• 전기의세계
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• v.26 no.2
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• pp.57-65
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• 1977

In roder to investigate the influence of treeing on electric breakdown of solid organic insulator the initiation and growing mechanism of tree itself, and the correlation between corona discharge and treeing phenomena in solid orgainc insulating materials, several experiments were carried out by means of needle test on polymethyl-methacrylate. The obtained results showed that the existence of voids in specimen had important effects on initiation voltage of trees and, when the direct voltage was applied, the initiation voltage of trees increased by space charge effect. And also the stagnation phenomena due to the transfer of vacancy cluster or polymekr cage in specimen might beconsidered in process of growth of trees, and corona discharge seemed to be the pre-phenomena of treeing because trees were normally initiated by internal discharge in voids.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.9
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• pp.672-675
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• 1999

Si-to-Si electrostatic bonding was carried out by employing LSG interlayer instead of conventional Corning #7740 interlayer in order to improve bonding properties. The surface roughness and dielectric breakdown field of the LSG interlayers deposited on Si substrates were investigated. Also, the bonding interface, bonding strength and bonding mechanism were discussed for the electrostatically-bonded Si-Si wafer pairs having LSG interlayers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11b
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• pp.19-22
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• 2004

Growth of Electrical Tree Under 50Hz~60Hz high electric stress has been studied on the Occurrence of a Pattern, to the Progression Speed at Y axis of electrical Tree. CCD Images of evolving tree structures could be obtained in both systems. Electrical Treeing was found to occur reproducibly, but in a markedly different manner in the two morphologimlly different but chemically identical materials. For the measurement of Electrical Tree, a visual measurement with an optical microscope has been used to explain breakdown mechanism in High-voltage systems.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1655-1657
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• 1994

To measure treeing, visual measurement with an optical microscope has been used to explain breakdown mechanism by treeing in materials. The conventional direct visual method of tree deterioration observation is difficult to measure in short time processing, and impossible to analyze the deteriorated area by treeing, direction of tree growth, tree patterns etc. In this paper, we have developed a tree-measuring system using image processing for the tree growth, the area of deterioration, and other progresses of treeing. As experimental result, image processing is an effective alternative to direct visual observation method.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1245-1250
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• 2003

Pseudo-first-order rate constants ($k_{obs}$) have been measured spectrophotometrically for the reactions of 4-nitrophenyl benzoate with a series of pyridines in $H_2O$ containing 20 mol % DMSO. The plots of kobs vs pyridine concentration are linear up to ca. 0.1 M pyridines, indicating that the effect of self-association of pyridines with their conjugate acids are insignificant in this concentration range. The Bronsted-type plot has been obtained to be linear with a ${\beta}_{nuc}$ value 1.11, suggesting that the pyridinolyses proceed through a rate-determining breakdown of the zwiterionic addition intermediate. The pyridines studied have shown higher reactivity than isobasic primary and secondary amines toward the substrate. 1-Benzoyl-4-dimethylaminopyridinium ion, a possible intermediate, has not been detected since the rate of its hydrolysis in the reaction condition is comparable with or even faster than its formation.

• Proceedings of the KIEE Conference
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• 2005.11c
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• pp.53-55
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• 2005

Because of the continuous growth of energy consumption and also the tendency to site power lines and pipelines along the same route, the close proximity of power lines and buried metallic pipelines has become more and more frequent. The lightning strokes collected by an electric substation or power line tower might cause arcing through the soil to an adjacent gas pipeline. This paper gives the review of the breakdown mechanism and the standards of separation distance between lower and pipelines.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.282-284
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• 1996

This paper presents prebreakdown characteristics of $SF_6$ gas stressed by the non-oscillating and oscillating impulse voltages in inhomogeneous fields disturbed by metallic protrusion. The purpose of this investigation is to present the predischarge development and dielectric characteristics of $SF_6$ gas under VFTOs. The experiments were carried out using a needle-to-plane gap geometries in the gas pressure ranges from 0.1 to 0.5 MPa. The gap separation was22 mm, and the needle-shaped protrusions were made of stainless steel 10 mm in length and 1.0 mm in diameter. As a result, it was found that the breakdown mechanism and predischarge current are principally dependent on applied voltage waveform and polarity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.58-63
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• 2002

For the experiment the four types of spacer were distinguished by arrangement. The flashover characteristic on each types of spacer was investigated and the flashover phenomena were observed to understand breakdown mechanism in liquid nitrogen($LN_{2}$). The spacer should be placed interior coil as an insulator, a cooling channel and s supporter of structures. The simulated electrode used in the experiment was made from five turns of HTS tape. Experimental results revealed that multi-layer and barrier effects did work well in Air but did not in $LN_{2}$. These result suggested that the flashover in LN2 caused by the bubbles due to partial discharge at micro gap, g. The flashover characteristics decreased to 70% when g is 0.2 mm. The degradation was improved by even treatment on surface of coil electrode.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.246-248
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• 2004

The lower voltage distribution box of service wire has been usually employed to supply an electric power to the consumers through low voltage overhead line. Now-a-days, electric shock accident at the distribution box of service wire installed in the seashore areas has been often occurred. The reason is mainly due to the electric leakage in the distribution box of service wire. This paper described insulation breakdown mechanism of distribution box of service wire, analysis of electric shock path and safety countermeasure of distribution box of service wire.

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1203-1208
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• 1995

Theoretical studies of the effect of the nonleaving group (RY) on the breakdown mechanism of the tetrahedral anionic intermediate, T-, formed by the addition of a less basic phenoxide nucleophile (X) to phenyl benzoates with a more basic phenoxide leaving group (Z) have been carried out using the PM3 MO method. The identity acyl transfer reactions (X=Z) are facilitated by an electron-withdrawing RY whereas they are inhibited by an electron-donating RY group. The results of non-identity acyl transfer reactions indicate that a more electron-donating RY group leads to a greater lowering of the higher barrier, TS2, with a greater degree of bond cleavage, and a greater negative charge development on the phenoxide oxygen atom, whereas the opposite is true for a more electron-withdrawing RY group, i.e., leads to a greater lowering of the lower barrier, TS1. The results provide theoretical basis for the signs of ρXY(>0) and ρYZ(<0) observations.