• 한국신뢰성학회지:신뢰성응용연구
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• 제15권3호
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• pp.197-206
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• 2015

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

• 한국건축시공학회지
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• 제24권4호
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• pp.437-445
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• 2024

본 연구는 창호에 사용되고 있는 Azon과 Azo-Core를 셔터에 활용하여 단열성능을 확보하고자 Therm 7.4 프로그램과 기밀, 단열성 시험을 통해 검토하였다. 시뮬레이션 결과 Azon 및 Azo-Core는 기존의 단열재에 비해 단열성이 우수했으며 셔터에 적용 시 1등급의 기밀성능과 평균2.018W/m²·k의 열관류율을 확인하였다. 이는 외부셔터 설치 기준 중부지방 1.5W/m²·k, 남부지방 1.8W/m²·k보다 높은 수치이지만 제주지방 2.2W/m²·k에는 적용 가능한 수치이며 Azon과 병행 적용이 아닌 Azo-Core만 적용할 수 있는 추가 연구가 검토된다면 셔터 단열재로 사용 가능성이 있다.

• 한국초전도ㆍ저온공학회논문지
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• 제23권1호
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• pp.7-11
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• 2021

Cryogenic vessels are special equipment that requires periodic evaluation of their thermal insulation performance. At the current standard, the test is considered as the loss product or heat leakage of cryogenic vessel, which takes over 72 h to evaluate; consequently, a large amount of working medium is discharged to the environment in the process. However, hydrogen is flammable and explosive, and the discharged gas may be dangerous. If liquid hydrogen is replaced with liquid nitrogen before testing, the operation then becomes complicated, and the loss product or heat leakage cannot respond to the thermal insulation performance of cryogenic vessels for liquid hydrogen. Therefore, a novel method is proposed to evaluate the heat leakage of cryogenic vessels for liquid hydrogen in self-pressurization. In contrast to the current testing methods, the method proposed in this study does not require discharge or exchange of working medium in all test processes. The proposed method is based on one-dimensional heat transfer analysis of cryogenic vessels, which is verified by experiment. When this method is used to predict the heat leakage, the comparison with the experimental data of the standard method shows that the maximum error of heat leakage is less than 5.0%.

• 한국건설순환자원학회논문집
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• 제4권4호
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• pp.356-362
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• 2016

경량 콘크리트는 기포제를 사용하여 건축자재의 경량화와 단열성을 추구하고 있다. 그러나 기포제의 사용은 콘크리트의 체적이 감소되고, 압축강도가 낮아지는 문제점이 있다. 본 연구에서는 별도의 기포제를 사용하지 않고 산업 부산물인 폐발포 폴리우레탄을 재활용하여 콘크리트의 경량화와 단열성을 확보하고자 한다. 그리고 콘크리트의 시공성과 재료분리를 방지하기 위해 소량의 혼화재를 사용한다. 이러한 혼화재의 혼입률이 폐발포 폴리우레탄이 혼입된 경량 콘크리트의 물성에 미치는 영향을 확인하고자 한다. 실험 결과, 두 개 회사의 혼화재 중에서 폐발포 폴리우레탄이 고르게 분산되는 것을 사용하였다. 혼화재의 혼입률을 다르게하여 배합한 결과는 혼화재의 혼입이 많을수록 콘크리트의 유동성이 감소된 반면, 콘크리트의 함수율과 압축강도는 소폭 증가하였다. 또한, 난연성능과 차음성능을 확보할 수 있는 것으로 나타났다.

• 한국건설순환자원학회논문집
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• 제7권4호
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• pp.431-437
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• 2019

본 연구는 유기계 기재에 무기계 바인더 소재를 함침시킴으로써 유기계 수준의 경제성을 가지며 우수한 단열성능 및 화재 안전성을 보유한 유무기 융합형 단열재 개발을 목적으로 한다. 유기계 기재는 폴리우레탄 소재의 상용 스펀지를 사용하였고, 함침용 무기 바인더 용액은 재활용 석고 부산물에 물과 첨가제를 혼합하여 제조하였다. 개발 소재의 성능평가 결과 열전도율 0.051W/mK 이하의 우수한 단열성능 뿐만 아니라 국토교통부 고시 제 2015-744호 기준에 명시된 준불연 재료임을 확인할 수 있었다. 또한 본 개발 소재는 제조 공정 과정에서 밀도 제어에 따른 열전도율 및 난연성 조절이 가능하여 다양한 용도의 단열재에 적용 가능할 것으로 판단된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.2014-2016
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• 2000

In order to meet recent increasing demand for electric power in large cities, plans are being made to introduce 345kV lines into large urban areas. Up to now, OF cables have been used for 345kV fines, but nowadays XLPE insulated cables are preferred as they are easier to maintain due to phenomenal advances in plastic insulation technology, therefore cable manufacturing companies are trying to improve the performance and reliability of UHV CV cables and their accessories. For the purpose, our company has developed facilities for testing UHV cables. In this paper, we describes the methodology adopted for the design and development of a test termination, conducted the electrical test of UHV cables. Based on detailed analytical studies for electrical field distribution, the internal electrical design for the testing end has been carried out.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.2008-2009
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• 2007

The paper considers the relation between on-line monitoring and diagnostics on the one hand and high-voltage (HV) withstand and partial discharge (PD) on-site testing on the other. HV testing supplies the basic data (fingerprints) for diagnostics. In case of warnings by on-line diagnostic systems, off-line withstand and PD testing delivers the best possible information about defects and enables the classification of the risk. Because alternating voltage (AC) is the most important test voltage, the AC generation on site is considered. Frequency tuned resonant (ACRF) test systems are best adapted to on-site conditions. They can be simply combined with PD measuring equipment. The available ACRF test systems and their application to electric power equipment -from cable systems to power transformers - is introduced.

• Transactions on Electrical and Electronic Materials
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• 제16권5호
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• pp.260-263
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• 2015

Epoxy/micro-sized alumina composite was prepared and the effects of alumina content on the electrical and mechanical properties were investigated in order to develop an insulation material for gas insulated switchgear (GIS). Nano-sized alumina (average particle size: 30 μm) was also incorporated into the epoxy/micro-sized alumina composite. An electrical insulation breakdown strength test was carried out in sphere-sphere electrodes and the data were estimated by Weibull statistical analysis. Tensile strength was measured at a crosshead speed of 10 mm/min using a universal testing machine. Alumina content was varied from 0 wt% to 70 wt%.). As micro-sized alumina content increased, insulation breakdown strength increased until 40 wt% alumina content and decreased after that content. The tensile strength of a neat epoxy system was 82.2 MPa and that value for 60 wt% alumina content was 91.8 MPa, which was 111.7% higher than inthe neat epoxy system. The insulation breakdown strength of micro-sized alumina (60 wt%)/nano-sized alumina (1 phr) glycerol diglycidyl ether (GDE) (1 phr) composite was 54.2 MPa, which was 116% higher than the strength of the system without nano-sized alumina.

• 한국태양에너지학회 논문집
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• 제37권4호
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• pp.35-47
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• 2017

Energy efficiency solutions are being pursued as a sustainable approach to reducing energy consumption and related gas emissions across various sectors of the economy. Vacuum Insulation Panel (VIP) is an energy efficient advanced insulation system that facilitates slim but high-performance insulation, based on a porous core material evacuated and encapsulated in a barrier envelope. Although VIP has been applied in buildings for over a decade, it wasn't until recently that efforts have been initiated to propose and adopt a global standard on characterization and testing of VIP. One of the issues regarding VIP is its durability and aging due to pressure and moisture dependent increase of the initial low thermal conductivity with time; more so in building applications. In this paper, the aging of commercially available VIP was investigated experimentally; thermal conductivity was tested in accordance with ISO 8302 standard (guarded hot box method) and long-term durability was estimated based on a non-linear pressure-humidity dependent equation based on study of IEA/ECBCS Annex 39, with the aim of assessing durability of VIP for use in buildings. The center-of-panel thermal conductivity after 25 years based on initial 90% fractile with a confidence level of 90 % for the thermal conductivity (${\lambda}90/90$) ranged from 0.00726-0.00814 (W/m K) for silica core VIP. Significant differences between manufacturer-provided data and measurements of thermal conductivity and internal pressure were observed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1897-1899
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• 2004

In this paper, in order to analyze the characteristics of degradation by salt water with insulation cover and OC wire(outdoor cross-linked polyethylene insulated wire) used in power receiving system, an experimental apparatus has been designed and fabricated. An insulation cover and OC wire were installed in an experimental apparatus, and degraded in each case of 2%, 5%, 10% salinity during 12 weeks. An optical microscope was used to observe a changing process of sample surface, and an electrical safety was analyzed by measuring dielectric breakdown voltages of samples. As salinity increased, so ununiformity of sample surface increased. The breakdown wasn't produced to 50kV about samples regardless of salinity, testing period.