Kazuhiko Hayashi

Ken-Ichi Sato

Ryosuke Hata

Shigeki Isojima

Takato Masuda

Yuichi Yamada

CiteSeerX

C I R E D 18th International Conference on Electricity Distribution Turin, 6-9 June 2005 
 
 
RECENT DEVELOPMENT OF HIGH-TEMPERATURE SUPERCONDUCTING (HTS) CABLE IN 
SUMITOMO ELECTRIC INDUSTRIES, LTD. 
 
Yuichi YAMADA, Shigeki ISOJIMA, Takato MASUDA, Kazuhiko HAYASHI, Ken-ichi SATO, Ryosuke HATA 
Sumitomo Electric Industries, LTD. - Japan 
yamada-yuichi@sei.co.jp, isojima-shigeki@sei.co.jp, masuda-takato@sei.co.jp, 
 hayashi-kazuhiko@sei.co.jp, sato-kenichi@sei.co.jp, hata-ryousuke@sei.co.jp 
 
 
INTRODUCTION 
 
Three HTS cable demonstrations in Yokosuka (Japan) by 
Tokyo Electric Power Company (TEPCO) and Sumitomo 
Electric Industries, Ltd. (SEI), Copenhagen (Denmark) by 
NKT and Carrollton (US) by Southwire were successfully 
implemented.  After these successful milestones, the HTS 
cable development has been entered into the 2nd stage.  
Three Bi-based cable projects, which are in the real 
network, have started in US under international 
collaborations.  Also, Asian HTS cable projects are on-
going in Japan, Korea and China.  SEI is now engaging in 
the US Albany Project and KEPRI (Korea Electric Power 
Research Institute) Project adopting Sumitomo’s 3-core in 
one cryostat type (3-in-OneTM) HTS cable for distribution 
network. 
 
HTS CABLE 
 
When compared with conventional power cables, HTS 
cable has much larger transmission capacity with smaller 
cable diameter. 
 
Non-Explosive
HTS
cable
AC
DC
*Safety
*Green
*Long Life
21st Cent.
*Large Current
*Energy-saving
*EMI Free
Advanced
Power
Cable
Non-Flammable
Green
No Thermal
Expansion & Contraction
(No degradation)
Not-Industrial 
waste
Li
qu
id
 N
itr
og
en
Superconductivity
Low Loss
Large Current
EMI Free
 
Figure 1: Merits of HTS cable 
Target Problem
Large Capacity & Energy-saving
Power Cables in Urban area
Cable route
Demand Increase by IT
(1)No space    *
for      (Right of Way)
*Sub-station 
(3)Difficulty in capacity increase       
with low loss (energy-saving)
[ I ] Replace Old Cable [ II ] Omission of sub-station
Duct
Old Cable
3 circuits
HTS Cable
2 circuits
Communication Line
1st
S/S
2nd/3rd
S/S
500kV 275/154/66kV 6.6kV
100or
200V
S/S
66kV 6.6kV
100or
200V
HTS Cable
Large Space and Many Devices
Tr
Tr
+
to meet
 
Figure 2: Effective applications for HTS cable 
 
This feature makes it so simple to increase the capacity of 
power transmission or distribution network, because it can 
be obtained by only replacing the existing conventional 
cable by HTS cable instead of constructing a new network.  
Figure 1 shows the merits of HTS cable and Fig. 2 shows 
the effective cases of HTS cable application respectively. 
For example, with conventional cable, three lines are 
normally required to transmit the power of one 66 kV, 1 kA 
circuit. With these lines, if the demand for electric power 
expands to the extent that a three-fold increase in 
transmission capacity is required, six new cables must be 
installed. Using a 3-core HTS cable, however, a 200% 
increase in transmission capacity can be obtained by 
installing just one HTS cable, that is, there is no need to 
construct new conduits (Fig. 3-(a)). The cost of line 
construction, especially in a large city like Tokyo or New 
York, is extremely high. Figure 3-(b) shows a comparison 
of the construction cost between conventional cable and 
HTS cable under the above conditions. HTS cable line 
construction cost, calculated assuming that current 
construction techniques and cooling system in every 5km 
are used, is likely to be much lower than the cost of 
constructing a new line of conventional cables. From the 
above reason, HTS cable is expected to be cost competitive. 
The feature, that the transmission energy loss of HTS cable 
is less than half of that of conventional cable, is another 
important factor to be pointed out (Fig. 4).  This feature 
contributes to reduce greenhouse gas emission such as CO2 
and NOx. 
Conventional Cable SC cable
Conventional Cable
69kV 1kA 3-phase in 3 duct
Increase
New ducts
69kV 69kV, 3kA in existing duct, , 1kAx2
3 phase in one cryostat
 
(a) Increasing capacity (1kA→3kA) 
 
0.00
0.20
0.40
0.60
0.80
1.00
1.20
SC
 c
ab
le
 c
on
st
ru
ct
io
n 
co
st
fo
r c
on
ve
nt
io
na
l c
ab
le
Conventional cable HTS cable
Present
HTS wire
cost
Civil work
1.0
0.6
0.3
69kV, 350MVA
Installation in Major city
Cooling system for HTS cable in each 5km
HTS wire
in 2005
Installation
Accessory
Cooling system
Cable
SC wire
SC
 c
ab
le
 c
on
st
ru
ct
io
n 
co
st
fo
r c
on
ve
nt
io
na
l c
ab
le
 
(b)Total installation cost comparison of conventional cable and SC cable 
Figure 3: Total installation cost of SC cable 
 
CIRED2005 
 
Session No 1 
C I R E D 18th International Conference on Electricity Distribution Turin, 6-9 June 2005 
 
0
0.2
0.4
0.6
0.8
1
1.2
Conventional cable
1.0
Conductor
Loss
Dielectric
Loss
Sheath
Loss
AC loss
Heat Invasion
Dielectric Loss
Loss of 
Cooling
System
Target
HTS cable
0.5
Evaluation 
for 350MW 
cable
 
Figure 4: Transmission loss 
 
HTS cable construction 
 
The structure of HTS cable is shown in Fig. 5. The 
conductor is formed by laying the Bi2223 wires in a spiral 
onto a former. PolyPropylene Laminated Paper (PPLP®) is 
used for the electrical insulation due to its good dielectric 
strength and low dielectric loss at low temperatures, liquid 
nitrogen works as compound liquid insulation in addition to 
coolant. On the outside of the insulation layer, Bi2223 
wires are wound in a spiral to form a shield layer. Each 
shield layer of each core is connected to each other at both 
ends of the cable, so that an electrical current of the same 
magnitude as that in the conductor is induced in the shield 
layer in the reverse direction, thus eradicating the 
electromagnetic field leakage outside the cable. Three cores 
are stranded together, and are placed inside the double-
layered SUS corrugated pipes. Thermal insulation is placed 
between the inner and outer SUS corrugated pipes, where a 
vacuum state is maintained to improve the thermal 
insulation performance. 
SC conductor
Electric insulation
LN2 path
Inner corrugated pipe
Thermal insulation
Outer corrugated pipe
Outer cover
Former
SC shield
Cable core 
 
Figure 5: Structure of HTS cable 
 
TEPCO project 
 
The demonstration test jointly conducted with TEPCO and 
CRIEPI in 2001 through 2002 involved the 100 m, 66 kV, 1 
kA class cable, and this test was successfully implemented 
for a year. The achievements are summarized below. 
*Withstand voltage test: Cleared AC 66 kV (Phase to 
Phase）. 
*Transmission capacity: A 200 MVA (at 2000 A) 
transmission capacity was confirmed. The Ic at that day 
was 50 A, but it exceeds 100 A at present. This means that 
the current HTS cable is expected to carry around 350 
MVA (3000 A class), the target value of this cable.  
*Cable length: Our 100 m long HTS cable confirmed the 
feasibility of producing a 500 m class cable, the target 
length taken from transportational restriction and a normal 
distance between manholes. To extend the cooling distance, 
the pressure loss must be reduced, and this can be achieved 
by decreasing AC loss of HTS wire, resulting in less 
amount of coolant flow. Now, SEI is keenly doing R&D on 
the reduction of AC loss of HTS wire. 
*Distance between Cooling Stations: The target cooling 
station installation interval is 3 to 5 km, which is 
comparable to that of oil feeding distance of Oil Filled (OF) 
cable. 
From the achievements, the further improvement of 
BSCCO 2223 wire is one of the most important factors for 
the utilization. 
 
DEVELOPMENT OF CT-OP BSCCO WIRE 
 
At present (Bi,Pb)2Sr2Ca2Cu3OX(Bi2223) HTS wire 
(Tc :110 K) is a promising candidate among various kinds 
of HTS wires which can be put into practical use. SEI has 
proceeded with R&D on Ag-sheathed wires using Bi2223 
superconductor and has developed long wires (in kilometer-
class) with high Jc that can be semi-mass-produced. Since 
“not 100% mass density” causes formation of pores and 
decreases supercurrent between Bi2223 grains grown 
during sintering, SEI decided to apply the ConTrolled Over 
Pressure (CT-OP) sintering, which attempts to obtain 
“100% mass density” by applying gas pressure to Bi2223 
wires during the second sintering. 
 
Process of Bi2223 HTS wires 
 
The manufacturing method of Bi2223 wires is called as 
Powder-In-Tube (PIT) method (Fig. 6). The appearance of 
wire is tape-shaped as shown in Fig. 8(a), the width is 
ranging from 4.0 to 4.5 mm and the thickness is from 0.2 to 
0.25 mm (Fig. 7). Bi2223 wire consists of multi-filaments 
(black parts) ensheathed by silver or silver-alloy (white 
part) [1]-[3] 
 
Sintering
Powder
filling up
Drawing 1
Drawing2
fitting
Rolling
Powder
synthesis
 
Figure 6: Manufacturing process of Bi2223 wire 
 
 
Figure 7: Cross-sectional view of Bi2223 wire 
 
Superconducting filament Ag 
4.0 ～ 4. 5 mm  
0.2～ 
0.25mm 
CIRED2005 
 
Session No 1 
C I R E D 18th International Conference on Electricity Distribution Turin, 6-9 June 2005 
 
 
 
 
 
 
Figure 8: Bi2223 superconducting wires: (a) appearance, (b) cross-
sectional view and (c) SEM image. 
 
CT-OP 
 
In order to manufacture high-performance Bi2223 wires, it 
is necessary to carry out second rolling and second 
sintering. After the second rolling, Bi2223 grains become 
little worse (Fig. 9(b)) and cracks appear and such cracks 
cannot be improved sufficiently by the second sintering. 
Therefore, SEI decided to apply the CT-OP sintering, in 
which external isostatic gas pressure (a mixture of oxygen 
and inert gas) is applied to Bi2223 wire in order to obtain 
100% mass density of Bi2223 filaments (Fig. 9(a)). 
 
 
A
Bi2223 
superconducting current direction 
(a) 
A
pore 
(b)
superconducting current direction
tape surface tape surface 
 
Figure 9: Connectivity between Bi2223 grains. (a)dense and (b) nondense 
state. 
 
Critical current performance 
 
Table 1 shows the comparison between normal and CT-OP 
sintering in terms of superconducting current. Ic, Je and Jc 
are defined as critical current, critical current density per 
cross-sectional area of wire and critical current density per 
cross-sectional area of filament, respectively. Jc values of 
normal sintered sample are 26.0 kA/cm2 and 32.3 kA/cm2 
and CT-OP sintered sample are 38.9 kA/cm2 and 40.0 
kA/cm2 in the wires of the silver ratios of 1.5 and 2.2, 
respectively. Jc becomes 130% or higher by CT-OP 
sintering. This suggests that CT-OP sintering is an effective 
method for improving the performance of Bi2223 wires due 
to 100% mass density of Bi2223 filaments. 
 
Table 1: Ic, Je, Jc of normal and CT-OP sintered samples (1µV/cm, 77 K). 
 Silver ratio: 1.5 Silver ratio: 2.2 
 normal pressure normal pressure
Ic (A) 99 131 74 92 
Je (kA/cm2) 10.6 14.3 8.7 10.4 
Jc (kA/cm2) 26.0 38.9 32.3 40.0 
 
Mechanical property 
 
Mechanical property is one of the important factors when 
Bi2223 wires are applied to practical products. To improve 
mechanical property, silver-alloy sheath is adopted. Silver 
ratio also affects mechanical property of Bi2223 wire. 
Considering that Bi2223 wires consist of filaments and 
silver or silver alloy, filaments also affect the mechanical 
property of wires. SEI measured the mechanical property of 
CT-OP sintered sample, which clearly changed the state of 
filaments. In a tensile stress tolerance test, Ic was measured 
at 77 K using stressed samples at room temperature. Figure 
10(a) and (b) show results in the silver ratio of 1.5 and 2.2, 
respectively. Ic0 of vertical axis represents Ic of no stressed 
sample. 
0
0.2
0.4
0.6
0.8
1
1.2
0 50 100 150 200
Tensile stress (MPa)
Ic
/Ic
0
normal
CT-OP
(a)Ag ratio : 1.5
 
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 50 100 150 200
Tensile stress (MPa)
Ic
/Ic
0
normal
CT-OP
(b)Ag ratio : 2.2
 
Figure 10: Ic dependence on the tensile stress of the normal sintered wire 
and CT-OP wire in case of the silver ratio of 1.5 (a) and 2.2(b). Ic and Ic0 
mean critical currents after and before tensile stresses are applied, 
respectively. 
 
The tensile stress value from which Ic/Ic0 degradation takes 
place is 85 MPa and 106 MPa on normal sintering and 144 
MPa and 167 MPa on CT-OP sintering in the wires of the 
silver ratio of 1.5 and 2.2, respectively. It is considered that 
CIRED2005 
 
Session No 1 
C I R E D 18th International Conference on Electricity Distribution Turin, 6-9 June 2005 
 
CT-OP suppresses pores and cracks so that mechanical 
property of filaments can be improved. Furthermore, 
considering that tensile stress value in CT-OP samples of 
silver ratio of 1.5 (144 MPa) is higher than that in normal 
sintered samples of silver ratio of 2.2(106 MPa), the 
strength of filaments clearly improves the mechanical 
property of Bi2223 wires. 
 
Applicability to liquid nitrogen cooling system  
 
Liquid nitrogen cooling system is essential for applications 
such as power cable and transformer using Bi2223 wire. 
When cooled in liquid nitrogen and warmed up to room 
temperature, wires may balloon by vaporization of liquid 
nitrogen that has entered into filaments through silver 
sheath. The ballooning will result in the significant 
degradation in Ic because filament shape is deformed. 
However, if no pores exist in filaments, wires should never 
be ballooned. The CT-OP wires with no pore and no crack 
are not ballooned even without additional hermetic 
materials, as is confirmed that 1,000m long wires are not 
ballooned at all after cooled in liquid nitrogen under 1 MPa 
for 24 hours. 
 
On-going HTS Cable project 
 
In the USA, the US Department of Energy’s (DOE) SPI 
project is promoting the development of HTS cables. The 
120 m long HTS cable test line in Detroit was not 
successful[4], but the Southwire Company’s 30 m long 
cable test has successfully been operating for over 28,000 
hours[5]. 
Three new projects started lately, and these are accelerating 
the development and application of HTS cables to 
strengthen the US power grid, which showed its 
vulnerability during the massive blackout in New York in 
August 2003[6]. These three projects are the Albany 
project (350 m, 34.5 kV, 800 A) [7], Ohio project (300 m, 
15 kV, 2 kA)[8], and LIPA project (600 m, 138 kV, 2.4 
kA)[9], and these projects are scheduled to begin operation 
over 2005-2006. 
Also, Asian HTS cable projects are on-going in Japan, 
Korea and China. 
 
Albany project 
 
The Albany project will use a 350 m, 34.5 kV, 800 A, 3-
core cold dielectric type HTS cable as part of the line 
between two sub-stations (Menands and Riverside) in 
Albany, New York, and this cable will be subjected to a 
long-term operation. Fig. 11 shows a photograph of the 
planned construction site[10]. 
 
 
Ａｌｂａｎｙ in NY
350m 
HTS cable
 
Figure 11: Test site of Albany project (Albany in NY state） 
 
The construction and test is planned to extend over a 4-year 
period (2002 to 2006) and will be the world first long HTS 
cable line to be utilized in an actual power grid. 
SEI’s role in this project is to manufacture, install, 
construct and connect the cable to the actual line as well as 
to operate a practical HTS cable line under actual loads. 
SuperPower Inc. serves as a primal contractor, Niagara 
Mohawk offers the test-site and supplies a power, The BOC 
group is in charge of cooling system. 
 
O/H line
joint
350mTermination
Cooling
station 30m 
O/H line
Highway
 
(a) Cable System Overview 
 
(b) 3-in-One Cable TM
 
(c) 3-in-One Termination TM 
 
(d) 3-in-One Joint TM
Figure 12: Schematic view of Albany cable system 
 
The cable system configuration is shown in Fig. 12. The 
cable is divided into two sections, one 320 m and the other 
30 m in length, and they will be connected by a joint. The 
CIRED2005 
 
Session No 1 
C I R E D 18th International Conference on Electricity Distribution Turin, 6-9 June 2005 
 
cable will be installed in a newly constructed underground 
duct with an inside diameter of 6 inches (152 mm). 
A 30m portion is planned to be replaced by 2G(YBCO) 
HTS cable manufactured by SEI, using SuperPower’s 2G 
wires during the latter half of the test period. 
 
KEPRI project 
 
In Korea, it is required to improve the reliability of electric 
power transmission and distribution network by increasing 
its capacity to catch up the rapid increase of electric power 
consumption especially in the urban area.  It is very 
difficult, however, to install a new power transmission or 
distribution line or sub-stations, due to luck of available 
space in the underground cable tunnels and cable ducts as 
well as the difficulty of obtaining the right of way for new 
cables.  Therefore, high power HTS cables are expected to 
be put into practical use soon. 
SEI is awarded the tender for HTS Cable System from 
Korea Electric Power Research Institute (KEPRI) that is the 
Central Research Laboratory of Korea Electric Power 
Corporation (KEPCO). 
SEI will supply not only cable and termination but also 
cooling system as well as implement the installation work 
at KEPRI’s test yard in Kochang, Korea.  The principal 
specification of the system is shown in Table 2 and the 
schematic view of the system is shown in Fig. 13, 
respectively. 
KEPRI will perform various kinds of tests and experience 
necessary matters related to the operation and maintenance 
of HTS cable system.  KEPRI will conduct feasibility study 
of applying HTS cable to real grid from these results.  The 
cable installation is scheduled to start in spring next year 
and start operation in summer 2005. 
 
Table 2: Principal specification of KEPRI HTS cable system 
Length 100 m 
Rated Voltage 22.9 kV 
Nominal Current 1250 Arms 
Cable Type 3-in-One(3 cores in one Cryostat) 
HTS cold dielectric type cable  
 
 
Terminatio
3-in-one HTS cable 
22.9kV, 1.25kA
Cooling 
System 
100m  
Figure 13: Schematic view of the KEPRI cable system 
 
CONCLUSION 
 
In this 21st century, supported by 3 key matters, 
“Environment”, “Energy”, “Natural resources”, the 
importance of HTS technology is increasing more and more 
to the human society.  HTS Cables with Large 
Transmission Capacity and Low Loss are environmentally 
friendly, hence indispensable for 21st Century's Power Grid 
and the innovated Bi-based wire is leading the HTS cable. 
 
REFERENCES 
 
[1] S. Kobayashi, T. Kaneko, N. Ayai, K. Hayashi, H. 
Takei, and R. Hata, Physica C, 357-360, 1115, (2001). 
[2] T. Kaneko, S. Kobayashi, K. Hayashi, and K. Sato, 
1997, Advances in Superconductivity IX, Tokyo: 
Springer, p907 
[3] S. Kobayashi, T. Kaneko, M. Ueyama, T. Hikata, K. 
Hayashi, K. Sato, 1998, SEI TECHNICAL REVEIW, 
153, p10 
[4] http://www.amsuper.com/press/2002/Detroit_Update.p
df 
[5] R. Hawsey, “Overview of U.S. High Temperature 
Superconductivity Program for Electric Power”, The 
2004 International DAPAS workshop 
[6] “Grid 2030, A National Vision For Electricity’s 
Second 100 years”, DOE (2003) 
[7] T. Masuda, et al., 2004, “Design and Experimental 
Results for ALBANY HTS Cable”, ASC2004, 1LT05 
[8] J. W. Lue, J.A. Demko et al., 2003, “Tests of 5-m long 
Triaxial HTS cable”, ICEC2003 
[9] M Hervey , M. Mccarthy, presented by EPRI 
Superconductivity Task Force Meeting (Oct. 2003) 
[10] C. Weber, presented by EPRI Superconductivity Task 
Force Meeting (Oct. 2003) 
[11] S. Kobayashi, T. Kato, K. Yamazaki, K. Ohkura, K. 
Fujino, J. Fujikami, E. Ueno, N. Ayai, K. Hayashi, K. 
Sato, 2004, “Controlled over pressure processing 
Bi2223 long length wires” ASC2004 
 
CIRED2005 
 
Session No 1 


RECENT DEVELOPMENT OF HIGH-TEMPERATURE SUPERCONDUCTING (HTS) CABLE IN SUMITOMO ELECTRIC INDUSTRIES, LTD

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RECENT DEVELOPMENT OF HIGH-TEMPERATURE SUPERCONDUCTING (HTS) CABLE IN SUMITOMO ELECTRIC INDUSTRIES, LTD

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