• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1569-1571
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• 2000

The ageing process was checked by leakage current monitoring in Salt Fog Method. In order to monitor leakage current, DAS with 12-bit, 8-channel A/D converter was prepared. The monitored components of leakage current were averages of the rms and peak, max peak, cumulative charge, and the cumulative number of peak pulses. The acquired data were stored to the disc periodically. And, surface conductivity was measured to investigate loss of hydrophobicity. The results suggest that surface conductivity and leakage current are well corresponding to initial loss of hydrophobicity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.82-85
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• 2000

Polymeric composite insulators are used for outdoor insulation. However, our knowledge about their long-term performance in an outdoor environment is still very limited. The electrical stress caused the surface of these insulators to become degradation. In order to evaluate the tracking resistance of polymer insulators, we performed the tracking wheel test which is recommended by CEA LWIWG-01. And the flashover voltage tests were conducted for understanding electrical characteristics after tacking wheel test. Also, these insulators are studied by characterization methods such as contact angle measurement, SEM, etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.395-398
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• 2000

In this study mechanical and environment ability of FRP pole for a distribution line about high strength and good insulation properties. The basic filament winding process creates a helical winding pattern. In mechanical analysis of splice with mechanical fastened joint it is important to evaluate a critical load of faster having maximum stress. It is also present a result of several examples to compare this with analytical one. On repair design this finite element method will be used as basis. The influence of environmental factors, such as elevated temperatures, high humidity, and corrosive fluids, and ultraviolet(UV) rays, upon the performance of polymeric matrix composite is of concern in many applications.

• 연구논문집
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• s.24
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• pp.81-96
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• 1994

To investigate failure mechanisms observed in carbon-phenolic thermal insulators, differential equations which govern the decomposition process in a deformable anisotropic porous solid are derived for three-dimensional axisymmetric constructions. The governing equations not only couple the material deformation with pore pressure, but also couple pressure and temperature, which means that heat convected by the pyrolysis gases is properly accounted for. Then the Bubnov-Galerkin finite element method is applied to these equations to transform them into a semidescrete finite element system. A thermal insulation liner in the cowl region under typical operating conditions is analyzed to find a mechanism for plylift. The results from the structural analysis show across-ply failure in the cowl zone. The mechanism for plylift is hypothesized as a sequential procedure : 1) the across-ply failure which is the precursor to plylift and 2) the local fiber buckling caused by generation of excessive in-plane compressive stress. To prevent plylift, the across-ply stress can be reduced by using appropriate material ply angles in cowl zone design.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1621-1623
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• 1999

Recently, high voltage outdoor ploymer insulators have been widely used commercially owing to their excellent electrical and mechanical properties, superior comtamination flashover performance, light weight, easy installation or handing, no maintenance during service, competitive price and so on. compared to porcelaain and glass insulators. For instance, silicone rubber(SR) for polymeric insulators specially has much superior insulating and anti-pollution performance due to its specific hydrophobicity even in severe contaminated environments. We have investigated surface discharge current characteristics of silicone rubbers(SR) for HV outdoor composite insulation specimen under accelerated aging codition using a computer measuring system. The relations of average leakage current and surface discharge current repetition rates and discharge current amplitude, the distribution of discharge current amplitude were studied to investigate electrical conduction of silicone rubber surface with the salt fog condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1063-1068
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• 2000

Water treeing in underground distribution power cable is not easy to observe by nondestructive method and it has very complex patterns. This study describes the principles and practices of a continuous observation of initiation and growth of tree in polymeric insulation material using an image measurement technique. Using this technique we could observe water tree and the growing process of electrical tree due to the water tree and the growing process of electrical tree due to the water tree. All of these growing process is analyzed quantitatively by image measurement program composed of borland c++. We fabricated the thin film type specimen to observe water tree easier and also the needle electrode was prepared by etching method using electrolytes. Initiation and the growth of three was observed somewhat different depending on the applied voltage and the water electrode. AgNO$_3$solution electrode accelerates the initiation and the growth of water tree, compared to those of distilled water electrode. The water and the electrical tree occurred by water tree has discontinuous growth characteristic.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4
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• pp.329-336
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• 2003

Intra-Vascular Ultra-Sound (IVUS) transducers were developed for the application to diagnose coronary diseases. The transducer consists of 32 piezoelectric elements with a front insulation layer and a polymeric acoustic backing layer on a hollow alumina tube. The optimal geometrical structure of the transducer was designed through theoretical analysis of radiation patterns of the transducer. Samples of the IVUS transducers of the diameter of 3㎜ were fabricated to illustrate the design scheme. For the piezoelectric elements, 2-2 mode piezocomposite materials were employed. Experimental performance of the transducers showed good agreement with the design results, which verified feasibility of the transducer for IVUS applications.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1758-1760
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• 1997

Automatic detection system to detect acoustic emission pulse and fractal dimension were developed, to observe tree deterioration phenomena in LDPE. The purpose of our work are to use acoustic emission system and fractal dimension and to investigate the treeing phenomena in polymeric insulation under applied AC voltage 11[kV] with an artificial needle-shaped void(1.5[mm]) using the above system. We analyzed and phase angle-acoustic emission pulse amplitude-deterioration time ($\Phi$-AEA-t) pattern and phase angle-acoustic emission pulse number-deterioration time($\Phi$-AEN-t) pattern using statistical operators such as skewness, fractal dimension. In this paper show that the correlation of $\Phi$-AEA-t, $\Phi$-AEN-t, fractal dimension using regression analysis by the method of least squares can be used to predict the breakdown just before the breakdown occurs.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.3
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• pp.195-200
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• 2016

In this study, compression tests for the polyisocyanurate foam which is recognized as the insulation material for the storage tank of the liquefied natural gas (LNG) were carried out for investigation of the material characteristic of mechanical behavior. Deformation recovery ratio according to the various initial deformation levels were estimated and the mechanical behavior of foams that are experienced compressive deformation was also obtained experimentally. The test results were analyzed based on the conditions of initially applied strain level and engineering strain rate.

• 전기의세계
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• v.25 no.1
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• pp.95-100
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• 1976

The main purpose of this paper is to study on the transient current due to the change of environmental temperature under no external field in the arrangement of M$_{1}$(metal)-P(polyver)-M$_{2}$(metal). The specimer of polymeric insulator sandwiched by two metal electrodes composes a parallel-plate condenser represented by Maxwell-model. The behaviors of short circuit current flowing in M-P-M arrangement are very complex and the analysis of its conduction mechanism appears to be much complicated. In this paper we can suggest that a contact potential difference as an energetic state exists in the thin film specimen both sides of which are contacted by two different metals having different cook functions. Futhermore the contact potential difference appears to be constant through the course of temperature change, however, the dielectric constant and caparitance of the specimen must be temperature dependent. Accordingly the charge difference induced on both sides of electrodes may be a cause for the shory circuited transient current flowing through the external circuit. It is also suggestive that the results of the observation must be considered in cases of insulation design of electrical machines and D.C. cable for high voltage use.