Physica C 468 (2008) 1710–1713

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Physica C

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Study on the quench protection of YBCO coated conductor tape

H.-I. Du a,*, S.-W. Yim b, S.-C. Han b, C.-R. Park a, B.-S. Han a

a Chonbuk National University, 664-14 Deokjin-Dong, Deokjin-Gu, Jeonju 561-756, Republic of Koreab Superconductivity and Applications group, Korea Electric Power Research Institute, Republic of Korea

a r t i c l e i n f o a b s t r a c t

Article history:Available online 17 July 2008

PACS:84.71.Mn84.71.Fk85.25.�j

Keywords:QuenchYBCO coated conductor tapeSFCLs

0921-4534/$ - see front matter � 2008 Elsevier B.V. Adoi:10.1016/j.physc.2008.05.181

* Corresponding author. Tel.: +82 63 270 2396; faxE-mail address: dudoc@chonbuk.ac.kr (H.-I. Du).

YBCO coated conductor tapes with high critical current density and index values are expected to be appliedto superconducting power device. In particular, it is characterized by possibilities of selecting a stabilizingmaterial surrounding superconducting tapes and of being applied to superconducting fault current limiters(SFCLs) and superconducting cables according to resistivity. In this study we conducted a test by selectingtapes with critical current of 85 A using copper as a stabilizing material in consideration of these propertiesto see their applicability to superconducting cables. We also conducted a test by selecting superconductingtapes using stainless steel as a stabilizing material to see their applicability to SFCLs. These tapes had thecritical current of 60 A, which was somewhat lower than those for superconducting cables. Finally, super-conducting tapes selected in this way were used to compare and review each of voltage–current and resis-tance properties; on the basis of those results of the review, an experiment of connecting those two kinds oftapes was carried out to see if superconducting tapes whose stabilizing material was copper applied as aprotected could operate within the range which didn’t exceed the critical temperature.

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1. Introduction power cables and YBCO tapes using stainless steel as a stabilizing

High-temperature superconducting tapes which have continu-ously been researched and developed are attracting attention as adevice for power-system application. In particular, BSCCO tapes,which are the first-generation superconducting tapes, were manu-factured into superconducting power cables and superconductingfault current limiters with which a mid-scale simulation was com-pleted for a power system [1]. Due to their mechanical weaknessand low critical current density and index values [2], however, a re-search is necessary to find out a device to make up for defects ofBSCCO tapes. In this study, therefore, we intend to conduct a re-search by using YBCO tapes called the second-generation tapes tomake up for defects of BSCCO tapes and apply them to power appli-cation devices. Strong points of YBCO tapes are that, first, their highcritical current density makes it possible to use a smaller amount oftapes than BSCCO ones to deal effectively with normal and faultcurrents. Second, their high index values lead to high speed of resis-tance occurrence in applying them to SFCLs, which may rapidly lim-it fault currents. Third, it is possible to select kinds of stabilizingmaterials surrounding a YBCO superconductor, which makes it pos-sible to adjust the degree of resistance in case of quench [3]. In thisstudy, therefore, we used two-kinds of YBCO tapes with differentstabilizing layers. First, YBCO tapes using copper as a stabilizingmaterial were used to assess their applicability to superconducting

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material were used to assess their applicability to SFCLs. In addi-tion, on the basis of the results of assessment of two kinds of super-conducting tapes, we intend to apply each of them to SFCLs andcables in order to see conduction of tapes for superconductingcables below the critical temperature by those for SFCLs througha test of connection between two kinds of devices.

2. Experimental set up

In this study, we first determined over-current properties of eachof YBCO tapes. To do this, resistance was measured for each of super-conducting tapes by changes in the critical temperature. Table 1shows specifications of superconducting tapes using copper as a sta-bilizing material and those using stainless steel as a stabilizing mate-rial. Manufacturers of tapes were German Superpower and US AMSC,respectively; superconducting tapes manufactured by Superpowerusing copper as a stabilizing material according to its resistivity wereassessed for applicability to superconducting cables while thosemanufactured by AMSC using stainless steel as a stabilizing materialwere assessed for applicability to SFCLs. Fig. 1 shows the critical tem-perature of superconducting tapes applied to superconductingcables and changes in resistance by changes in temperature. Thecritical temperature is 90 K, with resistance of superconductingtapes increasing rapidly beyond the critical temperature. Whilethe critical temperature of general BSCCO tapes is 105 K, they showan almost similar tendency with those using copper as a stabilizingmaterial when considered from the aspect of the critical tempera-

Fig. 1. Resistance variation of HTS tape with temperature.

Table 1Properties of HTS tapes

Applied Cable Producer YBCO Coated conductor (Superpower)Stabilizer CuLength of pattern 100 cmIC and TC 85 A (1 lV/cm, @ 77 K), 90 KRated Voltage 1.5–2 V/cm (@300 K)Resistance 0.198 mX (@ 300 K)

Applied SFCL Producer YBCO Coated conductor (AM SC)Stabilizer Stainless steelLength of pattern 200 cmIC and TC 60 A (1 lV/cm, @ 77 K), 90 KRated voltage 0.6 V/cm (@ 300 K)Resistance 3.7 mX (@ 300 K)

H.-I. Du et al. / Physica C 468 (2008) 1710–1713 1711

ture compared with the increase in resistance occurring in the vicin-ity of the critical temperature. To this contrary, the graph of tapesusing stainless steel as a stabilizing material shows a rapid increase

Fig. 2. Voltage–current properties of tapes applied 250 Ap and critical resistance properties of tapes (copper as a stabilizing material).

Fig. 3. Voltage–current properties of tapes applied 275 Ap and critical resistance properties of tapes (copper as a stabilizing material).

1712 H.-I. Du et al. / Physica C 468 (2008) 1710–1713

in resistance in the vicinity of the critical temperature and relativelygreat value. This suggests that such tapes are suitable for SFCLswhich need great resistance in a short time when a fault currentoccurs.

3. Results and discussion

3.1. Properties of YBCO tapes applied to superconducting cables

To replace BSCCO tapes composing the existing superconduc-ting cables, voltage–current properties of YBCO tapes using copperas a stabilizing material were examined. Fig. 2 shows voltage–cur-rent properties of tapes applied 250 Ap and critical resistance prop-erties of tapes on this basis. Although quench occurred byexceeding the critical current of 85 A for tapes with 250 Ap applied,the critical temperature still fails to exceed 90 K. Therefore, it is

Fig. 4. Voltage–current properties of tapes applied 250 Ap and critical res

Fig. 5. Voltage–current properties of tapes applied 275 Ap and critical res

judged that the current superconducting tapes maintain the mixof superconducting and normal conditions. Fig. 3 shows voltage–current properties and critical resistance properties with 270 Ap

applied. Between 5 and 6 cycle, resistance was found to reach thecomplete quench area beyond the critical temperature. If such asituation lasts, tapes will be converted completely into the normalcondition and burned away by thermal runaway.

3.2. Properties of YBCO tapes applied to SFCL

To determine competence as a SFCL, voltage–current and resis-tance properties of YBCO tapes using stainless steel as a stabilizingmaterial were examined. As can be seen in Fig. 4, with the currentof the similar value applied, tapes using stainless steel as a stabiliz-ing material showed much greater quench voltage than those usingcopper as a stabilizing material; the applied current began to de-

istance properties of tapes (stainless steel as a stabilizing material).

istance properties of tapes (stainless steel as a stabilizing material).

Fig. 6. Diagram of experiment of connecting tape for cables and SFCL.

Fig. 7. The curves of resistance change when applied 322 Ap of non shunt resistancewith tapes. Fig. 8. The curves of resistance change when applied 322 Ap of shunt resistance

with tapes.

H.-I. Du et al. / Physica C 468 (2008) 1710–1713 1713

crease after first cycle, showing a decrease by about 150% from theapplied current in the final cycle. Resistance properties in Fig. 4also begin to increase rapidly from the first cycle and already ex-ceed the critical temperature in 3 cycle. Fig. 5 with the higher ap-plied current shows that such a tendency is more remarkable. Fig.5 shows that they already have resistance exceed the critical tem-perature before 2 cycle, demonstrating that most currents flowthrough a stabilizing material at this point.

3.3. An Experiment of connecting tapes for cables and those SFCL

As with the circuit in Fig. 6, a connection experiment was con-ducted by using each of superconducting tapes. Fig. 7 shows resis-tance changes between two kinds of tapes when 322Ap wereapplied. The current limited by tapes for SFCLs controls an increasein resistance of tapes for cables; therefore, changes in resistance oftapes for cables begin to decrease after 3 cycle. However, just after5 cycle, resistance of tapes for fault current limiters exceed 300 K,reaching the thermal runway condition. To solve this problem, 2 Xshunt resistance was connected parallel with tapes for fault cur-rent limiters, the results of which are shown in Fig. 8. The temper-ature of tapes for fault current limiters decreased from 300 K to180 K and resistance of tapes for cables also decreased rapidly onthe basis of 3 cycle.

4. Conclusion

With these results, applicability of YBCO tapes as a power de-vice were examined. First, YBCO tapes for cables which used cop-per as a stabilizing material showed similar voltage–currentproperties with BSCCO tapes but a somewhat larger increase inquench voltage and resistance than BSCCO tapes. YBCO tapes forfault current limiters which used stainless steel as a stabilizingmaterial showed lower current limitation to YBCO thin films butcan be applied as a fault current limiter module if a module is man-ufactured which can improve efficiency in current limitation due tolarger mechanical strength and higher flexibility in device process-ing of tapes than YBCO thin films. Finally, the results of the connec-tion experiment demonstrated that superconducting tapes forcables can stably operate within the critical temperature.

References

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[2] J. Ogawa, H. Nakayama, S. Odaka, O. Tsukamoto, Cryogenics 45 (2005) 23.[3] O.-B. Hyun, H.-R. Kim, J. Sim, Y.-H. Jung, K.-B. Park, J.-S. Kang, B.-W. Lee, I.-S. Oh,

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