This paper describes equivalent circuit modelling of a quick-response type superconducting generator con-sidering accuracy for variations of field current and armature current. Comparison with testing results shows that the proposed equivalent circuit model has high accuracy. This model enables us to analyze accurately stability enhancement by introducing superconducting generators.

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The Bi-2212 bulk superconductors, with a proper amount of SrSO₄, were prepared by melt-casting process (MCP). The MCP started with heating of the calcined powders at 1000°C in air until a homogeneous melt was obtained. The obtained melt was poured into a copper mold to make solid bars. The solid bars were subjected to a heating procedure at 840°C in order to reach the two-CuO layer phase. Finally, the MCP samples were annealed at 700°C in air, and rapidly quenched into liquid nitrogen, to ensure better homogeneity of the oxygen concentration. The SEM analysis of fracture surfaces reveals that the BSCCO grains are plate-like with an apparent length of about 50 μm. Critical current in bulk Bi2212 bar (φ10.7mm) exceeded 50A at 77K in self field. The weak links have been largely eliminated in the MCP sample, and the zero resistance is observed above 80K. A significant enhancement of transport properties in Bi-2212 bulk superconductors has been achieved using MCP. The AC loss value is about one-half of the theoretical value obtained by the theory of Norris. This is attributed to the inhomogeneous J_c distribution along a radial direction in the sample.

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The generating characteristics of resistance in a Bi2223 bulk used for fault current limiter were investigated. We supposed that the fault current limiter with the Bi2223 bulk was installed to a 6.6 kV distribution system and calculated the time variation of the resistance generated in the bulk during the current limiting period. In the analysis, a very good cooling condition (Case 1) and adiabatic one (Case 2) were assumed. In Case 1, the resistance generated in the Bi2223 bulk is flux flow resistance which depends on the instantaneous value of the current through the bulk. Under the condition of Case 2, the normal resistance, which is affected by the joule heat induced in the bulk, is mainly used to suppress the fault current as well as the flux flow resistance. As a result, the relation between the limiting effect on the fault current and volume of the bulk was shown in concrete form of numerical data. The bulk of relatively large volume is required to use in Case 1. This means that the limiting ratio of the peak value of the fault current must be large under the condition of Case 1. On the other hand, when we use in Case 2, we must use the bulk having small volume resulting small limiting ratio.

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A large superconducting coil wound with Cable-in-Conduit (CIC) conductor caused an additional AC loss which cannot be estimated from short conductor sample test results. It was confirmed that the additional AC loss was generated by long current loops in the CIC conductor. Magnetic field decays of the loops with various long time constants were observed through Hall probes. We propose a mechanism forming the long loops. The CIC conductor is composed of several staged sub-cables. if one strand on the surface of a sub-cable contacts with the other strand on the surface of the adjacent sub-cable, the two strands must encounter each other again at LCM (Least Common Multiplier) distance of all staged cable pitches and thereby result in forming a pair of a long loop. We numerically traced each strand in the CIC according to a method that the sub-cables at all sub-stages rotate around a center of inertia. The long time constants of long loops were calculated and a little bit shorter than the observed ones. We orderly labeled all strands in a real CIC conductor, disassembling carefully the cable after peeling the conduit. It was found that the strands in a triplex were widely displaced from their original positions, and thereby their contacting lengths became longer than calculated ones. This fact makes the time constant of loop longer and hence can explain the observed long time constants. The proposed mechanism is effective for estimating the long loops causing additional AC losses in the coil

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Development of a 1 GHz-class NMR magnet system is going on at the Tsukuba Magnet Laboratory of the National Research Institute for Metals. This magnet will consist of the inner HTS coil and the outer LTS magnet, it is designed to generate a magnetic field of 23. 5 T. We are planning to operate the inner HTS coil and the outer LTS magnet in series in order to obtain high stability of the central magnetic field. To achieve the stability of 0. 01 ppm/h, the critical current of the inner HTS coil must be four times as high as the operating current. Simulation results of usual quench protection methods suggest that there is some possibility that the inner HTS coil is damaged when a quench occurs in the outer LTS magnet.
We designed a new quench protection circuit for the 1 GHz-class NMR magnet and confirmed its adequacy using quench simulation codes. Our new method is valid for any HTS-LTS hybrid magnet.

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We investigate the influences of stacks of Bi-2223 multifilamentary tape-shaped wires without twisting on AC losses observed in an external magnetic field perpendicular to the wide surface of them. The perpendicular-field losses decrease with increasing the number of stacks in the small range of field amplitude. In the larger amplitude, on the other hand, the AC losses have a good agreement with each other. This can be understood by the effects of magnetic interaction between wires. By taking into account the effective demagnetization factors on the basis of theoretical consideration, the perpendicular-field losses are plotted on a master curve for the maximum magnetic field applied to the wires. Furthermore, the perpendicular-field losses measured as a function of the field amplitude are well reproduced by the numerical evaluation of AC losses for a slab with infinitely wide faces.

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In a design of HTS power cables, the over-current withstanding design is very important. In a conventional case, when one of the 2-circuit power cables failed, the other cable should transport the previous total power continuously. If we adopt this idea also in case of superconducting power cables, the rating current should be decided carefully. In this paper, the authors show a fundamental idea for a short-time withstanding over-current design of HTS power cables.

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Studies on superconducting generators have been carried out around the world. Especially in Japan, it is worthy of attention that Super-GM led the national project concerning the successful development of the 70MW-class superconducting generators. Low temperature superconducting wires have been applied to field windings of generators. In Japan, the next generation coated conductors, namely, high temperature superconducting wires, have proceeded under the national project supported by NEDO. Provided that the next generation coated conductors are applied to field windings, the weight and volume of superconducting generators will be reduced. Furthermore, using liquid nitrogen as a coolant instead of liquid helium, the reliability of high temperature superconducting generators is expected to improve.
In this paper, tentative designs of a high temperature superconducting generator whose field windings are composed of YBa₂Cu₃O_7-X wires are given. By comparison with the low temperature superconducting generator developed by Super-GM, the usefulness of the high temperature superconducting generator is discussed.

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In order to study the basic performance of the superconducting generator in the actual electric power system, the quick response excitation type generator was connected to 77kV commercial power grid of the KANSAI Electric Power Co., Inc. In the test, the model machine was operated as a rotary condenser supplying about leading 40MV ar to the electric power system. In the tests, the model machine operated stably. The results show that the superconductig generator has effects for stabilizing voltage fluctuations of electric power system and also for reducing shunt reactor.

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Superconducting fault current limiters (SCFCLs) are expected to improve not only reliability but also stability of power systems. To introduce an SCFCL in a power system, various specifications such as trigger current level, impedance in current limiting operation, recovery time and so on are necessary. Especially, fault analyses point out that accuracy of the trigger current level is necessary. Therefore, an SCFCL of a transformer type with adjustable trigger current level was proposed and made. By use of the trial SCFCL adjustability of the trigger current level was confirmed experimentally. In addition, good limiting and recovery characteristics were confirmed, too. In this paper, characteristics of the SCFCL are considered from the viewpoint of specifications. Most of the specifications depend on the characteristics in current limiting operation. Therefore, the characteristics of the SCFCL in current limiting operation are considered. It is shown that these characteristics are useful for designing, and design criteria of the SCFCL are summarised.

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In this paper, a new method for the on-line identification of power system electro-mechanical modes (eigenvalues) by use of Superconducting Magnetic Energy Storage (SMES) is proposed. Modulated sinusoidal active power of small amplitude in the low frequency bandwidth (chirp signal) is given by SMES to the power system. From the system's response (active power oscillations at generator buses) low order models are estimated by output error modeling based on Gauss-Newton algorithm. Finally from the models estimated, eigenfrequencies and their damping are determined.
The method is useful in monitoring system steady state stability and in tuning power system control. The studies and results are based on the simulations of power system with SMES in PSCAD/EMTDC program.

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It is important to elucidate partial discharge (PD) inception characteristics in LN₂/solid composite insulation system for the practical insulation design of high temperature superconducting power cables. Especially, butt gaps between laminated insulating papers for electrical insulation of superconducting power cables may induce PD and deteriorate the insulation performance under high voltage operation.
This paper discusses PD inception characteristics in LN₂/PPLP composite insulation system with a butt gap. We obtained PD inception electric field strength (PDIE) for different butt gap location and surface pressure on PPLP. V-t characteristics for PD inception were also described in this paper. Experimental results revealed that (1) PD with 2_??_30pC were detected at inception voltage in the butt gap between PPLP. (2) PD IE with a butt gap in the middle layer was higher than those in the top and bottom layers. (3) PDIE was independent of the surface pressure on PPLP. (4) n value of V-t characteristics for PD inception decreased down to 33.7 at the lower surface pressure on PPLP.

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We have designed and constructed a new type of active-maglev system using YBCO bulk and two electromagnets and have demonstrated that levitation height was remarkably improved by continuous levitation. In the active-maglev system, however, the upper and lower coils differed in the coil size and an iron plate beneath the lower coil was used to enhance the magnetic field around the bulk. Considering the real application to maglev transporter in the axial direction, we must realize continuous levitation using a larger number of electromagnets without such the iron plate and enable the levitation height to control freely. In this paper, we demonstrate continuous levitation with controlling the levitation height using three and five electromagnets systems and investigate electromagnetic behavior within the bulk using a FEM computer program.

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We have developed a technology of the formation of high-Tc superconducting thin film, and report the basic research about thin film. We have prepared superconducting thin films on various kinds of single crystal substrates. YBCO thin films were formed on YSZ (Yettria Stabilized Zirconia) single crystal, and investigated the orientation of the prepared YBCO crystal. The effect of off-angle YSZ single crystal was also investigated, and degradation of Jc of YBCO was observed in increasing of off-angle. We have successfully developed HoBCO thin film on LaAlO₃ suvstrates, too. Deterioration of Jc of superconducting thin films on LaAlO₃ substrates was investigated under the condition of high temperature and humidity. the effect. of surface protestion above the high-Tc superconducting thin film was confirmed, and the difference of the properties between superconducting materials was also observed.

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A new method of fabricating HTS coils was proposed with excellent performance for the critical current and magnetization loss properties. In the winding process of the coil, continuous control of twist angles around tape axes is adopted to reduce the degradation of these properties due to flat-on oriented magnetic fields applied to the wound tape. The effect of this method on improvement of the current capacity of tapes was estimated theoretically for a large scale Bi-2223 magnet. The expected capacity at 77K, 66K and 20K becomes 1.80 times, 1.70 times and 1.46 times as large as that for the previous coil winding, respectively. This result shows that compared to the old coil, and under identical operating currents, the new type coil would allow a great reduction in the amount of Bi-2223 tapes needed. Another effect of this method on the magnetization loss is also estimated by using the data observed for short tapes; one order reduction of loss can be expected.

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The authors have proposed Flexible, Reliable and Intelligent Electrical eNergy Delivery Systems, FRIENDS as one of the future electric power distribution system. The most important idea of FRIENDS is to install the new facilities called Quality Control Center (QCC) between distribution substation and customers. By controlling QCCs appropriately, various purposes of FRIENDS can be achieved.
It is indispensable to design the concrete interior structure of QCC in order to realize FRIENDS. This paper proposes the interior structure and control methods of QCC from the viewpoint of power conditioning functions by energy storage system in QCC. In this paper, It is assumed that SMES is used as the energy storage system in QCC. The proposed interior structure is based on the concept of UPS (Uninterruptible Power Supply). In this paper, SMES is installed in DC-side of UPS. Further, this paper also proposes the control methods of SMES and PWM converters. The proposed control methods are used to satisfy with various purposes, such as load fluctuation compensation, load leveling, cooperation with dispersed-type generator. Finally, the validity of these control methods are confirmed through transient analysis PSCAD/EMTDC.

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A High-Tc superconducting cable (HTS cable) is expected as an underground power line supplying the electrical power to the densely populated city in future. Therefore, compact HTS cables that can replace the old cables in their existing ducts have been developed. This paper reports our development state of important technologies for realizing the HTS cable, such as decrease of AC losses, electrical insulation and the electrical properties due to mechanical stresses. Moreover, a 20m HTS model cable was fabricated by Furukawa's funds to establish manufacturing process of a long HTS cable and to investigate effect of the various manufacturing, handling, operating loads that an actual conductor will experience on superconducting properties.

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As load characteristics have a significant effect on system performance such as transient stability and voltage stability, appropriate of load characteristics improves system operation properly. Because of the uncertainty of the actual load characteristics, many field tests have been conducted and the load model parameters have been calculated all over the world. However, recent load model parameters are not well known.
In this paper, the parameters of the load models (general load model for active power and proposed load model for reactive power) are calculated with non-linear least-square method. The field data are obtained with the automatic measuring devices triggered by frequency deviation from 1992 to 1999 in western Japan 60 Hz system and Okinawa system. Accordingly the load model parameters are correlated closely with the constitution of electric power apparatus.

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Insulation diagnosis is strongly required for the purpose of high reliability of GIS, GIL on power supply. For doing this, we need the high-sensitive detection technique regarding partial discharge (PD). Revealing the complicated frequency response of UHF sensor, we can know the existence of defects, their location and their lads in GIS. However, UHF sensor does not work as a simple capacitive divider in higher frequency range over a few hundred MH. This makes it very difficult to find the difference in output signal between PD and noise.
We have measured and analyzed the fundamental frequency responses of UHF sensors with various configurations. We clarified that the frequency response of UHF senor worked as acapacitive divider except standing waves, which depended on the existence of a handhole. As a result, we could explain that the capacitive divider and the standing waves caused the output waveform of UHF sensor, which consisted of peaks andthe following oscillatory wave in time domaiprespectively. These results enable us to control and improve the output of UHF sensor, and contribute to discriminate PD from noises.

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In order to calculate lightning surge analysis in power systems, appropriate models and parameters describing the components of systems should be required. Moreover, it is necessary to clarify how much those models would influence result of simulation. In other words, it is important to confirm how much probability of back flashover accidents would occur in changing grounding model or its input parameter. This paper will examine to compare some models for components in transmission tower and will show influence to the back flashover result, especially focusing on grounding impedance model.

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This paper describes the development works of a SF₆ reclaiming equipment with zeolite for gas separation from a mixture of low concentrations of SF6 in N₂, especially from a viewpoint of reducing the residual SF₆ in separated N₂, which is exhausted into the atmosphere. A prototype SF₆ gas separation and liquefaction equipment has been assembled selecting suitable types of zeolite. This equipment is about lm cube in size and 130kg in weight. The performance tests of the equipment have shown successful results. For example, the ability of the equipment to handle gas mixture is 13 lit. /min. in average and the SF, concentrations in separated N₂ are realized to be zero (undetectable level by gas chromatography) by introducing an auxiliary adsorption system which adsorbs SF₆ much more actively than N₂. The effective renewal process of this auxiliary adsorption system has also been investigated. The investigation indicates that 2700 lit. of 5% SF₆ mixture is treated by less than 10 kg zeolite and 400 lit. of 33% SF₆ mixture is collected. This corresponds to the SF₆ collecting rate of 97%. The rest 3% remains adsorbed by the zeolite.

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Simulation program is developed to calculate the opening characteristics on 3 phase fault current interruption for 3 phase common operating mechanism type puffer GCB. This program allows to calculate the 3 phase opening characteristics on no load, and on 3 phase current. interruption and on 1 phase current interruption in that. common mechanism type GCB driven by hydraulic, spring or other force source. It is confirmed that the calculated results well agree with the measured results. Some fundamental interruption performances such as for small capacitive current switching, for 3 phase 100% terminal fault current interruption and for short line fault current interruption are understood from the calculation results, then the dimension of interruption chamber and the driving energy can be suitably determined at the time when a GCB is designed. Using this simulation program, new 72/84kV and 145kV 3 phase GCB driven by 1 mechanism could be reasonably and rapidly developed.

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This paper discusses the harmonic distortion of 6% series reactor in distribution power system. The recursive DFT algorithm is used to analyze the instantaneous impedance characteristcs of the reactor by magnetic saturation.

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