• Title/Summary/Keyword: unsymmetrical fault

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Current Limiting Characteristics of Superconducting Fault Current Limiter for Reduction of Unsymmetrical Fault Current in a Three-Phase Power System (삼상전력계통의 비대칭고장전류 저감을 위한 초전도한류기의 전류제한특성)

  • Kim, Min-Yeong;Lim, Sung-Hun;Hwang, Jong-Sun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.03b
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    • pp.8-8
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    • 2010
  • In this paper, the limiting characteristics of the fault current in a power system with a superconducting fault current limiter(SFCL) applied into neutral line of main transformer in a distribution power line were analyzed. The SFCL applied into the neutral line of main transformer power system can limit the unsymmetrical fault current from the single-line ground fault or the double-line ground fault. In addition, it could be decreased a number of SFCL and a load. This method could be expected to reduction of a power loss in the neutral line, because of a neutral line current is zero in ordinary times.

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Analysis on Reduction Method of Symmetrical Fault Current in a Power System with a SFCL applied into Neutral Line (전력계통의 중성선에 적용된 초전도한류기의 대칭고장전류 저감방안 분석)

  • Lim, Sung-Hun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.2
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    • pp.148-152
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    • 2010
  • The superconducting fault current limiter (SFCL) applied into the neural line of a power system, which can limit the unsymmetrical fault current from the single-line ground fault or the double-line ground fault, was reported to be the effective application location of the SFCL in a power system. However, the limiting operation for the symmetrical fault current like the triple line-ground fault is not effective because of properties of the balanced three-phase system. In this paper, the limiting method of the symmetrical fault current in a power system with a SFCL applied into neutral line was suggested. Through the short-circuit experiments of the three-phase fault types for the suggested method, the fault current limiting and recovery characteristics of the SFCL in the neutral line were analyzed and the effectiveness of the suggested method was described.

Operating properties of superconducting fault current limiters with a sing1e line-to-ground fault in a three-phase system (3상 전력계통의 1선 지락사고에 대한 초전도한류기의 동작특성)

  • 최효상;현옥배;김혜림;황시돌;차상도
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.02a
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    • pp.261-262
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    • 2003
  • We performed unsymmetrical analysis of a single line-to-ground fault in a three-phase system. The current limiting elements were meander type YBCO stripes coated with Au shunt. When the fault occurred, short circuit currents were effectively limited within 1-2 msec after fault instant. The unsymmetrical rate of fault phase was distributed from 6.4 to 1.4 and most of the fault current flowed in the grounding line due to its direct grounding system.

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Operating properties of resistive type superconducting fault current limiters with a single line-to-ground fault (1선지락사고에 대한 초전도한류기의 동작특성)

  • Park, Hyo-Sang;Park, Chang-Joo;Lee, Sang-il;Chung, Soo-Bok;Oh, Geum-Kon;Chung, Hun-Sang
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2003.11a
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    • pp.279-281
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    • 2003
  • We analysed the operating properties of resistive type superconducting fault current limiters (SFCLs) based on YBCO thin films with a single line-to-ground fault. When a single line-to-ground fault occurred, the short circuit current of a fault phase increased up to about 6 times of transport currents immediately after the fault instant and was effectively limited to the designed current level within 2 ms by the resistance development of the SFCL. The fault currents of the sound phases almost did not change because of their direct grounding system. The unsymmetrical rates of a fault phase were distributed from 6.4 to 1.4. It was found that the unsymmetrical rates of currents were noticeably improved within one cycle after the fault instant. We calculated the zero phase currents for a single line-to-ground fault using the symmetrical component analysis. The positive sequence resistance was reduced remarkably right after the fault but eventually approached the balanced positive resistance component prior to the system fault. This means that the system reaches almost the three-phase symmetrical state in about 60 ㎳ after the fault. The ground currents were almost 3 times of the zero phase mts since most of the fault currents flowed through the grounding line.

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Leakage Currents Flowing through Lightning Surge Arresters under Various Fault Conditions in Receiving and Distribution Power Systems (수배전계통의 여러 가지 고장조건에서 피뢰기에 흐르는 누설전류)

  • Lee, Bok-Hee;Kil, Hyeong-Joon;Kang, Sung-Man;Choi, Hwee-Sung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.18 no.5
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    • pp.132-139
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    • 2004
  • Unsymmetrical faults are classified into single line-to-ground faults, line-to-line faults, or double line-to-ground faults in receiving and distribution power systems. Many of overhead distribution-line faults are single line-to-ground faults, and lightning surge arresters are stressed by system frequency overvoltages due to unsymmetrical faults. In this work, the unsymmetrical faults in receiving and distribution systems were experimentally simulated, and the characteristics of total leakage current flowing through lightning surge arresters due to various unsymmetrical faults were investigated. As a result, a little variations of the leakage current flowing through Zinc oxide (ZnO) surge arresters in the range of $\pm$10[%] voltage regulations were observed. It could be concluded that the unsymmetrical faults have no effect on the long-term life performance of ZnO surge arresters in effective grounding systems. On the other hand, the magnitude of the leakage current flowing through ZnO surge arrester elements under single line-to-ground faults was more than 140 times as compared with that under normal operating voltages in ineffective grounding systems. But abnormal voltages caused by line-to-line faults and double line-to-ground faults have a little effect on total leakage current of ZnO surge arrester elements.

Characteristics of Fault Current Division Factor & Groud Potential Rise of a Substation fed exclusively by Power Cables (지중케이블 변전소의 고장전류 분류율과 접지전위상승 특성)

  • Choi, Jong-Kee;Jung, Gil-Jo;Kim, Seon-Gu
    • Proceedings of the KIEE Conference
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    • 1998.11a
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    • pp.295-297
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    • 1998
  • This paper shows characteristics of fault current division factor $S_f$, which is a ratio of earth- return current to total fault current, at a substation fed exclusively by power cables under unsymmetrical fault condition, such as single line-to-ground fault. In substation grounding system design, $S_f$ is a very important factor determining GPR, touch and step voltage at a substation under fault condition. In case of substations fed by overhead lines, 40-60% of $S_f$ has been typically used, although it is a very conservative value with no other network conditions considered. It is authors' hope that $S_f$ presented in this paper could hopefully be a basic reference in designing of substation grounding system, especially for a substation fed exclusively by power cables.

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Analysis of inrush current caused by voltage sag in three-phase transformer and induction motor (삼상 변압기와 유도전동기에서의 전압 sag에 의한 들입 전류 분석)

  • Kim, Kyoung-Nam;Ahn, Seon-Ju;Jung, Il-Yop;Moon, Sung-Il
    • Proceedings of the KIEE Conference
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    • 2005.07a
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    • pp.307-309
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    • 2005
  • This paper studies the effects caused by symmetrical and unsymmetrical voltage sags on three-phase transformer and induction machine. The voltage sag on transformer and induction machine gives rise to inrush current. This inrush current makes sag more severe. These effects depend or many elements such as sag magnitude and duration, type of sag, and fault and recovery voltage instants.

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