• 대한기계학회논문집
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• 제18권4호
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• pp.986-996
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• 1994

Insulation system of LNG carrier has made important roles such as maintaining a proper Boil off Ratio(BOR) for the cargo and avoiding the excessive low temperature of the adjacent inner hull beyond the permissible limit. At the same time, safety and economy of the LNG transportation by the ship are connected with the performance of the insulation system. Also, thermal insulation system of LNG carrier is one of the most advanced technique with the structure analysis of tank, welding and assembling. In this study a computer program is developed to calculate the hull temperature distribution and BOR, which are important factors in thermal design for the Moss Rosenberg Verft spherical tank type LNG carrier. Detailed results for hhull temperature distribution close to LNG tank, BOR and the thickness effect of insulation material are reported in this paper in the range of standare design sea condition.

• 전기의세계
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• 제22권3호
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• pp.13-24
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• 1973

In this report, as a method to solve the problems on impulse insulation coordination in ribbon core transformer owing to it's BIL stepping up, new design to alter winding distribution of multiple-layer concentric winding to Convex type winding is proposed. The main focus of this method is to settle the weakness of axial direction insulation strength and as a result of theoretical analysis through experiment of model transformers, the following conclusions are obtained; (a) As the electric loadings in a design which increases by strengthenning axial direction insulation endurance in presently avarilable transformers owing to it's BIL stepping up can be restricted in Convex type winding, reasonable design will be suited to the transformer with higher BIL. (b) Convex type winding is a very improved insulation design in respect of insulation coordination because it has shield plate effect to even impulse oscillation. (c) There is a disadvantage to cause leakage flux to increase in Convex type winding, however, the constancy of electric loadings in a design in spite of BIL stepping up restricts the increase of leakage flux to some extent.

• 한국안전학회지
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• 제25권6호
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• pp.81-85
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• 2010

In recent years, environmental concerns have been raised on the use of poorly biodegradable fluids in electrical apparatus in regions where spills from leaks and equipment failure could contaminate the surroundings. The vegetable insulation oils are highly biodegradable, have negligible effect on the environment, human health and ecosystem. Therefore, to assure their safe use in electrical power systems, it may require some processing and modification to improve some of their physical, chemical, thermal and electrical properties. This paper provides a comparative results of the electrical breakdown properties of several vegetable insulation oils and mineral oil to use as dielectric fluid in environmental-friendly pole transformer. Also, the electrical breakdown property of the Nomex and kraft insulation papers in vegetable insulation oil is examined.

• 한국표면공학회지
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• 제22권3호
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• pp.109-117
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• 1989

The effect of heft treatment on the characteristic properties of insulation layer is studied for two kinds of non-oriented silicon steels, which were insulation-coates with various kinds of inorganic and inorganic-organic complex coating solutions. In addition, how the carbon contained in the insulation layer would affect the carbon content and the magnetic properties of the steel substrates is examined. Lower temperature heat treftment ($480^{\circ}C$ for 0.5hr) is found to render morw favorable surface qualities, wheras higher temperature heat treatment ($790^{\circ}C$ for 2hr) better core loss due to grin growt occurred during the heat treatment. Decarburization of the steel substrate is also found unaffectrd by the presence of carbon in the insulation layer.

• 한국안전학회지
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• 제25권3호
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• pp.78-82
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• 2010

This study is to test insulation mortar mixed with wastepaper and sawdust to find out its insulation performance. Therefore, wastepaper and sawdust have been added to normal mortar. They are analyzed for the above purpose using compressive strength and insulation performance. It is found that the more wastepaper and sawdust will be mixed, the lower heat conductivity will be taken. Wastepaper and sawdust mixture will be more 2.0% then the insulation mortar quality can be compatible with the 3rd kind of the standard. Optimal mixture for insulation will be wast paper:sawdust=4:6. Cohesive test of materials showed that test material has stronger than stand are $0.10N/mm^2$. It is satisfactory the test result showed a range of $0.12{\sim}0.15N/mm^2$ from the test result. Optimal mixture of wastepaper and sawdust have been found out from the study comprehensively, exclusive of the proportion of wastepaper:sawdust = 8:2. It is thought that standard of length deformation; 0.5% is reasonable. This means that deformation of mortar itself can be considered. But it is also Shown that water mixture has also been sharply changed at first flow test. Therefore, it is thought that absorbed water content in the material gave considerable effect to variation rate.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1181-1187
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• 2015

Sulfur hexafluoride (SF₆) gas is used widely in electric power equipment such as Gas Insulated Switchgear (GIS), Gas Insulation transmission Line (GIL), and Gas Circuit Breaker (GCB). But applications of SF₆ should be restricted because SF6 gas is one of the greenhouse effect gases. To reduce use of SF₆ gas, a study on eco-friendly alternative insulation medium is needed. In this paper, we investigated lightning impulse (LI) breakdown of dry-air which is attracting attention as an ecofriendly alternative gas and the LI breakdown of hybrid insulation combined with dry-air and solid insulation (Room-Temperature Vulcanizing Silicone Rubber-RTV SIR) and dry-air in inhomogeneous fields according to gap distance and pressure. The experiment results showed that the LI breakdown strength of hybrid insulation system was higher than that of dry-air insulation system. It was verified that the development of technology related to eco-friendly power apparatus compact such GIS, GCB and GIL can be used as basic research data.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.585-591
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• 2021

Liquefied hydrogen have advantage which reduces the volume by about 800 times or more compared to hydrogen gas, so it is possible to increase the storage density. However, liquefied hydrogen produced by cryogenic cooling of 20 K or less at normal pressure has a problem of maximizing the insulation effect that blocks heat introduced from the outside. Representative insulation technologies include vacuum insulation and multi-layer insulation materials and in general, heat blocking is attempted by combining insulation technologies. Therefore, in this study, the pressure of the internal vacuum layer was changed to 10^-1, 10^-2, 10^-3 and 10^-4 Torr to confirm the thermal insulation performance of the vacuum jacket valve for transporting liquefied hydrogen. As a result, it was confirmed that the insulation performance improved as the degree of vacuum increased.

• 한국수소및신에너지학회논문집
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• 제29권4호
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• pp.386-392
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• 2018

Fuel cells are known as eco - friendly energy facilities that can use heat energy and electric energy at the same time. Fuel cells are classified according to the temperature and material used, and solid oxide fuel cell (SOFC) is relatively high temperature ($700-800^{\circ}C$). SOFC requires a hot box consisting of a high temperature stack, a reformer, a burner, and the heat exchangers in order to use energy efficiently. The hot box needs to maintain heat insulation performance at high temperature to reduce heat loss. However, Fibrous insulation, which is widely used, needs to be improved because it has a disadvantage that the thermal conductivity is rapidly increased due to the increase of temperature. Therefore, this study was carried out to develop a thermal insulation, which is applied to multiple layers insulation (MLI) technic, that can be used under SOFC operating conditions and prevent a drastic drop in thermal conductivity at high temperature. The developed insulation is consist of a thermally conductive material, a spacer, and a reflective plate. The thermal conductivity of the insulation was measured by in the thermal conductivity measuring device at high temperature range. As a result, it was confirmed that the developed layers insulation have an good thermal conductivity (0.116 W/mK) than fibrous insulation (0.24 W/mK) as a radiation shielding effect at a high temperature of 1,173 K.

• Transactions on Electrical and Electronic Materials
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• 제17권3호
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• pp.163-167
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• 2016

Inverter surge resistant enameled wire was prepared with an organic/inorganic hybrid nanocomposite, and the effect of ambient temperature on the insulation lifetime of the enameled wire in the form of twisted pair was studied by a withstanding voltage tester. The organic polymer was Polyesterimide-polyamideimide (EI/AI) and the inorganic material was a Nano-sized silica (average particle size : 15 nm). The enamel thickness was 50 μm and the ambient temperature was 100, 150, 200, and 250, respectively. Transmission electron microscopy (TEM) observation showed that Nano-sized Silica were evenly dispersed in EI/AI. There were many air gaps in a twisted pair, therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge accordi, ng to Paschen’s law. As ambient temperature increased, insulation lifetime decreased according to Arrhenius relationship, which was explained by the increasing mobility of polymer chains in EI or AI. And insulation breakdown voltage value at 10 kHz was 1,864.5 sec (31.1 min), which is 1.9 times higher than at 20 kHz, 981.6 sec (16.4 min).

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권1호
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• pp.15-20
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• 2004

This paper discusses electrical insulation characteristics at cryogenic temperature, especially focusing on partial discharge (PD) inception characteristics, for high temperature superconducting cables. In liquid nitrogen (L$N_2$) / polypropylene (PP) laminated paper composite insulation system, PD inception strength (PDIE) was evaluated in terms of volume effect and V-t characteristics. Different kinds of butt gap condition were applied in the experiments, using parallel plane and coaxial cylindrical cable samples. Experimental results revealed that the volume effect on PDIE could be evaluated by the statistical stressed liquid volume (SSLV) taking account the discharge probability not only in the butt gap but also in the other thin layers between PP laminated papers. Furthermore, the indices n of V-t characteristics at PD inception were estimated to be 80∼110, irrespective of the butt gap condition.