• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.25-28
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• 2009

A 154kV class high-temperature superconducting (HTS) power cable system is developing in Korea. For insulation design of this cable, it is important that study on cryogenic electrical insulation design to develop the cold dielectric type HTS cable because the cable is operated under the high voltage environment in cryogenic temperature. Therefore, this paper describes a design method for the electrical insulation layer of the cold dielectric type HTS cable adopting the partial discharge-free design under ac stress, based on the experimental results such a ac breakdown strength, partial discharge inception stress, $V_{ac}$-t characteristics, $V_{imp}$-n characteristics, and impulse breakdown strength of liquid nitrogen/laminated polypropylene paper (LPP) composite insulation system in which the mini-model cable is immersed into pressurized liquid nitrogen.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.529-531
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• 1999

In this Paper, the variable dielectric breakdown strengths of epoxy composites were investigated at belling absorption condition in order to observe the influences of moisture in out door use. Also. in order to improve withstand voltage properties at moisture absorbtion condition, IPN(interpenetrating polymer network) method was Introduced and the Influence was investigated. As Adding filler(SiO$_2$) classified by o(phr), 50(phr) and 100[phr] to two kinds of matrix resin, six kinds of specimens were manufactured. As a result, it was confirmed that dielectric breakdown strength wer degraded with boiling time and filer content increasing. But, it was confirmed that dielectric breakdown strength degrading rate were lowered by the Improvement of adhesion strength in IPN specimens.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.437-440
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• 2000

In this study, the interfacial dielectric breakdown phenomenon of interface between Epoxy and Rubber was discussed, which affects the stability of insulation system of power delivery devices. The breakdown strength of specimens are observed by applying high AC voltage at the room temperature. The breakdown times under the constant voltage below the breakdown voltage were gained. As constant voltage is applied, the breakdown time is proportion to the breakdown strength. The life exponent n is gained by inverse power law and the long time breakdown life time can be evaluated.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.128-132
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• 2003

This paper discusses several electrical properties of tape-type insulation impregnated with liquid nitrogen ($LN_2$) in superconducting cable. Synthetic polypropylene laminated paper has been tested for its short-term breakdown strength and partial discharge(PD) characteristics under AC voltage. furthermore, the effect of winding parameter on breakdown strength, PD incepti on and extinction electrical stress with different test samples are discussed.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.278-282
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• 2007

In the complex insulation system that is used in extra high voltage(EHV) devices, according to the trend for electric power equipment of high capacity and reduction of its size, macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. In this paper, the dielectric strength decrease of the macro interfaces between epoxy and ethylene propylene diene terpolymer(EPDM) was estimated by using the applied voltage to breakdown time characteristics. Firstly, the AC short time dielectric strength of specimens was measured at room temperature. Then, the breakdown time was measured under the applied constant voltage which is 70% of short time breakdown voltage. With these processes, the life exponent n was determined by inverse power law, and the long time breakdown voltage can be evaluated. The best condition of the interface was LOS(low viscosity(350 cSt) silicone oil spread specimen). When 30 years last on the specimens, the breakdown voltage was estimated 44% of the short time breakdown voltage.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1330-1337
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• 2018

In this study, 40, 50, 60, and 70 wt% filler dispersed samples were prepared for the current GIS Spacer or environmentally friendly GIS. In the AC electrical breakdown, EMSC and EMAC decreased with increasing filler content, and EMSC showed better breakdown strength than EMAC. The mechanical properties such as tensile strength and flexural strength of EMSC and EMAC were also increased with increasing filler content. In addition, EMSC results in better mechanical properties than EMAC. The reason for this is considered to be one in which the influence of the interface is important.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.99-99
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• 2010

Polymer nanocomposite has been attracting much attention as a new insulation material, since homogeneous dispersion of nm-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy based nanocomposites were made and AC breakdown strength of Nano-TiO2 and micro-silica filler mixture of epoxy based composites were studied by sphere to sphere electrode. Moreover, nano- and micro-filler combinations were adopted as an approach toward practical application of nanocomposite insulation materials. Nano-TiO2 particle size is about 10nm and composites ratio was resin (100) : hardener (82) : accelerator (1.5). AC breakdown test was performed at room temperature (25 [$^{\circ}C$], 80 [$^{\circ}C$] and 100 [$^{\circ}C$] in the vicinity of Tg (90[$^{\circ}C$]). And thermal conductivity were measured by ASTM-D5470.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.775-778
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• 2000

In this paper, the life-time of macro interface between Epoxy/EPDM which consists in underground power cable joints is predicted. The electrode system of specimen is designed by FEM(finite elements method). The breakdown strength of specimens are observed by applying high AC voltage at the room temperature. The breakdown times under the constant voltage below the breakdown voltage were gained. As constant voltage is applied, the breakdown time is proportion to the breakdown strength. The life exponent n is gained by inverse power law, and the long breakdown life time can be evaluated.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1539-1541
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• 2000

Insulation layers in XLPE power cables may have some patterns generated in the manufacturing process. They are called 'flow patterns' and show flow history of molten polyethylene between inner and outer semiconducting layers. Flow patterns are even seen with naked human eyes and suspected to be inhomogeniety of insulation, weakening insulation performance. Investigated in this paper is electrical treeing resistance and ac breakdown strength according to flow patterns. Experiments of electrical treeing and ac breakdown strength by means of ramp tests were conducted using newly developed electrode system with point-to-plane structure and sphere-to-sphere structure, respectively. All results were analyzed with the application of statistics, showing little differences.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.702-707
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• 1996

In this paper, in order to improve the withstand voltage properties of epoxy resin, IPN(interpenetrating polymer network) method was introduced and the influence was investigated. The single network structure specimen(E series), simultaneous interpenetrating polymer network specimen(EM series) and pseudo interpenetrating polymer network(EMP series) specimen were manufactured. In order to understand the internal structure properties, scanning electron microscopy method was utilized, and glass transition temperature was measured. Also, AC voltage dielectric breakdown strength, tensile strength and impact strength were measured to investigate the influence upon electrical and mechanical properties. As a result, it was confirmed that simultaneous interpenetrating polymer network specimen was the most execellent.