• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.46-50
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• 2011

The electrical insulation design of high voltage superconducting fault current limiters (SFCLs) should be confirmed to be applied for the stabilization of the power grid. This paper describes numerical analysis and AC dielectric experiments for developing high voltage SFCLs. The electric field distributions between applied high voltage part and ground were calculated by finite element method (FEM) simulation tool and AC criterion of liquid nitrogen at 200 kPa was calculated from correlation between the field utilization factor and FEM simulation results. This paper deals with ceonceptual insulation design of a 154 kV class single-phase no-inductively wound solenoid type SFCL which was focused on gap distance between the cryostat and superconducting coils. Furthermore, the shield ring effect was confirmed to reduce maximum electric field at applied high voltage part.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2065_2066
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• 대한전기학회논문지:전력기술부문A
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• 제49권1호
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• pp.26-30
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• 2000

Switching of the transmission lines(T/L) is one of the methods for wuppressing the short circuit capacity. This paper presents the T/L switching operation by using the Hopfield neural network(HNN). The switching of T/L can make the line powers and the bus voltages deteriorated, as well as the fault current decreased. Such an insecure state should be avoided when the T/L is operated to be open. In this studies, the inequality constraints are formulated into the objective function to be incorporated with the HNN. Test results show that the convergence characteristics of HNN lead to the adequate solution of T/L switching.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.14-19
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• 2005

A transient numerical simulation was conducted to have variation of temperature on an element of resistive Superconducting Fault Current Limiter (SFCL) under quench condition. It is very important engineering information for an optimum design of cryogenic system for cooling of a resistive SFCL element. A bifilar coil for resistive SFCL for 10 MVA system was incorporated as a model in this numerical study. From the numerical simulation result, it was found that the averaged temperature on the shunt and Bi-2212 element at 500 kW, 100 ms was 711.1 K and 198.4 K respectively. The temperature variation with the change of the hot-spot size and time is also obtained. The maximum temperature was continuously increased in all cases until the hot-spot stops at 100ms and it was going down after then. Such as, the details of temperature distribution on the SFCL element obtained from this numerical study and it should be very valuable information on the decision of the cooling capacity of cryogenic system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 전기설비전문위원
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• pp.49-51
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• 2009

전력계통 적용을 위한 초전도 한류기의 개발에서 빠질 수 없는 것이 용량 증대 방안이다. 여기서는 자속결합형 초전도 한류기의 용략 증대 측면에서 2차측 초전도 소자의 수를 늘렸을 때 사고전류 제한 특성과 초전도 소자의 권치 특성을 분석하였다. 소자의 수가 증가함에 따라 사고전류의 크기는 조금 증가 하는 것을 확인할 수 있었고, 초전도 소자의 전압은 크게 감소하는 것을 확인할 수 있었다. 이것은 초전도 소자 하나가 부담하던 사고전류를 분담하였기 때문에 소자의 부담이 줄어든 것이다. 실험을 통해 초전도 소자의 ��치시간도 알 수 있었는데 초전도 소자가 증가함에 따라서 ��치시간이 길어졌다. 이것은 초전도 소자의 치 시점이 늦어져 빠른 스위칭 동작을 할 수 없게 된다는 것이다. 초전도 소자의 수 증가는 소자의 부담을 감소시키고 용량증대를 측면에서는 장점이지만 스위칭 동작측면에서는 단점으로 작용한다.

• Transactions on Electrical and Electronic Materials
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• 제15권3호
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• pp.117-124
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• 2014

The calculation of short-circuit currents is important for power systems operation and restoration, and for determining the means to protect human lives and properties. In this paper, a part of a power system network, around the D$\breve{e}$tmarovice power station in Czech Republic, was simulated by the well known program EMTP-ATPDraw (Electromagnetic Transients Program-Alternative Transient Program), and short-circuit currents and voltages were calculated at different points in the electric network and presented as a time function by the PlotXY program. Calculations were done just for phase-to-ground, and for the three-phase short-circuit at the Kun$\check{c}$ice substation. The results were important for determining the characteristics of the equipment required to withstand or break the short-circuit current; for this reason, the calculations were repeated using earth-fault resistances only for the case of busbar KUN shown in Figs. 5 and 6.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.524-526
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• 1997

High speed DC circuit breakers (HSCB) are indispensable for protection of DC electric subway substations from fault current. However, the HSCB has mechanical contact to wear, which requires rather frequent maintenance, we have succeeded in developing and manufacturing a GTO DC circuit breaker using GTOs and ZnO varistors. In this paper, we describes the outline of the system itself, its characteristics and test data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2212-2213
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• 2008

In this paper, we studied the method for simultaneous quenching of a transformer type superconducting fault current limiter (SFCL) with two superconducting elements connected in series. Only an element between two elements of the transformer type SFCL was quenched like the case of the resistive type SFCL. By this quenching characteristics, the power burden of the superconducting element was increased. In order to solve this problem, we connected the neutral line between two superconducting elements and the center of secondary coils. The two elements were all quenched in the transformer type SFCL with a neutral line. As a result, the power burden of superconducting elements was decreased, so it was efficient for the increase of power capacity of the transformer type SFCL.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.151-152
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• 2015

Multi-terminal HVDC(MTDC) 시스템은 기존 전압형 HVDC 시스템이 갖는 능동적인 전력 조류 제어 및 불안정한 신재생에 너지원의 안정적 연계 기능을 극대화시킨 계통 구성 방식으로, 수퍼그리드의 구현에 가장 근접한 방식으로 각광받고 있다. 그러나 전압형 HVDC 시스템을 채택함으로써, 고장전류에 취약한 특징을 갖고 있으며 사고 구간의 분리를 위한 HVDC 차단기의 개발이 필수적으로 요구된다. 본 논문에서는, 추후 HVDC 차단기의 개발 및 적용을 위해 요구되는 MTDC시스템에서의 고장전류 특성 분석에 대한 내용을 기술하고 있다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2000년도 학술대회논문집
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• pp.251-256
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• 2000

The assessment of the condition of a transformer winding which is suspected of having suffered short circuit damage can be difficult. Conventional test such as winding resistance, magnetisation current or insulation resistance will only detect damage if a permanent electrical fault exists. Visual inspection of windings necessitates the removal of oil and in many cases only a very small proportion of the winding can be seen. We describe the characteristics. As the front rise time of recurrent-surge generator pulse less than 1000ns and the peak value of pulse is about 500V, we have the good results of detecting winding deformation in the LVI test of transformers.