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This paper proposes automatic power changeover switch system applied superconducting fault current limiter (SFCL) of the Korea electric railway using 25 kV-AC Scott transformer. The electric railway needs neutral section to separate two different electrical power phase to m phase and t phase. While the train passes through the neutral section, the electrical power supply phase is changed over to other phase. And that time, the train must turn off the circuit breaker to avoid transient as ‘inrush-current’ and ‘arc’. These cause negative problems as speed decline of the train, a shorter life of the train circuit breaker. To improve the problems, the inrush current limitation method is proposed. In addition, we analysed the effect of proposed method using time-domain transient simulation software (PSCAD/ EMTDC). [ABSTRACT FROM PUBLISHER]

Enlarging the electric power supply capacity of 22.9 kV distribution line by upgrading the main transformer from 60 MVA to 100 MVA has been under consideration in order to cope with increasing electric power demands of distribution line in Korea which aims to replace some 154 kV supply demands by 22.9 kV large-capacity distribution systems. In this case, the prospective fault current of 22.9 kV distribution line is much bigger than the rated withstand fault current level of conventional electric equipments. As a major feasible solution to reduce excessive fault current, superconducting fault current limiters (SFCLs) are considered to be installed at 154 kV/22.9 kV substation. But until now, certified specifications or test procedures were not available considering utilities' requirements. And the performances of various types of SFCLs were not deeply investigated regarding the reclosing scheme of conventional networks. In this paper, in order to determine the suitable type of SFCL for newly installed 22.9 kV large distribution line in Korea, requirements and specifications of SFCLs were proposed considering the installation spots of large-capacity distribution line. Four types of SFCLs were modeled and analyzed using EMTP and their performances focusing on the coordination with reclosers were investigated to verify the suitability into the large-capacity distribution line. Consequently, detailed specifications and expected installation sites were proposed and suitable types of SFCLs for 22.9 kV large-capacity distribution line were suggested. [ABSTRACT FROM AUTHOR]

A 100 MVA, commercial class high temperature superconducting (HTS) transformer was designed. In this paper the cryogenic system to extract the heat generated at the winding due to the AC loss and the heat penetration through the wall and the current lead and keep the winding temperature under design temperature is presented. The operation temperature is set at 67 K to increase the critical current and reduce the amount of HTS tape usage and the volume. The HTS winding was concentrically arranged to reduce the AC loss. The system consists of main cryostat with the windings and secondary cryostat with cooler, cryopump and the heat exchanger inside. The liquid nitrogen is entering the main cryostat at 65 K and assumed to be leaving at 67 K. The winding temperature distribution is simulated with the anticipated heat load using Fluent. The effect of the liquid nitrogen flow rate, inlet location is investigated and discussed. This work was supported by a grant from the Center for Applied Superconductivity Technology of the 21st Century Frontier R&D Program funded by the Ministry of Science and Technology, Republic of Korea. [ABSTRACT FROM AUTHOR]

HTS transformers which have been developed until now had only fundamental structures. Among the auxiliary functions of conventional transformers, voltage regulating is the most important one. For the voltage regulation, conventional transformers are equipped with on load tap changers (OLTCs). In this paper, we investigate the possibility of the HTS transformer with OLTC. For the case study, we designed a single phase 33 MVA HTS transformer with OLTC. It is one of three individual HTS transformers which composes a 3 phase, 100 MVA transformer. It is expected to substitute for a 3 phase, 60 MVA conventional transformer in Korea. The parameters of an HTS transformer are varied due to the gap length between primary and secondary windings. The length was decided for the transformer to have the impedance of 12%. Its size was limited to the one of the conventional transformer. The characteristics of the HTS transformer were analysed in both case of having OLTC and not. [ABSTRACT FROM AUTHOR]