• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.656-661
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• 2009

In this study, theoretical analysis and evaluation tests were performed to assess the pipe stability against compaction equipments and vehicle loads when conventional construction criteria for pre-insulation heating pipes are applied and the alternative material, crushed sand, are used for backfills. The research outcomes shows that (1) the conventional code criteria for pre-insulated heating pipes is well established to support compaction equipments and vehicle loads, (2) the crushed sands as an alternative is usable as backfill materials for pre-insulated heating pipes based on the suitability evaluations of various types of pipes, and (3) the crushed sand agree well with the design consideration of pre-insulated heating pipes construction in the points of economical efficiency and construction criteria.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.19-22
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• 2007

In this study, we investigated operating characteristics of natural gas fuel processor for polymer electrolyte membrane fuel cells (PEMFCs). The fuel processor consists of a natural gas reformer, a water-gas shift reactor, a heat-exchanger and a burner, in which the overall integrated volume is exactly(exceptionally) small, namely, about 10L except outer insulation. The producted hydrogen is $1Nm^3/hr$ and the maximum thermal efficiency is ${\sim}76%$(low heating value) at full operating load. A compact and highly efficient $1Nm^3/hr$ class natural gas fuel processor was developed at UNISON is an advantage for application in residential PEMFCs co-generation systems.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.1
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• pp.45-47
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• 2011

Recently, research works for electrical properties on the elastic epoxy have been also progressing to diagnose insulation materials by development of measure technology. The epoxy which specially applied for high voltage instruments have required for the electrical, mechanical and thermal properties. Nanocomposites were made from insulating material epoxy resin using for power transformer as varying g amount of addition of SiO2, we found the change of physical characteristics of nanocomposites by using SEM and XRD. To investigate the electrical properties according to the amount of addition and temperature, tested insulting breakdown in silicon oil. As the result of insulting breakdown testing, the insulting breakdown strength increased according to change of the amount of addition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.69-71
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• 2001

FRP has been used very much as high strength core materials for insulators because of its high strength and good insulation properties. In this study cantilever, tension and torsion stress were simulation along to the unidirection glass fiber. In addition, FRP was made by pultrusion method. This paper proposed the procedure of the finite element model updating and pretest using the commerical finite element code MSC.Nastran. To ehance the efficiency of experimental modal analysis. we proposed the process which is the selection of the locations and the number of measurement points for pre-test.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.397-400
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• 2009

When the metal sheet is subjected to the housing surface for fitting and insulating from harsh surroundings like fluid ingression or hot steam, both strength and formability have to be equally considered. In this regard, the main aim of this study is to design an apparatus of cost-effectively producing flexible fluted band with increasing the formability of embossed stainless steel sheet, which is utilized as a thermal insulation metal for housing ship engine exhauster. Designed to fabricate a maximum sheet width of 700 mm, this new apparatus consists of upper roll made of hard urethane and the female-etched lower roll made of SKD11, have a producing capacity up to 1-meter homogeneously embossed sheet for just 60 seconds. This machine is devised for the maximum operating efficiency from original sheet handling to machine setting. The embossing properties are characterized by 3-D profiling. After embossing plain metal sheet, both yield strength and elongation properties are improved simultaneously, indicating the effectiveness of the newly designed apparatus.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.6
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• pp.279-285
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• 2005

The lightning causes the damage of power system equipments as well as large power failure. Therefore, the insulation design should be established not only to decrease the damage of the facilities itself but also to increase the reliability of electric power system. This paper describes the useful way applying underbuilt ground wire and guy wire in transmission tower that safely protect the substation equipments. One or more shield wires under the phase conductor will not intercept lightning stroke, but they may improve reduce lightning voltages almost as effectively as if they were above the phase conductors. And the guy wires will mitigate the tower surge response. These would not only reduce backflashover possibility but also minimize crest and duration of surges entering the substation. EMTP is used to analyze the efficiency of the proposed methods.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.4
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• pp.89-97
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• 2008

A downdraft gasifier was manufactured for biomass gasification. The gasifier was designed based on the principles of gasification presented in previous studies. The pipes of 25mm diameter were used for both supplying air and discharging producer gas. Wood charcoals were mostly used for fuels. The concentration of CO ranged from 25 to 35%, comparable to the values presented in other studies. The temperature outside wall of the gasifier was measured up to $400^{\circ}C$, indicating a great heat loss. When glass wool was cover over the wall, some parts of wire mesh located in the bottom of the reactor were molten down. There were several modifications that should be made in order to improve its efficiency and obtain more stable continuous gasification, including insulation, reduction in pressure loss, durable bottom meshes, the optimum length of reaction part, and safety.

• Journal of Electrical Engineering and Technology
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• v.7 no.1
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• pp.23-33
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• 2012

The current paper deals with a new live-line insulator inspection tool system that will be used by the Korea Electric Power Corporation for its 154 kV power transmission lines in 2011. Unlike the existing contact type tools, the developed inspection tool automates parts of the insulator inspection process using a sensor and an actuator. The tool sustains its weight independently, not by a lineman. In addition, the inspection tool measures the insulation resistance of an insulator together with its distribution voltage, thus providing more information for analysis and diagnosis. Such characteristics improve the system's operation efficiency, measurement reliability, and usability. We confirmed its effectiveness through live-line field tests with actual power transmission lines.

• Journal of Power Electronics
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• v.16 no.3
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• pp.861-871
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• 2016

With high penetration of renewable energies, power electronic transformers (PETs) will be one of the most important infrastructures in the future power delivery and management system. In this study, an isolated bidirectional modular multilevel DC/DC converter is proposed for PET applications. A modular multilevel structure is adopted as switching valves to sustain medium voltages to achieve modular design and high reliability. Only one high-frequency transformer is used in the proposed converter, which significantly simplifies the circuit and galvanic insulation design. A dual-phase-shift modulation strategy is proposed to regulate the output power and achieve a simple voltage balancing control. A down-scaled (2 kW/20 kHz) prototype is constructed to demonstrate the proposed converter and verify the control strategy. The experimental results comply with the theoretical analysis well, with the highest power efficiency reaching 97.6%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.135-136
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• 2017

This paper examines the efficiency of the application of conventional and insulated gang forms for curing and protection of concrete by comparing the amount of electric energy required therefor. In addition, a thermal vision camera was used to identify heat loss from surfaces of the gang forms after each placement of concrete. Experimental results, show that the heat loss at the submerged temperature was large at the submerged surface due to the large calorific value at the surface of the mold. The insulated gang form had some heat loss in the horizontal bars. In the case of adiabatic reforming, the pattern shows a constant calorific value over time. In conclusion, the insulation performance is better than that of general gang form.