S. Mukoyama

Furukawa Electric, Edo, Tōkyō, Japan

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Publications (52)50.62 Total impact

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    ABSTRACT: A 30-m-long 275-kV 3-kA high-temperature superconducting (HTS) cable had been developed in a national project of the Materials and Power Applications of Coated Conductors project in Japan. The design of the cable was based on the design values obtained from ac loss properties, thermal behavior under short-circuit tests, and electrical properties, such as partial discharge properties, impulse withstand properties, and dielectric properties. Through the development, the material of the cable insulation was determined and designed on the basis of its design stresses and test conditions based on the IEC, JEC (Japan electrical standards), and other HTS demonstrations. This cable was also designed to withstand a short-circuit test of 63 kA for 0.6 s and to have low losses of 0.8 W/m at 3 kA, 275 kV, including ac loss and dielectric loss. Based on these designs, a 50-m cable was manufactured and tested. The short samples obtained from 50 m were confirmed to have the designed characteristics. Furukawa Electric constructed a demonstration system of a 30-m cable with two terminations and a cable joint. The demonstration had started since November 2012 at Shenyang in China. In this demonstration, a 30-day long-term test was conducted and monitored at a current of 3 kA and at a test voltage selected to verify a 30-year operational lifetime. Removal tests revealed the superior reliability of the 275-kV HTS cable system.
    IEEE Transactions on Applied Superconductivity 06/2015; 25(3):1-5. DOI:10.1109/TASC.2014.2385960 · 1.32 Impact Factor
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    ABSTRACT: A 275 kV 3 kA high temperature superconducting cable (HTS cable), which could be used as a backbone power line in the future, was developed in the NEDO project called M-PACC. One of the most important developments of a high voltage HTS cable was the high voltage insulation technology. A design guideline and a test specification that was necessary to design, product and demonstrate of a 275 kV, 3 kA HTS cable have been studied by obtaining the various experimental data such as AC withstand voltage, impulse withstand voltage, partial discharge inception stress, and the V-t characteristics of the insulation, on the basis of the Japan Electrical Standards (JEC) and the International Electrotechnical Commission (IEC). Moreover, the 275 kV, 3 kA HTS cable with a length of 30 m was demonstrated under a long-term voltage and current loading test.
    Physics Procedia 12/2014; 58. DOI:10.1016/j.phpro.2014.09.077
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    ABSTRACT: A 275 kV 3 kA high temperature superconducting (HTS) cable has been developed in the Materials & Power Applications of Coated Conductors (M-PACC) project. The cable is expected to be put to practical use as the backbone power line in the future because the capacity of 1.5 GW is about the same as overhead transmission lines. The 30 m cable has been designed on the basis of design values that had been obtained by various voltage tests, AC loss measurement tests, short circuit tests, and other elementary tests. Cable insulation was determined by the design stresses and test conditions based on IEC, JEC (Japan electrical standards), and other HTS demonstrations. This cable was also designed to withstand the short circuit test of 63 kA for 0.6 seconds and to have low losses, including AC loss and dielectric loss of 0.8 W/m at 3kA, 275 kV. Based on the design, a 30 m cable was manufactured, and short samples during this manufacturing process were confirmed to have the designed characteristics.Furukawa Electric prepared a demonstration of the 30 m cable with two terminations and a cable joint. The long-term test under a current of 3 kA, and test voltage determined from 30 years of insulation degradation has been conducted since November 2012 at Shenyang in China.
    Physics Procedia 12/2013; 45:277–280. DOI:10.1016/j.phpro.2013.05.021
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    ABSTRACT: The REBCO high-temperature superconducting cable, rated at 275 kV and 3 kA, was developed in the Materials and Power Applications of Coated Conductors project in 2008. The cable is expected to be put to practical use as a backbone power line in the future because the transmission capacity is about the same as the UHV overhead transmission line. Transmission loss is significantly reduced by using superconducting wires instead of Cu or Al conductors. Furukawa Electric plans a demonstration of the 275 kV high-temperature superconducting cable. The cable system consists of a 30-m cable, terminations, a cable joint, and a cooling system. The 30-m cable has already been manufactured and installed on a test site. In this demonstration, various electrical evaluations will be conducted, such as a long-term test under a current of 3 kA, and the test voltage will be determined assuming 30 years of insulation degradation.
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3):5402804-5402804. DOI:10.1109/TASC.2013.2243374 · 1.32 Impact Factor
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    ABSTRACT: A Japanese national project called “Materials & Power Applications of Coated Conductors (M-PACC)” started in FY2008. In this project, we are developing a 66 kV/5 kA large-current high-temperature superconducting (HTS) cable and 275 kV/3 kA high-voltage HTS cable, using rare-earth barium copper oxide (REBCO) tapes. These HTS cables are expected to offer a compact cable with a large capacity and low power transmission loss. After the cable design has been studied and elemental technologies for each component of the cable system, such as ac loss reduction, protection against over-current, and high-voltage electrical insulation have been developed, two cable systems will be constructed and verified to meet the required specifications in FY2012. This paper describes the progress and status of these HTS cable developments in the M-PACC project.
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3):5401405-5401405. DOI:10.1109/TASC.2012.2235497 · 1.32 Impact Factor
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    ABSTRACT: A Japanese national project, called "Materials & Power applications of Coated Conductors (M-PACC)", started in FY2008. In this project, we are developing 66 kV/5 kA large current high temperature superconducting (HTS) cable and 275 kV/3 kA high voltage HTS cable using REBCO tapes. These HTS cables are expected as a compact size with large capacity and low loss power transmission. We have examined AC loss, thermal characteristics of the cables under over-current, the optimum cable design and so on. After the design studies and elemental tests are completed, long cable systems will be built for verification purposes. This paper described the overview and current status of these HTS cables development in the M-PACC project. (PACS: 84.71.Fk) (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
    Physics Procedia 12/2012; 36:1153-1158. DOI:10.1016/j.phpro.2012.06.193
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    ABSTRACT: A 275kV–3kA high temperature superconducting (HTS) cable has been developed in the Materials & Power Applications of Coated Conductors (M-PACC) project.AC loss reduction of a two-layer HTS conductor was undertaken by removing the edges of YBCO tapes with low critical current density. The HTS conductor using these tapes was fabricated, and low loss of 0.235W/m at 3kArms was achieved.The 275kV–3kA cable was designed, and the 2m model cables were fabricated. This cable had 325mm2 copper stranded former inside the HTS conductor and a 310mm2 copper shield layer on the HTS shield layer for over-current protection. These cables withstood an over-current of 63.0kA for 0.6s, which is the worst situation for 275kV systems.The partial discharge (PD) and V–t characteristics of a liquid nitrogen (LN2)/polypropylene (PP) laminated paper composite insulation system have been integrated into the design of the insulation for the 275kV cable. The results revealed that the PD inception stress (PDIE) did not depend on the insulation thickness, and that lifetime indices of V–t characteristics at PD inception were as high as about 80–100.
    Physica C Superconductivity 11/2011; 471(21):1274-1278. DOI:10.1016/j.physc.2011.05.177 · 1.11 Impact Factor
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    ABSTRACT: The effects of removing low- J <sub>c</sub> edges of coated conductors by a laser for ac loss reduction were studied in two-layer superconducting power transmission cables. By removing the low- J <sub>c</sub> edges, narrower coated conductor with more uniform J <sub>c</sub> distribution can be obtained. The original 5 mm-wide coated conductors as well as the edge-removed 4 mm-wide and 3 mm-wide coated conductors were assembled spirally around cyrindrical formers in two layers to form a cable. The measured ac losses were compared with the ac losses calculated using a numerical model where the spiral structure is neglected. For ac loss calculations, we used the lateral J <sub>c</sub> distribution of the coated conductor measured by the magnetic knife method or those which are assumed based on the losses of the critical current by the edge removal.
    IEEE Transactions on Applied Superconductivity 07/2011; 21(3-21):943 - 946. DOI:10.1109/TASC.2010.2096375 · 1.32 Impact Factor
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    ABSTRACT: High-temperature superconducting (HTS) cables are considered the next generation transmission line because they are compact, lightweight, and demonstrate large capacity and low loss compared to conventional cables. In particular, since a coated conductor (YBCO wire) provides high critical current, high magnetic-field property, low AC loss, and low cost, it is expected to make the HTS cable more attractive than other superconducting wire. In Japan, 66/77 kV HTS cables have developed for about 20 years. We started developing 275 kV class HTS cables three years ago based on 66/77 kV HTS cables. The goal is a 275 kV 3 kA cable with a capacity of 1.5 GVA, the same capacity as a typical overhead transmission line, which serves as the backbone of Japanese power networks. The following technical developments will be carried out: high current and low AC loss cable conductors and high voltage insulation and low dielectric loss cables. Regarding high current and low AC loss cable conductors, 3-kA cables have been fabricated, and AC losses have been measured. We found that using thin YBCO wire reduced AC losses in experiments.
    IEEE Transactions on Applied Superconductivity 07/2011; 21(3-21):976 - 979. DOI:10.1109/TASC.2011.2117411 · 1.32 Impact Factor
  • S. Mukoyama · M. Yagi · N. Fujiwara · H. Ichikawa
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    ABSTRACT: High-temperature superconducting (HTS) cables are expected to be next generation transmission line because of the compact, lightweight, large capacity, and low loss features. Especially, since the YBa2Cu3Ox (YBCO) tape has a high critical current, high magnetic-field property, low AC loss, and low cost, using YBCO tapes for a HTS cable seems to be one of the most promising ways to make the HTS cable attractive. Therefore, YBCO HTS cables have been studied extensively in Japan, the United States, Korea, and many other countries.We now believe that 275 kV class HTS cables will be used for future large capacity lines based on the needs of Japanese transmission networks for bulk transmission power in overhead transmission lines or gas insulated transmission lines (GIL). We started to develop the 275 kV class HTS cable for the new energy and industrial technology development organization (NEDO) project at 2008, and we have studied the applicability and the environmental and economic advantages of the 275 kV cable. This paper will introduce advantages and a conceptual design of the 275 kV HTS cable.
    Physica C Superconductivity 11/2010; 470(20):1563-1566. DOI:10.1016/j.physc.2010.05.162 · 1.11 Impact Factor
  • H. Kono · X. Wang · H. Ueda · A. Ishiyama · T. Saitoh · Y. Aoki · M. Yagi · S. Mukoyama · N. Fujiwara
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    ABSTRACT: In high temperature superconductor applications used in electric power devices, YBCO coated conductors may be subjected to short-circuit fault-currents that are 10–30 times the normal operating current. These over-currents cause heat generation, resulting in Ic degradation of the YBCO coated conductor. Therefore, it is necessary to fully investigate the degradation characteristics of YBCO coated conductors. We previously conducted preliminary experiments on the degradation of YBCO sample tapes resulting from the over-current pulse drive.In this study, we analyzed the waveform of fault-current that is supposed to flow into the YBCO coated conductor when a short-circuit fault occurs in a power cable application, by using a newly developed numerical simulation program. We also carried out experiments in which an over-current with the analyzed fault-current waveform was applied to two YBCO sample tapes. We then investigated the degradation characteristics, focusing on the amount of current permitted. Experimental results showed that both the sample tapes (initial Ic = 118.6 A and 123.2 A) were degraded by applying an over-current with a peak value of 320 A.
    Physica C Superconductivity 11/2010; 470(20):1334-1337. DOI:10.1016/j.physc.2010.05.106 · 1.11 Impact Factor
  • S. Sato · X. Wang · H. Ueda · A. Ishiyama · M. Yagi · S. Mukoyama · T. Saitoh · Y. Aoki · N. Fujiwara
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    ABSTRACT: In Japan, the development of a 275kV class YBCO power cable was started in 2008 with the support of the New Energy and Industrial Technology Development Organization (NEDO). In the designing of 275kV YBCO power cable, the thickness of insulator is required to be 26mm. Thus, in order to design the 275kV YBCO power cable, it is important to estimate the thermal diffusion through the electrical insulation layer for designing the high-voltage YBCO power cable. Furthermore, YBCO power cables might be subjected to short-circuit fault currents that are 10–30 times a normal operating current. Therefore, in order to ensure stability and feasibility of superconducting power cables, we need to investigate the thermal characteristics and current distribution in the cable in the normal and fault conditions. The objective of this study is to investigate the thermal characteristics and dielectric performance in 275kV class power cables. We carried out experiments on dummy cables in a steady state to clarify the distribution of temperature. In order to estimate the thermal conductivity and the heat capacity of the insulation layer, we performed numerical simulations using a developed computer program on the basis of the 3D finite element method. We also measured a tanδ and permittivity of an insulation layer in order to investigate the dielectrical performance.
    Physica C Superconductivity 11/2010; 470(20):1572-1575. DOI:10.1016/j.physc.2010.05.164 · 1.11 Impact Factor
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    ABSTRACT: To achieve large current capacity and high mechanical flexibility, YBa2Cu3O7 (YBCO) superconducting cables consist of a number of YBCO coated conductors that are assembled and wound spirally on a Cu former. In practical applications, superconducting cables are vulnerable to short-circuit fault currents that are 10–30 times greater than the operating current. Therefore, in order to ensure the stability of YBCO superconducting cables in such a situation and to protect them from the fault currents, it is important to investigate the redistribution of the transport current and electromagnetic coupling between the conductor layer, shield layer, and Cu former. In this study, we carried out experiments on a 10-m-long YBCO model cable, which was manufactured by Furukawa Electric. An over-current with a peak of 31.8 kArms and a duration of 2.02 s was applied to the model cable. We performed numerical simulations using a novel computer program developed using the 3D finite element method to elucidate the electromagnetic and thermal behavior of the YBCO model cable in the presence of an over-current.
    Physica C Superconductivity 10/2009; 469(15):1717-1721. DOI:10.1016/j.physc.2009.05.034 · 1.11 Impact Factor
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    ABSTRACT: We fabricated 1mhigh temperature superconducting conductor (HTS conductor) using YBa2Cu3O7−x coated conductors (YBCO tapes) on textured metal substrates, which are expected to be lower in cost than YBCO tapes using ion-beam assisted deposition. Those substrate and intermediate layers were manufactured by Furukawa Electric, and YBCO and a protective layer were applied to the intermediate layer by Chubu Electric Power. Before fabricating the conductor, a 0.1mm thick copper tape was soldered to the YBCO tape, and 10mm wide YBCO tape was divided into three strips by a YAG laser. To have sufficient current capacity for 1kA, a two-layer conductor was fabricated, and its critical current (Ic) was 1976 A, but the magnetic properties of the textured metal substrates affected the increase in AC loss. In a low current region, the AC loss in this conductor was much higher than the Norris strip model, but approached the Norris strip model in the high current region because the magnetization was almost saturated. Low AC loss of 0.144W/m at 1kArms was achieved even though the conductor had a small outer diameter of 20mm and was composed of YBCO tapes with magnetic substrates.
    Physica C Superconductivity 10/2009; 469(15):1693-1696. DOI:10.1016/j.physc.2009.05.045 · 1.11 Impact Factor
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    ABSTRACT: High-temperature superconducting (HTS) power cables transmit bulk power with lower loss than conventional cables. Moreover, HTS cables are expected to be constructed as a new underground cable in urban areas at lower cost compared to a high voltage XLPE cable. To put promising HTS cables to practical use, we need (RE)BCO tapes with long length, high critical current, and low cost. Recently many organizations have improved the performance of the (RE)BCO tapes, such as YBCO tapes, or other coated conductor tapes that are made with a variety of different processes. We have fabricated the conductors for the HTS power cable that was constructed of different kinds of (RE)BCO tapes and measured the Ic and AC losses. We achieved significantly low AC loss of 0.1W/m at 1kA in the HTS conductor using narrow slit tapes that were cut by laser. Moreover, a 20m long HTS power cable model and a cable intermediate joint were developed. Short circuit current tests were conducted on the cable system that consisted of two 10m cables, a cable joint, and two terminations. The cables and the joint withstood the short circuit current of 31.5kA for 2s without damage.
    Physica C Superconductivity 10/2009; 469(15):1688-1692. DOI:10.1016/j.physc.2009.05.251 · 1.11 Impact Factor
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    ABSTRACT: YBCO tapes are expected to be used in future high temperature superconducting (HTS) applications because of their good J <sub>c</sub> characteristics at high temperatures and in high applied magnetic fields. In applications to electric power devices such as transmission cables, transformers, and fault current limiters, the HTS conductors will be subjected to short-circuit fault currents that are 10 to 30 times the normal operating current. These overcurrents are greater than the critical current, and degrade or burn-out the HTS conductors. Therefore, it is important to clarify the mechanism of the degradation caused by such overcurrent pulses. We carried out preliminary experiments on damage caused by overcurrent pulse drive, focusing on the temperature limitation without suffering degradation for overcurrent pulse operation. A 10-mm-wide YBCO tape was cut into 2-mm-wide sample tapes by a laser beam, and the sample tapes were soldered on silver-deposited 100-mum-thick copper plates. Overcurrent tests were carried out on these sample tapes and I<sub>c</sub> degradation was investigated. In addition the contact interface between YBCO and the Ag layer or buffer layer before and after the overcurrent drives has been investigated in order to clarify the correlation between the degradation and delamination of sample tapes.
    IEEE Transactions on Applied Superconductivity 07/2009; 19(3-19):3483 - 3486. DOI:10.1109/TASC.2009.2018734 · 1.32 Impact Factor
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    ABSTRACT: To achieve large current capacity and mechanical flexibility, high-temperature superconductor (HTS) power transmission cables consist of a number of YBCO coated conductors, which are assembled and wound spirally on a Cu former. In practical applications, superconducting cables might be subjected to short-circuit fault currents that are 10 to 30 times the operating current. Therefore, in order to ensure the stability and feasibility of HTS power cables and protect them from fault currents, it is important to estimate the redistribution of the transport current and electromagnetic coupling among the conductor layer, shield layer, and Cu former. In this study, we carried out experiments on a 20-m-long YBCO model cable, which was composed of two jointed 10-m-long YBCO model cables. Over-current with a peak of 31.8 kA<sub>rms</sub> and a duration of 2.02 s was applied to the model cable. We performed numerical simulations using a newly developed computer program based on the 3D finite element method (FEM) in order to clarify the electromagnetic and thermal behaviors of the YBCO model cable in the presence of an over-current.
    IEEE Transactions on Applied Superconductivity 07/2009; 19(3-19):1722 - 1726. DOI:10.1109/TASC.2009.2018316 · 1.32 Impact Factor
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    ABSTRACT: We have developed high-Tc superconducting (HTS) cables using YBCO tapes. A 10 mm-wide YBCO tape was divided into five strips using a YAG laser to reduce AC loss. A 0.3 m conductor and a 1 m conductor were fabricated achieving AC losses at 1 kArms and 50 Hz of 0.054 W m−1 and of 0.048 W m−1, respectively. Based on the successful AC loss reduction in the 0.3 and 1 m conductors, we fabricated a 10 m HTS cable with a three-layer HTS conductor, electrical insulation, and a one-layer HTS shield. The AC loss in this 10 m HTS conductor was 0.090 W m−1 at 1 kArms and 50 Hz. An HTS cable joint was designed and fabricated that included a three-layer HTS conductor and a one-layer HTS shield. Joint resistance of 5.2 nΩ for the HTS conductor and that of 10 nΩ for the HTS shield were achieved. The HTS cable joint was compact and had sufficient withstand voltage properties for 66/77 kV. In addition, we also confirmed the efficiency of joint construction. Moreover, a 20 m long HTS cable was successfully constructed and tested in January 2008. This HTS cable consisted of two 10 m HTS cables and the HTS cable joint. One 10 m HTS cable using HoBCO was made by Sumitomo, and the HTS cable joint and the other 10 m cable using IBAD YBCO were made by Furukawa and Chubu. The electrical resistance of the HTS cable joint was less than 10 nΩ, and the 20 m HTS cable including the joint withstood an over-current of 31.5 kArms whose duration was 2 s.
    Superconductor Science and Technology 06/2009; 22(8):085003. DOI:10.1088/0953-2048/22/8/085003 · 2.80 Impact Factor
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    ABSTRACT: Each superconducting coil manufacturing process using YBCO tape coated conductor was evaluated, and double pancake type copper stabilized coils were verified, in order to develop base technologies of a YBCO coil for power applications. Cost of YBCO tape including a stabilization process needs to be low in order for it to be a practical use wire for power application coils. Conduction cooling is also needed below the 50K temperature range, which is optimal for high magnetic field coils using YBCO tape. Therefore, we developed technology for each process for manufacturing of a conduction cooling type coil. Techniques for winding, stabilization, electrode formation, and impregnation were developed, considering YBCO tape configuration and a conduction cooling method. Several wire coils were then manufactured and verified using a conduction cooling system, and the high performances of thermal stability, low electrical joint resistance, etc. were achieved without degradation.
    IEEJ Transactions on Power and Energy 01/2009; 129:1326-1332. DOI:10.1541/ieejpes.129.1326
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    ABSTRACT: For the application to power transmission cables, a number of YBCO tapes would be assembled and wound in spiral on a Cu-former. YBCO tapes and the Cu-former are connected in parallel and they might be subjected to short-circuit fault currents 10–30 times the operating current. In this study, we constructed a 1 m long YBCO model cable. Over-current with a peak of 31.5 kArms and a duration of 2.0 s, which was established by JEC (Japanese Electrotechnical Committee), was applied to this cable in a liquid nitrogen bath. The redistribution of the transport current between YBCO tapes and the Cu-former were examined by using Hall sensors. The numerical simulations were carried out using a newly developed computer program based on the 3D finite element method (FEM) in order to clarify the over-current characteristics in the cable. From the comparison of the experimental and simulation results, the validity of the developed computer program was confirmed. Therefore, we performed the simulations of a 10 m long model cable when carrying a fault current of 31.5 kArms applied for a durations of 2.0 s, and also estimated the influence of the cross-section area of the Cu-former and the Cu shield layer on the thermal behavior of the model cable by using the developed computer program.
    Physica C Superconductivity 09/2008; DOI:10.1016/j.physc.2008.05.276 · 1.11 Impact Factor