• 전기학회논문지
• /
• 제59권5호
• /
• pp.912-917
• /
• 2010

It was known that oil-filled transformer's life depended on insulating paper which was applied to transformers for insulating of transformer. Therefore when paper was aged, its electrical, mechanical and chemical characteristics were changed. Especially if operating temperature was high, paper was quickly damaged. As cellulose paper which was mainly used for solid insulation of transformers was degraded, the cellulose polymer chains broke down into shorter lengths and gases such as CO, $CO_2$, $CH_4$, $C_2H_4$ and so on were produced from paper. Also by-product known as furan compounds were producted from paper and it were dissolved within insulating oil. In this paper accelerating aging cell was aged during 60 hours at 100, 150, 180 and $200^{\circ}C$, respectively, so evaluating the chemical characteristics of cellulose paper by thermal. An it were performed analysis such as tensile strength(TS), dissolved gas analysis(DGA) and high performance liquid chromatography(HPLC). Also for analyzing of correlation between insulating degradation characteristics, it was performed linear regression method as statistical treatment.

• 한국전기전자재료학회논문지
• /
• 제20권3호
• /
• pp.273-280
• /
• 2007

In this paper, the ZnO surge arrester performance of power distribution class has been studied under different manufacturing conditions such as housing materials(polymeric, porcelain), interface sealants and one-body molding type. In the recent years, the polymeric ZnO surge arresters have been developed and put into operations based on their excellent characteristics. For polymeric surge arresters, the inner gas volume is extremely small, especially in solid insulation polymeric arresters there are not any gas volume inside arresters in the structure due to polymeric materials are filled into the internal gas volume. The sealing integrity is related to safe operation of surge arrester, the prime failure reason of porcelain housed arresters is moisture ingress. In this paper, the sealing integrity of polymeric surge arresters is investigated with moisture multi-aging test and ingress test. The evaluation techniques are used to inspect the sealing integrity of polymeric arresters, including leakage current, surface temperature, reference voltage and dissipation factor.

• 연구논문집
• /
• 통권32호
• /
• pp.65-76
• /
• 2002

The intensity of x-ray or gamma-ray is attenuated according to density and thickness of the transmitted medium. In this study, by using this principle, on-line real-time radiometric system was developed using a 128 channels linear array of solid state detectors to measure wall thickness of insulated piping system. This system uses a Ir-192 as a gamma ray source and detector is composed of BGO scintillator and photodiode. Ir-192 gamma ray source and linear detector array mounted on a computer controlled robotic crawler. The Ir-192 gamma ray source is located on one side of the piping components and the detector array on the other side. The individual detectors of the detector array measure the intensity of the gamma rays after passing through the walls and the insulation of the piping component under measurement. The output of the detector array is amplified by amplifier and transmitted to the computer. This system collects and analyses the data from the detector array in real-time. The maximum measurable length of pipe is 120cm/mm. in the case of 1mm scanning interval.

• 센서학회지
• /
• 제15권1호
• /
• pp.53-57
• /
• 2006

This paper describes a novel processing technique for fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for super-temperature MEMS applications. PDMS (polydimethylsiloxane) mold is fabricated on SU-8 photoresist using standard UV photolithographic process. Liquid precursor is injected into the PDMS mold. Finally, solid polymer structure is cross-linked using HIP (hot isostatic pressure) at $400^{\circ}C$, 205 bar. Optimum pyrolysis and annealing conditions are determined to form a ceramic microstructure capable of withstanding over $1400^{\circ}C$. The fabricated SiCN ceramic microstructure has excellent characteristics, such as shear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}{\Omega}$) and BDV (min. 1.2 kV) under optimum process condition. These fabricated SiCN ceramic microstructures have greater electric and physical characteristics than bulk Si wafer. The fabricated SiCN microstructures would be applied for supertemperature MEMS applications such as heat exchanger and combustion chamber.

• Journal of Electrochemical Science and Technology
• /
• 제8권1호
• /
• pp.53-60
• /
• 2017

Fluoroethylene carbonate (FEC) was studied as an additive for the electrolyte in lithium ion batteries with the $LiNi_{0.5}Mn_{1.5}O_4$ (LNMO) spinel cathode operating at a high potential beyond 4.7 V (vs. $Li/Li^+$). It was found that the FEC additive was electrochemically active for the $1^{st}$ charge cycle on the LNMO cathode. The presence of a large amount of FEC (more than 40 vol%) in the electrolyte caused severe side reactions with abnormally long voltage plateaus. In contrast, when the electrolyte contained less than 30 vol% FEC, the surface of the LNMO cathode was stabilized by the formation of the solid-electrolyte interphase (SEI), leading to improved cyclability. However, the resistance from the SEI limited the rate capability because of sluggish lithium transportation through the SEI and electronic insulation between the particles in the electrode.

• 한국공간구조학회논문집
• /
• 제17권1호
• /
• pp.69-75
• /
• 2017

In fire design for floors, the three criteria of stability, integrity and insulation are required for the specified fire resistance duration. Among these, stability is not easy to confirm. For solid prestressed concrete slabs of uniform thickness, Eurocode 2 provides tabulated data and specifies an axis distance to the centroid of strands to achieve particular fire resistance ratings, but it is not clear if this data can be used for a wide range of different prestressed slab profiles. In order to verify the current code-fire ratings for precast prestressed slabs, both simple and advanced calculation methods are investigated. This paper examines the use of calculation methods, accounting for the real behaviour of unprotected simply supported prestressed concrete slabs exposed to the standard ISO 834 fire. The calculated fire resistance of each prestressed concrete slab is compared with tabulated data in Eurocode part 1.2, with detailed discussion.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.517-520
• /
• 2017

본 논문은 추진기관 기밀체결부의 설계변수가 기밀조립부의 갭 거동과 오링의 기밀성능에 미치는 영향을 분석하고 효과적인 설계변수 설정 방안을 도출하였다. 체결부의 설계변수를 구성하는 요소로서 노즐 플랜지 두께, 체결볼트에 가하는 예비하중을 단계별로 변화하여 연소관 내압거동에 따른 기밀조립부 갭 벌어짐을 최소화하고 나아가서 기밀용 오링의 기밀성능을 효과적으로 유지할 수 있는 설계변수 조건을 평가함으로써 추진기관 연소관 노즐 기밀체결부의 효율적인 설계 방법론을 제시하였다.

• 조명전기설비학회논문지
• /
• 제17권3호
• /
• pp.49-55
• /
• 2003

본 논문에서는 고온 초전도체의 냉매로서 주목받고 있는 액체질소 중에서 고체절연물 표면의 연면 방전과 트래킹 현상에 관하여 연구하였다 액체질소중 연면 방전에 많은 영향을 주는 기포 효과를 연구하기 위해 Knife형태의 전극과 평판형태의 전극을 사용하여 A-mod, B-mode, C-mode의 전극배치형태를 각각 구성하였다. 본 실험의 결과는 향후 연구되고 개발될 초전도·극저온 전력설비의 절연설계의 기초 데이터를 제공할수 있다고 판단된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 C
• /
• pp.1788-1790
• /
• 2003

GIS is a typical power equipment with higher reliability. It is compact and safe because all the energized parts are enclosed by a sealed cylindrical tank which is filled with $SF_6$. Generally gas insulated power equipments like GIS are designed to have sufficient electrical strength to prevent partial discharges under normal operating condition. Despite of the careful processes in manufacturing, transporting and assembling, voids or particles can be created, resulting in partial discharges at electrically weak points. The key factors causing partial discharges in GIS are; particles, voids in solid insulation, protrusions, poor contact of metal components, etc. The particle can be attached on; spacers, electrodes, internal wall of the GIS tank. It also moves in GIS freely. Most of partial discharges are likely to occur when particles are attached to spacers. In this paper, the electrical characteristics of a surface discharge were investigated under various conditions by using simulation program of FEMLAB.

• Advances in concrete construction
• /
• 제11권2호
• /
• pp.151-161
• /
• 2021

The major shortcoming of concrete in most of the applications is its high self-weight and thermal conductivity. The emerging trend to overcome these shortcomings is the use of foam-concrete, which is a lightweight concrete consisting of cement, filler, water and a foaming agent. This study aims at the development of a cost-effective high-volume fly-ash foam-concrete insulation wall cladding for existing buildings using natural fiber like rice straw in different proportions. The paper reports the results of systematic studies on various mechanical, acoustic, thermal and durability properties of foam-concrete with and without replacement of cement by fly-ash. Fly-ash replaces 60 percent by weight of cement in foam-concrete. The water-solid ratio of 0.3, the filler ratio of 1:1 by weight, and the density of 1100 kg/㎥ (approx.) are fixed for all the mixes. Rice straw at 1%, 3% and 5% by weight of cement was added to improve the thermal and acoustic efficiency. From the investigations, it was inferred that the strength properties were increased with fly-ash replacement up to 1% rice straw addition. In furtherance, addition of rice straw and fly-ash resulted in improved acoustic and thermal properties.