DFT) can calculate the phase and amplitude of the AC waveform directly from the sampled data. However, high performance microprocessor is inevitable to implement DFT into real time system, especially when conventional calculation algorithm is applied to high frequency sampling. Applying recursive algorithm to the DFT can drastically reduce the calculation amount. This paper studies about the phase detection error of DFT when recursive algorithm is applied. The proposed error correction method makes it possible to guarantee the correctness of detected phase, which is equivalent to the conventional DFT calculation algorithm. Also, this paper proposes the reset scheme of numerical error accumulation, which is unavoidable for the recursive algorithm applied DFT. The proposed method can guarantee high accuracy with minimum increment of calculation amount. The qualitative correctness estimated from the theoretical equations is confirmed through quantitative study by digital simulation.

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The output of a photovoltaic power generation system (PV system) fluctuates depending on weather conditions. Because the large scale introduction of PV systems may cause some difficulties in the operation of a power system, the evaluation of the influence of PV systems on the power system operation is important, where the smoothing effect by the dispersed introduction of PV systems should be considered.
This paper discusses the LFC (Load Frequency Control) capacity for the output fluctuation of PV systems based on the insolation data simultaneously observed at 5 points in Nagoya City area, from October-1999 to September-2000. In the calculation, it is assumed that PV systems output is independent of the electric load fluctuation. The results are summarized as follows; 1) LFC capacity for PV systems depends on the speed of the output fluctuation. If it is assumed that thermal plants respond to the output fluctuation of PV systems, the required LFC capacity is larger than that of PV systems. 2) Due to the smoothing effect, LFC capacity based on the averaged insolation for 5 points in a half of that based on the insolation observed at one point.

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Electricity generation in geothermal power plants depends on the characteristics of geothermal steam well. In this research, geothermal power generation model was constructed based on the characteristics of steam well, and the generation of electricity was estimated precisely by use of the constructed model. Many applications of the geothermal power generation model are introduced.

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Electric double layer capacitors (EDLC) have attracted much attention as energy storage devices in recent years because of their wide variety of applications. Use of EDLC-electronics combination, called Energy Capacitor System (ECS), as an integrated supply source in place of batteries in a PV system for load leveling will play a key role in the further development of new areas of applications in PV as well as other power systems. The Electrical and Electronic Engineering department of Kitami Institute of Technology has taken up a joint collaboration research program on PV-ECS system with four research and manufacturing companies, funded by New Energy and Industrial Technology Development Organization (NEDO). In this work an effort has been taken to develop a new small distributed generation system of PV-ECS with a daily load leveling function. Another aim is to investigate the performance of ECS in respect of charge-discharge characteristics, energy efficiency and life cycle as an integrated autonomous supply source in a grid connected PV system. The overall performance of the system as a load leveling power source has been evaluated and the results are drawn graphically and discussed.

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Recently the deregulation of the electric power industry has progressed in the world. In Japan the electric power industry law was revised to achieve a reduced electricity price in 1995, and competition in the power generation market was started in Japan. Moreover, the retail wheeling to large customers was launched in March 2000. Under this situation, 1PPs selectors (electric power utilities) have to think about efficient connection to existing systems by which they have select IPPs considering not only the cost but also the future demand. Therefore, in order to achieve efficient connection of IPPs to the existing systems some selection guidelines are needed. What IPPs selectors want to know is ‘Where’ and ‘How much’ in the existing system they want to have IPPs? It is thought that knowing good connecting point(s) and the appropriate capacity of IPPs becomes one of the IPPs selection guidelines. In this paper, we propose a method by which we can determine the connecting point(s) and the appropriate capacity of IPPs to plan the appropriate electric power system in the future. And, the proposed method in which IPPs selectors can select from both sides of reliability and economy is verified using simulations.

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Many researchers have proposed the application of diode rectifiers in the HVdc transmission systems, the major objective of which is cost reduction. However, simple replacement of thyristor converters at the rectifier station with diode ones while keeping line-commutated thyristor inverters on the other end will cause several problems which degrades HVdc system performance to a level that the HVdc system becomes impractical. The major problems are: (1) dc line overvoltage upon startup of the system, (2) large fault current upon occurence of dc line grounding fault, and (3) commutation failure of the inverters. To overcome these problems while almost keeping the cost reduction merit, the authors discuss the possible combination of diode rectifiers, line commutated thyristor converters and the voltage source converters. Series connection of diode and thyristor converters in the rectifier stations (which is called diode-thyristor hybrid rectifier station scheme) will solve problems (1) and (2). The use of voltage source converters in the inverter stations will remove problem (3). This combination will be a cost-effective solution when there is no need for bi-directional power flow and when the receiving end network needs the ability of voltage source inverters.

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This paper describes the locating system of line-to-ground fault on transmission line by wavelet transform. The possibility of the location with the surge generated by a fault has been theoretically proposed. In order to make the method practicable, we realize very fast processors. We design wavelet transform and location chips, and make a very fast fault location system by processing the measured data in parallel. This system is realized by a computer with three FPGA processor boards on PCI bus. The processors are controlled by UNIX and the system has the graphic user interface with X window system.

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In this paper, the temperature distribution within ACSR conductor was precisely measured and examined, conducted as part of a series of studies on large currents in transmission line. The study results may be summarized as follows. (1) The temperature difference within the conductor cross-section increases as the square of the current; however, even at a current equal to 50% more than the allowable current, the maximum temperature difference within the aluminum components is from 5°C (ACSR 410 mm²) to 6°C (ACSR 810 mm²). (2) The results of measurements of the conductance between outer-layer and inner-layer aluminum strands in the conductor, and analysis of the current distribution in the inner and outer layers, indicated that even if the conductance were to drop sharply to 10, 000S/m, any inhomogeneity or concentration in the current distribution at a conductor connection joint has disappeared by 1.5m or so from the tip of the joint. (3) According to measurements of the conductor temperature near a joint, the electrical resistance of the joint is lower than that of the same length conductor, so that the conductor temperature falls for 0.5m or so from the tip of the joint. (4) Based on the above findings, the temperature distribution within an ACSR conductor accompanying the passage of large currents can be regarded as nearly uniform both across the conductor cross-section, and in the conductor length direction.

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In recent years, especially electric power demand is concentrated on the daytime of summer by the spread of air-conditioners etc. And the demand gaps between daytime and nighttime and between seasons tends to spread. DSM (Demand Side Management) technology is expected as one of the methods which attains load leveling according to such a background. Especially, the concentrated load control system which controls directly the customer apparatus (air-conditioner) which is working at the summer peak hour, can reduce load electric power certainly as peak shaving technology, but the control method must be received by the customer and the degree of acceptance will influence the effect of DSM greatly. Then, authors searched for the control method which does not spoil the comfortableness of a customer by physical feeling experiment, and have grasped the fundamental electric power control effect when controlling an air-conditioner by this method. Furthermore, in order to evaluate the electric power control effect in a power distribution line unit, the average electric power control effect was searched for from operation of the air-conditioner at the time of carrying out DSM control of two or more air-conditioners. Moreover, as the means, it considered as the method of carrying out communication transmission of the control signal to the air-conditioner in customer's houses from our sales office, and the concentrated air-conditioner control system using the distribution automation communication system was developed.

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An experimental investigation was performed on a UHV long distance transmission line model for the EMTP calculation of lightning overvoltage at substation. The various lightning surge propagation characteristics were measured on an actual UHV transmission line.
In this paper, we present the traveling lightning surge waveshapes, propagation characteristics of peak voltage and front waveshapes and analyzed waveshapes by EMTP for insulation design of substation on UHV transmission line. In addition, we report on the relationships between peak voltage and propagation at 200km analyzed by EMTP.

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It is well known that the phase distribution of partial discharge in GIS depends on the source of discharge. However, the equivalent circuit model has not been considered sufficiently. On the other hand, the authors have proposed an extended Whitehead circuit model, and have explained the difference of the phase distribution of discharge. In this paper the case of needle on spacer is treated in a model GIS (300kV), and the difference of phase distribution is measured. Next the dust figures are obtained, and charged regions on the spacer are discussed. Finally, it is stated that the EMTP simulation by the extended Whitehead circuit model agrees with the result of experiments fairly well.

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A thermoelectric generator has been manufactured and evaluated for the purpose that the behavior of heat conduction and power generating performance of modules can be clarified when the thermoelectric generator is powered by high temperature heat transfer medium oil over 500K. The thermoelectric generator needs a compression fitting mechanism which holds heat sinks and thermoelectric generating modules so tight that desirable heat conduction can be maintained for the thousands of heat cycles. Pressure required for the compression fitting mechanism is experimentally investigated with the trially manufactured thermoelectric generator. As an experimental result the compression fitting mechanism of the modules requires 0.28MPa compressive load, which is 80% less than the recommended value by one of the module manufacturers. Electricity obtained by the trially manufactured thermoelectric generator with bismuth-telluride based modules increases in proportion to the square of logarithmic mean temperature difference between heat transfer medium oil and cooling water and attains to 165W at logarithmic mean temperature difference of 180K.

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A high speed circuit breaker has been developed using the transient electromagnetic field analysis coupling with motion based on the finite element method. This breaker has an opening time of 1ms and a break time less than 1cycle (20ms). The driving part of the breaker is composed of electromagnetic repulsion mechanisms and disk springs with nonlinear characteristics. Here 24kV-20kA rated high speed circuit breaker has been developed using this analytical method. This breaker has a new driving mechanism of Coil-Coil repulsion and we found that the new mechanism is better than the conventional Coil-Plate repulsive one.

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We have developed a 24kV-20kA-1200A-rated High Speed Circuit Breaker with a new electromagnetic repulsion mechanism for both open and close operations. The new operating mechanism has a opening fixed coil, a closing fixed coil and a movable coil housed in a metal coil case. Driving efficiency of new operating mechanism is achieved about two times larger than that of a conventional repulsion mechanism consisted of a fixed coil and a copper repulsion plate.
The 24kV High speed Circuit Breaker can open contacts within about 1ms from a trip signal and break current within one cycle, and close contacts within about 10ms. In a short circuit current interrupting test, this circuit breaker interrupted the current with a peak value of 50kA successfully.

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In Japan, about 30 years have passed since gas insulation equipment began to be operated. This old equipment must be maintained. But, when viewed in lower costs, life time extension is expected with minimum maintenance. For its purpose, maintenance style must be changed from TBM which implements maintenance every constant period to CBM which changes maintenance schedule by the condition of the equipment. TBM is the conventional style and CBM is the future style. Moreover, CBM has various styles such as RCM and RBM. RCM means reliability centered maintenance, and RBM means risk based maintenance. However, even if the maintenance changes to any style, the maintenance style called SBM (sensor based maintenance) is necessary to acquire the information.
We developed and evaluated the sensors for SBM-gas pressure sensor for detecting slow-leakage, SF₆ decomposition gas sensor for detecting overheat conductor (poor contact), and partial discharge sensor for insulation failure. We got the result that these sensors were suitable for CBM.

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This paper describes a wind tunnel facility specially designed for a test regarding heat conduction from an overhead transmission line to ambient air under very low speed wind condition, which ranges under 0.1 to 1m/s. To establish a uniform velocity distribution at such low speed, this wind tunnel is equipped with moving sidewalls, which considerably reduces the wall boundary layer thickness.
A screen was installed at the entrance of test section to improve the uniformity of the velocity. The results of the performance tests of this wind tunnel showed that the nonuniformity of the velocity profile at the test section is less than 0.01m/s. Also long-time unstability of air speed was proved to be sufficiently minimal.

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This paper describes dielectric breakdown characteristics of oil and oil-impregnated paper for very fast transient (VFT) voltage. Blumlein circuits generate VFT voltages of 60 and 300 nano-seconds in pulse width that simulate disconnecting switching surges in gas-insulated switchgears. We measured breakdown voltages of needle-to-plane, plane-to-plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V-t characteristics and Weibull probability distribution. The inclination n of V-t characteristics of insulating paper is 150 which is less than n=13.7 of the plane-to-plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil.

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The Large Helical Device (LHD) is a fusion plasma experimental facility using a superconducting coil system which consists of twelve superconducting coils. This coil system generates relatively high magnetic field of up to 3 T at the plasma center, and the total stored energy reaches about 1 GJ. Of course the superconducting coils in this system are designed to be stable enough, but there still remains possibility of a quench caused by some disturbance such as reaction from plasma current change.
To design a quench protection system, following two components are required. One is an external dump resistor to release the stored energy, and the other is a dc circuit breaker used in a commutation circuit which transfer a coil current from a dc power supply to the dump resistor. In a multi-coil system like LHD, the current decay of each coil is affected by the flux change caused by the others. Therefore the current decay depends on the operating currents, and a conventional design for a dump resister cannot be applied. The design of a circuit breaker is also difficult because conventional circuit breakers are too large and too expensive.
In this paper, We first designed necessary resistance for dump resisters using numerical simulations and obtained a set of resistance values that satisfies the requirements without any reconnection during operation. Next, a new circuit breaker using power fuses and a vacuum circuit breaker has been developed. This circuit breaker has self-commutation ability and is more compact than the conventional ones. Finally, this system has been tested successfully with actual LHD power supplies and coils.

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This paper introduces a compression technique for power disturbance data via discrete wavelet transform (DWT) and wavelet packet transform (WPT). The data compression leads to a potential application for remote power protection and power quality monitoring. The compression technique is performed through signal decomposition up to a certain level, thresholding of wavelet coefficients, and signal reconstruction. The choice of which wavelet to use for the compression is of critical importance, because the wavelet affects reconstructed signal quality and thedesign of the system as a whole. The Minimum Description Length (MDL) criterionis proposed for the selection of an appropriate wavelet filter. This criterion permits to select not only the suitable wavelet filter but also the best number ofwavelet retained coefficients for signal reconstruction. The experimental study has been carried out for a single-phase to ground fault event, and the data compression results of using the suitable wavelet filter show that the compression ratios are varied from 2% to 11% and are reduced to more than a half of those values by implementing an additional lossless coding.

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An experimental study of performance of the disk MHD generator with argon was carried out using a shock-tube driven facility. An inlet swirl was introduced in the MHD channel in order to improve the enthalpy extraction and the isentropic efficiency. The experimental results were compared with those of the disk MHD generator without the inlet swirl. The high enthalpy extraction of 25.7% was obtained and the highest isentropic efficiency for argon was achieved at the same time in the present experiment. The measured static pressure in the MHD channel waskept lower than that without the inlet swirl. This has suggested that the introduction of the inlet swirl reduces the retarding force for the flow and that theincrease of the enthalpy extraction is ascribed to the increase of the flow velocity and of the electrical efficiency. Furthermore, the flow without shock wave was observed at low seed fractions and low load resistances. At the same time, itwas found for the first time that when the shock wave did not exist, the isentropic efficiency became higher compared with the one with the shock wave.

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In order to evaluate aging effect on motor correctly, several data of high voltage induction motors in 17 nuclear power plants of Tokyo Electric Power Co. (TEPCO) have been collected since 1984. Collected data are nondestructive insulationdiagnosis test data including insulation resistance, static capacitance and the results of insulation destructive test after replacement of motors.
Evaluation based on the data shows that breakdown voltage (BDV) of motor coil has relationship with the motor parameters such as current increase ratio, maximum discharge magnitude, difference of dielectric dissipation factor, etc. From this viewpoint, BDV estimation formula for 6.6kV motors is established by using multiple linearregression analysis method, considering parameter used in D-map evaluation. However the measured parameters may vary due to the factors besides insulation deterioration, not only the estimated BDV but also visual inspection data are took into account for overall diagnosis. Further collection of data and evaluation willbe done continuously in order to enhance accuracy of the insulation diagnosis.
The current situation of diagnosis for insulation deterioration of 6.6kV class induction motors in nuclear power plants is described in this technical note. Alsocurrent situation of investigation on 3.3kV class motors is described.

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