• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.153-156
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• 2001

The transformer and the OF cable are cooled and insulated by insulating oils in their body. The insulating oil expands or contracts with the heat transfer according to the operating conditions of the electric facilities. So we install the $N_2$ gas tank connected with the insulating oil system to overcome the change. The change of the insulating oil volume for the operation temperature range must be calculated to decide the $N_2$ gas volume and to set the alarm point for safe operation. It is known that this change is proportional to the temperature change and to the insulating oil volume if the temperature change is small enough.[1][11] However this proportional formula has been accepted generally in the design of electric facilities for wide operation temperature range such as $40^{\circ}C{\sim}125^{\circ}C$. Hence, it makes large errors in calculation which car result in serious damage against safe operation of the electric facilities. This paper presents a improved method of calculating the accurate change of the insulating oil volume to insure the safe operation of electric facilities.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.436-444
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• 2016

Oil-paper insulation of valve-side windings in converter transformers withstand electrical stresses combining with AC, DC and strong harmonic components. This paper presents the physical mechanisms and experimental researches on partial discharge (PD) of oil-paper insulation at pulsating DC voltage. Theoretical analysis showed that the phase-resolved distributions of PDs generated from different insulated models varied as the increase of the applied voltages following a certain rule. Four artificial insulation defect models were designed to generate PD signals at pulsating DC voltages. Theoretical statements and experimental results show that the PD pulses first appear at the maximum value of the applied pulsating DC voltage, and the resolved PD phase distribution became wider as the applied voltage increased. The PD phase-resolved distributions generated from the different discharge models are also different in the phase-resolved distributions and development progress. It implies that the theoretical analysis is suitable for interpretation of PD at pulsating DC voltage.

• 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.

• 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 2004년도 하계학술대회 논문집 C
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• pp.1888-1890
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• 2004

현대사회에 들어서면서, 전력수요의 중가와 전력기기산업의 고집적화에 따라 사고시에 발생하는 파급효과가 대형화되는 추세에 있다. 따라서 이를 미연에 방지하기 위한 연구가 각 분야에 걸쳐 활발하게 진행되고 있다. 이에 당사에서는 초고압 계통에서 사용되는 SF6가스 절연 GIS(Gas Insulated Switchgear) 및 Oil-Transformer에서의 부분방전 측정/분석을 위하여 UHF/AE를 이용한 on-line/portable 측정 시스템을 개발하였다. 본 논문에서는 개발/상용화 되어 field에서 사용되고 있는 시스템의 전반에 대하여 설명한다. 또한 철재 선진사와 공동 진행중인 Risk Assessment에 대하여 언급하였다.

• 전기학회논문지
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• 제58권4호
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• pp.742-747
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• 2009

Many works on the temperature distribution of power apparatus have usually done by coupled magneto-thermal analysis. Such a method can not consider the internal gas or oil flow in the power apparatus such as gas insulated switchgear, GIS bus bar, and power transformer. Moreover it can not show the internal temperature distribution of the power apparatus exactly. This paper proposes a coupled magneto-thermal-flow analysis considering Navier-Stokes equations. The convection heat transfer coefficient is calculated analytically by applying Nusselt number for natural convection and is applied to the boundary condition of proposed method. Temperature distribution of the GIS bus bar model considering thermal flow is obtained by the proposed method and shows good agreement with the experimental data.

• 전기의세계
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• 제29권5호
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• pp.315-320
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• 1980

It has been appeared and widely used today SF6 Gas Insulated Substation(Hereafter called GIS) for the power supply to the densely populated area due to the superior insulation withstand ability of SF6 Gas. And to maximize the compact effect of this substation, it is normal practice to connect underground cables. If it is possible to elieminate the redundant lightning arresters using the physical characterestics of travelling waves in underground cables, economical advantages can be obtained together with easy maintenances. It is presented in this paper the possiblity of eliminating the transformer protection lightning arresters under some conditions for the 154kV GIS's (BIL:750kV) which Korea Electric Co. plans to construct using the general purpose digital computer program.