• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.969-970
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• 2007

In this thesis, an algorithm of fault detection and diagnosis during operation for induction motors under the condition of various loads and rates is investigated. For this purpose, the spectrum pattern of input cutterrents was used to monitor the state of induction motors, and by clustering the spectrum pattern of input currents, the newly occurrence of spectrums pattern caused by faults were detected. For diagnosis of the fault detected, the fuzzy fault tree was designed, and the fuzzy relation equation representing the relation between an induction motor fault and each fault type, was solved. The solution of the fuzzy relation equation shows the possibility of each fault's occurring.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.32-40
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• 2009

In order to reduce time-to-market, the demand for fast fault diagnosis has been increased. In this paper, a fault dropping technique with fault candidate ordering and test pattern ordering for fast fault diagnosis is proposed. Experimental results using the full-scanned ISCAS 89 benchmark circuits show the efficiency of the fault dropping technique with fault candidate ordering and test pattern ordering.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.595-599
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• 2018

Interruption system with the transformer type superconducting fault current limiter(TSFCL) is proposed in this paper. The interruption system with a TSFCL is a technology that it maximizes the interruption function of a mechanical DC circuit breaker using a transformer and a superconducting fault current limiter. By a TSFCL, the system limits the fault current till the breakable current range in the fault state. Therefore, the fault current could be cut off by a mechanical DC circuit breaker. The Interruption system with a TSFCL were designed using PSCAD/EMTDC. In addition, the Interruption system with a TSFCL was applied to the DC test circuit to analyze characteristics of a current-limiting and a interruption operation. The simulation results showed that the Interruption system with a TSFCL interrupted the fault current in a stable when a fault occurred. Also, The current-limiting rate of the Interruption system with a TSFCL was approximately 69.55%, and the interruption time was less than 8 ms.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.1-7
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• 2011

This paper proposes an enhanced noise robust algorithm for fault location on double-circuit transmission line for the case of single line-to-ground (SLG) fault, which uses distributed parameter line model that also considers the mutual coupling effect. The proposed algorithm requires the voltages and currents from single-terminal data only and does not require adjacent circuit current data. The fault distance can be simply determined by solving a second-order polynomial equation, which is achieved directly through the analysis of the circuit. The algorithm, which employs the faulted phase network and zero-sequence network with source impedance involved, effectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The proposed algorithm is tested using MATLAB/Simulink under different fault locations and shows high accuracy. The uncertainty of source impedance and the measurement errors are also included in the simulation and shows that the algorithm has high robustness.

• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.474-483
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• 2011

Solid-state fault current limiters (SSFCL) in power systems are alternative devices to limit prospective short circuit currents from reaching lower levels. Fault current limiters (FCL) can be classified into two categories: R-type (resistive) FCLs and L-type (inductive) FCLs. L-type FCL uses an inductor to limit fault level and is more efficient in suppressing voltage drop during a fault. In contrast, R-type FCL is constructed with a resistance and is more effective in consuming the acceleration energy of generators during a fault. Both functions enhance the transient stability of the power system. In the present paper, a novel SSFCL is proposed to enhance power system transient stability and power quality. The proposed SSFCL uses both functions of an L-type and R-type FCL. SSFCL consists of four diodes, one self-turn-off IGCT, a current-limiting by-pass inductor (L), and a variable resistance parallel with an inductor for improvement of power system stability and prevention of over-voltage across SSFCL. The main advantages of the proposed SSFCL are the simplicity of its structure and control, low steady-state impedance, fast response, and the existence of R-type and Ltype impedances during the fault, all of which improve power system stability and power quality. Simulations are accomplished in PSCAD/EMTDC.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.1769-1770
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• 2006

Arc Fault is an electric discharge which is occurred in two opposite electrode. In this paper, AFCI(arc fault circuit interrupter) is designed for the interruption of arc fault current which is occurred in the local electric network. This arc is one of the main causes of electric fire. Arc fault in electrical network has the characteristics of low current, high impedance and high frequency. Conventional interrupter does not have the arc current interrupt function. Hence, Arc fault circuit interrupter controller is designed for the interruption of arc fault current which has the modified arc characteristics.

• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.66-69
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• 2009

To manufacture YBCO-coated conductors as superconducting fault current limiters, it is important to conduct researches on their durability. To test their durability, it is necessary to investigate their properties before and after the quench in more severe conditions than in general operating conditions. In this study, their voltage-current and resistance properties were measured before and after a fault current was repetitively applied to them. For the applied voltage, the voltage grades of the YBCO coated conductors were considered. The current amplitude was controlled using protective resistance on an experimental track, and the time and number of applications were fixed to produce the quench occurrence at the fault angles of $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$. The operating conditions of the YBCO coated conductors as the main components of superconducting fault current limiters were determined using their voltage properties. The voltage properties of the YBCO coated conductors that were analyzed in this research will be used as important data for their practical application to superconducting fault current limiters.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1789-1794
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• 2014

This paper suggests an application method for a superconducting fault current limiter (SFCL) using an evaluation index to estimate the risk regarding the short-circuit capacity of the circuit breaker (CB). Recently, power distribution systems have become more complex to ensure that supply continuously keeps pace with the growth of demand. However, the mesh or loop network power systems suffer from a problem in which the fault current exceeds the short-circuit capacity of the CBs when a fault occurs. Most case studies on the application of the SFCL have focused on its development and performance in limiting fault current. In this study, an analysis of the application method of an SFCL considering the risk of the CB's short-circuit capacitor was carried out in situations when a fault occurs in a loop network power system, where each line connected with the fault point carries a different current that is above or below the short-circuit capacitor of the CB. A loop network power system using PSCAD/EMTDC was modeled to investigate the risk ratio of the CB and the effect of the SFCL on the reduction of fault current through various case studies. Through the risk evaluations of the simulation results, the estimation of the risk ratio is adequate to apply the SFCL and demonstrate the fault current limiting effect.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.141-144
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• 2002

This paper describes the correction of the protective relay equipped in the dedicated line used for connecting distributed generators (DG) to power grid. The fault current measured in a relaying point might be changed according to the fault conditions. Generally, the fault current of the line to line fault or the line to ground fault at the dedicated line is much higher than the protective set value due to the large fault level. However. when the high impedance fault is occurred in the dedicated line, we may not detect it because its fault level can be lower than the generating capacity of DG. And, the protective relay with conventional set value may generate a trip signal for insertion of DG due to the large transient characteristics of generators. Through the various simulations such as the fault in the dedicated line and the insertion of DG, we show that it would be necessary to modify the protective relay set value for detecting the high impedance fault occurred in the dedicated line and for preventing the mis-operation of protective relay caused by the insertion of DG.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.181-183
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• 1996

A novel model of an inductive superconducting fault current limiter with an inductive superconducting fault current limiter with the air-gap core was fabricated and tested. If its impedance is not high enough to limit the fault current, then destructive damage occurs in the power system. We attained a magnetic saturation under higher current by an effective air gap introduced in the core. The fault current was successfully limited to two times as much as the nominal current at a 60 Hz source having an effective voltage of 70 V. The fault current flowing under such conditions can be limited to a desired value without any fault current peak within 1/4 cycles.