• Proceedings of the KIEE Conference
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• summer
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• pp.394-396
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• 2004

In order to reduce the sheath circulating current, same arrangement and balanced length of cable are required for the underground cable system. But practically, changing the whole arrange of cable which is already constructed is impossible. Therefore, It is necessary to apply the restraining-unit of sheath circulating current at the cross-bonding wire of insulated joint because the impedance of restraining-unit is able to reduce sheath circulating current at a normal condition. Even at a transient state, the restraining-unit must maintain electrical and mechanical characteristics. In this paper, the features of restraining-unit developed by LG Cable as well as the electrical test results are described. It proves that the restraining-unit is applicable to the underground cable system where sheath circulating current rises.

• Fashion & Textile Research Journal
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• v.14 no.6
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• pp.1024-1031
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• 2012

The thermal bonding PET fabrics were produced through high temperature steaming (HTS) of low melting PET yarn as warp and composite fancy yarn containing low melting PET yarn as weft. The low melting PET yarn of sheath-core structure consisted of a regular PET in core portion and low melting PET in sheath portion. The composite fancy yarn consisted of regular PET yarn as inner part and effect part and low melting PET yarn as binding part. This study was carried out to investigate the melting behavior of thermal bonded PET fabric, the effect of HTS on the thermal bonding, mechanical properties, and dyeing properties. The melting peak of low melting PET yarn showed two melting peaks caused by sheath-core structure. Almost the entire thermal bonding of the fancy PET fabrics containing low melting PET yarn has formed at $200^{\circ}C{\times}3min$ of HTS. The tensile strength in warp and weft direction of the fancy PET fabrics slightly decreased as temperature of HTS increased. The total K/S value of the fancy PET fabrics decreased slightly to $180^{\circ}C{\times}3min$ of HTS, while increased slightly above $200^{\circ}C{\times}3min$ of HTS. The changes in the hue angle ($H^{\circ}$) of the thermal bonded fancy PET fabrics dyed with disperse dyes hardly ever happened.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.10
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• pp.510-517
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• 2002

The use of underground transmission cables has continuously increased in densely inhabited urban and suburban area. Due to a increasing demand of underground cables, two or more circuits are installed in parallel for several kilometers. It, however, has not been realized that the sheath circulating current is generated in the system where a large number of cables are laid in the same route. In this paper, sheath circulating current is analyzed by the EMTP and compared with the measured values. Unbalance arrangement of cables or cross-bonding length causes a significant effect on the magnitude of the sheath current. Sheath circulating current could be greatly reduced by the symmetrical configuration of cables and installation of the impedance reduction system. Especially, with the impedance system of 1Ω installed, the sheath circulating current is reduced by 85.7%.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.12
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• pp.713-721
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• 2003

This paper analyzes the switching overvoltage occurred on 345kV underground power cable system as well as combined transmission system using EMTP. Cable length and closing time, preinsertion resistance have effect on switching overvoltage. Therefore, this paper analyzes the switching overvoltage occurred on conductor and sheath with change of those parameters. Specially, the cross bonding position becomes discontinuity point because of the difference between surge impedance of metal sheath and that of lead cable. Thus, the transmission and the reflection of traveling wave complexly occur at this connection point. According to these influences, voltage between sheath and earth as well as voltage between joint boxes rise. Time to crest point of switching overvoltage is longer than lightning overvoltage. Even though the voltage induced by switching surge is smaller than lightning surge, that voltage may have serious effect on the metal sheath. Therefore, this paper also analyses the reduction effect of switching overvoltage when the preinsertion resistance of circuit breaker is considered.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.04a
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• pp.38-39
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• 2004

• Fashion & Textile Research Journal
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• v.15 no.3
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• pp.467-476
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• 2013

This study investigates the dyeability and the fastness of flame retardant polyester fabric developed by a thermal bonding with a low melting component of flame retardant bicomponent filament (LMFRPC). The fabrics were prepared with flame retardant polyester filaments (FRP) as warp and blended filaments of FRP and LMFRPC as weft. The LMFRPC have a sheath and a core where the core comprises a flame retardant polyester and the sheath comprises a thermoplastic polyester with a low-melting point. The thermal bonding of fabric was conducted in a pin tenter at $170^{\circ}C$ for 60 seconds. Fabric dyeing was conducted with an infrared dyeing machine at various dyeing temperatures and dyeing times. The dyestuffs used in this study were CI disperse Yellow 54, Red 60 and Blue 56 of E-type dyestuff and Orange 30, Red 167 and Blue 79 of S-type dyestuff. This study investigated the morphology of thermal bonded fabric, dyeability and fastness of dyed fabric. Dyeability increased with an increased dyeing temperature. The thermal bonded area increased with the increased LMFRPC content. The dyeability of S-type dyestuff was higher than E-type dyestuff; in addition, the saturated dyeing time was about 20minutes at $130^{\circ}C$ for E and S-type dyestuff. The fastness to washing and rubbing were excellent at a 4-5 Grade.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.905-912
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• 2013

Power system fault analysis is commonly based on well-known symmetrical component method, which describes power system elements by positive, negative and zero sequence impedance. In case of balanced fault, such as three phase short circuit, transmission line can be represented by positive sequence impedance only. The majority of fault in transmission lines, however, is unbalanced fault, such as line-to-ground faults, so that both positive and zero sequence impedance is required for fault analysis. When unbalanced fault occurs, zero sequence current flows through earth and skywires in overhead transmission systems and through cable sheaths and earth in cable transmission systems. Since zero sequence current distribution between cable sheath and earth is dependent on both sheath bondings and grounding configurations, care must be taken to calculate zero sequence impedance of underground cable transmission lines. In this paper, conventional and EMTP-based sequence impedance calculation methods were described and applied to 345kV cable transmission systems (4 circuit, OF 2000mm2). Calculation results showed that detailed circuit analysis is desirable to avoid possible errors of sequence impedance calculation resulted from various configuration of cable sheath bonding and grounding in underground cable transmission systems.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.470-471
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• 2008

SVL is installed at underground transmission system to protect cables and insulation joint-box from overvoltages caused by lightning, switching, and line-to-ground fault. Domestic underground power system adopts cross bonding type to reduce the induced voltage at sheath, but single-point bonding is required depending the system installation configuration. SVL can be easily broken by overvoltages induced at joint-box because single-point bonding has uneffective system structure to extract fault current. ANSI/IEEE recommends Parallel Ground Continuity Conductor(PGCC) to prevent SVL breakdown. In this paper, EMTP simulation is performed to analyze effects on SVL under PGCC installation when single-line-to-ground fault occurs. The result shows that PGCC and short single-point bonding distance can reduce overvoltages at SVL.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.736-737
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• 2007

The single point bonding in underground transmission system can induce high voltage on the sheath when ground fault, lightning serge and switching serge occurs, at that time underground cable systems cannot offer a return path of fault current. Accordingly if fault current, which cannot return to ground, flows at the single point bonding, high voltage can be induced in SVL and that voltage can cause aging and breakdown of SVL. Therefore this paper study on the effect of parallel ground conductor at the single point bonding when ground fault and lightning serge occurs by using ATPDraw.

• KIEE International Transactions on Power Engineering
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• v.4A no.4
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• pp.236-242
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• 2004

Previous research results indicated that the designed current reduction device could effectively reduce the sheath circulating current and that its RDP protection device could shield it against both fault and lightning strokes. In this paper, cable impedance is analyzed using wavelet analysis and distance relay algorithm following the installation of these devices so that the operation of distance relay can be estimated. The test results confirm that in these devices, the fault inception angle and SVL bonding types have no impact on the change of cable impedance. In other words, the conventional distance relay can be used without a new relay setting. Thus we can finally assert that the designed current reduction device and its protection device are effective and can be safely installed on the cable transmission system without disturbance.