• Title, Summary, Keyword: Limiting impedance

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Comparative Study of Current Limiting Characteristics for Hybrid Type and Flux-Lock Type SFCLs

  • Lim, Sung-Hun
    • Transactions on Electrical and Electronic Materials
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    • v.8 no.5
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    • pp.222-225
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    • 2007
  • In this paper, we compared the current limiting characteristics of both the hybrid type and the flux-lock type superconducting fault current limiters(SFCLs), which have a magnetic coupling structure between a primary winding and several secondary windings. The limiting impedances of two SFCLs were derived from each equivalent circuit considering the design parameters of SFCL such as the self-inductance of secondary winding and the resistance of $high-T_C$ superconducting(HTSC) element. Through the comparison for the limiting impedances of two SFCLs considering the dependence of the HTSC element's resistance on the applying voltage into the SFCL, the hybrid type SFCL was confirmed to have larger limiting impedance with smaller resistance of HTSC element than the flux-lock type SFCL. It was expected from the analysis that the hybrid type SFCL was more advantageous than the flux-lock type SFCL from the viewpoint of the fault current limiting level.

Increased impedance by quench at a shield layer of HTS power cable for fault current limiting function

  • Choi, Youngjun;Kim, Dongmin;Cho, Jeonwook;Sim, Kideok;Kim, Sungkyu;Kim, Seokho
    • Progress in Superconductivity and Cryogenics
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    • v.21 no.4
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    • pp.59-63
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    • 2019
  • To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.

Partial Discharge Measurement of Oil-Paper Insulation by Dual Measuring Impeadance (절연유-절연지에서 이중 임피던스에 의해 부분방전측정)

  • Kim, K.H.;Ryu, H.S.;Sun, J.H.
    • Proceedings of the KIEE Conference
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    • pp.1778-1780
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    • 1996
  • In this paper, we describe the partial discharge measurement with measuring impedance to have two wide frequency band transformers(filters) in the oil-paper and air insulation. The measuring impedance consists of high and low limiting frequency transformers. This measuring impedance could be measured the partial discharge current wave. We have the results that the amplitude partial discharge pulse ratio of low limiting frequency tranformer to high limiting frequency one is varied in the condition(in oil-paper insulation and air) to generate partial discharge.

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Study on the Necessity for Limiting Impedance of Superconducting Fault Current Limiter Considering Protective Coordination of power distribution (배전보호협조를 고려한 초전도 한류임피던스 제한에 필요성 연구)

  • Ahn, Jae-Min;Kim, Jin-Seok;Moon, Jong-Fil;Lim, Sung-Hun;Kim, Jae-Chul
    • Proceedings of the KIEE Conference
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    • pp.34-36
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    • 2008
  • In this paper, we study on the necessity for limiting impedance of Superconducting Fault Current Limiter(SFCL) considering protective coordination. Several countermeasures have been proposed to protect the power system effectively from the larger fault current. Among them, the SFCL has been expected as one of the most effective solutions. However, the application of SFCL into power system can cause some problems, such as non-operation of instantaneous elements, of protective coordination because of limiting fault current. So we suggest that impedance of SFCL is must limited for operation of instantaneous elements. 'This method is essential to introduce application of SFCL into power distribution system.

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Feasibility study on the inductive fault current limiting cable

  • Lee, Sang Yoon;Choi, Jongho;Kim, Dong Min;Sim, Kideok;Cho, Jeonwook;Kim, Seokho
    • Progress in Superconductivity and Cryogenics
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    • v.15 no.3
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    • pp.24-28
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    • 2013
  • Fault current limiting (FCL) cable is a kind of superconducting cable which has a function of limiting the fault current at the fault of power grid. The superconducting cable detours the fault current through its stabilizer to keep the temperature as low as possible. On the other hands, the FCL cable permits the temperature rise within some acceptable limit and the fault current is limited by the consequent increase of the resistance of superconducting cable. This kind of FCL cable is called 'resistive FCL cable' because it uses resistive impedance to limit the fault current. In this paper, we suggest a novel concept of FCL cable, which is named as 'inductive FCL cable'. The inductive FCL cable is similar as the magnetic shielding fault current limiter in its operating mechanism. The magnetic field of superconducting cable is almost perfectly shielded by the induced current at the shielding layer during its normal operation. However, at the fault condition, quench occurs at the shielding layer by the induced current higher than its critical current and the magnetic field is spread out of the shielding layer. It will induce additional inductive impedance to the superconducting cable and the inductive impedance can be increased more by installing some material with high magnetic susceptibility around the superconducting cable. We examined the feasibility of inductive FCL cable with simple elemental experiments. The current limiting performance of inductive FCL cable was estimated considering an arbitrary power grid and its fault condition.

Simulation Method on the Protection Effects of Voltage-Limiting Type SPDs Associated with the Protective Distance (보호거리에 따른 전압제한형 SPD의 보호효과에 대한 시뮬레이션기법)

  • Lee, Bok-Hee;Kim, You-Ha;Ahn, Chang-Hwan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.7
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    • pp.89-94
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    • 2013
  • This paper presents a method of simulating the protection effects of surge protective devices(SPDs) depending on the protective distance and types of input impedance of load to be protected. In order to analyze the protective performances of voltage-limiting type SPDs associated with the reflection and oscillation phenomena, the terminal voltage across load being protected and the residual voltage of SPDs were simulated by using EMTP model as functions of the protective distance and types of input impedance of loads. As a consequence, SPDs should be installed by taking into account the protective distance and input impedance of loads to achieve reliable protection of electrical and electronic equipment from lightning and switching surges. It is expected that the simulation method proposed in this paper could be practically used in design for installing SPDs in low-voltage distribution systems.

Characteristic Analysis of a Flux-Lock Type SFCL Considering Magnetization Characteristic of Iron Core (철심의 자화특성을 고려한 자속구속형 초전도 사고전류제한기의 특성 분석)

  • Lim, Sung-Hun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.11
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    • pp.995-999
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    • 2007
  • We investigated the characteristics of a flux-lock type superconducting fault current limiter(SFCL) considering magnetization characteristic of iron core. The flux-lock type SFCL, like other types of SFCLs using the iron core, undergoes the saturation of the iron core during the initial fault time. Therefore, if the design to prevent the saturation of the iron core is considered, the effective fault current limiting operation can be achieved. Through the analysis for its equivalent circuit including the magnetization characteristic of the iron core, the limiting impedance of the flux-lock type SFCL was drawn. The magnetization currents and the limited currents of SFCL, which were dependent on the winding direction and the turns' ratio between two coils, were investigated from the short circuit experiment. It was confirmed that their experimental results agreed with the analysis ones.

Investigation on the inductive and resistive fault current limiting HTS power cable

  • Lee, Sangyoon;Choi, Jongho;Kim, Dongmin;Kwon, Yonghyun;Kim, Seokho;Sim, Kideok;Cho, Jeonwook
    • Progress in Superconductivity and Cryogenics
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    • v.16 no.2
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    • pp.59-63
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    • 2014
  • HTS power cable bypass the fault current through the former to protect superconducting tapes. On the other hand, the fault current limiting (FCL) power cable can be considered to mitigate the fault current using its increased inductance and resistance. Using the increased resistance of the cable is similar to the conventional resistive fault current limiter. In case of HTS power cable, the magnetic field of HTS power cable is mostly shielded by the induced current on the shield layer during normal operation. However, quench occurs at the shield layer and its current is kept below its critical current at the fault condition. Consequently, the magnetic field starts to spread out and it generates additional inductive impedance of the cable. The inductive impedance can be enhanced more by installing materials of high magnetic susceptibility around the HTS power cable. It is a concept of SFCL power cable. In this paper, a sample SFCL power cable is suggested and experimental results are presented to investigate the effect of iron cover on the impedance generation. The tests results are analyzed to verify the generation of the inductive and resistive impedance. The analysis results suggest the possible applications of the SFCL power cable to reduce the fault current in a real grid.

Improvement of Current Limiting and Recovery Characteristics of Flux-Lock Type SFCL with Series Connection of Two Coils Using Its Third Coil

  • Ko, Seok-Cheol;Kim, Young-Pil;Lim, Sung-Hun
    • Journal of Electrical Engineering and Technology
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    • v.12 no.1
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    • pp.472-477
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    • 2017
  • In this work, the current limiting and recovery characteristics of a flux-lock type superconducting fault current limiter (SFCL) with series connection of two coils were effectively improved by adding a third winding into the conventional flux-lock type SFCL with series connection of two coils. To confirm the contribution of the third winding to the current limiting and recovery characteristics of this type of the SFCL, short-circuit testing was carried out with consideration of the third winding, and the effect of the third winding on the current limiting and recovery characteristics was examined by comparative analysis of the amplitude of the limited fault current and the power burden of the high-TC superconducting (HTSC) element comprising the SFCL. Through the analysis of both the limiting impedance and the operational current as the main design parameter of the SFCL, the improved current limiting and recovery characteristics of the flux-lock type SFCL using the third winding could be verified.

Design of HTS power cable with fault current limiting function

  • Kim, Dongmin;Kim, Sungkyu;Cho, Jeonwook;Kim, Seokho
    • Progress in Superconductivity and Cryogenics
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    • v.22 no.1
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    • pp.7-11
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    • 2020
  • As demand for electricity in urban areas increases, it is necessary to improve electric power stability by interconnecting neighboring substations and high temperature superconductor (HTS) power cables are considered as a promising option due to its large power capacity. However, the interconnection of substations reduces grid impedance and expected fault current is over 45 kA, which exceeds the capacity of a circuit breaker in Korean grid. To reduce the fault current below 45 kA, a HTS power cable having a fault current limiting (FCL) function is considered by as a feasible solution for the interconnection of substations. In this study, a FCL HTS power cable of 600 MVA/154 kV, transmission level class, is considered to reduce the fault current from 63 kA to less than 45 kA by generating an impedance over 1 Ωwhen the fault current is induced. For the thermal design of FCL HTS power cable, a parametric study is conducted to meet a required temperature limit and impedance by modifying the cable core from usual HTS power cables which are designed to bypass the fault current through cable former. The analysis results give a minimum cable length and an area of stainless steel former to suppress the temperature of cable below a design limit.