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The power demand is rapidly increasing in Korea, especially in the urban areas that include the metropolitan area. In addition, the transmission system in Korea is a network structure that ensures the high reliability and stability of power supply. Accordingly, the fault current rapidly increases in the case of a power system fault, due to the decrease in the line impedance. The superconducting fault current limiter (SFCL) was devised to address these existing problems refid="ref1"/refid="ref2"/refid="ref3"/ refid="ref4"/. [ABSTRACT FROM PUBLISHER] more...

We propose a new structure of superconducting fault current limiters (SFCLs) coupled with a conventional transformer. The proposed SFCL systems have structures that the primary winding and the secondary winding of a transformer are connected with normal power grids and the tertiary winding of a transformer is connected with superconductors. These structures have advantages of both a transformer type SFCL and a resistive type SFCL. Therefore our SFCL can easily control the current limiting ratio by variation of the turn number of a transformer and minimize quantity of superconductors. Also it can be invisible in normal power grids and not bulky structure unlike a transformer type SFCL or a flux-lock type SFCL. Experimental results are reported in terms of current limiting properties, fault voltages and quench characteristics of superconductors in this system. [ABSTRACT FROM PUBLISHER] more...

Most of the transmission system has a network structure to improve the reliability and stability of a power system. Fault current is continuously expected to increase by the increase of the power demand. If fault current exceeds the cutoff capacity of a circuit breaker, the circuit breaker is broken and the damage by fault current is expanded throughout the power system. Superconducting fault current limiter (SFCL) was designed to solve this problem in a power system. In this paper, we investigated the current limiting characteristics and power burden of superconducting elements of a flux-coupling type SFCL in three-phase power system. A Flux-coupling type SFCL is one of the resistive type SFCLs. The flux-coupling type SFCL was made by using a transformer. Reactors connected in each phase shared an iron core. When the superconducting elements were quenched in fault phase, the fault current flowed into the primary and secondary coils simultaneously. Thus, the current flowed into primary and secondary coils of sound phase by the magnetic coupling flux. Meanwhile, when the current of sound phase exceeded the critical current of the SFCL, superconducting elements connected in the sound phase were quenched. The value of the fault current tended to decrease as the first reactor's ratio increased. Furthermore, the power burden of the superconducting element was reduced. The reduced power burden of the superconducting elements shortens the recovery time of the superconducting element, which is advantageous for cooperation with a reclosing system when the SFCL is applied to the system. As a result, we confirmed that the flux-coupling type SFCL operated effectively in the three-phase power system. [ABSTRACT FROM AUTHOR] more...

We report the increase of the current limiting capacity of SFCLs by using the basic 1 \times 3 matrix module with 3 superconducting elements. To do this, we fabricated the basic superconducting module with the 1 \times 3 matrix structure which consists of a trigger part and current limiting parts. Firstly, we analysed the current limiting characteristics of the basic superconducting module with the 1 \times 3 matrix structure. Secondly, we investigated characteristics about the increase of the current limiting capacity of 2 \times 3 matrix-type SFCLs and 3 \times 3 matrix-type SFCLs which were connected in parallel with 2 or 3 basic 1 \times 3 modules. From this procedure, we approved that the easy increase of the current limiting capacity of SFCLs could be realized throughout the simply parallel connection of basic 1 \times 3 modules without complex wiring. We used YBCO superconducting thin films and constructed matrix-type SFCLs by using 9 superconductors and 3 reactors. Experimental results were reported in terms of the increase characteristics of the limiting capacity for fault currents and fault voltages. [ABSTRACT FROM AUTHOR] more...

The requirements for the application of the superconducting fault current limiter (SFCL) to the power system include larger SFCL capacity, linkage with the protection system in the power system and reliable operation in the reclosing system. Among the requirements, securing the reliability of the reclosing operation is the most important factor to apply an SFCL to the power system. In the cases of line-to-ground faults, which frequently occur in the power system, the reclosing system removes the fault cause by separating the fault section. The power can be supplied again later by reclosing the breaker. The separating operation is conducted again if the fault cause has not been removed. After the separating operation of the breaker, the superconducting element that has limited the fault current must recover to the superconducting state within the breaker opening duration. In this study, the recovery characteristic of the transformer-type SFCL in the case of reclosing operation was analyzed. It was proved that the power burden must be uniformly distributed by the simultaneous quench of superconducting elements, for the superconducting elements to completely recover within the breaking time of the circuit breaker. It was also found that all superconducting elements recovered to the superconducting state within the breaker opening time. Thus, it was found that the transformer-type SFCL with neutral lines coordinates well with the reclosing procedure in the power system, due to the quick recovery of superconducting elements. [ABSTRACT FROM AUTHOR] more...