• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 제5회 학술대회 논문집 일렉트렛트 및 응용기술연구회
• /
• pp.38-42
• /
• 2003

The use of VPI impregnated mica tape as high voltage insulation for large rotating electric machines requires a careful balance of processes and materials to obtain the desired electrical, mechanical and thermal characteristics. The stator insulation systems such as epoxy bonded high voltage mica tape have been produced for many years. One such system employing an epoxy and anhydride impregnating resin developed by Hyundai Heavy Industries, Co. (hereafter, HHI), to satisfy customer requests for an epoxy bonded insulation system. HHI applies the following electrical and thermal evaluations such as dielectric breakdown, voltage endurance, dissipation factor vs. temperature, isothermal weight loss, and so on. A detailed laboratory evaluation can describe specific physical limitations for an insulation system and permit development of long-term operation guidelines that permit full utilization of the proposed system. HHI has found these evaluations very helpful in qualifying insulation system for the repair of both large motors and generators.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제55권12호
• /
• pp.640-645
• /
• 2006

A 22.9kV/50MVA class high temperature superconducting(HTS) power cable system was developed in Korea. For the optimization of electrical insulation design for a HTS cable, it is necessary to investigate the ac breakdown impulse breakdown and partial discharge inception stress of the liquid nitrogen/laminated polypropylene paper(LPP) composite insulation system. They were used to insulation design of the model cable for a 22.9kV class HTS power cable and the model cable was manufactured. The insulation test of the manufactured model cable was evaluated in various conditions and was satisfied standard technical specification in Korea. Base on these experimental data, the single and 3 phase HTS cable of a prototype were manufactured and verified.

• 한국안전학회지
• /
• 제39권2호
• /
• pp.22-27
• /
• 2024

The purpose of this study is to explore the trend in insulation resistance values according to temperature and overcurrent by conducting an investigation on the actual condition and experiments on the electrical wiring during the melting furnace process. In addition, the Arrhenius equation is used to determine whether temperatures in the furnace operating process can be applied to the actual field. In the investigation of the actual condition, the insulation resistance started to decrease seven years after replacement, even though cables in oil pump A were replaced in 2010. Both the experimental and theoretical values of the insulation resistance obtained using the Arrhenius equation decreased with an increase in temperature. Errors in insulation resistance (MΩ) values between tests and the Arrhenius equation ranged from ±2 to ±10, demonstrating a high similarity. Results revealed that when the insulation resistance cannot be measured in a manufacturing workplace (quarterly analysis), it can be estimated by partially applying the Arrhenius equation.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.1057-1059
• /
• 2017

액체로켓엔진 개발에서 엔진 짐벌링 시 산화제라인의 벨로우즈 극저온 단열 방법을 연구하였다. 극저온 산화제의 열단열과 엔진구성품의 고온으로부터의 열차폐는 엔진 추진성능과 효율에 중요하다. 엔진 짐벌링중 고압배관과 재순환라인(예냉라인)이 단열부위로 기존의 극저온 단열과는 차별화된 디자인과 소재가 필요하다. 엔진 짐벌링중에 벨로우즈의 극저온 단열재가 열단열과 열복사를 고려하여 새로운 디자인으로 마찰력과 작동반경을 고려하여 PTFE소재의 단열재가 적용된다. 향후 엔진 시험을 통하여(짐벌링과 TVC) 새로운 벨로우즈 단열재가 향상되고 디자인 변경이 요구된다.

• 한국전기전자재료학회논문지
• /
• 제17권3호
• /
• pp.333-339
• /
• 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.

• 설비공학논문집
• /
• 제15권12호
• /
• pp.1078-1087
• /
• 2003

Kimchi refrigerator is a household electric appliance developed with the wholly domestic technology for maturing and keeping kimchi. However, the principle of keeping is not yet revealed obviously. This numerical study has been conducted to investigate the flow and heat transfer characteristics in a kimchi refrigerator. The effects of arrangement variation of a evaporation tube are examined. Also, the heat transfer characteristics through the insulation material are discussed in detail. The flow and temperature field was simulated using the commercial code of CFX-5.3. A natural convection flow is formed through about 5/6 region from the bottom within the keeping space and accordingly, the 90% region of kimchi containers satisfies the temperature requirement with 0$\pm$0.5$^{\circ}C$. The stagnant flow exists in the upper 1/6 region of the keeping space and accordingly, the stratified high temperature distributions appear in the upper region of kimchi containers. The upward shift of the start location of a evaporation tube improves the temperature concentration toward $0^{\circ}C$ but the pitch variation is of no effect. The heat fluxes on the insulation surfaces show two-dimensional distributions with being higher toward the center. Through the variation of insulation thickness, 3.5% saving of insulation material is obtained under the same heat transfer rate.

• 한국초전도ㆍ저온공학회논문지
• /
• 제12권3호
• /
• pp.12-15
• /
• 2010

Important key technologies of high-$T_c$ superconducting (HTS) transformer may include the HTS wire technology, bushing technology, cooling technology, AC loss, reduction technology, large current technology, and cryogenic temperature insulation technology. From among others, the cryogenic temperature insulation technology may be specifically a core technology for ensuring reliability for the smaller size, stability, economic efficiency, and power supply of a transformer. Therefore, the electric insulation technology of a superconducting transformer should be prerequisite. Such relevant studies are ongoing, but still, they are very insufficient for establishing the cryogenic insulation technology as of yet. Therefore, this paper simulated HTS transformer applied with continuous transposed conductor (CTC), which has been studied as a way of reducing AC loss. Also, the paper analyzed the insulation configuration of HTS transformer and bushing, and, accordingly, reviewed various characteristics of insulation breakdown out of liquid nitrogen. Thus, the paper constituted insulation database, and it is going to design the insulation of a transmission class HTS transformer and bushing.

• 한국초전도ㆍ저온공학회논문지
• /
• 제9권1호
• /
• pp.61-66
• /
• 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.

• 한국전기전자재료학회논문지
• /
• 제28권6호
• /
• pp.390-395
• /
• 2015

Molded insulation materials are widely used from large electric power transformer apparatus to small electrical machinery and apparatus. In this study, by adding MgO with the average particle of several tens nm and the excellent thermal conductivity into molding material, we improved the problem of insulation breakdown strength decrease according to rising temperature in overload or in bad environmental condition. We confirmed the life evaluation by using the insulation breakdown and inverse involution to investigate the electrical characteristics of nano-composites materials. By using a scanning electron microscope, it is confirmed that MgO power with the average particle size of several tens nm is distributed and the filler particles is uniformly distributed in the cross section of specimens. And it is confirmed that the insulation breakdown strength of Virgin specimens is rapidly decreased at the high temperature area. But it is confirmed that the insulation breakdown strength of specimens added MgO slow decreased by thermal properties in the high temperature area improved by the contribution of the heat radiation of MgO and the suppression of tree. The results of life prediction using inverse involution, it is confirmed that the life of nano-composites is improved by contribution of MgO according to the predicted insulation breakdown strength after 10 years of specimens added 5.0 wt% of MgO is increased about 2.9 times at RT, and 4.9 times at $100^{\circ}C$ than Virgin specimen, respectively.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 하계학술대회 논문집
• /
• pp.406-409
• /
• 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.