• Progress in Superconductivity and Cryogenics
• /
• v.10 no.1
• /
• pp.42-47
• /
• 2008

In this paper, the fault current limiting characteristics for the superconducting fault current limiter(SFCL) using magnetic coupling between two coils were investigated. The SFCL consists of a high-$T_c$ superconducting(HTSC) element and two coils. This SFCL has different characteristics that depend on the connection form, the winding direction and the inductance ratio of two coils. The impedance and the operational current of the SFCL can be adjusted higher or lower than the resistance and the critical current of HTSC element. Therefore, the SFCL can change the amplitude of the limited fault current. To confirm it, the HTSC element was modeled and the fault current limiting characteristics of the SFCL were analysed through computer simulation. It was obtained from the analysis that the connection form and the winding direction of two coils of the SFCL were the important design parameters.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.9
• /
• pp.714-717
• /
• 2010

The improved flux-lock type superconducting fault current limiter (SFCL) is composed of a series transformer and superconducting unit of the yttrium-barium-copper-oxide (YBCO) coated conductor. In this paper, we investigated current limiting characteristics through winding direction of coil 2 and variable number of coil 1 and coil 2 in improved flux-lock type SFCL. The better fault current characteristics and the burden of YBCO coated conductor can be confirmed from the experimental result in the higher turn ratio of coil 1 and coil 2 in the additive conditions. In case of subtractive condition, we can confirm a similar result in the same case of experimental conditions. but the burden of YBCO coated conductor has been increased from an increase in winding numbers of coil 2.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.188-189
• /
• 2006

The flux-lock type superconducting fault current limiter (SFCL) has the attractive characteristics that can adjust the current limiting level by the turns ratio and the winding direction of two coils. To apply this type SFCL into power system, the analysis for the recovery characteristics of it together with the current limiting characteristic is needed. In this paper, the experiments of the current limiting and the recovery characteristics of the flux-lock type SFCL with YBCO thin film were performed. The recovery characteristics of the flux-lock type SFCL dependent on the winding direction of two coils were analyzed through the comparison with the resistive type SFCL.

• Proceedings of the KIEE Conference
• /
• 2000.11a
• /
• pp.236-242
• /
• 2000

NZP velocities were investigated on Ag sheathed multi filamentary Bi-2223 tape and direction type HTS cable. The critical current($I_c$) of Ag sheathed Bi-2223 tape and direction type HTS cable were 12 A, 63 A at 77 K, 0 T. NZP velocities of tape with two condition of DC and AC were almost same at each temperature. In case of DC, the NZP velocities of numerical analysis and experiment were almost same. NZP velocities of direction type HTS cable were 1.9-2.4 cm/sec. The result shows that the total transport current of spiral type HTS cable in $LN_2$ was 475[A], and transport current passed through almost the outer layer (2-layer). Also, AC transport losses in outer layer of HTS cable was proportion to $I^2$ and higher than losses of inner layer. And in case of $I_p=I_c$, calculated numerical loss density was concentrated on the edge of tape and most of loss density in cable was distributed outer layer more than inner layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.8
• /
• pp.694-697
• /
• 2009

The separated three-phase flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In this paper, we investigated the current limiting characteristics through winding number of coil 2 and winding direction in the flux-coupling type SFCL. Through the analysis, it was shown that additive polarity condition and lower winding number of coil 2 have advantaged from the point of view of fault current limiting and burned of YBCO coated conductor.

• Korean Linguistics
• /
• v.74
• /
• pp.169-197
• /
• 2017

The purpose of this paper is to seek the development direction of the studies on improving of broadcasting language, by examining the fruits and the limitations of existing research. Firstly, this paper makes sure that the study on improving of broadcasting language is one of the subtypes of study on broadcasting language. Then the current state of the studies on improving of broadcasting language is analyzed by genre, problem, and assessment standard. According to this analysis, existing research is concentrated too much in certain genres such as current affairs and news, but also in certain problems such as accuracy or publicness infractions. Finally, this paper concludes by suggesting three development directions of the future studies on improving of broadcasting language as follows: (1) Accuracy or publicness related problems need no more studies on themselves but continuous and systematic monitoring and institutional device. (2) We need more interest and research on language used in certain genres such as TV home shopping and commercial break. (3) Fairness or soundness related problems need more studies on themselves, because the judgement or assessment standard of these problems is not only difficult to find out, but also in need of viewer and listener awareness investigation and social agreement procedure.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.6
• /
• pp.2971-2978
• /
• 2013

Recently, with the world-wide issues about global warming and CO2 reduction, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with the distribution systems. However, DGs can change the direction of the power flow from one-direction to bi-direction, and also change the direction and amount of fault current of existing distribution systems. Therefore, it may cause the critical problems on the power quality and protection coordination. This paper proposes an operation algorithm for bi-directional protection coordination using and apply it for the evaluation system for protection coordination. From the simulation results It is found that the proposed method is more effective and convenient than existing method.

• Journal of the Korean Data and Information Science Society
• /
• v.17 no.4
• /
• pp.1107-1117
• /
• 2006

In this thesis, we conduct a comprehensive analysis of the current situation and the inherent problems found in modern statistics education in Korea. We investigate the American probability and statistics curriculum currently used in Wisconsin and discuss the overall state of statistics education in The United States. Through comparison of both the Korean and Wisconsin model, we explore the future direction of statistical education.

• 한국초전도학회:학술대회논문집
• /
• v.13
• /
• pp.82-82
• /
• 2003

• Proceedings of the KWS Conference
• /
• 1994.10a
• /
• pp.134-137
• /
• 1994

In this study, The mean weld current is used to correct depth direction, and weight-value, specially devised to check right-left deviation by placing more weight on the left- and right-most part of weld current during weaving, to correct weaving direction. The methodology of “design of experiments” was introduced to find out dorminant weld parameters affecting these for values.