• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.390-395
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• 2015

Molded insulation materials are widely used from large electric power transformer apparatus to small electrical machinery and apparatus. In this study, by adding MgO with the average particle of several tens nm and the excellent thermal conductivity into molding material, we improved the problem of insulation breakdown strength decrease according to rising temperature in overload or in bad environmental condition. We confirmed the life evaluation by using the insulation breakdown and inverse involution to investigate the electrical characteristics of nano-composites materials. By using a scanning electron microscope, it is confirmed that MgO power with the average particle size of several tens nm is distributed and the filler particles is uniformly distributed in the cross section of specimens. And it is confirmed that the insulation breakdown strength of Virgin specimens is rapidly decreased at the high temperature area. But it is confirmed that the insulation breakdown strength of specimens added MgO slow decreased by thermal properties in the high temperature area improved by the contribution of the heat radiation of MgO and the suppression of tree. The results of life prediction using inverse involution, it is confirmed that the life of nano-composites is improved by contribution of MgO according to the predicted insulation breakdown strength after 10 years of specimens added 5.0 wt% of MgO is increased about 2.9 times at RT, and 4.9 times at $100^{\circ}C$ than Virgin specimen, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.333-339
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• 2004

For an electrical insulation design of HTS cable, it is important to understand the dielectric characteristics of insulation materials in L$N_2$ and the insulation type. Generally, the electrical insulation of HTS Cable is classified into two types of the composite insulation and solid insulation type. In this research, we selected the insulation paper/L$N_2$ composite insulation type for the electric insulation of a HTS cable, and studied electric insulation characteristics of synthetic Laminated Polypropylene Paper(LPP) in liquid nitrogen(L$N_2$) for the application to high temperature superconducting(HTS) cable. Furthermore, we compared the breakdown characteristics of the butt gap and bended mini-model cable. It is necessary to understand the winding parameter of insulation paper/LN2 composite insulation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.141-142
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• 2019

As part of the recent low-energy policy, insulation standards for buildings are increasing every year. In addition, the conventional styrofoam heat insulation material has a problem in that the thickness of the heat insulation material to achieve the standard heat transmission rate is rapidly increased. Although the risk of spreading the structure vulnerable to fire due to insufficient spacing between buildings due to thickened insulation is increasing, the high cost of high efficiency insulation is difficult to solve. On the other hand, it is known that the method to be used as a formwork using insulation is excellent in cost reduction effect by reducing the amount of formwork used and simplifying the subsequent insulation work. The purpose of this study is to evaluate the strength characteristics of multi - layered insulation materials with appropriate strength by reducing the thickness of the insulation by appropriately combining high performance phenolic foam insulation and styrofoam insulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1136-1141
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• 2003

The primary insulation materials used in an oil filled transformer are kraft paper, wood, porcelain and oil. Modern transformers use chemically treated paper to improve its tensile strength and resistance to aging caused by immersion in oil. But these insulation papers are mainly aged by thermal stress. Over the life time of the insulation paper and oil, it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper used in the layer insulation. We made two aging cells in which insulation papers and mineral oil are conducted to test thermal properties. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.222-223
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• 2018

Recent government policies are increasing interest in zero-energy housing, a building that minimizes energy consumption (90% reduction). As the importance of building passive performance is emphasized, the role of insulation is increasing as a way to reduce indoor heat loss in order to minimize the use of cooling and heating energy. There are two main types of insulation. Organic insulation is widely used for various construction structures such as construction and industrial due to some merits such as the convenience of construction and construction cost. However, it has been pointed out as a main cause every time a fire accident occurs, Jecheon Sports Center', the fire damage of buildings caused by the use of organic insulation materials is expanding to social problems, so it is urgent to research on nonflammable inorganic insulation materials.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1012-1018
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• 2006

In this study, the insulation performance of thermal insulation materials such as glass wool, polyetylene and flexible lastomeric foam according to water vapor permeance was estimated by using experimental correlation equation. The results showed the conductivity increment of flexible lastomeric foam which has very low-permeability (${\le}0.15[ng/{\cdot}s{\cdot}Pa]\;or\;{\mu}{\ge}1,000$) is about 50% lower than that of glass wool with the lapse of ten years. The conclusion is that moisture inevitably accumulated in permeable Insulations reduces insulation performance and also accelerates surface condensation in the case of cold water system.

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.43-47
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• 2003

For an electrical insulation design of HTS cable, it is important to understand the dielectric characteristics of insulation materials in $LN_2$ and the insulation type. Generally, the electrical insulation of HTS Cable is classified into two types of the composite insulation and solid insulation type. In this research, we selected the insulation paper/$LN_2$ composite insulation type for the electric insulation of a HTS cable, and studied electric insulation characteristics of synthetic Laminated Polypropylene Paper (LPP) in liquid nitrogen ($LN_2$) for the application to high temperature superconducting (HTS) cable. Furthermore, we compared the breakdown characteristics of the butt gap and bended mini-model cable. It is necessary to understand the winding parameter of insulation paper/$LN_2$ composite insulation.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.302-304
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• 1997

Chemical structure and electrical properties such as water treeing and space charge accumulation of various raw materials(XLPE) used for power cable insulation were investigated. It was found that chemical structure was changed after crosslinking reaction and every materials have different amounts of DCP and antioxidant. Electrical properties were also changed after extraction using $CHCl_3$ and xylene. Water tree length was smaller with additives such as DCP and antioxidant and bigger with low molecular weight components of polyethylene than that of extracted samples. Heterocharge was changed into homocharge after extraction. This shows that additives and low molecular weight components of polyethylene cause the heterocharge.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.571-577
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• 2020

Thermal analysis was performed for a cold box of a hydrogen liquefaction pilot plant with 0.5 ton/day capacity. The pilot plant has adopted a hydrogen liquefaction process using two-stage helium Brayton cycle with precooling of liquid nitrogen. The cold box for hydrogen liquefaction has generally vacuum insulation but inevitable heat invasion by conduction and radiation exists. The heat loads were calculated for cold box internals according to multilayer insulation emissivity. Total heat load of 181.7 W is estimated for emissivity of 0.03 considered in field condition.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.5
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• pp.701-710
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• 2009

This study was conducted to develop excellent insole with good thermal insulation using new materials. We investigated that aerogel/fiber composite can be used as padding materials of shoes by comparing surface shape, moisture regain, water vapor permeability, thermal insulation and compression rate of insole materials tried with nonwoven fabric padding materials and insole sold in market. The results are as follows. Surface shapes were shown that the most appropriate material for sealing aerogel/fiber composite was high density fabric as per size of particle of aerogel. Moisture regain of aerogel/fabric composite was better than nonwoven fabric padding samples. However, when compared to insole sold in market, its moisture regain was worse than those of insole merchandises. Water vapor permeability was higher in material padded with nonwoven fabric than materials padded with aerogel/fiber composite in all three kinds of sealing fabrics. Thermal conductivity of aerogel/fabric composite was lower than nonwoven fabric material regardless of sealing fabrics. Thermal insulation of aerogel/fiber composite was higher than padding material of nonwoven fabric regardless of sealing fabrics. Compression rate of nonwoven (SP1) was higher than that of aerogel/fiber composite (SP2). Compressive elastic recovery rate of SP1 was also higher than that of SP2, which its compression rate and compressive elastic recovery rate were both poor. As the above result, ultra porous aerogel/fiber composite were proved to be material of good thermal insulation with lower thermal conductivity and also compression rate was proved to be low. Therefore, we can say that aerogel/fiber composite have high possibility to be used as insole materials for cold winter shoes requiring good thermal insulation protection.