• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1015-1018
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• 1999

Partial discharge patterns were analyzed in the pumped storage generator stator winding. These were measured using partial discharge analyzer(PDA) and digital partial discharge detector(PDD). Slot discharge was discovered in phase A. Discharges at conductor surface were occurred in phase B and in Phase C. Partial discharge patterns from on-line PDA system were compared with those off-line PDD system. The results of two systems are very same in phase A, B and C.

• Transactions of Materials Processing
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• v.28 no.5
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• pp.239-246
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• 2019

Various surface texturing techniques have been studied because of the effective applicability of micro or nano scale surface patterns. Particularly, the most promising types of patterns include the hierarchical patterns, which consists of micro/nano structures. Different processes such as MEMS, laser machining, micro cutting and micro grinding have been applied in the production of hierarchical patterns on various material surfaces. This study demonstrates the process of hot imprinting to induce the hierarchical patterns on the Al alloy surfaces. Wire electrical discharge machining (WEDM) process was used to imprint molds with micro scale sinusoidal pattern. In addition, the sinusoidal pattern with rough surface morphology was obtained as a result of the discharge craters. Consequently, the hierarchical patterns consisting of the sinusoidal pattern and the discharge craters were prepared on the imprinting mold surface. Hot imprinting process for the Al plates was conducted on the prepared mold, and the replication performance was analyzed. As a result, it was confirmed that the hierarchical patterns of the mold were effectively duplicated on the surface of Al plate.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.5
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• pp.199-204
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• 2002

In order to recognize the deterioration of insulation system by partial discharge (PD), the characteristics of PD patterns which are occurring at the interface between epoxy and rubber materials in extra high voltage cable joints, have been investigated. The artificial defects such as voids, metal particles, insulation fiber and water impregnated insulation fiber are planted between the interfaces. A high frequency partial discharge detection system was used for measuring PD signals. An analysis of the PD patterns is focused on the shape of PD pattern, phase, width and time-dependence for each artificial defect. The PD Patterns in each defect show the different behaviors and it is suggested that the precise discrimination of PD patterns could be used for the diagnosis of deterioration in the insulation systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.2
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• pp.8-17
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• 2000

In this work, two approaches were proposed for the recognition of partial discharge patterns. The first approach was neural network with backpropagation algorithm, and the second approach was angle calculation between t재 operator vectors. PD signals were detected using three electrode systems; IEC(b), needle-plane and CIGRE method II electrode system. Both of neural network and angle comparison method showed good recognition performance for the patterns similar to the trained patterns. And the number of operators to be used had a great influence on the recognition performance to the untrained patterns.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.132-135
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• 1999

In this work, two approaches were proposed for the recognition of partial discharge patterns. The first approach was neural network with backpropagation algorithm, and the second approach was angle calculation between two operator vectors. PD signal were detected using three electrode systems; IEC(b), needle-plane and CIGRE method II electrode system. Both of neural network and angle comparison method showed good recognition performance for the patte군 similar to the trained patterns. And the number of operators to be used had a great influence on the recognition performance to the untrained patterns.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4B
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• pp.309-314
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• 2011

Analysis of discharge characteristics through control gates at river crossing structures is important for an effective water level control and water resources management. In recent years, many river control structures in four major rivers are under construction but only few researches on discharge characteristics at control gates could be found in Korea. The discharge characteristics depend on both shape of control gates and the effects of downstream water-depth. In this research, classification index for discharge patterns (free weir, submerged weir, free orifice, submerged orifice) through a control gate were reviewed with $h_g/h_1$, $h_3/h_g$, and $h_3/h_1$. Classification criteria of discharge patterns were also suggested. Representative discharge estimation equations for each discharge patterns were adopted and discharge coefficients were developed from a hydraulic model for a specific control gate which will be constructed in Nakdong river. Reliability of the derived discharge equation and coefficients were confirmed by comparisons between the real discharge in a model and the predicted discharge from the results of this research.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1624-1626
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• 1999

PD in defect of solid insulation system is very harmful since It often leads to deterioration of insulation by the combined action of the discharge ions bombarding the surface and the action of chemical compounds that are formed by the discharge. PD can indicate incipient failure, so it has been used to determine degradation of insulation. In this paper. we investigated PD in defects of solid insulation by using statical method and classified PD patterns with surface discharge, electrical tree and void discharge by using Kohonen network. we used peak charge, average discharge power, average discharge current, repetition rate, skewness, kurtosis, QN of the max pulse height vs. repetition rate $H_q(n)$ for analysis and classification.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.42-47
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• 2010

Polymer insulating materials such as cross linked polyethylene (XLPE) are employed in electric cables used for extra high voltage. These materials can degrade due to chemical, mechanical and electric stress, possibly caused by voids, the presence of extrinsic materials and protrusions. Therefore, this study measured discharge patterns, discharge phase angle, quantity and occurrence frequency as well as changes in XLPE under different temperatures and applied voltages. To quantitatively analyze the irregular partial discharge patterns measured, the discharge patterns were examined using a statistical program. A three layer sample was fabricated, wherein the upper and lower layers were composed of non-void XLPE, while the middle layer was composed of an air void and copper particles. After heating to room temperature and $50^{\circ}C$ and $80^{\circ}C$ in silicone oil, partial discharge characteristics were studied by increasing the voltage from the inception voltage to the breakdown voltage. Partial discharge statistical analysis showed that when the K-means clustering was carried out at 9 kV to determine the void discharge characteristics, the amount discharged at low temperatures was small but when the temperature was increased to $80^{\circ}C$, the discharge amount increased to be 5.7 times more than that at room temperature because electric charge injection became easier. An analysis of the kurtosis and the skewness confirmed that positive and negative polarity had counterclockwise and clockwise clustering distribution, respectively. When 5 kV was applied to copper particles, the K-means was conducted as the temperature changed from $50^{\circ}C$ to $80^{\circ}C$. The amount of charge at a positive polarity increased 20.3% and the amount of charge at a negative polarity increased 54.9%. The clustering distribution of a positive polarity and negative polarity showed a straight line in the kurtosis and skewness analyses.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1653-1655
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• 2003

The purpose of this paper is to evaluate the effects of pre-formed space charge by negative DC voltage on partial discharge(PD) patterns of XLPE. We have suggested a modified pulsed electro-acoustic method and demonstrated that the PD patterns are strongly influenced by the pre-formed space charge distributions, which are hardly disappeared up to AC 8kV in electrode configuration including air gap between XLPE layer and electrode.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.175-179
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• 1998

The insulation of cable which used for Ultra-High Voltage(UHV) underground power transmission requires excellent insulation capability for high voltage. The typical insulation materials are used XLPE, EPR, etc, but insulation efficiency of these is affected by void or alien substances, existed at the inside of insulators. In this paper, the partial discharge patterns of the defects within insulation cable are observed and analyzed. In this test, void, fiber and metal inclusions which possibly exist in cables, are simulated and investigated the patterns of partial discharges for each models Also the relations between calculated field strength and the insulation breakdown voltage. The experiment shows distinct partial discharge patterns in accordance with the kinds of defects within Insulation cable.