• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.28-34
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• 2001

월성2호기가 100% 출력 운전중 2001.4.6일 20:16분에 345kV 신경산변전소 GIS모선#1측 지락고장 파급으로 주발전기 정지중 기동시 보호 용계전기(50/27)가 동작되어 발전정지 되고 원자로 출력은 60%까지 감발 되었음. 본 보호계전기는 발전기 정지나 터닝기어로 저속운전 중 인적 실수에 의해 발전기 병입용차단기 투입시 발전기가 과도한 돌입전류로 손상되는 것을 방지하기 위한 계전기로, 정상운전중이거나 외부사고시에는 동작할 수 없는 보호계전기임. 따라서 본 보호계전기의 동작원인을 당시 동작 상황과 기록데이터를 정정치와 함께 분석하고 적정동작을 위한 대책을 제시함.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.71-79
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• 2008

High voltage distribution lines in the electric railway system placed according track with communication lines and signal equipments. Case of the over head lines is occurrence the many fault because lightning, rainstorm, damage from the sea wind and so on. According this fault caused protection device to wrong operation. One line ground fault that occurs most frequently in railway high voltage distribution lines and sort of faults is line short, three line ground breaking of a wire, and so on. For this reason we need precise maintenance for prevent of the faults. The most important is early detection and fast restoration in time of fault for a safety transit. In order to develop an advanced fault location device for 22.9[kV] distribution power network in electric railway system this paper deals with new fault locating algorithm using flow technique which enable to determine the location of the fault accurately. To demonstrate its superiorities, the case studies with the algorithm and the fault analysis using PSCAD/EMTDC (Power System Computer Aided Design/Electro Magnetic Transients DC Analysis Program) were carried out with the models of direct-grounded 22.9[kV] distribution network which is supposed to be the grounding method for electric railway system in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2619-2627
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• 2009

The ground fault is occupying 70% among the total number of faults in ungrounded distribution power system. When the ground fault occurs in ungrounded system, the fault current is so small that it is hard to detect. But fault handling is very important because to continue power supply during fault conditions may cause the fault spreading and the distribution device in trouble. This paper presents the fault line detection method by using GPT signal detecting zero sequence voltage, and the fault section detection method by detecting whether GPT signal is disappeared or not during shifting normally open switch, which is connecting switch between distribution lines with open state in order to restore the outage area under emergency situation, and during isolating each section one by one which belongs to the fault line. This method is efficient because there is no whole power interruption during the fault section detection, and it is possible to perform both the fault section detection and the service restoration for the outage area at the same time, and it can apply to various distribution system configuration. Program for the fault restoration was developed applying proposed method, and it has been validated by applying to the pilot project of distribution automation system in Vietnam which has the ungrounded distribution system.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.283-285
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• 2005

This paper presents a new two-terminal numerical algorithm for fault location estimation and for faults recognition using the synchronized phasor in time-domain. The proposed algorithm is also based on the synchronized voltage and current phasor measured from the PMUs(Phasor Measurement Units) installed at both ends of the transmission lines. Also the arc voltage wave shape is modeled numerically on the basis of a great number of arc voltage records obtained by transient recorder. From the calculated arc voltage amplitude it can make a decision whether the fault is permanent or transient. In this paper the algorithm is given and estimated using DFT(Discrete Fourier Transform) and the LES(Least Error Squares Method). The algorithm uses a very short data window and enables fast fault detection and classification for real-time transmission line protection. To test the validity of the proposed algorithm, the Electro-Magnetic Transient Program(EMTP/ATP) and MATLAB is used.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.182-190
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• 2011

This paper proposes a LVRT (Low Voltage Ride Through) control strategy which should be satisfied by grid-connected wind power system when grid faults occur. The LVRT regulation indicates rules or actions which have to be executed according to the voltage dip ratio and the fault duration. Especially the wind power system has to support the grid with specified reactive current to secure the grid stability when voltage reduction ratio is over 10%. The LVRT regulation in this paper is based on the German Grid Code and full-scale variable speed wind power conversion system is considered for LVRT control strategy. The proposed LVRT control strategy satisfies not only LVRT regulation but also makes power balance between wind turbine and power system through additional DC link voltage regulation algorithms. Because it is impossible to control grid side power when the 3-phase to ground fault occurs, the DC link voltage is controlled by a generator side inverter using the DC link voltage control strategy. Through the simulation and experiment result, the proposed LVRT control strategy is evaluated and its effectiveness is verified.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.240-242
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• 2005

전력계통안정화장치(PSS)는 전력안정화를 위하여 발전기의 여자기에 보조신호를 주입하여 전력계통의 진동문제를 해결할 수 있는 장치이다. 본 논문은 기존의 비실시간 툴 (PSS/E, EMTDC/PCAD.,)을 사용한 경우와 달리 실시간 시뮬레이션 툴을 사용하여 전력계통안정화장치(Power System Stabilizer : PSS)의 영향 및 효과를 검토하였다. 이에 사용된 실시간 툴은 RTDS의 PC 버전인 RSCAD를 이용하여 분석하였다. 모의에 사용된 선로는 3상 3회선 송전선로이며 무한모선에 연결하였다. 사고는 3회선 중의 1회선 중앙에 3상 지락 상정사고를 발생시켜 선로 차단 및 재투입을 고려하여 실시하였다. 본 연구에서 RSCAD에 대한 기존의 전통적인 형태인 IEEE의 PSS1A type과 보다 정교한 이중구조를 가진 PSS2A type을 사용하여 검토하였다. IEEE의 PSS1A type은 각속도 ${\omega}$를 측정하여 사용하고 PSS2A type은 각속도 ${\omega}$와 유효전력 P를 측정하여 사용할 수 있는 형태이다. 그리고 실시간 시뮬레이션 결과는 각속도 ${\omega}$와 유효전력 P를 측정하여 PSS의 입력에 주입하고 이에 대한 효과를 비교하였다.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.354-356
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• 2006

This paper presents a new one-terminal numerical algorithm for fault location estimation and for faults recognition. The proposed algorithm are derived for the case of most frequent single-phase line to ground fault in the time domain. The arc voltage wave shape is modeled numerically on the basis of a great number of arc voltage records obtained by transient recorder. From the calculated arc voltage amplitude it can make a decision whether the fault is permanent of transient. In this paper the algorithm uses a very short data window and enables fast fault detection and classification for real-time transmission line protection. To test the validity of the proposed algorithm the Electro-Magnetic Transient Program(EMTP/ATP) is used.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.76-84
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• 2002

Voltage sags caused by line faults in transmission and distribution lines have become one of the most important power quality problems facing industrial customers and utilities. Voltage sags are normally described by characteristics of both magnitude and duration, but phase angle shifts should be taken account in identifying sag phenomena and finding their solutions. In this paper, voltage sags due to line faults such as three phase-to-ground, single line-to-ground, and line-to-line faults are characterized by using symmetrical component analysis, for fault impedance variations. Voltage sags and their effect on the magnitude and phase angle are examined. Balanced sags of three phase-to-ground faults show that voltages and currents are changed with equivalent levels to all phases and the zero sequence components become zero. However, for unbalanced faults such as single line-to-ground and line-to-line faults, voltage sags give different magnitude variations and phase angle shifts for each phase. In order to verify the analyzed results, some simulations based on power circuit models are also discussed.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.173-179
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• 2001

This paper represents the control algorithm of the instantaneous voltage sag corrector for the power quality enhancement in distribution line. Especially, a novel detection technique of the symmetrical components is proposed for the analysis of the three-phase unbalanced and asymmetrical problems caused by the single line ground fault which is he most frequent event. This proposed method is based on the simple calculation and the control references of the symmetrical components for voltage compensation can be described as dc value without any other phase detection procedure. And also, for the generation of the reference voltages, the UF and MF defined by IEC is considered. Using this proposed control algorithm, the compensator has the fast dynamic characteristics and the THD of the compensated voltage waveform is very low. Finally, the validity of the proposed algorithm is proved by the PSCAD/EMTDC simulation and experimental results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.12
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• pp.903-913
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• 1988

Induced voltage causing disturbances on the communication lines of electric train is dealt with when the AT power supply system is employed. Induction interference is of three types, namely, normal state induced voltage, unusual induced voltage in case of power faults, and noise-induced voltage. Calculation of induced voltages occurring in the AT system is more complicated and extensive than in the BT system. In this paper we obtain an algorithm to calculate the induced voltages on the communication lines in the AT system and an algorithm for the induced current in case of the accident that the line falls to the ground. These algorithms are developed to a package of computer programs and their validity was checked on a simulated system. We supply the measures to protect the communication lines suitable for the AT system and we can also evaluate the protection capabilities. Because of the ability to evaluate the protection measures, this package is expected to be very useful when electric train system is constructed on communication lines near the railroad.