• Title, Summary, Keyword: Sheath characteristics

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A Study on SVL Transient Characteristics by Switching Overvoltage at Single Point Bonding Section in Underground Transmission Cables (개폐과전압 발생시 지중송전선로 편단접지 구간에서 SVL에 미치는 과도특성에 관한 연구)

  • Jung, Chae-Kyun;Kang, Ji-Won
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.6
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    • pp.764-769
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    • 2014
  • This paper describes sheath voltage limiter(SVL) transient characteristics by switching overvoltage considering single point bonding in underground transmission cables. The crossbonding system is generally used for grounding methods of underground transmission system. However, the single point bonding system is used in selective area which is difficult to consist of crossbonding major section. The sheath voltage limiters are connected between joints in the single point bonding. Specially, the high overvoltage might be generated in that section as well as the aging of sheath voltage limiter might be progressed by various electrical stress including lightning overvoltage, switching overvoltage and power frequency overvoltage. Therefore, in this paper, the switching overvoltage characteristics in underground cables are firstly analysed using EMTP simulation. Then, the switching overvoltage of sheath voltage limiter is also studied in single point bonding. Finally, the reduction method of sheath voltage limiter switching overvoltage is proposed by various simulation studies including circuit breaker operating order.

Detail relation of negative ion density with positive ion mass and sheath parameters

  • Kim, Hye-Ran;Woo, Hyun-Jong;Sun, Jong-Ho;Chung, Kyu-Sun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.470-470
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    • 2010
  • Negative ions are generated in fusion edge plasmas, material processing plasmas, ionospheric plasmas. Analytic formulas for the deduction of the absolute density of negative ions was given by using the current-voltage(IV) characteristics of two electric probes at two different pressures [1], and negative ion density has been measured by one electric probe using the current-voltage characteristics of three different pressures [2]. Ratios of ion and electron saturation currents and electron temperatures and sheath areas of different pressures are usually incorporated into two equations with two unknowns for the negative ion density. In the previous publications, the sheath factor(sheath area, sheath density, sheath velocity) and effective masses of background ions with different pressures are qualitatively incorporated for the deduction of negative density. In this presentation, the quantitative and detailed relation of negative ion density with sheath factor and effective masses are going to be given. The effect of these parameters on the change of IV characteristics will be addressed.

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Characteristics of Sheath Circulating Current by Underground Transmission Systems Analysis (지중송전시스템 해석을 통한 시스순환전류 특성 분석)

  • Jung, Chae-Kyun;Lee, Jong-Beom;Kang, Ji-Won
    • Proceedings of the KIEE Conference
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    • pp.449-451
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    • 2002
  • Sheath circulating current rises from the change of sheath mutual impedance which is caused by imbalanced cable system, and different section length between joint boxes. However, mixed burying typo and imbalance section length take many parts of main reasons of sheath circulating current increment in domestic underground transmission power cables. Therefore, the increment reason and variation characteristics of sheath circulating current is analysed with simulation using EMTP/ATPDraw and measuring data of practical cable system which has a problem of exceeding sheath circulating current in this paper.

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I-V Characteristics of Negatively DC Pulsed Target in ECR Plasma for Landmine Detection (지뢰탐지를 위한 ECR 플라즈마에서 타깃에 고전압 DC 펄스 인가시 전압-전류 특성 분석)

  • Kim, Seong Bong;Lee, Hui Jea;Park, Seungil;Yoo, Suk Jae;Cho, Moohyun;Han, Seung-Hoon;Lim, Byeongok
    • Journal of the Korean institute of surface engineering
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    • v.47 no.1
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    • pp.53-56
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    • 2014
  • I-V characteristics of a cylindrical target in an ECR plasma were studied for sheath spatial evolutions when the target was pulsed biased to a high negative potential. The magnetic field effects on sheath thickness and sheath boundary speed were investigated by comparison between the experimental results and the theoretical results using the Child-Langmuir sheath model. The results showed that the magnetic field suppressed electron motion away from the target so that sheath thickness and sheath boundary speed decreased.

Preparation and Characteristics of Sheath/Core Complex Structured String for Badminton (배드민턴 라켓용 Sheath/core 복합구조 String의 제조 및 특성)

  • Choi, Yong-Dae;Park, Young-Mi
    • Textile Science and Engineering
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    • v.52 no.5
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    • pp.309-314
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    • 2015
  • This paper presents a method of preparing a high-strength sheath/core complex badminton string and examines its playability and durability performance. From repeated experiments at the laboratory scale, it was determined that the tensile characteristics of sheath/core complex strings are better than those of widely used general strings. The key process of braiding, in which the string is prepared by twisting sheath multifilament around the core of a 3-ply monofilament, and the time required for applying a thin layer of coating, have decisive effects on the physical properties. The yarn diameter was found to be optimal when the string was coated three times and the structure of the sheath/core was composed of multifilament 1890d/monofilament 100d. SEM identified an increase in the inner thickness of the sheath/core string with braiding and coating. To conclude, Sample D displayed high tenacity, tensile extension, and tensile strength, which can affect durability, while its tensile modulus was the lowest (54.13 g/tex), which is indicative of good playability.

Development of Restraining-unit of Sheath Circulating Current and Its Electrical Characteristics (시스 순환전류 저감장치의 개발 및 전기적 특성 검토)

  • Ha C. W.;Kim J. N.;Kim D. W.;Kang J. W.;Kim J. S.
    • Proceedings of the KIEE Conference
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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.

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Sheath Circulating Current Analysis of a Crossbonded Power Cable Systems

  • Jung, Chae-Kyun;Lee, Jong-Beom;Kang, Ji-Won
    • Journal of Electrical Engineering and Technology
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    • v.2 no.3
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    • pp.320-328
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    • 2007
  • The sheath in underground power cables serves as a layer to prevent moisture ingress into the insulation layer and provide a path for earth return current. Nowadays, owing to the maturity of manufacturing technologies, there are normally no problems for the quality of the sheath itself. However, after the cable is laid in the cable tunnel and is operating as part of the transmission network, due to network construction and some unexpected factors, some problems may be caused to the sheath. One of them is the high sheath circulating current. In a power cable system, the uniform configuration of the cables between sections is sometimes difficult to achieve because of the geometrical limitation. This will cause the increase of sheath circulating current, which results in the increase of sheath loss and the decrease of permissible current. This paper will study the various characteristics and effects of sheath circulating current, and then will prove why the sheath current rises on the underground power cable system. A newly designed device known as the Power Cable Current Analyser, as well as ATP simulation and calculation equation are used for this analysis.

Study on Thermal Treatment of Hybrid Technical Yarns

  • Ishtiaque, S.M.;Das, A.
    • Fibers and Polymers
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    • v.5 no.1
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    • pp.25-30
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    • 2004
  • The present paper reports the impact of thermal treatment on the characteristics of core-sheath type hybrid technical yarns. The core-sheath type hybrid yams are prepared using DREF-III technology. Polyester and glass multifilaments are used as core components whereas the cotton and polyester staple fibers are the sheath components wrapped around the core filament with different proportions to form a hybrid structure. The thermal treatment is carried out both in dry and in wet state under relaxed condition and the thermal shrinkage, sheath-slipping resistance and tensile and bending properties of hybrid yarns have been studied. Thermal treatment markedly increases the thermal shrinkage and sheath-slipping resistance of hybrid yarns with polyester multifilament in core, but insignificant effect for yarns with glass multifilament in core. Breaking elongation of hybrid yams with polyester multifilament in core increases with treatment temperature. The hybrid yarns with glass multifilament in core are least affected by thermal treatment.

Analysis on the Effects of the Induced Noise Voltage with the Grounded or Non-grounded Cable Sheath in the Power Inducting Situation (전력 유도 발생 시 케이블 쉬스 접지 여부에 따른 유도 잡음 전압 영향 분석)

  • Lee, Sang-Mu;Choi, Mun-Hwan;Cho, Pyoung-Dong
    • 한국정보통신설비학회:학술대회논문집
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    • pp.285-288
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    • 2007
  • This article presents the change characteristics of induced noise whether the sheath layer of the cable is grounded or not. As what affects the induced noise, there are power influence or longitudinal transverse voltages and its weighted filtered voltage. The sheath ground is basicaly predicted to have the effects of alleviation on the power influence. But practically the effects may not happen in the case of common cable's sheath layer. Rather there are cases that the ground of sheath affects so that the noise level could increase. So we need to scrutinize the effects of the sheath gorund in the measures for the protection against electromagnetic induction by powerline or traction line system. And the evaluation of using the designated shielding purpose cable is needed.

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Analysis of Sheath Induced Voltage and CCPU Operating Characteristic in Underground Transmission Cable (지중송전계통에서 시스유기전압 및 CCPU 동작 특성 해석)

  • Jin, Hye-Young;Lee, Jong-Beom;Kim, Young;Cho, Han-Koo
    • Proceedings of the KIEE Conference
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    • pp.494-496
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    • 2001
  • This paper describes sheath induced voltage and operating characteristic of cable cover protection unit(CCPU) in underground transmission cable. Real cable system operating by 154kV XLPE cable was modelled for simulation. Sheath induced voltage and operating characteristic of CCPU were analyzed. In particular, sheath induced voltage was analyzed in case of individual grounding and common grounding, respectively, and operating characteristics of CCPU were compared each other.

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