• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.292-295
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• 1991

The life of the transformers is significantly dependent upon the rate of thermal deterioration in the employed insulating materials. Therefore, the study should be based on hot-spot temperature considerations for the life expectancy and possible overload of transformer. We have measured directly temperature of the winding using thermocouples and these test results are compared with those obtained from computer simulation. In this work, our fundamental investigations are well described for the analysis in the thermal distribution of the oil-immersed transformer with the rating of 30kVA.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.447-454
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• 2020

Since SF₆ gas was discovered in the early 1900s, it has been widely used as an insulation material for electrical equipment. While various indicators have been developed to diagnose oil-immersed transformers, there are still insufficient indicators for the diagnosis of gas-insulated transformers. When necessary, chemical diagnostic methods can be used for gas-insulated transformers. However, the field suitability and accuracy of those methods for transformer diagnosis have not been verified. In addition, since various types of decomposition gases are generated therein, it is also necessary to establish appropriate analysis methods to cover the variety of gases. In this study, a gas-insulated transformer was diagnosed through the analysis of decomposition gases. Reliability assessments of both simple analysis methods suitable for on-site tests and precise analysis methods for laboratory level tests were performed. Using these methods, a gas analysis was performed for the internal decomposition gases of a 154 kV transformer in operation. In addition, simulated discharge and thermal fault experiments were demonstrated. Each major decomposition gas generation characteristics was identified. The results showed that an approximate diagnosis of the inside of a gas-insulated transformer is possible by analyzing SO₂, SOF₂, and CO using simple analysis methods on-site. In addition, since there are differences in the types of decomposition gas generation patterns with various solid materials of the internal transformer, a detailed examination should be performed by using precise analysis methods in the laboratory.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.10
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• pp.485-491
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• 2006

This paper describes that the distribution of electromagnetic field occurred by PD(Partial Discharge) pulse was calculated with simulation program and characteristics of calibration and PD pulses measured with folded dipole types sensors were analyzed. As the distribution of electromagnetic field in simulation was very random the wide band measuring methods were good. Therefore three folded dipole antenna types sensors which had different their widths were designed and made. The signal according to direction and distance between sensor and pulse source in these sensor was measured and the spectrum of surface PD were acquired in the experiment of model transformer. In this result the characteristics of sensor which had middle width was better than others and the main spectrum of PD signals in surface discharge were existed in around 220MHz, 320MHz and from 450MHz to 750MHz.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.92-94
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• 2003

The autotransformer currently used on the electric railway system is made of class A insulation material and uses the paper insulation method. As a power converter supplying power to the trolley wire, the autotransformer is one of critical equipment in the railway system. In the autotransformer, load irregularly changes and overload often occurs. These cause overheating of the autotransformer and facilitate deterioration of the autotransformer resulting in burnout accidents due to insulation breakdown. Also, the current autotransformer has poor insolation and short-circuit strength which often badly affect the service life of the transformer, and needs to improve its quality urgently. To overcome one of existing shortcomings of the mold transformer, manufacturers use epoxy resins that have superior flame retardancy to get rid of fro and explosion possibilities during accidents. Currently, new mold transformers are used in indoor distribution facilities with fire-fighting equipments. Coils molded in epoxy resins do not have their insulation performance compromised by humidity, dust, etc enabling easy inspection and maintenance. Comparing to the oil immersed transformer, the mold transformer does not have any concern about environmental pollutions by oil leak or replacement Therefore, to reduce breakdowns and improve reliability of the autotransformer, it is necessary to develop a new mold autotransformer with low loss suitable for our environment to suppress breakdowns of the autotransformer and improve the reliability. This study is about development of a low-loss mold autotransformer necessitated by reasons mentioned earlier.