• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.52-56
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• 2007

A high temperature superconducting (HTS) DC cable is ideal for transmitting large blocks of electrical power over a long distance. However, it must be designed to operate reliably within the constraints of the electrical systems. Therefore, a study of the electrical insulation is important to develop a HTS DC cable because it is operated in a cryogenic high voltage environment. This paper discusses the dielectric constructions of the cable and summarizes the experimental results on the DC and impulse dielectric characteristics of the insulation material. in sheet form and mini-model cable configuration. This shows how to design such insulation to be operated reliably. These studies are essential for the insulation design of a HTS DC cable operated in cryogenic environment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.545-549
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• 2013

To realize the high-Tc superconducting (HTS) DC cable system, it is important to study not only high current capacity and low loss of conductor but also optimum electrical insulation at cryogenic temperature. A model HTS DC cable system consists of a HTS conductor, semi-conductor, cooling system and insulating materials. Polypropylene laminated paper (PPLP) has been widely adopted as insulating material for HTS machines. However, the fundamental insulation characteristics of PPLP for the development of HTS DC cable have not been revealed satisfactorily until now. In this paper, we will discuss mainly on the breakdown characteristics of 3 sheets PPLP in liquid nitrogen ($LN_2$). The characteristics of the diameter, location of butt-gap, distance between butt-gap length, pressure effect, polarity effect under DC and impulse voltage were studied. Also, the DC polarity reversal breakdown voltage of mini-model cable was measured in $LN_2$ under 0.4 MPa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.148-151
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• 2002

In order to prevent the failures of underground distribution power cables we need to measure insulation condition in the field. Until now we used DC high voltage as a power source for the cable diagnosis but it was not proper method to the XLPE insulation cables because DC high voltage can affect sound insulation and can't diagnose exactly insulation degradation. For these reasons we imported isothermal relaxation current measurement system called by KDA-1 from germany but it's reliability did not proved in our URD cables. DC voltage decay measurement system was developed by domestic company but they don't have field experience. In this paper we tried to prove reliability of these two systems in the field. Through the field diagnosis and Ac breakdown test the two systems showed similar results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.613-616
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• 1999

Polyehtylene[PE] in polymer insulation materials of used power cable have carried out in abundance of experiment and study for electrical conduction, insulation breakdown, dielectric character and so on. when apply to field for power cable to make PE, application of DC withstand test to put in practice for inspection is get to effect accumulated space charge. In this paper, to make use of Pulsed Electro-Acoustic(PEA), It is analysis to take shape space charge under AC and DC, clear up the point at issue for DC withstand test impressing

• Progress in Superconductivity and Cryogenics
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• v.13 no.3
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• pp.5-9
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• 2011

DC high-temperature superconducting(HTS) cable system has attracted a great deal of interest from the view point of low loss, dense structure and large capacity. A HTS cable system is made of cable and termination. The insulating materials and insulation technology must be solved for the long life, reliability and compact of cable system. In this paper, we will report on the dielectric breakdown characteristics of insulating materials for HTS cable and termination. The AC, DC and lightning impulse breakdown strength of laminated polypropylene paper(PPLP) and glass fiber reinforced plastic(GFRP) have been measured under nitrogen pressures in the range of 0.l-0.4MPa. PPLP and GFRP are found to have a significantly higher DC breakdown strength. Also, DC surface flashover voltage of negative polarity is slightly higher than that of positive polarity in GFRP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.86-86
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• 2010

Recently, CV, CNCV, CNCV-W cable are used to transmit and distribute electric power. And a lot of researchers put more effort to realize high performance. The dielectric breakdown strength characteristic is a standard to design insulators. Examination of that is a main factor to determine long term insulation performance, which is used to diagnose Insulation deterioration. In this paper, we prepared XLPE, XLPE/nano-filler, LDPE/nano-filler for comparing each of the dielectric breakdown strength characteristics.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1960-1962
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• 2000

Polyehtylene[PE] in polymer insulation materials of used power cable have carried out in abundance of experiment and study for electrical conduction. insulation breakdown. dielectric character and so on. When apply to field for power cable to make PE, application of DC withstand test to put in practice for inspection is get to effect accumulated space charge. In this paper, to make use of Pulsed Electro-Acoustic(PEA). It is analysis to take shape space charges under AC and DC voltage, clear up the point at issue for effect of DC withstand test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.155-155
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• 2009

This paper introduces the findings of a detailed study on breakdown voltage strength under DC voltage and the development of HVDC cable. Recently, Nano-fillers are attracting attentions of many researchers and engineers, since they seem to bring higher potentials for advancement of electrical insulating properties as nano-composites. Additives and fillers are often adopted to polymeric materials for improving insulating and machanical properties. We have improved the polymer composition and developed a new insulation material for HVDC cable. Each specimen blended at LDPE1 to antioxidant, LDPE2 to antioxidant, pure XLPE was manufactured respectively. The insulation performances of the proposed insulator were compared with specimens blended at nano powders. DC breakdown strength of LDPE1 specimen at 90[$^{\circ}C$] was higher than other specimens. The experimental results show that polar groups intorduced in moleculars chains of blended specimen plays an important role in enhancement of thermal conductivity.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.7
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• pp.400-405
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• 2000

In order to improve the reliability of XLPE cables, it is necessary to understand the mechanism of electrical and water tree degradation. Especially, electrical tree initiation and propagation are important in XLPE cable insulation. This paper deals with the changes of electrical properties of XLPE cable insulation with electrical tree degradation. To understand the electrical properties of XLPE insulation, specimens were prepared by 22.9kV distribution cable and made in a type of block. Ogura needles having tip radius of 10${\mu}{\textrm}{m}$ were inserted into each block pieces. AC voltages of 8kV, 10kV and 12kV at 60Hz were applied to needle. We investigated the relationship between electrical properties(PD quantity, tan$\delta$ and DC current) and the growth of electrical tree. The electrical properties of the specimens were measured from initiation of tree to breakdown and their characteristics were analyzed.

• Progress in Superconductivity and Cryogenics
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• v.14 no.4
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• pp.32-35
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• 2012

A high-$T_c$ superconducting (HTS) DC application has advantages such as the ultimately lower loss, more compact dimensions, and large capacity compared to AC application. In order to optimize the insulation design of a HTS DC machines, it is important to understand the high voltage insulation and materials at cryogenic temperature. Polypropylene laminated paper (PPLP) has been widely used as an insulating material for HTS AC machines. However, the fundamental data under DC voltage have not been revealed satisfactorily until now. In this paper, we will discuss mainly on the breakdown and dielectric characteristics of PPLP in liquid nitrogen ($LN_2$). The polarity effects of DC and impulse voltage were studied by using the semi-rod to cylindrical electrode. The volume resistivity of PPLP in $LN_2$ was studied. Also, the space charge distribution at room temperature was studied. However, it is necessary to study this topic at cryogenic temperature in the near future.