• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.540-548
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• 2019

This study was conducted to develop insulation for solid oxide fuel cell (SOFC). The developed insulation is based on the lamination technology and the radiation shielding technology of the satellite insulation. The insulation material is consisting of insulation material for conduction resistance, spacer, and radiation shielding material. The experimental apparatus consisting vacuum bell jar, pump, heater and temperature recording device has developed to verify the performance of the insulation. The experimental values were used as reference data for the modeling development. In this paper, heat transfer is assumed to be one- dimensional phenomena for the prediction of insulation performance and internal temperature distribution in high temperature region of SOFC. The developed model was used to compare the performance difference of insulation types according to composition materials. The analysis result shows that the insulation including spacer and radiation shielding has better heat insulation performance than other cases. In this study, the thickness reduction effect of about 20% was shown compared to the insulation including only conductive material. It is noted that the radiant shielding material should be carefully selected for durability, because SOFC insulation should be used for a long time at high temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.289-290
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• 2008

The purpose of this paper is to analyze AC Breakdown of solid/air composite insulation depending on the thickness and the pressure of dry air for eco-friendly insulation. SF6 gas has been widely used in electric equipment as gas insulation because of high dielectric strength and arc extinguishing performance. However, because SF6 gas is one of the green house effect gases, alternative insulation such as SF6 mixture, extremely low temperature gas, vacuum, liquid and solid insulating are being investigated.

• 전기의세계
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• v.14 no.2
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• pp.8-13
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• 1965

It is expected that the impurities contained in a solid state insulation material will affect a considerable influence on its break-down voltage, dielectric loss, and insulation resistance. In this thesis, as a preliminary experimental research for the investigation described above, the effect of metalic barrier between the electrodes on the creepin flash over discharge voltage along the surface of a solid insulation material has been investigated, and got some interesting results. It was found that generaly the flash over voltage rises when a metalic barrier is located between the electrodes. The results of this investigation will be taken into account as an important components on the insulation design to prevent the creeping flash over discharge in insulators, bushings, and so on.

• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.4
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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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1045-1047
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• 2017

In this study, we focused on development of the all-in-one case insulation for end-burning solid rocket motors. Material of insulation used unvulcanized rubber based on EPDM/kevlar. In case of boots insulation, preforms was made by using hot press molding, and then the tape was inserted between two preforms for all-in-one curing in the case. Finally bladder method was applied for curing of insulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.630-635
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• 2015

A vacuum Interrupter (VI), a core part that composes the breaking part of medium-voltage vacuum circuit breaker (VCB), has the excellent insulation performance and arc-extinguishing capability. $SF_6$ gas had been used for the external insulation of VIs since the dielectric strength of $SF_6$ gas is superior to that of other insulation gases. However, because of environmental problems related with global warming, a solid-insulated technology was recently researched. The functionally graded material (FGM), as changing spatially the distribution of the relative permittivity inside an insulator, can reduce the electric field stress at the specific region. Especially, the external insulation performance of the VI with the molded FGM insulator is greatly improved as compared with that of the existing VI or the VI with a new external shield. In this paper, the effectiveness of this FGM insulator is verified by the numerical simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.9-16
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• 2023

This paper investigated the method to predict a thermal response of internal insulation in a solid rocket motor considering both thermal decomposition and ablation. Changes in properties due to the thermal decomposition, swelling of char layer and movement of decomposition gases inside the material were considered during a modeling. And radiative/convective heat flux from the exhaust gas were applied as boundary conditions, while the chemical ablation of the material surface is modeled with algebraic equations. Test SRM with thermocouples was solved for a validation purpose. The results showed that predicted temperatures have identical trends and values compared to the experimental values. And an error of predicted thermal destruction depth was around 0.1 mm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.69-74
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• 2018

With the increasing development of industrial society and the availability of high quality electrical energy, the simplification of operation and maintenance procedures is required, in order to ensure the reliability and safety of electrical systems. In this paper, the dielectric breakdown characteristics of $N_2-O_2$ mixed gas solid insulation, which is used as an alternative to SF6 in various electric power facilities, are verified. When the gas mixture has a composition ratio similar to that of the atmosphere, the dielectric breakdown characteristics are relatively stabilized. It was confirmed that the breakdown voltage of the gas in the electrode near an equal electric field increased with increasing pressure according to Paschen's rule. The breakdown voltage of the surface increased linearly with increasing pressure, and the difference was caused by the mixing ratio of $O_2$ gas. This change in the surface insulation breakdown voltage was caused by the influence of the electrically negative $O_2$ gas and the intermolecular collision distance. In this study, the influence of the intermolecular impact distance was larger (than that in the absence of the electrically negative $O_2$ gas). The breakdown voltage relation applicable to Teflon according to the surface insulation characteristics was calculated. The characteristics of the surface insulation properties of Teflon, which is used as a solid insulation material, were derived as a function of pressure. It is thought that these results can be used as the basic data for the insulation design of electric power facilities.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.512-520
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• 2017

This paper is a numerical study of various methods of applying SOFC hot BOP insulation. The application methods are four cases from case 1 to case 4, and the performance difference between the result of applying powdered insulation and the result of zoning using composite multi-layer insulation was examined. Numerical results show that the thermal stability of composite multi-layer insulation is better than that of powder insulation when the thermal conductivity is 0.04 W/mK. In the future, we will increase the thermal conductivity of the composite multi-layer thermal insulation material and find the greatest value of thermal conductivity with a similar result to that of the powder insulation.