• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.114-119
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• 2011

Large Power transformer is a complex and critical component of power plant and consists of cellulosic paper, insulation oil, core, coil etc. Insulation materials of transformer and related equipment break down to liberate dissolved gas due to corona, partial discharge, pyrolysis or thermal decomposition. The dissolved gas kinds can be related to the type of electrical faults, and the rate of gas generation can indicate the severity of the fault. The identities of gases being generated are using very useful to decide the condition of transformation status. Therefore dissolved gas analysis is one of the best condition monitoring methods for power transformer. Also, on-line multi-gas analyzer has been developed and installed to monitor the condition of critical transformers. Rogers method, IEC method, key gas method and Duval Triangle method are used to failure diagnosis typically, and those methods are using the ratio or kinds of dissolved gas to evaluate the condition of transformer. This paper analyzes the reliability of transformer diagnostic methods considering actual dissolved gas concentration. Fault diagnosis is performed based on the dissolved gas of five transformers which experienced various fault respectively in the field, and the diagnosis result is compared with the actual off-line fault analysis. In this comparison result, Diagnostic methods using dissolved gas ratio like Rogers method, IEC method are sometimes fall outside the ratio code and no diagnosis but Duval triangle method and Key gas method is correct comparatively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.353-358
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• 2022

Bulky iron-core potential transformers (PT) are installed in a tank of gas insulated switchgears (GIS) for a system voltage measurement in power substations. In this paper, we studied an electronic voltage transformer (EVT) embedded in a spacer for miniaturization, eco-friendliness, and performance improvement of GIS. The prototype EVT consists of a capacitive probe (CP) that can be embedded in a spacer and a voltage Follower with a high input and a low output impedance. The CP was fabricated in the form of a Flexible-PCB to acquire the insulation performance and to withstand vibration and shock during operation. Voltage ratio of the prototype EVT is about 42,270, and the frequency bandwidth of -3 dB ranges from 0.33 Hz to 3.9 MHz. The voltage ratio error evaluated at about 6%, 12% and 18% of the rated voltage of 170 kV was 0.32%, and the phase error was 12.9 minutes. These results were within the accuracy for the class 0.5 specified in IEC 60044-7 and satisfy even in ranges from 80% to 120% of the rated voltage. If the prototype EVT replaces the conventional iron-core potential transformer, it is expected that the height of the GIS could be reduced by 11% and the amount of SF₆ will be reduced by at least 10%.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.137-138
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• 2008

가스절연변압기(GITr)는 우수한 절연내력과 높은 신뢰성을 장점으로 가지고 있기 때문에 운전 시 유지 보수가 불필요하도록 설계목표를 정하여 제작되고 있지만, 제작과 운전 단계에서 치명적인 결함이 발생할 수 있고, 이러한 결함들은 전력기기 사고의 원인이 될 수 있다. 따라서 사고발생 전 단계에서 대규모 전력 사고의 발생 요인 중 하나인 전력기기 내부의 결함에 대한 상시 진단 및 원인 분석이 반드시 선행되어야 하며, 이와 같은 진단 분석 기법의 하나로 전력 기기의 내부 결함의 위치 판별에 대한 연구의 필요성이 절실히 요구되고 있다. 따라서 본 논문에서는 일반적으로 Cubicle 구조체 위치의 판별에 사용되는 기법 중 하나인 상변측정법(Trilateration)을 적용함으로써, GITr Mockup(170kV 급)의 세 개의 센서를 이용하여 결함에서 발생되는 부분방전 신호를 3차원적으로 분석하기 위한 연구를 위해 3개의 센서가 구성하는 평면상에 인위적 결함을 위치시켜 결함의 위치를 2차원적으로 분석하는 연구를 수행하여 약 5cm 오차 범위 내에서 결함을 판별하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1124-1128
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• 2021

As regulations of emissions from ships become more stringent, electric propulsion systems have been increasingly used to solve this problem in vessels ranging from large merchant ships to small and medium-sized ships. Methods for improving the efficiency of the electric propulsion system include the improvement of power sources; the use of a system linked to environmentally friendly power sources, such as batteries, fuel cells, and solar power; and the development of hardware and control methodology for rectifiers, power conversion devices, and propulsion motors. The method using a phase-shifting transformer with diodes has been widely used for rectification. Power semiconductor devices with grid connection to an environmentally friendly power source using DC distribution, a variable speed power source, and the application of small and medium-sized electric propulsion systems have been developed. Accordingly, the demand for active front-end (AFE) rectifiers is increasing. In this study, a method using a neural network rather than a conventional proportional-integral controller was proposed to control the AFE rectifier. Tested controller data were used to design a neural network controller trained through MATLAB/Simulink. The neural network controller was applied to a rectification system designed using PSIM software. The results indicated the effectiveness of improving the waveform and power factor DC output stage according to the load variation. The proposed system can be applied as a rectification system for small and medium-sized environmentally friendly ships.

• Analytical Science and Technology
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• v.18 no.3
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• pp.232-240
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• 2005

The total PCBs level in the transformer insulation oil samples using GC/ECD and HRGC/HRMS were ranged from 0.087 to $223.6{\mu}g/g$ and ranged from N.D. to $154.04{\mu}g/g$, respectively. The calculated TEQ values were ranged from 0.00067 to 6.8 ng WHO-TEQ/g. Among the samples, 6 samples showed higher than 2 ppm concentration (specific waste criterion of Korea). A variety in the concentration of total PCBs were observed between ECD and HRMS analysis. This is maybe due to quantification mehtod. The Aroclor 1248 wasn't present in the samples. The distribution pattern of Co-PCB congeners showed that the ratio of monoortho substituted congeners were higher than non-ortho substituted congeners. Among that, PCB-167 congener was predominant. In addition, the distribution of Co-PCBs congeners was different with that of flue gas and ambient air samples as well as commercial PCB formulations (Aroclor, Kanechlor).

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.203-209
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• 2017

Research on condition monitoring and diagnosis of power facilities has been conducted to improve the safety and reliability of electric power supply. Although insulation diagnostic techniques for unit equipment such as gas-insulated switchgears and transformers have been developed rapidly, studies on monitoring of cables have only included aspects such as whether defects exist and partial discharge (PD) detection; other characteristics and features have not been discussed. Therefore, this paper dealt with PD characteristics against void sizes and positions, and with defect localization in XLPE cable. Four types of defects with different sizes and positions were simulated and PD pulses were detected using a high frequency current transformer (HFCT) with a frequency range of 150kHz~30MHz. The results showed that the apparent charge increased when the defect was adjacent to the conductor; the pulse count in the negative half of the applied voltage was about 20% higher than that in the positive half. In addition, the defect location was calculated by time-domain reflectometry (TDR) method, it was revealed that the defect could be localized with an error of less than1m in a 50m cable.

• 전기의세계
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• v.27 no.5
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• pp.33-54
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• 1978

(차례) 1.산학협동심포지업 (1)우리나라에서의 연구개발과 산학협동 (2)산학협동과 산업계의 역할 (3)산학협동의 현황과 진로 2.학술회의A (1)전력게통의 계층구조와 협조원리에 관한 연구 (2)2중층괴상회전자 유도전동기의 이론해석 (3)초고주파가열장치에 사용하는 철공진변압기의 해석적 설계 (4)한국전기기시험연구소 대전력단락 시험설비설계 (5)직류전동기제어를 위한 Thyristor Chopper정류회로에 관한 연구 (6)선로의 개폐정보를 포함하는 전력계통의 상태추정 (7)단일신경세포에 대한 ITEM 신호 특성 3.학술회의B (1)MMM-1 Computer System의 설계 및 제작 (2)Adaptive Delta Modulation System의 성능비교 연구 (3)6GHZ FMD마이크로파 무선전송장치의 개발 (4)적선도에 의한 회로망함수의 결정 (5)동맥혈압의 해석과 그의 전기적 유사모델 (6)피부감각의 정보전달 특성에 관하여 (7)선형직접회로의 공정설계 및 그 특성 조성 (8)DH L.D의 전기적포화현상에 관한 이론적 해석 (9)Potocoupler를 이용한 Isolator 4.학술회의C (1)Al-Al$_{2}$O$_{3}$ -Al박막구조의 전기적 특성 (2)이종금속에 샌드위치된 고분자물질의 단락전조 (3)유전체가 일부체워진 직 6면체의 캐비티의 다중모오드 해석 (4)반도체 가스 검지소자의 제조 및 그의 전기적 특성 (5)실리콘 산화공정에 대한 실험적 고찰 (6)진공증착법에 의한 InSb 박막제도에서 열처리효과 (7)(Ba$_{1}$-xBix) Tio$_{3}$ PTC thermistor의 첨가량의 최적건안 (8)금속박막증착시 두께조절 5.특별강연회 (1)일본에 있어서의 절력계통공학연구 (2)Linear Motor의 최근개발동향량도 높았다. valine과 leucine 및 aspartic acid, glycine과 glutamic acid, leucine과 aspartic acid 간에는 고도의 정상관, glycine과 serine, valine과 phenylalanine, threonine과 proline, phenylalanine과 arginine, methionine과 glutamic acid, histidine과 lysine 간에는 유의 정상관, 그리고 isoleucine과 lysine 간에는 유의한 부상관이 있었다. 4. lysine 함량은 단백질 함량과 정산곤, isoleucine 함량은 단빅질 함량과 부상관을 보였으며, alanine, valine, leucine 함량은 지방함량과 각각 유의한 정산관을 보였다. 5. 대두 단백질은 7.5% acrylamide gel 전기영동에 의해 품종에 따라 12～16개의 구성분으로 분리되었으며, 이들중 주구성분들은 상대이동도가 0.06(a), 0.14(b). 0.24(d) 이었고, 구성분 b의 함량이 품종간에 가장 변이가 컸으며, 구성분 b는 그밖의 주요 구성분들의 함량과 부의 상관이 있었고, 구성분 a는 단백질 함량과 정상관이 있었다. 6. 종실단백질 구성분들의 조합 특성 면에서 공시 86품종은 11개 유형군으로 분류되었으며, 우리나라와 일본품종은 미국품종에 비해 단백질구성분 조성이 훨씬 다양하였다. 7. 이동도가 매우 빠른 단백질 구성분 o(Rm 0.77) p(Rm 0.81)를 모두 갖고 있는 품종은 3품종, 모두 갖고 있지 않은 품종은 1품종이었고, 나머지 82품종은 o나 p중 한 구성분을 갖고 있었으며 그 분포율은 30 : 65 이었는데 미국계 품종은 우리나라 품종에 비해 구성분 o를 간고 있는 비율이 현저히 적었다. 8. 대두 종실은 개화후 22일까지 완만히, 그 이후 20～30일간 급속히