• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.704-711
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• 2013

Data center is an information hub and resource for information-centric society. Since data center houses hundreds to ten thousands servers, networking and communication equipment, and supporting systems energy saving is one of the hottest issues for green data center. Among several solutions for green data center this paper introduces higher voltage direct current (DC) power feeding system. Contrary to legacy alternating current (AC) power feeding system equipped with Uninterruptible Power Supply (UPS), higher voltage DC power feeding system is reported to be a more energy efficient and reliable solution for green data center thanks to less AC/DC and DC/AC conversions. Main focus of this paper is on reliability issue for reliable and continuous operation of higher voltage DC power feeding system. We present different types of configuration of the power feeding systems according to the level of reliability. We analyze the reliability of the power feeding systems based on M/M/1/N+1/N+1 queueing model. Operation of the power feeding system in case of failure is also presented.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.369-371
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• 2002

The railway power feeding system is divided into AC power feeding system and DC power feeding system. In downtown area. DC power feeding system is used and AC power feeding system is used in intercity railway system. AC power feeding system raises a inductive disturbance that is divided into electrostatic induction and electromagnetic induction. Especially, it has a bad effect on communication lines. So inductive disturbance reduction method has been adopted in many system. In this paper, we deals with the inductive disturbance reduction method of railway power feeding system and of sides affected by inductive disturbance.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1137-1144
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• 2014

A parallel-feeding AC traction power system increases the power supply capacity and decreases voltage fluctuations, but the circulating power flow caused by the phase difference between the traction substations prevents the system from being widely used. A circuit analysis shows that the circulating power flow increases almost linearly as the phase difference increases, which adds extra load to the system and results in increased power dissipation and load unbalance. In this paper, we suggest a phase shifter for the parallel-feeding AC traction power system. The phase shifter regulates the phase difference and the circulating power flow by injecting quadrature voltage which can be obtained directly from the Scott-connection transformer in the traction substation. A case study involving the phase shifter applied to the traction power system of a Korean high-speed rail system shows that a three-level phase shifter can prevent circulating power flow while the phase difference between substations increases up to 12 degrees, mitigate the load unbalance, and reduce power dissipation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1621-1627
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• 2013

This paper compares power losses between voltage controlled before and after using power conversion device in AC feeding system. For this purpose we present voltage control procedures and criteria and model high speed line and train using PSCAD/EMTDC to compare power losses in various feeding condition. Power losses of the simulation result in power control before and after in single point feeding system was reduced maximum 0.37 MW(23.8 %) and average 0.23 MW(20.5 %) when one vehicle load operates maximum load condition. When three vehicles operate maximum load condition in one feeder section, power losses after voltage control was reduced 1.03 MW(49.5%) compared to before voltage control. And, power loss of parallel feeding system is reduced the average 0.08 MW(7.2 %) compared to the single feeding system. In conclusion, adaptive voltage control method using power conversion device can reduce power losses compared with existing method.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.272-273
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• 2015

This paper analyze scenario of feeder wire fault that occurs in the AC feeding system considering train position. The fault location of AC feeding system is calculated by measuring impedance. However, in this way, estimation error can be occurred because of tie connection, boosting current, etc. Therefore, it's hard to find fault location, so that it is required to detailed circuit analysis according to fault location. We analyze the short circuit impedance values with respect to feeder wire fault according to a train position. In this paper, PSCAD is used for modeling and analysis of AC railway feeding system.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.92-94
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• 2005

In this paper, when electric train is in dead-section the effect on electric train system was dealt. The feeding system of electrical railway is AC or DC. When the electric train is passed AC feeding system to DC, vice versa or phase is changed in between AC feeding systems, there is a dead section. A dead section usually makes the electrical system complex md may have an adverse effect on the electrical system inside the train. Accordingly, it is important to analyze the effect on trains in dead-section. Modeling an electric train and simulation using PSCAD/EMTDC was accomplished to analyze how power quality problem such as inverter switching surge is propagated to electric train through the feeding line, railway, pantograph.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.490-496
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• 2002

This paper presents exact Autotransformers(ATs)-fed AC electric Railroad system modeling using constant current mode far locomotives. An AC electric railroad system is rapidly changing single-phase load, and at a feeding substation, 3-phase electric power is transferred to paired directional single-phase electric power. As the train moves along a section of line between two adjacent ATs. The proposed AC electric railroad system modeling method considers the line self-impedances and mutual-impedances. The constant current mode model objectives are to calculate the catenary and rail voltages with the loop equation. When there are more than one train in the AC electric railroad system, the principle of superposition applies and the only difference between the system analyses for one train. Finally, this paper shows the general equation of an AC electric railroad system, and that equation has no relation with trains number, trains position, and feeding distance.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.9
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• pp.493-499
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• 2003

This paper presents exact Autotransformers(ATs)-fed AC electric Railroad system modeling using constant current mode for locomotives. An AC electric railroad system is rapidly changing single-phase load, and at a feeding substation, 3-phase electric power is transferred to paired directional single-phase electric power. As the train moves along a section of line between two adjacent ATs. The proposed AC electric railroad system modeling method considers the line self-impedances and mutual-impedances. The constant current mode model objectives are to calculate the catenary and rail voltages with the loop equation. When there are more than one train in the AC electric railroad system, the principle of superposition applies and the only difference between the system analyses for one train. Filially, this paper shows the general equation of an AC electric railroad system, and that equation has no relation with trains number, trains position, and feeding distance.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1248-1250
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• 2002

AC AT feeding system is possible to do the long distance feeding due to compensate the voltage drop. Nowaday this is a typical and efficient type all over the world in high speed train and heavy transport capacity. Normally a Auto-transformer is installed at regular internal (5 to 10km) between Substation and Sectioning post, this study is reviewed the voltage drop according to train movement and the optimal location of auto transformer, and provided the efficient feeding configuration.

• 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.