• Tribology and Lubricants
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• 제35권3호
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• pp.151-157
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• 2019

Insulated oil degradation produces charged by-products, such as acids and hydro-peroxides, which tend to reduce the insulating properties of the oil. In this study, UV-vis spectroscopy measurement technology is developed and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate its ability to monitor the degradation of electrical insulating paper. The degradation characteristics of the insulating paper are appropriately represented through various types of measurement methods, such as the Tan (delta) method, $CO_2$ gas production measurement, the titration method, and IR spectroscopy. The results are demonstrated to be well comparable to a change in the fluorescence emission ratio (FER), which is defined as the shift in fluorescence intensity in the measured wavelength range, and also to the chromatic ratio, which is defined as a color shift to longer wavelength ranges. The results also show that, by using UV-vis spectroscopy, it is possible to detect the degradation of the insulating paper. This study suggests that UV-vis spectroscopy can be applied as an alternative to high-performance liquid chromatography, which is the internationally recognized measurement technology for cellulose paper degradation. The FER detector is also verified to be useful as an effective condition-monitoring device for 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.

• 조명전기설비학회논문지
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• 제16권5호
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• pp.97-103
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• 2002

본 논문은 LVI 시험기를 개발하여 모델 변압기 및 유입식 변압기에 적용해 LVI 시험 분석기술을 개발하였다. LVI시험기는 본체, 터미널 박스 및 케이블로 구성하였고, ANSI규격에서 요구하는 출력특성을 갖도록 설계 제작하였다. 모델 변압기는 탭들을 만들어 변압기의 권선변형 모델을 만들 수 있도록 하였고, 유입식 변압기는 실제 현장에서 사용되는 3상 변압기이다. LVI 시험기는 펄스폭이 1000 ㎱ 이하의 파두 시간과 펄스 최대 전압 500 V로 제작되었다. LVI 시험기로써 실험을 실시하여 성능을 평가한 결과 측정된 파형 분석으로 권선의 축방향과 반경방향으로의 움직임을 구별할 수 있어 변압기 예방 진단에도 효과가 기대된다.

• 전기학회논문지
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• 제65권11호
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• pp.1937-1942
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• 2016

Unlike oil immersed transformers, cast-resin transformers have the solid insulator 'epoxy resin' in sealed structure. Therefore, they reveal a lot of limitations in checking aging conditions and predicting an accident. This study analyzed the characteristics of Cast-resin transformers by the measurement distance and measurement sensitivity with a corona defect sample, using antenna sensor. Therefore, the experiment has proven that the antenna sensor-based measurement method proposed in this study is able to detect the insulation defect location of the cast-resin transformer, unlike conventional measurement methods. It is expected that the result of this study will be used to develop a new type of measuring method in order to measure insulation defects and to use in safety inspection of domestic cast-resin transformers.

• 한국안전학회지
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• 제19권4호
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• pp.36-41
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• 2004

This paper presents an qualitative assessment for hazard on the electric power installations of a construction field using FMEL The power installations have the mission to maintain the highest level of service reliability on the works. The more capital the electric power invest the higher service reliability they plausibly will achieve. However, because of limited resources, how effectively budgets can be allocated to achieve service reliability as high as possible. The assessment typically generates recommendations for increasing component reliability, thus improving the power installation safety. The FMEA tabulates the failure modes of components and how their failure affects the power installations being considered. Tn order to estimate the risks of a failures, the FMEA presents criticality estimation or risk priority number using the severity, occurrence, and detectability. The results showed that the highest components of the risk priority number among components were condenser, transformer, MCCB and LA. And In case of the criticality estimation, the potential failure modes were abnormal temperature rise, insulation oil leakage, deterioration for the transformer, overcurrent for the MCCB and operation outage fir the LA.

• Journal of Power Electronics
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• 제18권2호
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• pp.395-406
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• 2018

Marine controlled-source electromagnetic transmitters (MCSETs) are important in marine electromagnetic exploration systems. They play a crucial role in the exploration of solid mineral resources, marine oil, and gas and in marine engineering evaluation. A DC-DC controlled-source circuit is typically used in traditional MCSETs, but using this circuit in MCSETs causes several problems, such as large voltage ringing of the high-frequency diode, heating of the insulated-gate bipolar transistor (IGBT) module, high temperature of the high-frequency transformer, loss of the duty cycle, and low transmission efficiency of the controlled-source circuit. This paper presents a clamping-diode circuit for MCSET (CDC-MCSET). Clamping diodes are added to the controlled-source circuit to reduce the loss of the duty ratio and the voltage peak of the high-frequency diode. The temperature of the high-frequency diode, IGBT module, and transformer is decreased, and the service life of these devices is prolonged. The power transmission efficiency of the controlled-source circuit is also improved. Saber simulation and a 20 KW MCSET are used to verify the correctness and effectiveness of the proposed CDC-MCSET.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.214-216
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• 2001

In this paper, we developed the on-line Diagnostic & Monitoring system of distribution transformers using wireless communication. The Diagnostic system consists of the top oil temperature sensing, ambient temperature sensing. load current sensing, acoustic emission peak-value sensing, acoustic emission pulse counter and wireless communication part. The Monitoring system consists of the communication setting, online monitoring and database construction part. The Diagnostic system send the date acquired from the some sensors of the distribution transformers to the host PC. The Monitoring program of the host PC store the data to database. And the Monitoring system estimates the loss of life from the DB. Thus it could be managed the career and the functional lifetime of the transformer more efficiently than existing methodologies.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.177-179
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• 2000

In this paper, we developed the online Monitoring & Diagnostic(MD) system of distribution transformers. It consists of the Data Acquisition(DA) module and the DataBase(DB) module. The acquired data from the distribution transformers is stored to the DB in an on-line. The DB is planned and made to the RDBMS (Relative DataBase Management System) to manage the data efficiently. The developed MD system estimates the loss of life from the DB. Thus, it could be managed the career and the functional lifetime of the transformer more efficiently than existing systems. In the case study, the oil temperature rising experiment is performed by using the back loading method in the laboratory level. From the results, the proposed MB system can be a practical applications for the distribution transformers.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.7-11
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• 2014

The Polarization and Depolarization Current (PDC) measurement is an efficient and effective diagnostic technique based on time domain measurement, for evaluating the high voltage insulation condition. This paper presents a review and comparison results from several published papers on the application of the PDC method to finding the conductivity and moisture content of various types of insulators. For solid insulation, the study was focused on cable insulation, electric machine stator insulation, and paper insulator in transformer insulation with different conditions. For liquid insulation, the review and comparison was done on biodegradable and mineral transformer oils, with fresh oil condition, and aged condition. The results from previous researchers tests were complied, analyzed and discussed, to evaluate the application of the PDC method to monitor the conductivity and moisture of HV equipment insulation systems. From the review results, the PDC technique successfully gives an indication of the conductivity and moisture level of high voltage insulation.

• 조명전기설비학회논문지
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• 제13권3호
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• pp.56-63
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• 1999

전력계통의 변전소 설비들은 계통의 확장에 따라 점점 복잡하고 거대해지고 있다. 또한, 몇몇 장비들은 점점 노후되고, 종종 예상치 않은 고장을 일으킨다. 변전소 설비들 중 변압기의 신뢰도를 증가시키기 위해서, 변압기의 진단기법 개발이 매우 필요하다. 본 연구에서는, 전력용 변압기의 용해 가스들을 근거로 KSOM(Kohonen Self Organizing Map)에 의한 열화정도와 원인의 분석기법을 개발하였다. KOSM은 용해가스에 의해 구성된 다차원 패텅을 이차원 평면에 지형학적 맵핑이 가능하다. 그리고 정장변압기에 대한 열화의 정도와 잠재적인 열화의 가능성을 제안된 정량적 지표에 의해 제시하였다. 아울러, 변압기의 열화과정을 제안된 지표를 근거로 특정한 변압기에 대해 분석하였다. 제안된 방법의 타당성을 입증하기 위해서 사례연구가 수행되고, 그 결과를 제시하였다.