- Email: [email protected]
Development of YBCO HTS cable with low AC loss
Physica C 468 (2008) 2037–2040
Contents lists available at ScienceDirect
Physica C journal homepage: www.elsevier.com/locate/physc
Development of YBCO HTS cable with low AC loss M. Yagi a,*, S. Mukoyama a, N. Amemiya b, S. Nagaya c, N. Kashima c, Y. Shiohara d a
Energy Transmission Research Department Ecology and Energy Laboratory, The Furukawa Electric Co., Ltd., 6, Yawata-Kaigandori, Ichihara, Chiba 290-8555, Japan Yokohama National University, 79-5, Tokiwadai, Hodogaya, Yokohama 240-8501, Japan Chubu Electric Power Co., Inc., 20-1, Kitasekiyama, Ohdaka-cho, Midori-ku, Nagoya 459-8522, Japan d Superconductivity Research Laboratory, 1-10-13, Shinonome, Koto-ku, Tokyo 135-0062, Japan b c
a r t i c l e
i n f o
Article history: Available online 6 June 2008 PACS: 84.70.+p 84.71.Fk Keywords: High-Tc superconducting (HTS) cable HTS conductor AC loss Overcurrent HTS joint YBCO
a b s t r a c t High temperature superconducting (HTS) cables using YBCO tapes are expected to be more economical because AC losses will be much smaller than conventional cables. To reduce AC loss, 10 mm wide YBCO tapes were divided into five strips using a YAG laser. Using narrower strips and optimizing the space between the strips were effective in reducing AC loss. A 1 m conductor was fabricated, and AC loss was 0.048 W/m at 1 kA and 50 Hz. Based on the successful AC loss reduction in the 1 m conductor, we will fabricate a 10 m HTS cable with a three-layer HTS conductor, electrical insulation, and a one-layer HTS shield and cupper protection layer for overcurrent. In addition, we have developed a prototype of the HTS cable joint that can withstand an overcurrent condition of 31.5 kA for 2 s. Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
2. Development of conductor with low AC loss
A high temperature superconducting (HTS) cable using YBCO tapes has been developed for the increasing demand of electricity in the near future [1,2]. YBCO tapes have higher Jc characteristics and fewer costly components, such as silver, than BSCCO tapes. Therefore, we can expect the YBCO HTS cable to demonstrate lower AC loss and to be more economical than conventional cable and BSCCO cable [3]. However, the manufacturing process for YBCO tapes is more complicated, and development was delayed. Recently, there has been great progress in the manufacture of YBCO tapes, and an HTS cable using these tapes is in an advanced stage of development. In this paper, we fabricated a 1 m YBCO conductor, where Cu tape was soldered to YBCO tapes for overcurrent protection, and the YBCO tapes were divided by the laser to reduce their AC loss. The AC loss in this conductor was measured and low AC loss was confirmed. Twenty-meter YBCO cable and cable joints will be demonstrated in January 2008. The layout of the demonstration, joint design, and specifications of the cable will be reported.
2.1. Specification of 1 m YBCO conductor
* Corresponding author. Tel.: +81 436 42 1716; fax: +81 436 42 9359. E-mail address: [email protected] (M. Yagi). 0921-4534/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2008.05.250
The YBCO superconducting tapes were fabricated by multistage CVD at Chubu electric power company [4]. The width of the tape was 10 mm, and the thickness of each layer of Hastelloy, IBAD-Gd2Zr2O7, PLD-CeO2, CVD-YBCO, and Ag were 100 lm, 1.0 lm, 0.4 lm, 0.7 lm, and 20 lm, respectively. The critical current (Ic) was about 110 A. A copper tape with a thickness of 0.1 mm and a width of 10 mm was soldered to the Ag layer of the YBCO tapes for protection of overcurrent accidents. There was no degradation of the Ic during this procedure. The YBCO tapes with copper were divided into five strips by a YAG laser. The specifications for the 1 m YBCO conductor are listed in Table 1. In the table, the 1 m YBCO conductor had a 200 mm2 stranded copper former with a diameter of 18.0 mm and two HTS layers. Each HTS layer had 30 strips with a width of 2 mm. Those strips were wound spirally on the copper former, and the spaces between each strip were very small to reduce AC loss. The AC loss due to the magnetic field component parallel to the wide face of YBCO tapes (parallel magnetic field component) is much smaller than that due to the finite magnetic field component perpendicular to the wide face of YBCO tapes (perpendicular magnetic field component). Therefore, the reduction in the perpendicular magnetic field
2038
M. Yagi et al. / Physica C 468 (2008) 2037–2040
component is a key to AC loss reduction. Fabricating the HTS conductor using a large number of narrow strips and a decrease in the space between strips approaches the structure of the HTS cylinder which does not have the perpendicular magnetic field [5]. To obtain narrow strips, original YBCO tapes having 10 mm wide were divided by a YAG laser. But the Ic of these strips was decreased because the YBCO area was lost during the laser processing. The five strips were obtained by the laser processing four times. In this case, the Ic degradation through the laser processing from the original to the five strips was about 10%. 2.2. Experimental setup The 1 m YBCO conductor had 1130 A of Ic at 77.3 K and did not have the capacity of 1 kA rms. To have sufficient capacity at 1 kA rms, this conductor was installed in the cryostat shown in Fig. 1. Liquid nitrogen in this cryostat was cooled by reducing the pressure. The temperature was controlled by regulating the valve between the cryostat and the vacuum pump. And, this cryostat had the insulation break at the both of the outer and inner cryostat pipe that prevented an induced current from occurring between the current lead and cryostat pipes. 2.3. Measurement of Ic and AC loss Fig. 2 shows the V–I characteristics of the 1 m conductor. The Ic (and n-value) at each temperature, 77.3 K, 70.0 K, 67.5 K, and 66.0 K were 1130 A (11.4), 1875 A (11.3), 2177 A (10.3), and 2365 A (10.9), respectively. N-values of each temperature are the almost same, and V–I characteristics are in agreement when normalized by Ic as shown in the inset of Fig. 2. The changing rate of Ic in the YBCO conductor is greater than that of BSCCO because the critical temperature of YBCO is 90 K, which is closer to the LN2 temperature than BSCCO (110 K). Fig. 3 shows the measurement of AC loss. In this figure, the AC loss of 1 kA and 50 Hz at each temperature, 70 K, 67.5 K, and 66.0 K are 0.15 W/m (It/Ic, which is the peak current divided by Ic, is 0.78), 0.067 W/m (It/Ic = 0.65) and 0.048 W/m (It/Ic = 0.60), respectively.
Table 1 Specification of 1 m YBCO conductor Former Length YBCO tape Tape width/strips/layer/ outer diameter
Cu stranded 200 mm2 1m IBAD-MOCVD five strips from 10 mm-width original (Ic = 110 A) 0.1 mm-thick Cu tape soldered on YBCO 2 mm/60 strips/2 layer/u20.0 mm
In Fig. 4, the AC loss normalized by Ic is almost in agreement at each temperature, and there is no dependence on the LN2 temperature. Therefore, we can simply regard the cooling HTS conductor as the increasing Ic of a YBCO conductor and YBCO tapes. In Fig. 4, when It/Ic is over 0.6, the normalized AC loss becomes larger than the Norris strip model [6]. It indicated that some YBCO strips were degraded, but it was uncertain whether it was done by the laser processing or non-uniformity of Ic along the width of the YBCO. During the laser processing, the concentration or deconcentration of the laser energy occurs due to fluctuations of the laser focus or of the process speed. To reduce AC loss, it is also important to use YBCO strips that have the same Ic, and the YBCO tapes need to maintain the uniformity of Ic along the width. 3. Design of HTS cable joint and overcurrent test Fig. 5 shows the HTS cable joint, which has a compact design for use in the conventional vault. The diameter of the HTS joint is the same as that of the HTS conductor. The prototype joint was fabricated using two YBCO HTS cables, which had a length of 1.5 m, 200 mm2 Cu stranded former, and three YBCO strips, which were 3.33 mm in width and spirally wound, with an insulation layer 6.5 mm-thick. Each Cu former was cut and shaped into a single V groove, which was cut at an oblique angle, connected, and then welded. As shown in Fig. 6a, HTS1 with Cu tape with a length of 1.5 m and a width of 3.33 mm are butted up against HTS2 with Cu. Using HTS3 with Cu, the Cu side of the HTS3 was placed on the Cu side of the HTS1 and HTS2 and soldered. Next, electrical insulation for the HTS conductor joint and cryostat pipes was constructed. The HTS joint resistance, which is defined as the slope in the V–I characteristics when the HTS conductor keeps superconductivity, was 0.3 lX, shown in Fig. 6b where the generated voltage was 18 lV at 60 A. Although there is still plenty of room for improvements, such as an optimal joint length and solder thickness and work efficiency, the joint resistance of 0.3 lX was an acceptable level. This joint was cooled by 73 K, and an overcurrent of 31.5 kA for 2 s was applied. According to the specifications of electrical instruments installed in the 66/77 kV line in Japan, they must endure an overcurrent of 31.5 kA for 2 s. The generated voltage was set as a voltage tap on the HTS1 and HTS2 and increased to 7.50 104 lV peak/cm; however, a rising trend was not observed when an overcurrent of 31.5 kA for 2 s was applied. In addition, the temperature rising which was measured by Pt thermometers on the HTS conductor was 68 K and the recovery time required about 50 min. The degradation of Ic in the HTS was not observed after the overcurrent.
Fig. 1. Experimental setup.
M. Yagi et al. / Physica C 468 (2008) 2037–2040
2039
Fig. 2. V–I characteristics of the 1 m YBCO conductor. The inset shows the V–I characteristics normalized by Ic.
Fig. 6. (a) Schematic view of the HTS joint and (b) V–I characteristics of the HTS joint that was the jointing of three YBCO strips with a width of 3.33 mm.
4. Demonstration of 20 m YBCO HTS cable
Fig. 3. Measurement of AC loss (50 Hz) in the 1 m HTS conductor.
Fig. 7a shows the schematic view of a 20 m YBCO HTS cable, including two types of 10 m HTS cables and a joint. One 10 m HTS cable using RABiTS-type YBCO will be made by Sumitomo electric, and the joint and the other 10 m cable using IBAD-type YBCO will be made by Furukawa electric. The specifications for the IBAD-type 10 m cable are listed in Table 2. The YBCO HTS cables have 200 mm2 Cu stranded former and a three-HTS-conductor layer for a demand of high capacity current, such as more than 3 kA. In this demonstration, the capacity of the HTS conductor will be 1 kA class because we will use 100 A/cm-width YBCO tapes. And these cables have electrical insulation with a thickness of 6.5 mm
Fig. 4. Normalized AC Loss in the 1 m HTS.
Fig. 5. Design of the HTS cable joint.
Fig. 7. (a) Schematic view of 20 m YBCO HTS cable and (b) structure of YBCO HTS cable.
2040
M. Yagi et al. / Physica C 468 (2008) 2037–2040
Table 2 Specification of 10 m IBAD-type YBCO HTS cable Former Length YBCO tape
HTS conductor tape width/ strips/layer/outer diameter Inner semi-conductor Electrical insulation Outer semi-conductor HTS Shield Protection layer
Cu stranded 200 mm2 10 m IBAD-MOCVD five strips from 10 mm-width original (Ic = 100 A) 0.1 mm-thick Cu tape soldered on YBCO 2 mm/82 strips/3 layer/u21.0 mm Carbon paper 2 layer Semi-synthetic paper 6.5 mm-thick Carbon paper 2 layer 2 mm/50 strips/1 layer/u36.0 mm Cu tape (0.1 mm-thick) 8 layer non-woven cloth
for 66/77 kV [7] and one-HTS shield layer and eight-protection layer using Cu tape with a thickness of 0.1 mm, shown in Fig. 7b. The 20 m HTS cable including the joint will be demonstrated in January 2008. 5. Conclusion A 1 m YBCO conductor was fabricated and cooled by reducing the pressure of LN2 to evaluate AC loss (50 Hz). This conductor had Ic of 2365 A and AC loss of 0.048 W/m at 1 kA rms. A prototype of HTS cable joint was constructed and withstood an overcurrent condition of 31.5 kA for 2 s. Two types of 10 m YBCO cable and a joint will be made and tested in January 2008.
Acknowledgements This study was carried out as Collaborative Research and Development of Fundamental Technologies for Superconductive Application of the Ministry of Economy, Trade and Industry (METI) and was cosigned by the New Energy and Industrial Technology Development Organization (NEDO). All YBCO tapes were supplied by Chubu Electric Power Company, which developed and manufactured them in the project. We wish to express our gratitude to all parties concerned. References [1] M. Yagi, S. Mukoyama, H. Hirano, N. Amemiya, A. Ishiyama, S. Nagaya, N. Kashima, Y. Shiohara, Physica C 463–465 (2007) 1154. [2] S. Mukoyama, M. Yagi, H. Hirano, Y. Yamada, T. Izumi, Y. Shiohara, Physica C 445–448 (2006) 1050. [3] S. Mukoyama, M. Yagi, N. Hirano, N. Amemiya, N. Kashima, S. Nagaya, T. Izumi, Y. Shiohara, Physica C 463–465 (2007) 1150. [4] N. Kashima, T. Niwa, M. Mori, S. Nagaya, T. Muroga, S. Miyata, T. Watanabe, Y. Yamada, T. Izumi, Y. Shiohara, IEEE Trans. Appl. Supercond. 15 (2005) 2763. [5] N. Amemiya, Z. Jiang, M. Nakahata, M. Yagi, S. Mukoyama, N. Kashima, S. Nagaya, Y. Shiohara, IEEE Trans. Appl. Supercond. 17 (2007) 1712. [6] W.T. Norris, J. Phys. D 3 (1970) 489. [7] T. Takahashi, H. Suzuki, M. Ichikawa, T. Okamoto, S. Akita, S. Maruyama, A. Kimura, IEEE Trans. Appl. Supercond. 15 (2005) 767.
Contents lists available at ScienceDirect
Physica C journal homepage: www.elsevier.com/locate/physc
Development of YBCO HTS cable with low AC loss M. Yagi a,*, S. Mukoyama a, N. Amemiya b, S. Nagaya c, N. Kashima c, Y. Shiohara d a
Energy Transmission Research Department Ecology and Energy Laboratory, The Furukawa Electric Co., Ltd., 6, Yawata-Kaigandori, Ichihara, Chiba 290-8555, Japan Yokohama National University, 79-5, Tokiwadai, Hodogaya, Yokohama 240-8501, Japan Chubu Electric Power Co., Inc., 20-1, Kitasekiyama, Ohdaka-cho, Midori-ku, Nagoya 459-8522, Japan d Superconductivity Research Laboratory, 1-10-13, Shinonome, Koto-ku, Tokyo 135-0062, Japan b c
a r t i c l e
i n f o
Article history: Available online 6 June 2008 PACS: 84.70.+p 84.71.Fk Keywords: High-Tc superconducting (HTS) cable HTS conductor AC loss Overcurrent HTS joint YBCO
a b s t r a c t High temperature superconducting (HTS) cables using YBCO tapes are expected to be more economical because AC losses will be much smaller than conventional cables. To reduce AC loss, 10 mm wide YBCO tapes were divided into five strips using a YAG laser. Using narrower strips and optimizing the space between the strips were effective in reducing AC loss. A 1 m conductor was fabricated, and AC loss was 0.048 W/m at 1 kA and 50 Hz. Based on the successful AC loss reduction in the 1 m conductor, we will fabricate a 10 m HTS cable with a three-layer HTS conductor, electrical insulation, and a one-layer HTS shield and cupper protection layer for overcurrent. In addition, we have developed a prototype of the HTS cable joint that can withstand an overcurrent condition of 31.5 kA for 2 s. Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
2. Development of conductor with low AC loss
A high temperature superconducting (HTS) cable using YBCO tapes has been developed for the increasing demand of electricity in the near future [1,2]. YBCO tapes have higher Jc characteristics and fewer costly components, such as silver, than BSCCO tapes. Therefore, we can expect the YBCO HTS cable to demonstrate lower AC loss and to be more economical than conventional cable and BSCCO cable [3]. However, the manufacturing process for YBCO tapes is more complicated, and development was delayed. Recently, there has been great progress in the manufacture of YBCO tapes, and an HTS cable using these tapes is in an advanced stage of development. In this paper, we fabricated a 1 m YBCO conductor, where Cu tape was soldered to YBCO tapes for overcurrent protection, and the YBCO tapes were divided by the laser to reduce their AC loss. The AC loss in this conductor was measured and low AC loss was confirmed. Twenty-meter YBCO cable and cable joints will be demonstrated in January 2008. The layout of the demonstration, joint design, and specifications of the cable will be reported.
2.1. Specification of 1 m YBCO conductor
* Corresponding author. Tel.: +81 436 42 1716; fax: +81 436 42 9359. E-mail address: [email protected] (M. Yagi). 0921-4534/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2008.05.250
The YBCO superconducting tapes were fabricated by multistage CVD at Chubu electric power company [4]. The width of the tape was 10 mm, and the thickness of each layer of Hastelloy, IBAD-Gd2Zr2O7, PLD-CeO2, CVD-YBCO, and Ag were 100 lm, 1.0 lm, 0.4 lm, 0.7 lm, and 20 lm, respectively. The critical current (Ic) was about 110 A. A copper tape with a thickness of 0.1 mm and a width of 10 mm was soldered to the Ag layer of the YBCO tapes for protection of overcurrent accidents. There was no degradation of the Ic during this procedure. The YBCO tapes with copper were divided into five strips by a YAG laser. The specifications for the 1 m YBCO conductor are listed in Table 1. In the table, the 1 m YBCO conductor had a 200 mm2 stranded copper former with a diameter of 18.0 mm and two HTS layers. Each HTS layer had 30 strips with a width of 2 mm. Those strips were wound spirally on the copper former, and the spaces between each strip were very small to reduce AC loss. The AC loss due to the magnetic field component parallel to the wide face of YBCO tapes (parallel magnetic field component) is much smaller than that due to the finite magnetic field component perpendicular to the wide face of YBCO tapes (perpendicular magnetic field component). Therefore, the reduction in the perpendicular magnetic field
2038
M. Yagi et al. / Physica C 468 (2008) 2037–2040
component is a key to AC loss reduction. Fabricating the HTS conductor using a large number of narrow strips and a decrease in the space between strips approaches the structure of the HTS cylinder which does not have the perpendicular magnetic field [5]. To obtain narrow strips, original YBCO tapes having 10 mm wide were divided by a YAG laser. But the Ic of these strips was decreased because the YBCO area was lost during the laser processing. The five strips were obtained by the laser processing four times. In this case, the Ic degradation through the laser processing from the original to the five strips was about 10%. 2.2. Experimental setup The 1 m YBCO conductor had 1130 A of Ic at 77.3 K and did not have the capacity of 1 kA rms. To have sufficient capacity at 1 kA rms, this conductor was installed in the cryostat shown in Fig. 1. Liquid nitrogen in this cryostat was cooled by reducing the pressure. The temperature was controlled by regulating the valve between the cryostat and the vacuum pump. And, this cryostat had the insulation break at the both of the outer and inner cryostat pipe that prevented an induced current from occurring between the current lead and cryostat pipes. 2.3. Measurement of Ic and AC loss Fig. 2 shows the V–I characteristics of the 1 m conductor. The Ic (and n-value) at each temperature, 77.3 K, 70.0 K, 67.5 K, and 66.0 K were 1130 A (11.4), 1875 A (11.3), 2177 A (10.3), and 2365 A (10.9), respectively. N-values of each temperature are the almost same, and V–I characteristics are in agreement when normalized by Ic as shown in the inset of Fig. 2. The changing rate of Ic in the YBCO conductor is greater than that of BSCCO because the critical temperature of YBCO is 90 K, which is closer to the LN2 temperature than BSCCO (110 K). Fig. 3 shows the measurement of AC loss. In this figure, the AC loss of 1 kA and 50 Hz at each temperature, 70 K, 67.5 K, and 66.0 K are 0.15 W/m (It/Ic, which is the peak current divided by Ic, is 0.78), 0.067 W/m (It/Ic = 0.65) and 0.048 W/m (It/Ic = 0.60), respectively.
Table 1 Specification of 1 m YBCO conductor Former Length YBCO tape Tape width/strips/layer/ outer diameter
Cu stranded 200 mm2 1m IBAD-MOCVD five strips from 10 mm-width original (Ic = 110 A) 0.1 mm-thick Cu tape soldered on YBCO 2 mm/60 strips/2 layer/u20.0 mm
In Fig. 4, the AC loss normalized by Ic is almost in agreement at each temperature, and there is no dependence on the LN2 temperature. Therefore, we can simply regard the cooling HTS conductor as the increasing Ic of a YBCO conductor and YBCO tapes. In Fig. 4, when It/Ic is over 0.6, the normalized AC loss becomes larger than the Norris strip model [6]. It indicated that some YBCO strips were degraded, but it was uncertain whether it was done by the laser processing or non-uniformity of Ic along the width of the YBCO. During the laser processing, the concentration or deconcentration of the laser energy occurs due to fluctuations of the laser focus or of the process speed. To reduce AC loss, it is also important to use YBCO strips that have the same Ic, and the YBCO tapes need to maintain the uniformity of Ic along the width. 3. Design of HTS cable joint and overcurrent test Fig. 5 shows the HTS cable joint, which has a compact design for use in the conventional vault. The diameter of the HTS joint is the same as that of the HTS conductor. The prototype joint was fabricated using two YBCO HTS cables, which had a length of 1.5 m, 200 mm2 Cu stranded former, and three YBCO strips, which were 3.33 mm in width and spirally wound, with an insulation layer 6.5 mm-thick. Each Cu former was cut and shaped into a single V groove, which was cut at an oblique angle, connected, and then welded. As shown in Fig. 6a, HTS1 with Cu tape with a length of 1.5 m and a width of 3.33 mm are butted up against HTS2 with Cu. Using HTS3 with Cu, the Cu side of the HTS3 was placed on the Cu side of the HTS1 and HTS2 and soldered. Next, electrical insulation for the HTS conductor joint and cryostat pipes was constructed. The HTS joint resistance, which is defined as the slope in the V–I characteristics when the HTS conductor keeps superconductivity, was 0.3 lX, shown in Fig. 6b where the generated voltage was 18 lV at 60 A. Although there is still plenty of room for improvements, such as an optimal joint length and solder thickness and work efficiency, the joint resistance of 0.3 lX was an acceptable level. This joint was cooled by 73 K, and an overcurrent of 31.5 kA for 2 s was applied. According to the specifications of electrical instruments installed in the 66/77 kV line in Japan, they must endure an overcurrent of 31.5 kA for 2 s. The generated voltage was set as a voltage tap on the HTS1 and HTS2 and increased to 7.50 104 lV peak/cm; however, a rising trend was not observed when an overcurrent of 31.5 kA for 2 s was applied. In addition, the temperature rising which was measured by Pt thermometers on the HTS conductor was 68 K and the recovery time required about 50 min. The degradation of Ic in the HTS was not observed after the overcurrent.
Fig. 1. Experimental setup.
M. Yagi et al. / Physica C 468 (2008) 2037–2040
2039
Fig. 2. V–I characteristics of the 1 m YBCO conductor. The inset shows the V–I characteristics normalized by Ic.
Fig. 6. (a) Schematic view of the HTS joint and (b) V–I characteristics of the HTS joint that was the jointing of three YBCO strips with a width of 3.33 mm.
4. Demonstration of 20 m YBCO HTS cable
Fig. 3. Measurement of AC loss (50 Hz) in the 1 m HTS conductor.
Fig. 7a shows the schematic view of a 20 m YBCO HTS cable, including two types of 10 m HTS cables and a joint. One 10 m HTS cable using RABiTS-type YBCO will be made by Sumitomo electric, and the joint and the other 10 m cable using IBAD-type YBCO will be made by Furukawa electric. The specifications for the IBAD-type 10 m cable are listed in Table 2. The YBCO HTS cables have 200 mm2 Cu stranded former and a three-HTS-conductor layer for a demand of high capacity current, such as more than 3 kA. In this demonstration, the capacity of the HTS conductor will be 1 kA class because we will use 100 A/cm-width YBCO tapes. And these cables have electrical insulation with a thickness of 6.5 mm
Fig. 4. Normalized AC Loss in the 1 m HTS.
Fig. 5. Design of the HTS cable joint.
Fig. 7. (a) Schematic view of 20 m YBCO HTS cable and (b) structure of YBCO HTS cable.
2040
M. Yagi et al. / Physica C 468 (2008) 2037–2040
Table 2 Specification of 10 m IBAD-type YBCO HTS cable Former Length YBCO tape
HTS conductor tape width/ strips/layer/outer diameter Inner semi-conductor Electrical insulation Outer semi-conductor HTS Shield Protection layer
Cu stranded 200 mm2 10 m IBAD-MOCVD five strips from 10 mm-width original (Ic = 100 A) 0.1 mm-thick Cu tape soldered on YBCO 2 mm/82 strips/3 layer/u21.0 mm Carbon paper 2 layer Semi-synthetic paper 6.5 mm-thick Carbon paper 2 layer 2 mm/50 strips/1 layer/u36.0 mm Cu tape (0.1 mm-thick) 8 layer non-woven cloth
for 66/77 kV [7] and one-HTS shield layer and eight-protection layer using Cu tape with a thickness of 0.1 mm, shown in Fig. 7b. The 20 m HTS cable including the joint will be demonstrated in January 2008. 5. Conclusion A 1 m YBCO conductor was fabricated and cooled by reducing the pressure of LN2 to evaluate AC loss (50 Hz). This conductor had Ic of 2365 A and AC loss of 0.048 W/m at 1 kA rms. A prototype of HTS cable joint was constructed and withstood an overcurrent condition of 31.5 kA for 2 s. Two types of 10 m YBCO cable and a joint will be made and tested in January 2008.
Acknowledgements This study was carried out as Collaborative Research and Development of Fundamental Technologies for Superconductive Application of the Ministry of Economy, Trade and Industry (METI) and was cosigned by the New Energy and Industrial Technology Development Organization (NEDO). All YBCO tapes were supplied by Chubu Electric Power Company, which developed and manufactured them in the project. We wish to express our gratitude to all parties concerned. References [1] M. Yagi, S. Mukoyama, H. Hirano, N. Amemiya, A. Ishiyama, S. Nagaya, N. Kashima, Y. Shiohara, Physica C 463–465 (2007) 1154. [2] S. Mukoyama, M. Yagi, H. Hirano, Y. Yamada, T. Izumi, Y. Shiohara, Physica C 445–448 (2006) 1050. [3] S. Mukoyama, M. Yagi, N. Hirano, N. Amemiya, N. Kashima, S. Nagaya, T. Izumi, Y. Shiohara, Physica C 463–465 (2007) 1150. [4] N. Kashima, T. Niwa, M. Mori, S. Nagaya, T. Muroga, S. Miyata, T. Watanabe, Y. Yamada, T. Izumi, Y. Shiohara, IEEE Trans. Appl. Supercond. 15 (2005) 2763. [5] N. Amemiya, Z. Jiang, M. Nakahata, M. Yagi, S. Mukoyama, N. Kashima, S. Nagaya, Y. Shiohara, IEEE Trans. Appl. Supercond. 17 (2007) 1712. [6] W.T. Norris, J. Phys. D 3 (1970) 489. [7] T. Takahashi, H. Suzuki, M. Ichikawa, T. Okamoto, S. Akita, S. Maruyama, A. Kimura, IEEE Trans. Appl. Supercond. 15 (2005) 767.