• Progress in Superconductivity and Cryogenics
• /
• v.10 no.1
• /
• pp.24-27
• /
• 2008

For the development of superconducting fault current limiters(SFCLs) having large current capacity, we fabricated an SFCL element that consists of Bi-2212 superconductor and Cu-Ni alloy tubes. First, Ag was plated on the surface of the Bi-2212 for the enhancement of soldering process. On the Ag-plated Bi-2212 tube, a Cu-Ni alloy tube was soldered using optimized solders and soldering conditions. The BSCCO/Cu-Ni composite was processed mechanically to have a helical shape for the improvement of the SFCL characteristics. The total current path of the SFCL element was 1330 mm long with 12 turns, and had critical current of 340 A at 77 K. Finally, we carried out the fault test using the fabricated SFCL element. It showed successful current limiting performance under the fault condition of 50 $V_{rms}$ and 5.5 kA. From the results, the rated voltage of the SFCL element was decided to be 0.4 V/cm, and the power capacity was 12 kVA at 77 K. The fabrication process of the SFCL and the fault test results will be presented.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.8
• /
• pp.27-37
• /
• 2010

Downdrag force develops when a pile is driven through a soil layer which will settle more than a pile. There is no obvious criterion for application of the current pile design method considering the negative skin friction. Therefore, in this study, numerical analyses were performed to investigate the behavior of a single pile subjected to negative skin friction and their results were used to determine the applicability of the current design method. Including three different sites in Song-do area and two different cases with friction pile and end bearing pile conditions, total six cases were considered. The load-settlement relationships and the neutral points were estimated for different end bearing conditions and the allowable bearing capacity of piles with negative skin friction was investigated through parametric studies. Based on the results showed that the negative skin friction made a major influence on the settlement of a pile and its stress. However the allowable bearing capacity may not be influenced by the negative skin friction. Compared with the allowable bearing capacity obtained from the ultimate bearing capacity with the safety factor of 3, the current design method with the safety factor of 3 underestimated the allowable bearing capacities regardless of the end bearing conditions. On the other hand, the current design method with the safety factor of 2 yielded reasonable results depending on the end bearing conditions.

• 한국전기화학회:학술대회논문집
• /
• 1998.12a
• /
• pp.7-27
• /
• 1998

In order to design capacity of lithium ion battery, some calculations were carried out based on the characteristics of materials by the given battery shape and dimension. The principle of design was built by the interpretation of the correlation of material, electrochemical and battery factors. Parameters of materials are fundamental physical properties of constituent such as cathode. separator, anode, current collectors and electrolyte. Electrochemical factor includes potential pattern as a function of specific capacity, specific discharge capacity(or initial irreversible specific capacity or Ah efficiency) as a function of specific charge capacity and material balancing. Parameters of battery are dimension, construction hardware and performance. Battery capacity was simulated for a lithium cobalt dioxide as cathode and a hard carbon as anode to achieve 1100 mAh for the charge limit voltage of 4.2V, the weight ratio(+/-) of 2.4 and ICR18650. A fabricated test cell (ICR18650) which have weight ratio(+/-) of 2.4 discharged to 1093 mAh for the charge limit voltage of 4.2V. The sequential discharge capacity show good correspondence with designed capacity.

• Earthquakes and Structures
• /
• v.1 no.4
• /
• pp.391-410
• /
• 2010

There are several important considerations that need to be made in the capacity design of RC frame-wall structures. Capacity design forces will be affected by material overstrength, higher mode effects and secondary loadpaths associated with the 3-dimensional structural response. In this paper, the main issues are identified and different means of predicting capacity design forces are reviewed. In order to ensure that RC frame-wall structures perform well it is explained that the prediction of the peak shears and moments that develop in the walls is particularly important and unfortunately very challenging. Through examination of a number of case study structures it is shown that there are a number of serious limitations with capacity design procedures included in current codes. The basis and potential of alternative capacity design procedures available in the literature is reviewed, and a new simplified capacity design possibility is proposed. Comparison with the results of 200 NLTH analyses of frame-wall structures ranging from 4 to 20 storeys suggest that the new method is able to predict wall base shears and mid-height wall moments reliably. However, efforts are also made to highlight the uncertainty with capacity design procedures and emphasise the need for future research on the subject.

• Environmental and Resource Economics Review
• /
• v.25 no.1
• /
• pp.113-140
• /
• 2016

Achieving the two goals of providing stable remuneration and promoting market based incentive for generation capacity with only one kind of capacity price is a difficult proposition. This paper suggests a market design in which two different kinds of capacity prices are used to achieve these goals. It maintains the current capacity price that is determined administratively based on the fixed cost of the gas-turbine generator. A second capacity price is added that covers generators with higher fixed costs and lower fuel costs such as combined-cycle gas turbine, coal-powered, and nuclear generators. This second capacity price is conditional on a lower energy price ceiling and determined by the interaction of the market supply and a demand schedule derived from the optimal fuel mixed principle.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.169.1-169.1
• /
• 2010

Due to global warming, the need to secure an alternative resource has become the international issue. Not like other renewable energy sources, TCP is the high reliable and predictable and continuous energy source as the current pattern and speed can be predicted throughout the year. Having very strong tidal current speeds, there are many suitable site for the application of TCP (Tidal Current Power) on the west and south coastal region in Korea. The maximum current speed in the south is recorded up to 6.5m/s. Due to the high tidal current speed on the west coast of Korea, numerous tidal current projects are being planned. To extract a significant quantity of power, a tidal current farm with number of devices is required in the ocean. However, it is important to estimate the potential quantity of energy in the area. Also the realistic quantity that can be extracted is to be investigated. Based on the estimated energy production considering the number of devices and the interactional effects, system type, the water depth and etc., the cost of the development and the benefit from SMP can be estimated. The feasibility study for the 200MW tidal in Incheon, Korea has been performed recently. Based on the actual feasibility study, the procedure and the key points for the application of tidal current power farm are introduced in the paper.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.8
• /
• pp.1163-1171
• /
• 2017

The problem of fault current to exceed the rated capacity of a power circuit breaker can cause a serious accident to hurt the reliability of the power system. In order to solve this issue, current limiting reactors and circuit breakers with increased capacity are utilized but these solutions have some technical limitations. Back-to-back high voltage direct current(BTB HVDC) may be applied for reducing the fault current. When BTB HVDCs are installed for reduction in fault current, selecting the optimal location of the BTB HVDC without causing overload of line power becomes a key point. In this paper, we use genetic algorithm to find optimal location effectively in a short time. We propose a new methodology for determining the BTB HVDC optimal location to reduce fault current without causing overload of line power in metropolitan areas. Also, the procedure of performing the calculation of fault current and line power flow by PSS/E is carried out automatically using Python. It is shown that this optimization methodology can be applied effectively for determining the BTB HVDC optimal location to reduce fault current without causing overload of line power by a case study.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.7 no.2
• /
• pp.107-120
• /
• 1987

This study is directed for the evolution of the rational approaches to the systematic evaluation of the load carrying capacity of bridges based on the practical and second moment reliability methods. A new approach for the evaluation of load carrying capacity of exsisting bridges is proposed in this study. The key idea behind this approach is in the fact that the load carrying capacity of an existing bridges under extreme traffic truck loadings may be measured by evaluating and classifying the reliability state of the bridge in terms of reliability index(${\beta}$). The rating formulas developed in this study are applied for the evaluation of load carrying capacity of the several actual deteriorated bridges inspected and tested for the capacity rating, and the results are compared with those calculated by using the current rating formulas. It may be concluded that the proposed rating formulas which is derived based on reliability methods, have to eventually replace the current rating formula when the basic statistical data for the resistance and load effects become available in the near future.

• Journal of IKEEE
• /
• v.28 no.1
• /
• pp.14-19
• /
• 2024

To determine the performance of recycled cells for application to residential BESS, cells used over the past 5 years were selected. The basic specifications of the cell used in the test are nominal voltage of 3.7[V], nominal capacity of 2,200[mAh], charging voltage of 4.05[V], continuous discharge current of 1[C](2,200[mA]), continuous charging current of 0.5[C](1,100[mA]). For new cells, the internal resistance was 21.3±1[mΩ], but for recycled cells, the average internal resistance was 25.38[mΩ], an increase of about 19.1[%]. The charge·discharge capacity was approximately 18.9~19.3[%] lower than that of a new cell. Because internal resistance and charge·discharge capacity are closely related to cell aging, cells to be applied to BESS need to use products with an initial internal resistance of 1.5 times or less and a charge·discharge capacity performance of 70[%] or more.

• Journal of the Korean Geotechnical Society
• /
• v.32 no.11
• /
• pp.61-72
• /
• 2016

For the construction of high-rise structures and the optimized foundation design, the use of the large-diameter PHC pile has increased. Especially, the use of the 600 mm diameter PHC pile has significantly increased. In this study, for the evaluation of the suitability of the current design practice, the 46 dynamic pile load tests, which were carried out in the 600 mm diameter preboring PHC pile, are analyzed. The end bearing capacity is obtained from the end of initial driving test and the shaft capacity is estimated from the restrike test. The allowable capacities estimated by the dynamic load test are compared with those based on the current design practice. The analyses show that the allowable end bearing capacity evaluated by the dynamic pile load test is greater than the design practice in most piles. The allowable shaft capacity, however, is smaller than the design practice in many piles. The higher end bearing capacity and the smaller shaft capacity may result from the improvement of the drilling equipment and the increase in the penetration depth. Thus, the portion of the end bearing capacity in the total capacity increases.