• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.639-640
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• 2006

We investigated fault current limitation characteristics of the resistive superconducting fault current limiter(SFCL) which consisted of a Bi-2212 bulk coil and a shunt coil. The Bi-2212 bulk coil and the shunt coil were connected in parallel. The Bi-2212 bulk coil was placed inside the shunt coil to induce field-assisted quench. The fault test was conducted at an input voltage of 200 $V_{rms}$ and fault current of 12 $kA_{rms}$ and 25 $kA_{rms}$. The fault conditions were asymmetric and symmetric, and the fault period was 5 cycles. The test results show that the SFCL successfully limited the fault current of 12 $kA_{rms}$ and 25 $kA_{rms}$ to below $5.5{\sim}6.9kA_{peak}$ within $0.64{\sim}2.17$ msec after the fault occurred. Limitation was faster under symmetric fault test condition due to the larger change rate of current. We concluded that the speed of fault current limitation was determined by the speed of current rise rather than the amplitude of a short circuit current. These results show that the Bi-2212 bulk coil is suitable for distribution-class SFCLs.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.221-224
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• 2002

Superconducting electrical devices are under development in a national project in Korea. And KEPCO and LGIS are in charge of development of a resistive type fault current limiters(FCLs) with YBCO thin films. In order to realize FCLs, the rated power of FCLs must be increased. For this purpose, it is of great interest to increase of allowed voltage of unit component without electrical and thermal damages. So, meander lines were widely used for the conducting path to increase maximum electric field. In this research, numerical simulations on the electromagnetic behaviors of the device were carried out, especially focusing on the effect of meander line structures on the YBCO thin films. To evaluate the structures of meander lines, three types of meander lines were considered for numerical analysis using finite element method (FEM). In this simulation, both normal state and fault conditions were considered for calculation of electric field, current density, magnetic field density. And the simulation resulted are compared to find the optimum design of meander lines for resistive FCLs.

• Progress in Superconductivity
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• v.10 no.1
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• pp.45-49
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• 2008

For the development of superconducting fault current limiters (SFCLs), fault current limiting elements were fabricated out of Bi-2212 bulk tubes and tested. The SFCL elements consisted of tube shaped Bi-2212 bulks and metal shunts for the stabilizers. Firstly, the Bi-2212 bulk tubes were processed based on a design of monofilar coils in order to acquire large resistance and high voltage rating. 300 mm-long Bi-2212 tubes were designed to have the current path of 410 cm in length with 24 turns and 41 mm in diameter. The processed monofilar coil, as designed, had 300 A $I_c$ at 77 K. The fabricated superconducting monofilar coils were affixed to Cu-Ni alloy as that of stabilizers. The Cu-Ni alloys were processed to have the same shape of the superconducting monofilar coils. The Cu-Ni coil had resistivity of 32 ${\mu}{\Omega}$-cm at 77 K and 37 ${\mu}{\Omega}$-cm at 300 K. The metal shunts were attached to the outside of the Bi-2212 monofilar coil by a soldering technique. After the terminals made of copper were attached to both ends of the superconductor-metal shunt composite, the gap between the turns and the surface of the elements was filled with an epoxy and a dense mesh made of FRP in order to enhance the mechanical strength. The completed SFCL elements went through fault tests, and we confirmed that the voltage rating of 143 $V_{rms}$ (E =0.35 $V_{rms}$/cm) could be accomplished.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.216-219
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• 2002

This paper describes the modelling method of the Superconducting Fault Current Limiters (SFCL) for Real-Time Digital Simulator (RTDS). The simulations in this paper were carried out using the R type SFCL. The R type SFCL is developed by using User Defined Component (UDC).

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.200-202
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• 2006

We investigated the operating characteristics of a flux-lock type superconducting fault current limiters according to the number of the serial connection each the superconducting element at the additive polarity winding of a transformer. This SFCL consists of two coils wound in parallel on the same iron core, and the secondary coil is connected to the elements in series. Operating characteristics can be controlled by adjusting the inductances and the winding directions of the coils. It turns ratio between the primary and the secondary coils is 63:21. The analysis of voltage, current, and resistance in serial connection each element was performed to increase the applied voltage of flux-lock type SFCL. When the applied voltage was 200/$\sqrt{3}[V_{rms}]$ with three elements connected in seres, the peak value of the line current increased up to 26,24[A]. On the other hands, resistive SFCL increased up to 36.35[A], under the same conditions. This enabled the flux-lock type SFCL to be easy to increase the capacity of power system.

• 한국초전도학회:학술대회논문집
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• v.13
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• pp.65-65
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• 2003

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.49-53
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• 2006

A high temperature superconductor (HTS) has been developed for power applications such as power cables, fault current limiters and superconducting magnetic energy storage devices. For such applications it is required to understand the DC voltage-current characteristic of the HTS. which is important in analyzing AC loss and flux flow loss quantitatively. In this work, we have experimentally investigated influence of several factors, e.g. critical current density. degradation and AC external magnetic field, on the DC voltage-current characteristic. The measured results have been discussed in engineering application point of view.

• Progress in Superconductivity
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• v.3 no.2
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• pp.241-246
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• 2002

We have performed the current and voltage loading tests of resistive superconducting fault current limiters (SFCLS) based on $YBa_2$$Cu_3$$O_{7}$(YBCO) films with the diameter of 2 inch. The SFCL consists of meander-type YBCO stripes covered with 200 nm Au layer grown in situ for current shunt and heat dispersion at hot spots. The minimum quench current of an SFCL unit was about 25 Apeak. Seven SFCL units were connected in parallel fur the current load ing tests at power source of 100 $V_{rms}$ $/2,000A_{rms}$. This SFCL units had maximum limiting current of 170 Apeak during the fault instant and then successfully controlled the fault current below 100 Apeak within 1~2 msec after short circuit. Increased short current also reduced the quench completion time with little change of current limiting characterization. We connected six SFCL units in series fur the voltage loading tests at power source of $1,200 V_{rms}$/170 $A_{rms}$ at this time. The shunt resistors were inserted into each SFCL unit to eliminate power imbalance originated from serial connection of SFCL units. Each SFCL unit was quenched simultaneously during the fault condition. The current increased up to 40 $A_{peak}$ and decreased to 14 $A_{peak}$ after 3 cycles. Quench was completed within 1 msec after the fault. We confirmed operating characteristics of 140 kVA($120 A_{rms}$ $\times$ 1,200 $V_{rms}$) SFCL and presented the manufacturing possibility of 3.3 kV SFCL using 4 inch YBCO films.BCO films.lms.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.292-293
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• 2011

We proposed a new power system, Superconducting Power System. The SPS consists of superconducting power cables, fault current limiters, and transformers. The basic concept is to replace 154kV conventional cables with 22.9kV superconducting cables and to convert a 154kV substation into a 22.9kV switching station in downtown area. For the application of the SPS to real power system, it is very important to construct the protection system of the SPS. This study presents a protection system for the new Superconducting Power System (SPS).

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.52-55
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• 2010

A sub-cooled liquid nitrogen system is known as a promising method to develop high voltage superconducting apparatuses such as superconducting fault current limiters (SFCLs) and superconducting cables. To develop a high voltage superconducting machine adopting the sub-cooled liquid nitrogen system with a constant pressure. injecting a non-condensable gas is indispensable. In this study. the dielectric characteristics of insulation gases are investigated and analyzed by using electric utilization factors ($\xi$). It is found that the maximum electric field at sparkover that occurs with 50 % probability. $E_{MAX.50%}$ exponentially decreases as the S increases. This means that the $E_{MAX.50%}$ at sparkover can be estimated with the $E_{MAX.50%}$