• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.12
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• pp.578-584
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• 2005

This paper describes development of management software for transformers based on artificial intelligent analysis technology of dissolved gases in oil. Fault interpretation using the artificial intelligent analysis is performed by the artificial neural network and a rule based on the analysis of dissolved gases. The used gases are acetylene($C_{2}H_{2}$), hydrogen($H_2$), ethylene($C_{2}H_{4}$), methane($CH_4$), ethane($C_{2}H_{6}$), carbon monoxide(CO) and carbon dioxide($CO_2$). This software is mainly composed of gases input, fault's causes, expected fault's phenomena in detail, the decision on maintenance as well as report and gas trend windows. It is indicated that this is very powerful software for the efficient management of oil-immersed transformers using data analysis of gas components.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.230-234
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• 2006

One of the methods currently being investigated as a possible non-intrusive diagnostic tool for condition monitoring of power transformer and cable is the recovery voltage measurement, which will be improving the ability to detect the content of water concentration and the ageing process in the insulation system and may thus be an indicator of insulation quality and its ageing status. The polarization phenomenon was studied using RVM with oil-paper samples. In order to interpret its mechanism, the Extended Debye model was introduced. With different circuit parameters, various simulation results were gotten. Furthermore, with the test samples of different ageing condition, measurements are accomplished in the lab. On the basis of this experiment as well as theoretical analysis, correlations between polarizations and ageing were analyzed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.87-90
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• 2004

This paper describes development of power transformer maintenance system using intelligent dissolved gases in oil analysis. The used gases are acetylene(C2H2), hydrogen(H2), ethylene(C2H4), methane(CH4), ethane(C2H6), carbon monoxide(CO) and carbon dioxide(CO2). The rule and neural network based gas analysis methods are used for artificial intelligent diagnosis. It is indicated that this program is efficient for diagnosis of oil immersed transformers diagnosis from application of gas analysis data of serviced transformer which has local overheating

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.780-782
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• 2001

The mold transformer has anti-burnt and possibility of small size contrary to oil-immersed transformer. The mold transformer has generally cooling duct between low voltage coil and high voltage coil and also made by one body molding for small size and low loss. In this paper, the temperature distribution of designed 50kVA pole mold transformer for power distribution is investigated by FEM program. The designed transformer is also manufactured and temperature rise test is carried out.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.97-102
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• 2012

A hermetically sealed oil transformer is designed by applying expanding function of the tank due to the volume changes of the insulation oil according to the temperature rises. When the insulation oil expands, an increase in the volume of the corrugated fin prevents a pressure rise of the transformer. For a wind turbine transformer, a vegetable-oil-immersed transformer has the advantages of excellent biodegradation and fire-resistant properties like an exceptionally high fire point. When vegetable oil is substituted for mineral oil, however, the maximum winding temperature rises because of the decrease in the internal circulation flow rate resulting from the variations of the oil's physical characteristics, such as density and viscosity. The purpose of this study is to develop a hermetically sealed vegetable oil transformer that can be applied in a wind turbine and to analyze the thermal stability of the active part of the transformer to deal with pressure variations due to the temperature changes. In addition, thermal tests for the vegetable oil transformer have been performed, and the measured values are compared with the analysis results.

• Proceedings of the KIEE Conference
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• 2004.11d
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• pp.97-99
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• 2004

Liquid-immersed pole transformers have utilized an insulation system consisting of natural cellulose-based materials and mineral oil for many years. If the transformers are installed with the abruptly changing load over limitation, its insulation materials are apt to unexpected aging with high temperature. Therefore we have been conscious of developing a transformer that is more thermally stable then conventional types. To measure temperature distribution in the winding of conventional and newly designed transformers, temperature sensors were installed fordirect reading of oil and conductor temperatures at transformers. And we conducted accelerating aging test for these transformers. The measuring data had made use of the design to hybrid insulation system. Also we could find the possibility of this insulation system to apply in pole mounted transformers.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1896-1898
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• 2002

In this paper, to developing thermally and mechanically upgraded ones, we dismounted pole transformers used in the fields for over 13 years and conducted aged oil analysis. Also, when the cellulose and aramid papers in test cell were aging with oil at $130^{\circ}C$ for 3000 hours, with the testing period cellulose paper deteriorated more rapidly than the others. For example dielectric strength and dissipation factor of papers deteriorated with aging time. For evaluation of thermal aging characteristics, a mineral oil-immersed transformer was constructed with hybrid insulation system comprised of aramid paper and cellulose insulation. A Hybrid system has economic advantages. Cellulose materials are confined to cooler regions of the transformer winding. And aramid papers are served to insulate contact parts of hot conductors.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.497-500
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• 2001

Shunt reactors are used to compensate for capacitive VARs generated by lightly loaded transmission lines or underground cables. They are normally connected to the transformer tertiary winding. Dry-type shunt reactors have the advantage compared with oil-immersed shunt reactor as followings. Lower investment and maintenance cost, No fire hazard and no environmental concerns, Simple insulation to ground, Response to transient overvoltage less severe, Linearity of inductance versus load current, Lower-acoustic noise, Easier transport and handling due to lower weight, No oil-collecting system must be provided since there is no oil that can leak into the ground.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.12
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• pp.532-539
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• 2005

The demand of Gas Insulated Transformer(GIT) using $SF_6$ gas as insulating and cooling medium is being increased dramatically in the underground substation of urban area because it has the advantages of non-flammable and non-explosive, etc. This paper describes the structural features and advantages of the gas insulated transformer compare to an oil immersed transformer, and presents a brief overview of the consideration and technology which apply to $SF_6$ gas insulated transformer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.157-166
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• 1999

Numerical calculations of turbulent natural convection in an enclosure of the 20 kYA oil-immersed transformer model are presented. The transformer is modelled as two concentric cylinders with different heights and diameters. The thermal boundary layers are well represented in the temperature distributions along the wall of the transformer model. The flow stratification between the hot and cold walls can not be seen in the transformer model. The turbulence eddy viscosity has its maximum at the center of the core and its maximum values at the top of the core are larger than those at the bottom of the core.