• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1552-1553
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• 2011

The HVDC transformer which is one of the main equipments for HVDC(High Voltage Direct Current) electric power transmission systems is exposed to not only AC voltage but also the inflowing DC voltage which comes from the DC-AC converter systems. Therefore, the HVDC transformer insulation system is required to withstand the electric field stress under AC, DC and DC polarity reversal conditions. However the electric field distributions under those conditions are different because the AC electric field and DC electric field are governed by permittivity and conductivity, respectively. In this study, the changes of electric potential and electric field of conventional AC transformer insulation system under DC polarity reversal test condition were analyzed by FEM(Finite Element Method). The DC electric field stress was concentrated in the solid insulators while the AC electric field stress was concentrated in the mineral oil. In addition, the electric stress under that condition which is affected by the surface charge accumulation at the interfaces between insulators was evaluated. The stress in some parts could be higher than that of AC and DC condition, during polarity reversal test. The result of this study would be helpful for the HVDC transformer insulation system design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기설비전문위원
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• pp.35-38
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• 2004

본 연구는 국내에서 사용되고 있는 유입식변압기의 유중가스분포 특성에 대해서 설명하고 있다. 정상적으로 국내에서 운전중에 있는 변전용변압기와 발전기승압용 변압기, 산업체에서 사용되고 있는 배전용변압기의 유중가스분석결과로부터 데이터를 얻었다. 분석가스종류는 H2와 C2H2, C2H4, C2H6, CO, CO2, TCG 이며, 분포특성과 각 유중가스진단규격에서 제시하고 있는 진단기준치와의 비교 검토를 수행하였다.

• 조명전기설비학회논문지
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• 제18권6호
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• pp.136-144
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• 2004

본 논문에서는 유침절연에 대한 열열화와 전기적열화 실험을 실시하여 유중가스분석법을 이용한 유침절연의 고장원인 진단에 대한 신뢰성을 향상시키는 방안에 대하여 연구하였다. 유침절연의 고장원인에 대하여 주도가스법과 탄화수소가스의 구성률, CO/$CO_2$비와 같은 진단요소를 단독으로 사용하는 것보다는 진단요소들의 상호관계를 이용하는 것이 유침절연의 고장원인을 신뢰성 있게 진단하는 것으로 나타났다.

• 전기학회논문지
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• 제63권2호
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• pp.297-305
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• 2014

Nowadays new water supply projects have been on the decline as the water-power constructions have saturated, which means that the existing power equipment have slowly aged and they require more efforts to maintain the system performance. An effective asset management method of power equipment has become a great necessity from both economical and technical aspects. To be balanced, the asset management should look into all three parts: management, engineering, and information. The purpose of this paper is to study a Risk-Based Maintenance (RBM) matrix method through the deterioration evaluation algorithm for an efficient reliability assessment of oil-immersed power transformers by considering both asset management and technical evaluation. Make use of this result, the equipment will be decided to be replace or repair otherwise on service.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 춘계학술대회 논문집
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• pp.35-38
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• 1993

Pressboard is used for insulation oil-immersed equipment such as transformer. It's low cost, good electrical properties when immersed in oil, ease of storage and installation, and general reliability have made it virtually a universal choice. This study has examined fabricating specimen and specimen characteristics of pressboard.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.114-120
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• 2014

In this paper, a method for multi-physics analysis of the temperature-dependent properties of an oil-immersed transformer is discussed. To couple thermal fields with electromagnetic and fluid fields, an algorithm employing a user defined function (UDF) is proposed. Using electromagnetic analysis, electric power loss dependent on temperature rise is calculated; these are used as input data for multi-physics analysis in order to predict the temperature rise. A heat transfer coefficient is applied only at the outermost boundary between transformer and the atmosphere in order to reduce the analysis region. To verify the validity of the proposed method, the predicted temperature rises in high-voltage (HV) and low-voltage (LV) windings and radiators were compared with the experimental values.

• 한국전기전자재료학회논문지
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• 제23권1호
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• pp.53-60
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• 2010

This paper dealt with the acoustic detection of partial discharge (PD) in insulation oil for insulation diagnostics of oil immersed transformers. Electrode systems such as needle to plane, plane to plane, and floating were fabricated to simulate some defects in transformers. A wide band acoustic emission(AE) sensor with the frequency ranges of 100 kHz~1 MHz and a narrow band AE sensor with the resonant frequency of 140 kHz were used in the experiment. Also, a decoupler and an amplifier were designed to detect and amplify the acoustic signal only. The decoupler separates acoustic signal from DC source without any distortion, and the amplifier has the gain of 40 dB in frequency ranges of 11 kHz~4 MHz. In the experiment, frequency components and propagation characteristics of acoustic signal were analyzed, and an algorithm of positioning of PD occurrence by the time difference of arrival was proposed. From the results, the frequency components of the acoustic signal exist from 50 kHz to 200 kHz and the positioning error of PD calculated by three AE sensors was within 1%.

• 조명전기설비학회논문지
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• 제18권2호
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• pp.55-62
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• 2004

본 논문에서는 유중가스 분석법을 이용하여 실리콘 유입변압기를 효과적으로 진단할 수 있는 전문가 시스템의 개발에 관하여 연구하였다. 변압기 진단 방법은 유입기기에 대한 진단 방법으로서 현재까지 많은 연구가 진행되어 왔고 비교적 효과적인 분석법으로서 신뢰를 얻고 있는 유중가스분석법을 이용하였다. 그러나 유중가스 분석법은 경계 및 규칙의 불확실성이 필연적이기 때문에 이를 처리하기 위하여 소속정도 및 퍼지척도를 적용하여 해결하였다. 개발한 전문가 시스템은 크게 지식베이스 모듈, 추론엔진 모듈, 사용자 인터페이스 모듈로 이루어져 있으며, 지식베이스 모듈은 규칙을 이용한 지식표현을 사용하였고, 추론엔진 모듈은 후방향 추론을 이용하고, 퍼지규칙을 도입하였다. 사용자 인터페이스 모듈은 현장의 사용자가 쉽게 사용할 수 있도록 GUI 환경으로 구성하였다. 또한 변압기 개개의 이력 관리를 통하여 좀 더 효과적인 진단을 할 수 있도록 전문가 시스템을 데이터베이스와 연계하였다. 제안한 전문가 시스템에 대하여 실리콘유의 유중가스 데이터를 이용하여 검증한 결과 모든 사례에 대하여 정확한 판단 결과를 얻음으로써 실리콘 유입변압기를 효과적으로 진단할 수 있음을 증명하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.292-295
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• 1991

The life of the transformers is significantly dependent upon the rate of thermal deterioration in the employed insulating materials. Therefore, the study should be based on hot-spot temperature considerations for the life expectancy and possible overload of transformer. We have measured directly temperature of the winding using thermocouples and these test results are compared with those obtained from computer simulation. In this work, our fundamental investigations are well described for the analysis in the thermal distribution of the oil-immersed transformer with the rating of 30kVA.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.374-376
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• 2001

In this paper, we developed the fault diagnostic expert system of silicone-immersed transformer using dissolved gas analysis. The knowledge base module consists of the knowledge using the rule: if Then . The inference engine uses the fuzzy rule for the management of uncertainty of the boundary and rule and derivate the Belief and Plausibility of the normality and fault using Dempster-Shafer theory. The expert system is connected to the database and it can manages the history of gas-data of the transformer.