• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.406-409
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• 2002

The primary insulation system used in an oil-filled transformer is Kraft paper, wood, porcelain and, of course, oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. These insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life 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 using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.474-480
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• 2012

Diagnostic tests were performed on two high voltage(HV) motor stator windings. These tests included the measurement of insulation resistance, polarization index, AC current, dissipation factor($tan{\delta}$) and partial discharge(PD) magnitude. Surface contamination of HV motor stator windings has an effect on the AC current and $tan{\delta}$. When the stator windings were finished cleaning and insulation reinforcement, the increase rate of AC current(${\Delta}I$) and dissipation factor(${\Delta}tan{\delta}$) were very small compared to those before cleaning. However, the PD magnitude remained the same. These tests show that cleaning and insulation reinforcement of HV motor stator windings can reduce the insulation failure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.10
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• pp.641-646
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• 2016

Coil specimen was prepared by coating a copper wire with two varnish thin layers: the first was polyamideimide (PAI)/nanosilica (5 wt%) varnish and the second was anti-corona PAI/nanosilica (15 wt%) varnish. Insulation breakdown voltage was investigated under inverter surge condition at $20^{\circ}C$, $70^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$, respectively. The insulation lifetime of the two layered coil was tens of times longer than that of original PAI coil. And the insulation lifetime decreased with increasing ambient temperature because there was weak binding strength between copper and varnish layer.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.45-46
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• 2023

CLC is used as a filling material for many buildings, and according to energy saving design standards, CLC also requires insulation performance. However, it shows lower insulation performance compared to organic insulation, so additional research is needed. Therefore, in this study, the insulation properties of CLC were analyzed by incorporating EPS beads with high insulation performance into CLC. In this experiment, EPS beads and blast furnace slag were replaced, and W/B was fixed at 33%. The EPS Bead mixing ratio was divided into 5 levels: 0, 0.5, 1.0, 1.5, 2.0 (%), and the experimental items were measured for apparent density and thermal conductivity. As a result of the experiment, the apparent density and thermal conductivity tended to decrease as the mixing ratio of EPS beads increased. It is judged that the density decreased due to the low density and the micropores inside, and the thermal conductivity also decreased.

• Journal of the Korean Solar Energy Society
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• v.40 no.2
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• pp.11-23
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• 2020

The application of the high-performance insulation materials for buildings seems to be an essential measure for reducing energy use in buildings. Phenolic foam is a readily available insulation material with thermal conductivity of about 0.018 to 0.020 W/(mK). It has the advantage of higher thermal resistance and better fire resistance compared to other conventional building insulation materials. Insulation material used for building envelope is regarded as one of the decisive factors for building's energy load. Furthermore, the degradation of its thermal performance over time increasingly affects the building's energy use demand. Generally, the life span of conventionally built buildings is expected to be more than 50 years, so the long-term performance of insulation materials is critical. This paper aims to evaluate the long-term performance of phenolic form boards through an accelerated aging test. The tests were conducted according to BS EN 13166 and KS M ISO 11561. Based on the results of the accelerated aging test, the thermal performance variation of the material was analyzed, and then its aged value after 25 years was computed. Also, the characteristics of the phenolic foam board's long-term performance were also examined based on the standard testing methods adopted.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.11
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• pp.746-751
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• 2008

The best plan to reduce the building energy consumption is that the insulation performance should be improved because the insulation and airtight of building envelopes have an effect on the energy consumption basically. New insulation materials, which have the high performance and are above insulation standard, have been developed steadily. Because there are not studies on the building energy rating system and economic evaluation considering new insulation materials, these matters should be studied. In result alternatives, which applied 6 high performance material each, reduce the annual heating energy and raise the building energy rating. Applying the vacuum insulation material(Case 1, 2) and vacuum or triple glazing can retrieves the investment with $120 and $140$\sim$150 per barrel each.

• Progress in Superconductivity and Cryogenics
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• v.14 no.4
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• pp.16-19
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• 2012

In power cables as one of the important power applications adopting HTS tapes, a good insulation should be kept at its optimum performance. As an insulation material for superconducting device applications, polypropylene laminated paper (PPLP) is now widely used instead of the conventional Kraft paper. In addition to its dielectric property, the insulation material should also possess superior mechanical property at cryogenic temperatures and operability that is necessary for the insulation winding process. This study aims to evaluate the mechanical property of the PPLP material at ambient and cryogenic temperatures. At cryogenic temperature, the failure stress of PPLP increased significantly as compared with that at ambient temperature. The failure stress at both temperatures depended upon the sample orientation to the load application.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.243-256
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• 2012

This study is the experimental study to improve the insulation of the fastening unit system, which has the most vulnerable insulation in the curtain walls. The Fastening Units were designed and fabricated to minimize the connection part of mullions. In addition, slight movements were taken into account and the performance of the middle layer was evaluated by forming an insulation layer with the vibration-proof rubber and the silicon to satisfy the mechanical and thermal performance criteria. A total of 10 experiments were performed under various conditions, such as indoor-outdoor temperature difference, type of insulation material, thickness of insulation material, and others. using the fabricated Fastening Units. As a result, the vibration-proof rubber insulation showed the temperature difference of $2.2^{\circ}C-5.0^{\circ}C$, and the silicon insulation showed the temperature difference of $2.8^{\circ}C-4.5^{\circ}C$, compared to the non-insulated Fasteniirature difference, typesng Units. When these results were compared with the psychometric chart graph, the insulated Fastening Unit designed in this study can be considered to prevent the dew condensation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.1024-1028
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• 2008

It is important that study on cryogenic electrical insulation design to develop the cold dielectric(CD) type HTS cable because the cable is operated under the high voltage environment in cryogenic temperature. This paper proposes two types of insulation design to carry out the maximum insulation design for 154 kV-class HT cable. The proposed insulation design method takes into consideration AC and lightning impulse withstand voltage so as to prevent AC breakdown for power frequency operating voltage during operating the cable and breakdown for lightning impulse voltage. The final insulation thickness is determined by selecting high value out of two insulation thickness calculated through the two insulation design methods. And we researched electrical insulation characteristics of HTS cable according to bending ratio and the number of bending.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.61-66
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• 2007

A transmission class high-temperature superconducting(HTS) power cable system is being developed in Korea. For insulation design of this cable the grading method of insulating paper is proposed. Two kinds of laminated polypropylene paper that has different thickness has been used as the electrical insulation material. The use of graded insulation gives improved mechanical bending properties of the cable. In a HTS cable technology the terminations are important components. A HTS cable termination is energized with the line-to-ground voltage between the coaxial center and outer surrounding conductors. in the axial direction. There is also a temperature difference from ambient to about 77 K. For insulation design of this termination, glass fiber reinforced plastic(GFRP) was used as the insulation material of the termination body, and the capacitance-graded method is proposed. This paper will report on the experimental investigations on impulse breakdown and surface flashover characteristics of the insulation materials for insulation design of a transmission class HTS power cable and termination. Based on these experimental data, the electrical insulation design of a transmission class HTS power cable and termination was carried out.