• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.22-24
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• 2001

This paper presents a fault phase selection algorithm for transmission line protection by means of the symmetrical components. Accurate fault phase selection is necessary for collect functioning of transmission line relaying, particularly in Extra High Voltage (EHV) networks. The conventional phase selection algorithm used the phase difference between positive and negative sequence current excluding load current. But, it is difficult to abstract only fault current since we can not know the time which a fault occurs. The proposed algorithm can select the accurately fault phase using fault current contained pre-fault current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.1033-1037
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• 2013

Coercion transformer is commonly used in the electrical grid which in three phase of distribution system. The accident of the electrical grid is divided into a single, a double, a third line-to-ground faults and a double, a third line-to-line faults. A single line-to-ground fault accounts for nearly 75[%] among them. In this research, when a Superconducting Fault Current Limiters (SFCL) was applied to the three phase power system, operation in a single line-to-ground fault and limiting characteristics of fault current according to turns ratio of third winding were analyzed. When a single line-to-ground fault happened, secondary winding's circuit was open. Then third winding's circuit with a SFCL was closed. So fault current was limited by diverted circuit. At this time, we could find out that size of the limited fault current could be changed according to third winding rate. We confirmed that limiting operation of the fault current was carried out within one-period. These results will be utilized in adjusting the size of the SFCL.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.7
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• pp.397-404
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• 2004

This paper describes a study of transient characteristics in 765kV untransposed transmission lines. As the 765(kV) system can carry bulk power, some severe fault on the system nay cause large system disturbance. The large shunt capacitance and small resistance of 765kv transmission line make various difficulties for its protection. These problems including current difference between sending and receiving terminals on normal power flow, low order harmonic current component in fault current and current transformer saturation due to the long DC time constant of the circuit etc. must be investigated and solved. The analysis of transient characteristics at sending terminal has been carried out for the single phase to ground fault and 3-phase short fault, etc. The load current, charging current in normal condition and line flows, fault current, THD(Total Harmonic Distortion) of harmonics, time constants have been analysed for the 765kV untransposed transmission line systems.

• Progress in Superconductivity
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• v.3 no.2
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• pp.235-240
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• 2002

In this paper, we investigated the current limiting characteristic in the magnetic shielding type fault current limiter(MSFCL). The circuit analysis was executed by using finite differential method(FDM). This paper suggests that the current limiting performance can be achieved in two ways (resistive and inductive one), according to design parameter. By comparing current limiting characteristics in two ways and surveying the important parameters which determine the operational way after fault occurs in the design of MSFCL, it is shown that the magnetic shielding type fault current limiter can be operated in either resistive or inductive way.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.26-30
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• 2008

The simulation and experiment for the fault current limiting characteristics of the superconducting fault current limiter (SFCL) using the magnetic coupling of series connected two coils were performed. The magnetic fluxes generated from two coils were canceled out during a normal time. However, the resistance generation of high-Tc superconducting (HTSC) element after a fault occurrence allows the magnetic fluxes of two coils and contributes to the fault current limiting operation. Through the computer simulation and the current limiting experiment for this SFCL, the operational current and the limiting impedance of the SFCL could be confirmed to be improved by adjusting the inductance ratio of two coils.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.547-550
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• 2004

Superconducting fault current limiter(SFCL) is expected to be introduced into electric power system in future as an effective countermeasure for the increase of the short-circuit current due to the growth of the electric power system. SFCL has a merit that the fault current can be limited by the resistance generated when a superconductor transits from a superconducting state to a normal state without additional detecting device. In this paper, we investigated the resistance variance of resistive type SFCL and the fault current limiting characteristics due to the amplitude of source voltage. We could obtain the more effective fault current limiting characteristics of SFCL as the source voltage increased.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.49-53
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• 2006

This paper specifies the new power supply paradigm converting 154kV voltage level into 22.9kV class with equivalent capacity using superconducting rower facilities and analyze the fault current characteristics with and without HTS-FCL (High Temperature Superconducting-Fault Current Limiter). Superconducting new power system is the power system to which applies the 22.9kV HTS cable in parallel to HTS transformer and HTS-FCL with low-voltage and mass-capacity characteristics replacing 154kV conventional cable and transformer. The fault current of superconducting new power system will increase greatly because of the mass capacity and low impedance of HTS transformer and cable. This means that the HTS-FCL is necessary to reduce the fault current below the breaking current of circuit breaker. This paper analyze the fault current and suggests the parallel HTS-FCL scheme complementing the inherent problem of HTS-FCL, that is recovery after quenching is impossible within shorter than a few seconds.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.213-216
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• 2007

The computer simulation for the fault current limiting characteristics of the superconducting fault current limiter (SFCL) using the magnetic coupling of two coils was performed. The magnetic fluxes generated from two coils were canceled out during a normal time. However, the resistance generation of high-$T_c$ superconducting (HTSC) element after a fault occurrence keeps up the magnetic fluxes of two coils and contributes to the fault current limiting operation. Through the computer simulation for the fault current limiting characteristics based on its electrical equivalent circuit, its operational current and the limiting impedance could be improved by adjusting the inductance ratio between two coils.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.2
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• pp.73-79
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• 2004

Nowadays, one of the serious problems in KEPCO system is the larger fault current than the SCC(Short Circuit Capacity) of circuit breaker. There are many alternatives to reduce the increased fault current such as isolations of bus ties, enhancement of SCC of circuit breaker, applications of HVDC-BTB(Back to Back) and FCL(fault current limiter). However, these alternatives have some drawbacks in viewpoints of system stability and cost. As the superconductivity technology has been developed, the HTS-FCL(High Temperature Superconductor-Fault Current Limiter) can be one of the attractive alternatives to solve the fault current problem. Under this background, this paper presents the EMTDC model for resistive type HTS-FCL considering the nonlinear characteristic of final resistance value when quenching Phenomena occur.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.63-64
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• 2008

The increase of fault current due to large demand has caused the capacity of power machines in power grid to increase. To protect the power system effectively from the large fault current, several superconducting fault current limiters have been proposed. however, in order to apply superconducting fault current limiters into power system, there are many problems such as cost, recovery, AC loss, and cryogenic. In order to solve these problems, hybrid superconducting fault current limiter(HSFCL) was proposed. However, HSFCL also has a problem that is protective coordination in distribution system with HFSCL. In this paper, HSFCL limiting after half cycle modeled and analyzed about protective coordination.