• KIEAE Journal
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• v.13 no.6
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• pp.45-53
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• 2013

For the target goal of Zero-energy House construction in 2025, the government announced that the insulation regulations will be continuously enhanced. It has been predicted that high-performance insulation materials, such as vacuum insulation panel (VIP), should be used to decrease the thickness of outer walls. The aim of this study was to evaluate the performance of adhesively fixed external insulation and finish system (EIFS) with VIP. The energy performance of a base model with conventional internal insulation system and three alternatives of EIFS with VIP were analyzed by three-dimensional heat transfer simulation. Construction cost and convenience of each alternative were also evaluated and compared. As results, effective alternatives in terms of each performance as well as overall performance considering the weighting factors of each performance were suggested.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.495-498
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• 2004

In the sound insulation measurements, the influence of background (extraneous) noise is often serious problem and how to reduce its effect and to improve the signal-to-noise(S/N) ratio is an important theme. As the background noise, such extraneous noises as road traffic noise and machine noise often disturb the measurement. In laboratory measurements on specimens with high sound insulation performances, even the internal noise of the measurement system can become a problem. To improve the signal-to-noise ratio and to improve the measurement accuracy, various kinds of digital signal processing techniques can be applied. In this paper, four kinds of digital signal processing techniques are applied and their effectiveness is examined by a simple sound insulation measurement.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.1-8
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• 2022

This study analyzed the characteristics of insulation resistance and operating time based on an accelerated degradation test of a low-voltage circuit breaker. The experimental sample used a molded case circuit breaker (MCCB) and an earth leakage circuit breaker (ELCB). After measuring the insulation resistance of the circuit breakers, the leakage current was affected by an external rather than an internal structure. Furthermore, the insulation resistance of the circuit breakers with accelerated degradation was measured using a Megger insulation tester. In the accelerated degradation test, aging times of five, ten, 15, and 20 years were applied according to a temperature derived using the Arrhenius equation. Circuit breakers with an equivalent life of ten, 15, and 20 years had increased insulation resistance compared to those with less degradation time. In particular, the circuit breaker with an equivalent life of ten years had the highest insulation resistance. Component analysis of the circuit breaker manufactured through an accelerated degradation test confirmed that the timing of the increase in insulation resistance and the time of additive loss were the same. Finally, after analyzing the operating time of the circuit breakers with degradation, it was confirmed that the MCCB did not change, but the ELCB breaker failed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.219-220
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• 2023

The thermal conductivity of the insulation material has a great influence on the heat transmission coefficient, which is currently used for energy evaluation of buildings. The thermal conductivity of insulation changes with changes in the environment, such as humidity and ultraviolet rays, and can be expected to with the passage of time. But there is a lack of data on this, so this study measured the thermal conductivity of organic insulation according to environmental conditions and time, As a result, in the case of XPS, the thermal conductivity value increased over time, which is estimated to be due to the decrease in insulation performance as the foaming gas escapes to the outside, and in the case of PIR class2 No.2 and PIR noncombustible, the increased thermal conductivity value is similar, but in the case of PIR class2 No.2, a relatively moderate increase can be seen, and in the case of PIR noncombustible, a large increase is seen at the beginning, which is judged to be due to the decrease in insulation performance as the internal foaming gas is substituted with air from the outside.

• The Journal of the Acoustical Society of Korea
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• v.11 no.2
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• pp.50-58
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• 1992

To improve the quality of dwelling environment of domestic apartment house, it is required to establish the sound insulation standard and the performance evaluation method which is suitable to the domestic residential conditions. In this study, the properties of internal noisy sources of a single unit in apartment houses and the sound insulation performance of party walls are investigated and analyzed, as a primary step to the establishment of sound insulation standard. Based on these data, the differences in sound insulation index of each plane type are investigated along with their causes. Also, the factor which affect and decide the insulation performance are analyzed in an effort to improve the performance of party wall structures.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.280-285
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• 2014

In order to evaluate the insulation deterioration in the stator windings of five gas turbine generators(137 MVA, 13.8 kV) which has been operated for more than 13 years, diagnostic test and AC dielectric breakdown test were performed at phases A, B and C. These tests included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ${\Delta}I$ and ${\Delta}tan{\delta}$ in all three phases (A, B and C) of No. 1 generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable and bad level to the insulation condition. Overall analysis of the results suggested that the generator stator windings were indicated serious insulation deterioration and patterns of the PD in all three phases were analyzed to be internal, slot and spark discharges. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. The breakdown voltage at phases A, B and C of No. 1 generator stator windings failed at 28.0 kV, 17.9 kV, and 21.3 kV, respectively. The breakdown voltage was lower than that expected for good-quality windings (28.6 kV) in a 13.8kV class generator. In the AC dielectric breakdown and diagnostic tests, there was a strong correlation between the breakdown voltage and the voltage at which charging current increases abruptly ($P_{i1}$, $P_{i2}$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.645-649
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• 2007

Partial discharge(PD) test for simulated insulation defects of used hydro generator stator winding was conducted to analyze the PD Parameters. Simulated insulation defects are classified by 5 types corona, slot, internal, multi and aging defect. Phase resolved partial discharge, statistical parameter (skewness, kurtosis), PD magnitude as a function of the test voltage(Q-V curve) and PD magnitude change under test voltage for 2 minutes are used as PD parameters. The analysis of PD parameters by 4 types are proved to be useful methods. In particular, PD parameter characteristics of aging defect could help to assess the aging condition of stator winding because aging defect has more weak insulation strength than other insulation defects : PD distribution is wide and flat, PD rises rapidly near $0^{\circ}\;and\;180^{\circ}$ and Q-V curve rises sharply and then gently drops.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.119-126
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• 2022

A growing number of gas-insulated transformers in underground power substations in urban areas are approaching 20 years of operation, the time when failures begin to occur. It is thus essential to prevent failure through accurate condition diagnosis of the given facility. Various solid insulation materials exist inside of the transformers, and the generated decomposition gas may differ for each gas-insulated equipment. In this study, a simulation system was designed to analyze the deterioration characteristics of SF₆ decomposition gas and insulation materials under the conditions of partial discharge and thermal fault for diagnosis of gas-insulated transformers. Degradation characteristics of the insulation materials was determined using an automatic viscometer and FT-IR. The analysis results showed that the pattern of decomposition gas generation under partial discharge and thermal fault was different. In particular, acetaldehyde was detected under a thermal fault in all types of insulation, but not under partial discharge or an arc condition. In addition, in the case of insulation materials, deterioration of the insulation itself rapidly progressed as the experimental temperature increased. It was confirmed that it was possible to diagnose the internal discharge or thermal fault occurrence of the transformer through the ratio and type of decomposition gas generated in the gas-insulated transformer.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.131-136
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• 2008

The double-walled steel vessel with powder insulation in the space between the walls is used to minimize heat transfer by radiation and conduction in cryogenic storage tank. The vacuum required the insulation is much less extreme than with high-vacuum or multilayer insulations. The solid supports are used to bear the weight of the inner container. Thermal and structural analysis of the tank have been carried out to study the effect of vacuum and weldment geometry of the internal supports. Heat flux in wall is increased with increasing of thermal conductivity of perlite. Heat flux and stress of support is not affected by weldment geometry.