Short Circuit Test of HTS Power Cable - ASL

Short Circuit Test of HTS Power Cable 

S. Torii, H. Kado, M. Ichikawa, H. Suzuki, M. Yagi and S. Mukoyama 

Abstract—The 500 m high temperature superconducting (HTS) 

cable developed by the Super-ACE project included copper layers 

as protection against short circuit current. The design policy was 

that liquid nitrogen would not vaporize when it was exposed to the 

short circuit current of 31.5 kA with 0.5 s. In order to establish the 

design policy, we have made nine 10 m samples with the same 

construction of the 500 m HTS cable and set three cables in the 

liquid nitrogen vessel. Both of balanced fault of 3LG and 

unbalanced faults of 1LG and 2LG have been set and fault 

currents have been applied to the HTS cables. After each fault, the 

critical current has been measured and we have confirmed no 

variation of Ic before and after each fault. HTS cables have not 

been damaged mechanically by the fault current of 31.5kA with 

0.5 s 

Index Terms— HTS cable, Short circuit current, Protection, 

Critical current, Mechanical damage 

I. INTRODUCTION 

A 

HTS cable is expected for large capacity and high density 

transmission of electric power to the urban grid with low 

voltage. Therefore, many projects had been conducted in the 

world [1-8]. The verification test of 500 m HTS cable had been 

conducted by CRIEPI under the Super-ACE project in Japan 

[7-11]. In this test, high stability, potential and reliability of 

HTS cable had been verified. A feature of 500 m HTS cable had 

included copper layers as a protection against short circuit 

current for both of core and shield. In this paper, we described 

the short circuit test results with the HTS cable. 

II. CABLE DESIGN AND SPECIFICATIONS 

The 500 m HTS cable had been constructed by HTS tapes, 

electrical insulators and copper conductors. The schematic 

construction is shown in Fig. 1. The former was a stranded 

cooper hollow conductor with the cross section of 250 mm 2 and 

outer diameter of 28.4 mm, and this former was expected to 

play protection of core conductor against short circuit current. 

On the copper former, 20 HTS tapes were wound with 1 layer, 

300 mm pitch and the outer diameter of 30.9 mm. As an electric 

Manuscript received August 28, 2006. This work has been carried out as a 

part of the Super-ACE (R&D of fundamental technologies for superconducting 

AC power equipment) project of METI, under consignment by NEDO. 

S. Torii, H. Kado, M. Ichikawa and H. Suzuki are with Central Research 

Institute of Electric Power Industry (CRIEPI), Yokosuka, Japan (phone: 

+81-46-856-2121; fax: +81-46-856-3540; e-mail: tori@criepi.denken.or.jp, 

kado@criepi.denken.or.jp, michi@criepi.denken.or.jp and 

ksuzuki@criepi.denken.or.jp ). 

M. Yagi and S. Mukoyama are with Furukawa Electric Co. Ltd., Japan 

(e-mail: m-yagi@ch.furukawa.co.jp and mukoyama@ch.furukawa.co.jp ). 

insulator, laminated papers were wrapped with 8 mm thickness 

and the outer diameter of 49.3 mm. Then 30 HTS tapes were 

wound as a shield layer with 1 layer, 400 mm pitch and the 

outer diameter of 49.8 mm. On the HTS shield layer, 64 copper 

braids with the cross section of 2 mm 2 were wound as a shield 

layer protection. Each core or shield layer and protection 

coppers were soldered at the end of cable. Because of the most 

dangerous destruction of HTS cable was the breakdown of 

electrical insulator caused by bubbling of liquid nitrogen inside 

electrical insulation layers, so the concept of protection was to 

avoid vaporizing of liquid nitrogen under pressurized condition 

when short circuit current flowed in the HTS cable. To realize 

this concept, the temperature rise of core conductor and former 

has to limited below boiling point of the pressurized liquid 

nitrogen. At first, we defined the condition of short circuit 

current of 31.5 kA and duration time of 0.5 s in this test. By the 

calculation of Joule heating temperature below boiling point, 

we determined the cross section of former as 250 mm 2 . 

Protection of shield 

layer (copper braid) 

Fig. 1 The schematic construction of HTS cable. 

SC shield layer 

Insulation layer 

SC core layer 

Former (copper stranded 

hollow conductor) 

Fig. 2 Photograph of a set of three phase cables in a vessel. 

Three sets of three phase 10 m length HTS cables and three 

vessels were prepared. Each cable was inserted in a corrugated 

tube because the shield layer had a possibility of mechanical 

1

Critical current, Ic, of each cable both of core conductors and 

shield layers are listed in Table I. The criterion of Ic is 1 µV/cm 

in the core conductor and shield layer. 

A. 3LG short circuit current tests 

3LG short circuit tests of 10 kA, 20 kA and 315 kA were 

conducted with “north”, “south” and “center”, respectively. 

These test results are listed in Table II, and a current wave 

forms of 3LG, 31.5 kA and 0.52 s is shown in Fig. 6. 

Cable 

Voltage 

(kV) 

North 8.24 

South 8.26 

Center 8.26 

Phase 

TABLE II 

TEST RESULTS OF 3LG. 

Peak 

value of 

first 

wave 

(kApeak) 

RMS 

value 

after 3 

cycles 

(kArms) 

Measured Ic after test 

Core (A) 

Shield 

(A) 

R 28.5 10.2 1,320 2,010 

S 22.0 10.2 1,220 1,920 

T 21.1 10.2 1,080 1,780 

R 57.1 20.0 1,470 2,260 

S 43.5 20.2 1,410 2,110 

T 43.3 20.1 1,320 2,010 

R 90.2 31.2 1,480 2,270 

S 64.4 31.7 1.520 2,350 

T 73.4 31.4 1,570 2,200 

Fig. 6 The current wave forms of 3LG, 31.5 kA, 0.5 s short circuit. 

From the test result, phases R and T were injected large DC 

component and reduced about 0.2 s. From the signals of 

Rogowski coils, it was cleared that short circuit current mainly 

flowed in protection copper conductor both of core and shield. 

Critical currents of these core and shield layer did not vary after 

short circuit tests. Also, the HTS cable was not injured 

mechanical damage against 3LG short circuit test. 

B. Unbalanced short circuit test results (1LG and 2LG) 

Unbalanced short circuit current tests both of 2LG and 1LG 

were conducted by “center” set. The test results of 2LG and 

1LG are listed in Table III and Table IV, respectively. Current 

wave forms of 31.5 kA both of 2LG and 1LG are shown in Fig. 

7 and 8, respectively. 


Voltage 

(kV) 

Center 12 

Center 12 

Center 11.6 

Phase 

TABLE III 


Peak 


first 

wave 

(kApeak) 

RMS 

value 

after 3 

cycles 

(kArms) 


Core (A) 

Shield 

(A) 

R 27.8 9.88 1,500 2,260 

S 15.0 10.1 1,550 2,350 

T 0.83 0.56 - - 

R 51.4 18.3 1,480 2,260 

S 30.7 18.4 1,540 2.350 

T 1.29 0.85 - - 

R 92.3 32.3 1,480 2,270 

S 64.1 32.6 1,520 2,340 

T 1.25 0.81 - - 

Fig. 7 Current wave forms of 2LG, 31.5 kA, 0.5 s short circuit. 


Voltage 

(kV) 

Center 12 

Center 12 

Center 16.9 

Phase 

TABLE IV 


Peak 


first 

wave 

(kApeak) 

RMS 

value 

after 3 

cycles 

(kArms) 


Core (A) 

Shield 

(A) 

R 27.4 10.2 1,480 2,260 

S 1.25 0.87 - - 

T 1.25 0.85 - - 

R 53.3 19.8 1,470 2,260 

S 1.30 0.90 - - 

T 1.30 0.88 - - 

R 83.6 31.4 1,480 2,270 

S 1.30 0.90 - - 

T 1.29 0.88 - - 

3

Short Circuit Test of HTS Power Cable - ASL

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