• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권10호
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• pp.523-529
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• 2004

Faults of cellulosic insulations greatly affect the life span of oil immersed transformers because their performance recovery is impossible. Therefore, the reliable diagnosis technologies are needed for detection of the faults. Dissolved gas analysis technologies using CO and $CO_2$ gases have been widely used for fault diagnosis of cellulosic insulations. In this research, we described Degradation diagnosis of insulation paper CO and $CO_2$ gases in oil immersed Transformers using. We considered the distribution characteristics of CO, $CO_2$ gases' concentrations and ratios of $CO_2$/CO not only in serviced transformers but in experiments with typical fault causes such as heat, partial discharge and moisture. As result, the reliability of diagnosis results for the cellulosic insulations can be improved when the concentrations of CO, $CO_2$ and the ratio of CO/$CO_2$ satisfy each diagnosis criterion at a tim

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2348-2355
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• 2015

Transformer mineral oil which is normally hydrocarbon based is non- biodegradable and pollutes the environment in all aspects. Though vegetable oils are eco-friendly in nature and potentially could be used in transformers as a replacement for the mineral oil, there usage is restricted because of their oxidative instability. The present work focuses on using rapeseed oil and pongamia (pongamia pinnata) oil as effective alternatives for the traditional mineral oil in power transformer. The oxidative stability of the rapeseed oil and pongamia oil is increased by using combinations of the natural and synthetic anti-oxidants as additives. The parameters like breakdown voltage, viscosity, flash point, fire point are measured for the rapeseed oil and pongamia oil with and without the additives as per IEC and ASTM standards. The results shown encouraging changes in the parameter values and ensures the use of the oils as a potential alternative insulation in power transformers.

• 공업화학
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• 제25권3호
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• pp.254-261
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• 2014

변압기 내부에서 발생한 열의 냉각과 절연의 목적으로 채워지는 전기절연유는 광유가 널리 이용되고 있지만, 유출 시야기되는 환경오염 문제와 열적 불안정성 등의 문제가 있다. 친환경적이고 넓은 온도 범위에서 사용 가능한 전기절연유를 합성하기 위해, 디글리세롤과 두 종류의 지방산을 반응시켜 diglycerol ester를 합성하였다. 서로 다른 특성을 가진 올레산과 카프릴산의 몰비에 따른 절연특성을 분석한 결과, 지방산의 몰비가 Oleic acid:Caprylic acid = 1:3일 때 유동점은 $-50^{\circ}C$, 인화점은 $306^{\circ}C$로 가장 우수한 절연특성을 보였다. 또한, 합성물은 지방산의 전환율이 상승할수록 인화점은 상승하고 유동점은 감소하였다. $SO_4{^{2-}}/ZrO_2$의 소성온도에 따른 촉매특성 및 전환율을 살펴본 결과, $600^{\circ}C$에서 소성한 $SO_4{^{2-}}/ZrO_2$가 결정성을 가지면서 비표면적 당 산점의 밀도가 높아 가장 높은 전환율을 보였다. 합성한 diglycerol ester는 식물성 절연유와 비교했을 때 전반적으로 식물성 절연유보다 우수한 특성을 보였다.

• 동력기계공학회지
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• 제10권4호
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• pp.78-82
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• 2006

Recently, The demands for the reduction of noise generated by transformers have been increasing. Almost all of the noise generated by transformers is a result of magnetostricitive vibration in the core. The noise radiates into the atmosphere from the tank through the insulation oil. As the noise of transformer irritates residents, needs for decreasing the noise of transformer have been arised. One method of reduction such a noise is to build a free-standing enclosure of concrete and steel plates around the transformer. However, this method has some disadvantages. Another method of noise reduction is to mount a close-fitting sound insulation panel on the side of a transformer tank. Side plate vibrations of transformer are transmitted to such a sound insulation panel along two paths. In one case, they are transmitted through air by sound pressure and in the other through supporting structures. In the paper, the vibration and noise effect which is transferred from reinforce channel to insulation panel generated by transformer have been identified for the several kinds of insulation panel and damping sheet analytically and experimetally.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.203-207
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• 2002

In order to evaluate the aging of mineral oil immersed distribution transformers, it gathered some insulation oil in over loaded and long time(exceed their service life, 13yrs.) aged transformers in the field, we measured moisture content, acid number, dielectric strength of the oil as defined in KS C 2101 standard. And also, it had been measured dielectric constant, specific resistant, $tan{\delta}$ on aged transformer oil at from $10^{\circ}C$ to $130^{\circ}C$. These results are compared with a new mineral oil. From this study, it can be considered that the analysis of mineral oil may be suitable for evaluation of life expectancy in distribution transformers

• 한국전기전자재료학회논문지
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• 제25권10호
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• pp.791-797
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• 2012

Mineral insulating oils are an important insulating materials in oil-filled transformer. However, the mineral oil is the cause of the environmental problem. The vegetable oils are substitutes for mineral oil because of its biodegradability characteristic. As large size and high rating of the transformer increases, the losses increase at a faster rate. So insulating oil is forced circulation in the oil-filled transformer by using oil pumps. The flow electrification occurs when insulating oil was forced to be circulated. To check the flow electrification, had conducted experiments varying factors. As a result, the streaming electrification could see the changes according to flow velocity, oil temperature and insulation materials.

• 한국컴퓨터산업학회논문지
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• 제4권4호
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• pp.579-588
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• 2003

지중전선로에 있어서 케이블을 연결하는 중간 접속재에 발생하는 전계 집중, 각종 불순물의 침투 및 케이블 절연층의 손상은 궁극적으로 열화 및 절연파괴를 야기하게 되어 케이블의 수명을 단축시키고 있다. 본 연구에서는 경계요소법을 이용하여 초고압 케이블 절연재료로 널리 사용되고 있는 가교폴리에틸렌과 접속재 키트의 절연층으로 사용되고 있는 EPDM의 전계분포를 시뮬레이션 하였다. 시료는 두께 1[mm]로 3장을 중첩한 것으로 모델링하여 컴퓨터 시뮬레이션을 하였다. 전계해석 결과 보이드 내부의 defect는 silicone oil에 의해 전계집중을 약화시킴을 확인하였고, XLPB보다 EPDM의 전계분포가 낮게 유지됨을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.308-311
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• 1990

This paper presents the insulation design of 345kV OF cable normal joint which is essential to construction of underground transmission system. The insulation designs of stress relief cone, pencilling and sleeve were proposed in this paper, and the final insulation design was decided by the results of the electric field and thermal analysis using FEM. It is shown that the designed normal using proves the effect when the developing test is carried out to construct 345kV OF cable if the domestic underground transmission system.

• Journal of Electrical Engineering and Technology
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• 제1권4호
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• pp.534-542
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• 2006

This paper presents results of frequency domain spectroscopy (FDS) measurements on oil-impregnated pressboard insulation, their analyses and use of the data for modeling high frequency response (FRA) of transformers. The dielectric responses were measured in a broad frequency range, i.e. from 0.1 mHz to 1 MHz, on model samples containing different amount of moisture. The responses were parameterized with terms representing dc conductivity, low frequency dispersion and Cole-Cole polarization mechanisms and they were thereafter used to model the FRA response of a three-phase transformer.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.912-918
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• 2009

In this paper, we carried out a comparative analysis of partial discharge(PD) patterns caused by deterioration of cast-resin and oil insulation systems. Various electrode systems were fabricated such as needle-needle, needle-plane and plane-plane to simulate defects that may exist in the insulation system of transformers. A low-noise amplifier which has a gain of 40 dB and a frequency bandwidth of 500 kHz $\sim$ 30 MHz (-3 dB) was designed to detect small PD signals. From the analysis of acquired PD signals, we could find that a unique PD pattern is formed according to types of defect. These data will be applied usefully to diagnose insulation condition of transformers.