• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.219-223
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• 2002

Voltage and current signals during impulse tests on transformer are treated as non-stationary signals. A new method incorporating signal-processing method such as Wavelets and courier transform is proposed for failure identification. It is now possible to distinguish failure during impulse tests. The method is experimentally validated on a transformer winding. The wavelet transforms enables the detection of the time of occurrence of switching or failure events. After establishing the time of occurrence, the original waveform is split into two or more sections. The wavelet transform has ability to analysis the failure signal on time domain as well as frequency domain. Therefore, the wavelet transform is superior than courier transform to analysis the failure signal. In this paper, the fact was proved by real data which was achieved.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.262-267
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• 2011

In the power system, the transformer's neutral earth reactor line 1 grounding failure may occur. By limiting the magnitude of the failure grounding current flow, it will aid to reduce the failure of the transformer. Consequently, this also may avoid the failure of the disconnection of the industrial insulator line that cause by melting. Besides, utilizing the decreasing circuit breaker or others related equipment can use to avoid the possibility of explosion of the transformer. If the failure happen during the operation of the power system, a huge interference will definitely may occur. Therefore, by installing the DONGBUSAN S/S #3M.Tr neutral earth reactor among TOP and BOTTOM BRACE part in the power system, the causes of the rising temperature and reason of the over-current flow that cause by over-current can be analyze.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.169-171
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• 2009

In recent years, environmental concerns have been raised on the use of poorly biodegradable fluids in electrical apparatus in regions where spills from leaks and equipment failure could contaminate the surroundings. For development of the environmental-friendly pole transformer using vegetable oil, we discussed the insulation construction of the transformer and the dielectric characteristics of the Nomex insulation paper in vegetable oil. Based on the experimental data, the insulation of the transformer is designed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.3
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• pp.177-183
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• 1999

This paper presents how to evaluate the transformer damage caused by reclosing scheme at the distribution substation. We describe a quantitative relationship between the reclosing scheme and the number of fault current flowing through transformer wsing the probability of a reclosing success/failure. The transformer damage from reclosing scheme is presented using a weight function and a damage function. A weight function is associated with the number of reclosing attempts and the reclosing deadtime to consider cumulative stress caused by reclosing scheme. A damage function is associated with a transformer impact ratio and a transformer functional life. In the case study, the transformer damage is simulated for the probability of a reclosing success. And the evaluation of transformer damage using KEPCO's operation data is performed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.5
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• pp.857-862
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• 2017

The management of the electric power facilities became important in accordance with the industrial development and electric power facilities were influenced by weather. Even if the same kind of electric power facilities is estimated for extracting the time-varying failure rate, the failure rate could be different depending on external effect such as climate. This research will show the data mining modeling of the weather-related outage and influence of weather on the electric power facility with recent data.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.8
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• pp.343-349
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• 2005

The gas in oil analysis of transformer is the most widely used technology for diagnosis of transformer in the world. It has brought excellent results to prevention of transformer failure. The criteria for maintenance and judgement, however, is still required continuous supplement to improve the accuracy of the diagnosis on the basis of accumulated data of gas analysis and investigations in the transformer In this study, the relationship between the detection rate of the defects and the source of troubles are analyzed according to the investigation in the transformer, which was conducted by KEPCO in 2004. As a result, the validity of the criteria being used at present was examined thoroughly.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.615-621
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• 2014

Power transformer is one of the most important equipments in electrical power system. The detection of certain gases generated in transformer is the first indication of a malfunction that may lead to failure if not detected. Dissolved gas analysis (DGA) of transformer oil has been one of the most reliable techniques to detect the incipient faults. Many conventional DGA methods have been developed to interpret DGA results obtained from gas chromatography. Although these methods are widely used in the world, they sometimes fail to diagnose, especially when DGA results falls outside conventional method codes or when more than one fault exist in transformer. To overcome these limitations, fuzzy inference system (FIS) is proposed. 250 different cases are used to test the accuracy of various DGA methods in interpreting the transformer condition.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.219-226
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• 1997

This paper investigates and analyzes the installation and failure status of mold transformer being used in domestic subways and describes the extinguishing process by time through the combustion test of winding part of mold transformer. Condition of installed mold transformers and classes of fire were surveyed and the mold transformer was burned in a horizontal heating furnace. It was confirmed that the mold transformer is self extinguishing and nonflammability. According to this results, the suitable standard of fire protection for the mold transformer was demanded after review of domestic and abroad law. It is expected that the cost of fire protection equipment can be reduced by using the status and combustion test result of mold transformer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.10
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• pp.1770-1775
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• 2010

An acceleration life test for rubber gasket of pole transformer was performed. The Arrhenius method was applied as an accelerated degradation test. The failure mode was considered as an elongation, and the failure mechanism is counted as a heat. It is found that both the current material(NBR: Nitrile Butadiene Rubber) and recommended alternative material(HNBR: Hydrogenated Nitrile Butadiene Rubber) have the same Weibull distribution as a life characteristic. For life expectation 95% reliability level of characteristic life is used at using temperature. The test results for NBR and HNBR are 7.7 years and 28.0 years on $50^{\circ}C$ of using temperature, respectively.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.114-119
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• 2011

Large Power transformer is a complex and critical component of power plant and consists of cellulosic paper, insulation oil, core, coil etc. Insulation materials of transformer and related equipment break down to liberate dissolved gas due to corona, partial discharge, pyrolysis or thermal decomposition. The dissolved gas kinds can be related to the type of electrical faults, and the rate of gas generation can indicate the severity of the fault. The identities of gases being generated are using very useful to decide the condition of transformation status. Therefore dissolved gas analysis is one of the best condition monitoring methods for power transformer. Also, on-line multi-gas analyzer has been developed and installed to monitor the condition of critical transformers. Rogers method, IEC method, key gas method and Duval Triangle method are used to failure diagnosis typically, and those methods are using the ratio or kinds of dissolved gas to evaluate the condition of transformer. This paper analyzes the reliability of transformer diagnostic methods considering actual dissolved gas concentration. Fault diagnosis is performed based on the dissolved gas of five transformers which experienced various fault respectively in the field, and the diagnosis result is compared with the actual off-line fault analysis. In this comparison result, Diagnostic methods using dissolved gas ratio like Rogers method, IEC method are sometimes fall outside the ratio code and no diagnosis but Duval triangle method and Key gas method is correct comparatively.