• Title, Summary, Keyword: Insulating oil

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Analyses on Electrical-Mechanical Characteristics of Environment-friendly Transformer Insulating Material by Accelerated Thermal Aging (가속 열 열화에 따른 환경친화형 변압기 절연물의 전기적-기계적 특성 분석)

  • Shim, Myeong-Seop;An, Jung-Sik;Choi, Sun-Ho;Jeong, Jung-Il;Lee, Tae-Ho;Huh, Chang-Su
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.10
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    • pp.1832-1838
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    • 2010
  • Aging of transformer insulating material in natural ester insulating oil is compared to that in conventional transformer oil. Aging of insulating paper and insulating oil have been studied by performing accelerated thermal aging test. Sealed aging test vessels containing cooper, laminated core, Kraft paper and insulating oil(natural oil or mineral oil) were aged at $140^{\circ}C$ for 500, 1000, 1500 and 2000 hours. Insulating oils after aging are investigated with total acid number, breakdown voltage and viscosity. Also, degradation of insulating paper after aging is determined using breakdown voltage and mechanical strength. Accelerated aging studies demonstrate a slower aging rate for natural ester insulating oil compared to the rate for conventional mineral oil.

Research of Flow Electrification Phenomena of the used Environment-Friendly Vegetable Insulating Oils (친환경 식물성절연유의 유동대전현상 연구)

  • Choi, Sun-Ho;Huh, Chang-Su
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.4
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    • pp.580-584
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    • 2012
  • The insulating oils perform a cooling and insulation action in electric power transformer. The mineral oil has immanent fire dangerousness and environmental contamination problem. Vegetable insulating oil has higher ignition point, flash point and more excellent biodegradability than conventional mineral oil. In a real oil-filled transformers, some of the power is dissipated in the form of heat. And transformer require the heat to be removed from the winding and insulator by forced convection of the insulating oil. The flow electrification occurs when insulating oil was forced to be circulated. In this paper, influence of temperature, velocity of flow, and insulating pipe and diameter on streaming electrification of vegetable insulating oil was investigated using forced circulation apparatus. Temperature effects were most significant, and it showed a peak in the temperature $30^{\circ}C$ to $35^{\circ}C$ at insulating and copper pipe. The change of flow electrification according to area variety could be checked by change of diameter.

A study on electrical conduction of streaming insulating oil (유동 절연유의 전기전도에 관한 연구)

  • Shim, J.H.;Park, J.Y.;Lee, D.Ch.;Kim, W.G.
    • Proceedings of the KIEE Conference
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    • pp.296-298
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    • 1991
  • When insulating oil was flowed through a pipe, the electrostatic charge in the oil was increased using inflammability oil, an electrostatic phnomena which may cause significantly problems as explosion must be circumvented by some methods. In this paper, Streaming insulating oil electrificated by streaming electrification of electrification pipe and standing insulating oil were affected under the high field strength, temperature of insulating oil, and concentration of surfactant. The electrical conduction was compared and analysed by these influence.

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Research of Accelerated Aging According to Long-term Stability of Vegetable Oil (식물성절연유의 가속열화에 따른 장기적 안정성 분석)

  • Choi, Sun-Ho;Huh, Chang-Su
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.8
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    • pp.1148-1152
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    • 2012
  • The vegetable-based insulating oils are substitutes for mineral oils in oil-filled transformer. The important properties of vegetable insulating oil is their higher flash/fire point and biodegradability than conventional mineral oils. The large oil-filled transformer eliminate the risk of explosion and fire should the transformer fail and oil ignite owing to high flash/fire point of vegetable insulating oil. In addition, higher biodegradability of vegetable insulating oils can let the oil spill damage reduced. In this experiment, the real oil-filled transformers using mineral oil and vegetable oil have accelerated aging. After working on the 100% accelerated aging experiment were conducted comparing the transformer. The hottest-spot temperature using thermal coefficients were calculated to determin the degree of accelerated aging. As a result, apply mineral oil transformer in accordance with the accelerated aging life come to an end. In contrast, vegetable insulating oils showed the opposite characteristics. Vegetable insulating oil compared to the mineral oil are found to be an long life. As a result, the vegetable oil has a long-term stability.

A Study on Conductivity Characteristics of Insulating Oil by Corona Discharge in Oil (유중(油中)코로나 방전(放電)으로 인(因)한 절연유(絶緣油)의 도전특성(導電特性)에 관한 연구(硏究))

  • Kim, Young-Ill
    • Journal of radiological science and technology
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    • v.2 no.1
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    • pp.71-83
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    • 1979
  • Not only the insulating oil used for extra high voltage and high capacity transformer has a lot of possibilites of a corona discharge in oil, but the oil is easily degraded by a response of light oxidization. This study is either to classfy, with priority given to a transformer oil produced in Korea belonging to, the insulating oil No. 2, the sample irradiated the ultraviolet rays, treated a corona discharge in oil by a high voltage DC source and done nothing, or to measure the characteristics of breakdown, V-i, I-t and electrode material. The obtained results can be summarized as followings: (1) Unless the sample is contacted with the air, on the process to irradiate the ultraviolet rays, the sample less influence on the changes of the electric characteristics. At the same time, if the sample is contacted with the air and irradiated the ultraviolet rays, the sample shows a remarkable changes of the electric characteristics, and a declined breakdown strength. This tells us that the influence of the light irradiation must be considered as a primary factor of degrading the insulating oil. (2) In the oil treated by a corona discharge, breakdown voltage is declined more than in the oil not to be treated with it. This means that the degradation of the insulating oil is getting increased by a corona discharge in oil. (3) It shows that the increase of conducting current has little to do with breakdown voltage. (4) The conducting current depending on the electrode materials can be put in order by value as Al>Cu>Fe. This is due to the differences of the work function of each metals, and an chemical reaction with the insulating oil. These result can be a great help in verifying the degradation progress of the insulating oil and furnish a new technical information to the manufacturers of the insulating oil and electrical equipment designers and operators. Besides, this study would be helpful to improve the electrical characteristics of the insulating oil produced in Korea.

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Research of Flow Velocity and BTA According to the Streaming Electrification of Vegetable Insulating Oils (식물성 절연유의 유속과 BTA에 따른 유동대전 현상 연구)

  • Choi, Sun-Ho;Bang, Jeong-Ju;Huh, Chang-Su
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.10
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    • pp.791-797
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    • 2012
  • Mineral insulating oils are an important insulating materials in oil-filled transformer. However, the mineral oil is the cause of the environmental problem. The vegetable oils are substitutes for mineral oil because of its biodegradability characteristic. As large size and high rating of the transformer increases, the losses increase at a faster rate. So insulating oil is forced circulation in the oil-filled transformer by using oil pumps. The flow electrification occurs when insulating oil was forced to be circulated. To check the flow electrification, had conducted experiments varying factors. As a result, the streaming electrification could see the changes according to flow velocity, oil temperature and insulation materials.

Measurement of Electrical Insulating Oil Oxidation by Evaluating the UV Fluorescence Emission Ratio (자외선 형광 방출비 평가에 의한 전기 절연유의 산화측정)

  • Wicaksono, Britantyo;Kong, Hosung;Han, Hung-Gu
    • Tribology and Lubricants
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    • v.29 no.1
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    • pp.51-55
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    • 2013
  • In this work, a new fluorescence emission measurement technology was introduced and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate it for the oil oxidation measurement of electrical insulating oil. The oxidation characteristics of insulating oil were found to be fairly represented by the titration method and IR spectroscopy, and the results are comparable to a change in the fluorescence emission ratio that is defined as the shift in fluorescence intensity in the measured wavelength range. The result also shows that by the measurement of fluorescence emission ratio, it is possible to detect the oxidation of oil relatively earlier than by other methods. This study suggests that the developed technology can provide sufficient information for evaluating the insulating oil quality, and that the developed FER sensor can be used as an effective condition monitoring device of electrical insulating oil oxidation.

Evaluation of Insulating Oil by Terahertz Time Domain Spectroscopy (테라헤르츠파 분광법에 의한 절연유 특성 평가)

  • Kim Geun-Ju;Jeon Seok-Gy;Sun Jong-Ho;Jin Yun-Sik
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.8
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    • pp.411-416
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    • 2006
  • A new method on the evaluation of insulation oil was proposed. Terahertz time-domain spectroscopy (THz-TDS) was applied to investigate the properties of the insulating oil. For the diagnostics of oil degradation, three kinds of oils have been analyzed by THz-TDS. The degraded oil showed different optical and electrical constants compared with a new one. Generally, the power absorption coefficient, the refractive index, the dielectric constant and loss $tan{\delta}$ of the oil increase as the aging of insulating oil proceed. And the characteristics of two kind of insulation oil, 1-4 and 7-4, was compared in terahertz spectral region. Difference in refractive index and complex dielectric constant has been observed between the samples. The results of this study suggest that THz-TDS is a promising new means for evaluating degradation and identification of insulating oil.

Copper Particle Effect on the Breakdown Strength of Insulating Oil at Combined AC and DC Voltage

  • Wang, You-Yuan;Li, Yuan-Long;Wei, Chao;Zhang, Jing;Li, Xi
    • Journal of Electrical Engineering and Technology
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    • v.12 no.2
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    • pp.865-873
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    • 2017
  • Converter transformer is the key equipment of high voltage direct current transmission system. The solid suspending particles originating from the process of installation and operation of converter transformer have significant influence on the insulation performance of transformer oil, especially in presence of DC component in applied voltage. Under high electric field, the particles easily lead to partial discharge and breakdown of insulating oil. This paper investigated copper particle effect on the breakdown voltage of transformer oil at combined AC and DC voltage. A simulation model with single copper particle was established to interpret the particle effect on the breakdown strength of insulating oil. The experimental and simulation results showed that the particles distort the electric field. The breakdown voltage of insulating oil contaminated with copper particle decreases with the increase of particle number, and the breakdown voltage and the logarithm of particle number approximately satisfy the linear relationship. With the increase of the DC component in applied voltage, the breakdown voltage of contaminated insulating oil decreases. The simulation results show that the particle collides with the electrode more frequently with more DC component contained in the applied voltage, which will trigger more discharge and decrease the breakdown voltage of insulating oil.

A study on the improvement of the thermal expansion formula of the insulating oil in electric facilities (전력설비 절연유 열팽창 계산식 개선에 관한 연구)

  • Rim, Seong-Hwang;Moon, Bong-Soo
    • Proceedings of the KIEE Conference
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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.

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