• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.1-5
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• 2001

This paper describes the electrical characteristics of Nomex paper employed as an insulating material of distribution transformers. The relative permittivities(dielectric constants) and $tan{\delta}$(dielectric dissipation factors) were measured as a dielectric characteristic and the partial discharge inception voltages(PDIVs) and breakdown voltages were also measured as an electrical strength characteristic of Nomex paper. As a result, the permittivity and $tan{\delta}$ of Nomex paper showed temperature and frequency dependency. Especially, the permittivity of 0.18mm Nomex paper was 2.4 according to the ASTM condition. And the PDIVs and breakdown voltages were, almost linearly increased with the thickness of Nomex paper and its electrical strength was better than conventional kraft paper.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.572-574
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• 1993

In order to obtain superior breakdown properties of Epoxy/$SiO_2$ composite materials at room and high temperature, the simultaneous interpenetrating polymer networks(SIN) is introduced into the Epoxy resin. As a result, it is observed that dielectric breakdown strength tends to increase according to the following order ; Epoxy/$SiO_2$ specimens, specimens treated with coupling agent and SIN introduced specimens which have stable temperature characteristics at room and high temperature. For introducing SIN Epoxy/$SiO_2$ composite material, rise of glass transition temperature and suppression of defects in its internal structure is achieved. This in turn improves the dielectric breakdown strength and the heat proof property of Epoxy/$SiO_2$ composite materials.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1645-1647
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• 1999

Epoxy compound has been used as insulation material in electrical equipment because of its properties 1) Nowadays, becoming higher voltage system, the properties of interface between epoxy and its metal insert become more important. In this paper, we suggest two types semiconducting paste. One is epoxy type and the other is olephine type. After sprayed the semiconducting paste on metal insert sanded, we procedure the test one is the adhesion strength test, the other is electrical breakdown strength test. So we knew that the epoxy type paste became more higher adhesion strength than olephine type paste because of its homogeneity at the interfaces. And at the breakdown strength test, olephine type paste became less higher than epoxy type paste because of its volatility. So in this study, we suggest the optimum interface condition by adjusting the semiconducting paste and surface roughness.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.85-92
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• 2008

Occurring forest fire or burning bushes beneath overhead transmission lines have caused breakdown disturbances of the system in many countries. In this study, experiments for flashover characteristics in the simulated condition of vertical power lines were conducted so as to investigate the reduction in insulation strength caused by combustion flame. As the results of an experimental investigation, it is demonstrated that flame can reduce breakdown voltages of the model lines according to height(h) of flame. The breakdown voltages were decreased with decreasing the height(h) of flame it can be seen that the average reduction of flashover levels, in comparison with the no-flame case, are 46.2[%] for h=9[cm] and 62.5[%] for h=3[cm] when ac voltage is applied.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.2
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• pp.151-156
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• 2003

High temperature superconductor can only be applied against an engineering specofication that has to be determined for each particular application form the design requirements for economic viability and for operation margins in service. However, in order to realize the HTS transformer, it is necessary to establish the high voltage insulation technique in cryogenic temperature. Therefore, the composite insulation of double pancake coil type transformer are described and AC breakdown voltage characteristics of liquid nitrogen(LN$_2$) under HTS pancake coil electrode made by Bi-2223/Ag are studied. The Breakdown of LN$_2$ is dominated electrode shape and distance. The influence of pressure on breakdown voltage is discussed with th different electrode. For the electrical insulation design of turn-to-turn insulation for the HTS transformer, we tested breakdown strength of insulation sheet under varying pressure. And we investigated surface flashover properties of LN$_2$ and complex conition of cryogenic gaseous nitrogen(CGN$_2$) obove a LN$_2$ surface. The surface voltage of GFRP was measured as a function of thickness and electrode distance in LN$_2$ and complex condition of CGN$_2$ above a LN$_2$ surface. this research presented information of electrical insulation design for double pancake coil(DPC) type HTS transformer.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1407-1409
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• 1998

It was investigated that space charge characteristics and Breakdown characteristics of XLPE/EPDM laminates as a function of interfacial condition. When the chemical A was pasted in laminate interface, there was little space charge in XLPE/EPDM interface and it was shown that breakdown strength of XLPE/EPDM laminate was influenced by laminate condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.421-424
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• 1996

Effects of humidity absorbing deterioration on AC dielectric breakdown characteristics of modified epoxy resin system with SN(succinonitrile) were investigated. As the forced humidity absorbing deterioration proceeded under high temperature and humidify, glass transition temperature increased. The dielectric breakdown strength increased and then decreased at deterioration cycles higher than 2. Not only, the increment of thermal stability but also, the physical detects such as Internal cracks and voids occurred during the humidity absorbing deterioration cycle were the main causes of the change in dielectric properties.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1171-1173
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• 1993

Dielectric breakdown strength of LDPE films was investigated using metal electrodes and semiconductive electrodes respectively. In both of two cases, the results show that there are characteristics of dependence on thickness and dependence on temperature. However, there are some differences in both cases.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.251-254
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• 2001

Internal and external forces may be applied on the power cable in the both process of transportation and installation. Even though the EHV power cables have the structure of metal sheath and plastic jacket etc. to minimize these negative influences, the unusual forces result in the unexpected deformation of the cable. Compressing moulded XLPE model cable sheets were prepared and locally dented with round-edge and square-edge tools. All data were analyzed employing Weibull distribution. The breakdown strength of dented molded specimens showed lower values than the normal ones by 10-60%.

• Transactions on Electrical and Electronic Materials
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• v.17 no.3
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• pp.155-158
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• 2016

The effect of microsilica content modified with silicone-modified epoxy on electrical and mechanical properties of cycloaliphatic epoxy/microsilica system was investigated. The cycloaliphatic epoxy resin was diglycidyl 1,2-cyclohexanedicarboxylate and curing agent was an anhydride. Surface of microsilica was modified with silicone-modified epoxy. Electrical breakdown strength, the most important property for electrical insulation materials was tested. Tensile and flexural tests were also performed using universal testing machine (UTM). The microcomposite with 60 wt% microsilica shows maximum values in electrical breakdown strength.