• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2317-2322
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• 2011

In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using Sinulink.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1892-1897
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• 2010

In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. PSIM(Power Electronics Simulator) is optimal simulation software in field of the power electronics and provide the simple and convenient user interface. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using PSIM.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.1
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• pp.54-60
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• 2003

Feeding traction loads from the public power system may lead to some current and voltage unbalance and consequently affects the operation of its energy-supply system and other equipment connected with it. This paper introduces an analysis of the current unbalance caused by the demands of an electric railway on a public power system. And the results with compensator and without compensator are simulated, and eventually the formula about the current unbalance is suggested. The Scott-connected transformer is adopted in Korea National Railway System. So Scott-connected transformer among the various transformer connection schemes is analyzed in this paper. Also, the formulas about the unbalance and compensating current can be derived by using two parameters(M-phase and T-phase current) of secondary Scott-connected transformer. So, the practical and accurate simulation can be done through dynamic models by using scheduling of traction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.394-399
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• 2017

In Korean AC power railway substations, SCOTT winding transformers are under operation to have a single phase power supply together with a phase angle of $90^{\circ}$ on the secondary side of the main transformer. In the case of an internal fault of the transformer, the transformer protection relay should be cut off on the primary side, the transformer should be inoperative to the external fault of the transformer or to the normal train operation. Reducing the malfunction of the relay through an exact fault determination is very important for securing a stable power system and improving its reliability. The main transformers are protected using Buchholtz's relay and a differential relay as the internal fault detection devices, but there are some cases of the main transformer operation under the deactivation of this protection function due to a malfunction of the differential relay. In this paper, the characteristics of the SCOTT transformer and differential relay as well as the malfunctioning of the protection relays are presented. The modeling of the SCOTT transformer protection relay was accomplished by the power system analysis program and the Comtrade file from 'A substation', which was used as the input data for the fault wave, and the harmonics were analyzed to determine if the relay operates or not. In addition, an improvement plan for malfunctioning cases through wave form analysis is suggested.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1398-1406
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• 2018

Owing to the consistent increase in accurate analysis issue for energy consumption of the AC electric railway systems, there is controversy about the adequacy of the present watt-hour metering configuration. Due to the unusual load characteristics and facilities, the discussions have not been active. Therefore, in order to achieve more accurate watt-hour metering for AC electric railway system, this paper proposes numerical formulas for watt-hour metering that reflects the highly-varying characteristics of the railway load and the structural characteristics of the Scott transformer. The proposed formulas have been verified by comparison with site-measured data, and a more suitable metering configuration for AC railway system has been proposed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1121-1127
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• 2016

In this paper, modeling of overcurrent relay(OCR) to protect domestic AC electric railway Auto Transformer(AT) feeding system and operation characteristic analysis on overload condition are described. The target system of this paper is actual site where overload trip of circuit breaker occurs frequently. Because this AT feeding system is made of parallel single track which had a load(electric train) respectively, and is connected with only T phase of Scott Transformer. In addition, this system has been feeding 66kV voltage by KEPCO, not 154kV. We focus on protective coordination of Scott Transformer primary side and secondary side OCR for Korea single track AC electrical railway system in operation currently. We modeled single track AT feeding system and OCR. Also we performed faults and overload analysis for verification of OCR's setting values and system modeling. To analyze above mentioned research, we used PSCAD/EMTDC software tool.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.12
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• pp.624-629
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• 2002

This paper presents the first Simulation model using EMTDC program to analyze the electrified train voltage distribution characteristics in ac auto-transformer 1110 railroads. In general, all of the electrified train supply system has the characteristics that the train supply line is a naturally non-symmetrical and unbalanced system. Also, it is needed to model the Scott transformer which invert the balanced 3-phase quantity into 2-phase. Therefore, the general simulation methodology using previous simplified equivalent circuit or RMS based program can't obtain the accurate results to reflect the real-time operation because these methodology is basically assumed on completely 3-phase balanced system. To overcome these defects, in this paper, the EMTDC simulation model to analysis the completely electrified railroad system with Scott transformer and AC auto-transformer is presented. Also, the correctness of EMTDC modeling is confirmed by the old basic concepts and we think that this EMTDC model has the future powerful capability for application of railroad system analysis.

• Journal of the Korean Society for Railway
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• v.5 no.4
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• pp.253-259
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• 2002

This paper presents the first simulation model using EMTDC program to analyze the electrified train voltage distribution characteristics in ac auto-transformer fed railroads. In general, all of the electrified train supply system has the characteristics that the train supply line is a naturally non-symmetrical and unbalanced system. Also, it is needed to model the Scott transformer which invert the balanced 3-phase quantity into 2-phase. Therefore, the general simulation methodology using previous simplified equivalent circuit or RMS based program can't obtain the accurate results to reflect the real-time operation because these methodology is basically assumed on completely 3-phase balanced system. To overcome these defects, in this paper, the EMTDC simulation model to analysis the completely electrified railroad system with Scott transformer and AC auto-transformer is presented. Also, the correctness of EMTDC modeling is confirmed by the old basic concepts and we think that this EMTDC model has the future powerful capability for application of railroad system analysis.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.387-389
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• 2005

Scott 결선 변압기는 3상전원에서 단상부하를 공급해야하는 계통에서 많이 사용되고 있다. 특히 전기철도가 이에 해당되며 국내에서는 전기철도의 화장으로 Scott변압기가 154kV급의 송전계통에 연계되어 설치 운전되고 있다. Scott변압기의 특성상 단상인 부하측 또는 3상인 전원측에서 사고 발생시 각상에 흐르는 불평형 사고전류의 예측이 어려워 관련기기의 선정과 각종 보호계전기의 정정이 쉽지 않았으며 과도현상 해석도 쉽지않았다. ATP(Alternative Transient Program)는 전력계통의 과도현상뿐만 아니라 단락 및 지락과 같은 정상상태 해석 및 고조파 분석도 가능하며 그래픽 유저 인터페이스를 위한 ATPDraw도 개발되어 데이터 입력과 사용법이 보다 간편하게 되었으며, 출력파형을 위한 PlotXY도 개발되어 계산결과를 다양한 형태의 그래프로 출력할 수 있게 되었다. 무엇보다도 User Group에 가입하면 무료로 모든 프로그램을 사용할수 있는 장점도 있다. 본고에서는 ATP를 사용하여 Scott변압기의 모델링과 이를 통한 단락 및 지락 사고 둥의 해석 사례를 소개하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1737-1742
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• 2012

The scott transformer is used to supply single-phase power to the AC railway system. Since the scott transformer is a passive facility, it cannot regulate load-side voltage according to load change. Meanwhile, the Voltage Source Converter (VSC) is able to convert the voltage and control active and reactive power. In this paper, the feasibility of a AC railway system based on Back-to-Back (BTB) VSC which is composed of a rectifier, a DC-DC converter, a inverter, has been proposed. A three-phase to single-phase BTB VSC is modeled. The proposed AC railway system based on BTB VSC is tested on Matlab/Simulink.