• 한국화재소방학회논문지
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• 제15권4호
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• pp.78-85
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• 2001

본 논문에서는 몰드변압기의 난연성 및 NAF S-III에 의한 소화특성에 관해 연구하였다. 연구방법으로써 몰드변압기의 주재인 에폭시수지의 연소과정과 최근 청정소화약제로 사용되고 있는 NAF S-III의 소화과정을 이론적으로 고찰하였다. 또한 이의 증명을 위해 몰드변압기에 대한 연소.소화실험을 실시하였다. 실변압기를 전기실과 유사한 조건의 수평가열로에 장치하여 발화시킨 후, 이의 소화과정을 자연소화와 인위적 소화로 구분하여 관찰하였다. 발화된 변압기의 소화에는 NAF S-III계 소화약제가 분사되었다. 분사된 약제량은 연소중인 몰드변압기에 대한 소화능력을 갖춘 경제량이며, 이는 행정자치부 고시를 근거로 산출되었다. 이렇게 계산된 소화약제의 분사에 의해, 발화된 변압기는 1분만에 완전히 소화되었다. 연구 결과, 몰드변압기가 설치된 전기실의 경제적 소화약제량을 산출할 수 있었으며, 실험을 통해 몰드변압기의 난연성과 청정소화약제인 NAF S-III의 소화능력을 확인하였다. 이를 토대로 국내 전기실에 채용된 소화설비를 경제적이며, 환경보전의 목적으로 적용할 수 있는 규모를 예측할 수 있었다.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.332-335
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• 2012

A molded transformer is maintenance-free, which makes it unnecessary to replace the insulating material, like in an oil-filled transformer, because the epoxy, which is a molded insulating resin, does not suffer variations in its insulating performance for heat cycles over a long time, as compared to insulating oil. In spite of these advantages, a molded transformer may still be accessed by the user, which is not good in regards to reliability or noise compared to the oil transformers. In particular, a distrust exists regarding reliability due to the long-term insulating performance. These properties have been studied in regards to the improvement of epoxy composites and molded transformer insulation. There have nevertheless been insufficient investigations into the insulation properties of epoxy composites. In this study, it is a researching of the epoxy for insulating material. In order to prepare the specimens, a main resin, a hardener, an accelerator, and a nano/micro filler were used. Varying amounts of TiO2 and ZnO nano fillers were added to the epoxy mixture along with a fixed amount of micro silica. This paper presents the DC insulation breakdown test, thermal expansion coefficient, and thermal conductivity results for the manufactured specimens. From these results, it has been found that the insulating performance of nano/micro epoxy composites is improved as compared to plain molded transformer insulation, and that nano/micro epoxy composites contribute to the reliability and compactness of molded transformers.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권5호
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• pp.191-195
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• 2005

This paper presents an assessment method in integrity of the windings in cast resin molded transformers by using vertical analysis of thermal distribution. The proposed method is to compare the temperature distribution in a sound specimen with that in the faulted specimen with a layer to layer short circuit. Temperature distribution was acquired by an infrared thermography system, and the Arrhenius equation was adopted to the accelerated test. The proposed method can be used to detect the failures in the transformers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마
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• pp.23-28
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• 2000

Insulator systems using resin casting apparatus are useful to realize the high capacity, small size, and combined electric power equipments, and are expected to bring various advantages. In Korea, epoxy resin molded apparatus have been restricted to indoor uses till now. On the other hand, in Europe, molded insulators and transformers and so forth have been practically used since the former half of 1960's. Recently, investigation on epoxy resin materials and molded apparatus for outdoor use have ben intensively carried out. Probably, this is because electric power outdoor apparatus such as distribution transformer can be given multi-functions by using outdoor epoxy resin compound This study describes the trend on the development of epoxy mold transformers, and important technologies applied for outdoor use.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권4호
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• pp.180-184
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• 2001

The high operation frequency mainly reduces transformer volume in the power supply. A high frequency and high voltage pulse transformer is designed, fabricated, and tested. Switching frequency of the transformer is 100 kHz. Input and output voltages of the transformer are 250 V and 4 kV, respectively. Normal operation power of the transformer is 3 kW. Maximum volume of the transformer is 400 $cm^3$. The power density is thus 7.5 W/$cm^3$. The transformer will be installed in a metal box that has nominal operation temperature of 85 degree centigrade. The transformer and other high voltage components in the box will be molded with Silicon RTV(Room Temperature Vulcaniza) that has a very low thermal conductivity. Procedure of design and test results are discussed. Analytical as well as experimental results of varous paramters such as transformer loss, leakage inductance, distributed capacitance are also discussed. In addition, thermal analysis results from ANSYS code for three different operation conditions are discussed.

• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.376-380
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• 2006

Temperature distribution measured to estimate the condition of an electrical apparatus is an absolute reference for the apparatus conditions and the difference between the reference temperature and the current temperature. Because of passive thermography, without the external thermal stimulation, the difference in surface temperature between the region of interest and back ground shows that the results can apply only to the estimation or the monitoring for the condition of loose terminal and the overload pertaining to the rise in temperature. However, a thermal diffusion in the active thermography is differently generated by the structure and condition of the surface and subsurface. This paper presents a nondestructive test using this behavior and deals with the results by heat injection and cooling to the apparatus. The buried discontinuity of subsurface could be detected by these techniques.

• 한국산학기술학회논문지
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• 제18권3호
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• pp.209-214
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• 2017

현재 철도 차량에 쓰이고 있는 대부분의 계기용 변압기는 장치 내부에 절연유가 충진되어 있는 유입식 계기용 변압기 방식으로서, 내구 연한 도래와 더불어 차량 운행 중 내부 압력 상승에 의해 폭발의 위험성이 있다. 이에 대한 해결책으로 절연 수지를 사용하여 방압 기능이 탁월한 몰드형 건식 계기용 변압기 개발이 필요하다. 이에 제품의 국산화가 가능하도록 한국철도기술연구원에서는 몰드형 건식 계기용 변압기를 개발 진행 중에 있다. 그 연구의 일환으로 개발 제품의 진동 특성 분석과 함께, 진동 환경하에서 변압기의 성능 유지 여부를 확인하여야 한다. 이번 연구에서는 철도 차량 부품의 진동 시험 방법 규격인 KS R 9144 및 IEC 61373 에 따라서 개발 제품의 공진시험과 모의 장기 수명 시험을 진행하였다. 고유 진동수는 해석을 통한 모달 분석과 공진 시험을 병행하여 결과를 비교 분석하였으며 규격 조건을 만족함을 확인하였다. 또한 모의 장기 수명 시험 후 성능 시험을 통해 오랜 시간 진동 환경 하에서도 개발 변압기의 기능에 문제가 없음을 확인하였다.

• 전기학회논문지
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• 제65권10호
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• pp.1688-1693
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• 2016

In this study shall investigate the influence upon the electrical property of transformer oil due to the heat among accelerated heat degradation experiment for a constant hour in the typical insulation oils of mineral base oil, silicon base oil and vegetable oil. In addition, the electric insulation performance of insulation materials in transformer shall be evaluated through the electric property analysis according to the heat degradation of epoxy insulation material, which has been used for electric facilities such as a molded transformer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2106-2108
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• 2005

This paper describes a method of lifetime expectation for the dry-type molded transformer which is widely used in the domestic distribution system. And the result of the temperature accelerated aging test for the winding insulation and the analyzed report on the reliability are included in this study.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.105-105
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• 2010

Voltage circuit breakers are widely used in power distribution systems to interrupt fault current rapidly and to assure the reliability of the power supply. Power distribution system requires the transformer with higher capacity than ever, but this ever, but this may be the cause. of the increasing of short circuit current in contrast to conventional one when short-circuit accident is occurred. Therefore molded case circuit breaker improved in aspects of interrupting capacity of short circuit current in this system is needed. By using the proposed methods in this paper, such as new arc quenching structure of grid would contribute to minimizing the MCCB, realization of high interrupting performance and reducing the design time and development cost.