• Tribology and Lubricants
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• v.35 no.3
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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 the Earthquake Engineering Society of Korea
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• v.22 no.2
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• pp.87-94
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• 2018

In this study, seismic performance of bushings and their connection parts was analyzed by performing shaking table tests for various types of bushings widely used as auxiliary equipment of main transformers in domestic substations. As a result of the seismic tests of five types of 154 kV bushings according to the manufacturers, all the bushings secured the structural integrity even at the acceleration of 1.4 g and it was found that leakage of insulating oil didn't occur. Also, the average acceleration amplification rate at the upper part of the bushings was about 2.5 to 3.0 times higher than the lower one. On the other hand, when a representative 345 kV bushing was subjected to the seismic test, the structural integrity was secured even at 1.0 g acceleration similar to the design earthquake load level, but in this test, leakage of insulating oil occurred. However, when a stiffener restricting the connection of the bushing is installed in the same 345 kV bushing, the displacement of the bushing connection is controlled and the stiffener prevent the oil from leaking even at the acceleration of the designed seismic level.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.1
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• pp.6-11
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• 2013

In this paper, the temperature characteristics of mold transformer for the distribution power system have been analyzed by using computational fluid dynamics(CFD). The model has been modeled by coil, cores, insulating materials and frames about 3MVA grade mold transformer and analyzed the temperature distribution of the structure with a heat fluid. The fluid, which is incompressible ideal gas, is analyzed as a turbulent flow phenomenon on the assumption that it is natural cooling of transformer cooling system. Through this study, by examining the temperature distribution and hot-spot of the structure field of the mold transformer, cooling design and temperature distribution information, which are demanded for designing are estimated.

• 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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.15-21
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• 2011

This paper presents an analyzing method of the capacitance of the power transformer for initial voltage distribution and insulation design. When a high incoming surge voltage is accidently occurred in windings of transformer, it does not distribute equally in the windings. This phenomenon makes electric field concentration and the insulating material could be break. Initial voltage distribute mostly depends on capacitances between winding to winding or winding to core in the transformer. If the C network can be structuralized into the equivalent circuit model and be calculated each capacitance element value by circuit analysis and FEM(Finite Element Method) simulation program, the transformer designer could know the place where the structure is to be modified or the insulation to be reinforced. This method quickly provides the data of the voltage distribution in each winding to the designer.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.53-56
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• 2007

In the response to the demand for electrical energy, much effort was given to develop and commercialize high temperature superconducting (HTS) power equipment has been made around the world. Especially, a HTS transformer is one of the most promising devices. Recently, Korea Polytechnic University and Gyeongsang National University are developing a power distribution and transmission class HTS transformer that is one of the 21st century superconducting frontier projects in Korea. For the development of 154 kV class HTS transformer, the cryogenic insulation technology should be established. We have been analyzed insulation composition and investigated electrical characteristics such as the breakdown of $LN_2$, barrier, kapton films, and the surface flashover of FRP in $LN_2$. Furthermore, we are going to compare with measured each value and apply the value to the most suitable insulating design of the HTS transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.81-81
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• 2010

This paper presents results of experimental investigations on natural ester regarding the breakdown strength. Aging of insulating material in a pole transformer has been studied by performing accelerated thermal aging test. Sealed aging test vessels containing copper, laminated core, Krapt paper and insulating oil(Natural oil and Mineral oil) were aged at $140^{\circ}C$ for 30days. Compared to the conventional transformer oil, electric property of the natural ester fluid is excellent.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.181-189
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• 1998

In order to investigate the effect of base oil composition on the electronic insulating oil's performances, an experimental study has been conducted using different oils. Owing to their properties, like lower pour point and gas absorbing, naphthenic base oils are used more often than paraffmic base oils for the electronic insulating oil application. Naphthenic and paraffinic base oils are significantly different in their aromatic hydrocarbon content. In this paper, PXE(para xylyl ethane), LAB(linear alkylbenzene), C13 aromatic hydrocarbon mixture and C17 aromatic hydrocarbon mixture are investigated regarding their influence on insulating oil's performances. According to present study, breakdown voltage decreased with increasing aromatic lydrocarbon content in a deep dewaxed paraffmic base oil. However, any changing in the dissipation factor was not recognizable at small treated level. Furthermore, the volume resistance was not influenced by aromatic hydrocarbon content. The gassing tendency was found as a highly sensible property, changing with treating aromatic hydrocarbons. The higher benzene ring content in the hydrocarbon, the better gassing tendency.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2105-2119
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• 2015

This paper reported the experimental result of dielectric properties of Refined, Bleached and Deodorized Palm Oil (RBDPO) combined with 0-50% of Refined, Bleached and Deodorized Soybean Oil (RBDSO). The dielectric strength and relative permittivity of RBDPO/RBDSO was higher compared to mineral oil at all ranges of ratios and temperatures which indicated a positive sign for its possible use as insulating liquid in a transformer. All ratios of the RBDPO/RBDSO mixture also demonstrated lower dissipation factor compared to mineral oil at 40℃, 70℃ and 90℃. Apart from that, the kinematic viscosity for the oil mixtures shown exceeded the IEC 60296 as well as the mineral oil results. 70%RBDPO/30%RBDSO mixture ratio was chosen as the best mixing percentage after comparison was made with the mineral oil and IEC 60296 standard where the mixture accumulated the most satisfactory of dielectric properties hence making it as the potential candidate for palm and soybean-based transformer oil.

• 전기의세계
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• v.22 no.4
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• pp.30-34
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• 1973

The main purporse of this paper is to study on the influence of temperature effect on electrical-properties, i.e., dielectric breakdown voltage, dielectric constant and resitivity of homemade insulating oil containing antioxidant. Transformer oil manufactured in Korea is taken for a sample, and this sample is classified into seven samples in which antioxidant is contained and not contained, and antioxidant is divided into three kinds of amount: 0.3%, 0.5%, 0.8%. Changing the tempe5rature of the samples by oil bath, the electric properties measured from the samples are as follows: (1) the variation of either the dielectric breakdown voltage or the resistivity are considerably large, but the dielectric constants are almost unchanging. (2) In view of electrical characteristic, the deterioration rate of the samples containing antioxidant is somewhat lower than that of other samples. (3) Nearly the same value is shown in the dielectric-breakdown voltage of the samples, in which contained the different amount of antioxidant: 0.3%, 0.5%, 0.8%, but the decrease rate of resitivity is lowest, 0.3%, of all. As the result of the experiment, This study can suggest that 0.3% be the optimum amount of antioxidant which will be added transformer oil manufactured in Korea and is useful for the understanding about the electrical properties of transformer oil containing antioxidant.