• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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• pp.183-186
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• 2002

It is well known that a discharge in oil is the source of various physical and chemical phenomena. One of them is ultra-sonic wave, and its detection is a useful method to the diagnosis of the transformer insulation condition. Conventionally, ultra-sonic waves are detected by Piezo-electric trans-ducer(PZT), and we use optical method that has many advantages. In this paper, we constructed a Mach-Zehnder interferometer with optical fiber and investigated the principle of operation. Test of the ultrasonic-detecting ability was performed for both of PZT and fiber-optic sensor. Discharge test arrangement is based on the needle-plane electrode system in oil and applied AC high voltage. Ultrasonic waves were detected and showed time-delay characteristics. We analyzed the data with frequency domain and wavelet transform.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1912-1914
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• 2005

The electrical, chemical and mechanical characteristics in transformer insulations are changed due to thermal stress. It is known that characteristics of transformer insulations is deteriorated such as decrease of dielectric strength, deterioration of dielectric constant and tensile strength of paper as transformer oil and paper are aged by thermal stress. Furthermore, chemical characteristics of them are deteriorated as like increment of moisture contents and dissolved by-products in oil, etc. In this paper we have been investigated chemical characteristics of transformer by accelerated thermal aging. For this working we have made experimental test cell and aged at a temperature up to $140^{\circ}C$ for 500 hours. The oil-paper insulation samples have been measured at intervals of 100 hours. For analysis we used Karl-Fisher titration method and high performance liquid chromatography (HPLC).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.444-445
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• 2008

This paper reviews the known techniques for diagnosing the condition of OF cable system and improving the service reliability. These tests are periodically achieved and intended to provide indications that the insulation system has deteriorated. One of these tests is analyzing the gas in oil on Oil-filled cable that is well known and widely accepted method. In this paper, this method of analysis and the relevant measurement standards overview and the concrete example of preventing fault incidence by performing this test is introduced.

• 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 2000년도 하계학술대회 논문집 C
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• pp.2023-2025
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• 2000

Globally, movements for an environmental preservation have been further extended in all the areas of industries. In the manufacturing area. environment-friendly properties for all the manufactured products are increasingly required by many national standards. For EHV oil-filled cables. Hard Alkylbenzen has been applied as an impregnated insulating oil. But as it flows into the soil during failures, such as oil leakage, the oil is not dissolved by microbes and then causes an environmental pollution. Recently some countries are increasingly requiring Soft Alkylbenzen which is dissolved by microbes. This paper describes the electrical and environmental properties of Soft Alkylbenzen. applied for a 230kV oil-filled cables at a Singapore's project.

• 에너지공학
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• 제25권3호
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• pp.18-26
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• 2016

대부분의 변압기에 사용되고 있는 절연유는 석유계 원료를 이용한 광유계 절연유였으나 유출시 환경오염, 낮은 인화점으로 인한 화재 위험성을 가지고 있어 보다 친환경 식물성 원료를 활용한 절연유 도입이 최근 검토되고 있다. 그러나 식물성 절연유의 높은 생분해성과 인화점으로 절연유로서의 높은 적용가능성에도 불구하고 장기운전에 의한 열화가 미치는 영향에서는 아직 많은 연구가 필요한 실정이다. 따라서 본 연구에서는 변압기의 구성요소를 감안하고 실제 운전조건보다 높은 $150^{\circ}C$에서 2주간의 가속열화 시험을 통해 전산가, 수분, 절연파괴전압 등의 주요물성 변화를 통해 식물성 절연유 산화특성과 이 과정에서 생성되는 용존 가스 분석을 실시였다. 이를 통해 식물성 절연유가 기존 광유계 절연유 대비 친수성에 의한 전산가 상승에도 불구하고 절연성능을 유지하는 특징을 가지고 있으며 가스 성분 비교를 통해 주어진 온도 조건에서 우수한 열안정성을 나타내고 있음을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.865-873
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• 2017

Converter transformer is the key equipment of high voltage direct current transmission system. The solid suspending particles originating from the process of installation and operation of converter transformer have significant influence on the insulation performance of transformer oil, especially in presence of DC component in applied voltage. Under high electric field, the particles easily lead to partial discharge and breakdown of insulating oil. This paper investigated copper particle effect on the breakdown voltage of transformer oil at combined AC and DC voltage. A simulation model with single copper particle was established to interpret the particle effect on the breakdown strength of insulating oil. The experimental and simulation results showed that the particles distort the electric field. The breakdown voltage of insulating oil contaminated with copper particle decreases with the increase of particle number, and the breakdown voltage and the logarithm of particle number approximately satisfy the linear relationship. With the increase of the DC component in applied voltage, the breakdown voltage of contaminated insulating oil decreases. The simulation results show that the particle collides with the electrode more frequently with more DC component contained in the applied voltage, which will trigger more discharge and decrease the breakdown voltage of insulating oil.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.415-418
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• 1991

This paper described an instrument for the detection and geometric location of partial discharge(PD) sources in oil transformer. This instrument measures electric current pulse and ultrasonic pulse simultaneously in order to determine the geometric location of PD in transformer. Laboratory experiment systems are made for detection and location of PD in oil transformer. It was observed that there are effects of the barrier, such as insulation papers, silicon steel plate and actual transformer with location and detection of PD in model transformer. Through the laboratory actual test, it was clarified that this measurement device could be used satisfactorily for location of pd in oil transformer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.35-40
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• 1997

As demand of electric power are growing and transmission line limited owing to enlargement of the downtown area The eonfidence of underground transmission cable which shows gradual growth are high. It is found whether insulating ability is good or not. In this paper, The exper iment result is shown that the fall of insulating ability and take preventive measure through the analysis of tans, water content, dielectric breakdown voltage, total acid number, volume resistivity , and gas in the oil in an accordance with the characteristic change of oil used very much for insulating oil of cable.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.190-195
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• 2002

The intermittent high vibration has been occurred one or two times a day for a 500MW large steam turbine during 5 months. This abnormal vibration was caused by the rubbing between the rotor and the carbide accumulated on the seal tooth of oil deflector. It was found that the accumulated carbide was insulation material installed on the HIP casing from the examination of the chemical composition. Also, this paper presents the mechanism of the intermittent high vibration and the proper method to eliminate this vibration problem. This result would be good practice to find the solution of similar high vibration in the steam turbines for power plant as well as industrial rotating machineries.