• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.534-539
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• 2015

The DC overhead line voltage of an electric railway substation swings depending on the accelerating and regenerative-braking energy of trains, and it deteriorates the energy quality of the electric facility in the DC railway substation and restricts the powering and braking performance of subway trains. Recently, an energy storage system or a regenerative inverter has been introduced into railway traction substations to diminish both the variance of the overhead line voltage and the peak power consumption. In this study, the variance of the overhead line voltage in a DC railway substation is modelled by RC parallel circuits in each feeder, and the RC parameters are estimated using the recursive least mean square (RLMS) scheme. The forgetting factor values for the RLMS are selected using simulated annealing optimization, and the modelling scheme of the overhead line voltage variation is evaluated through raw data measured in a downtown railway substation.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1193-1198
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• 2004

This paper describes the lightning protection system for railway signaling equipments installed at subway car depots in Seoul metropolitan Rapid Transit Cooperation. Several measures for improving lightning protection performance are adopted; newly organized grounding system for neutral line of power system, rolling method to minimize damages induced by direct lightning strike, new measures to reduce voltage differences between the signaling equipments and the ground, and improvement of grounding system. The proposed system has greatly reduced the grounding resistance and also the voltage difference between the signaling equipments and the ground, and has prevented the accident related with lightning surges since it was installed. The proposed approach can be viewed as a useful alternative of dealing with lightning protection for railway signaling equipments.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.516-518
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• 1995

This paper presents an integrated fault diagnosis expert system for power systems. The proposed system diagnoses various faults occurred in both substations and transmission lines even in the case that substation fault is spreaded over the network. To cope with this problem, A meta-inference method is proposed. This scheme shares same the data structure with the pre-developed intelligent operational aid expert system installed in a practical sub-control center, without modification. This advanced integrated diagnosis system is developed using a low cost personal computer owing to the special modular programming technique. Case studies show a promising possibility of the proposed method.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.595-600
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• 2007

Greater expansion and more frequent operation of the railroad transportation system anticipated due to its characteristics including low cost, safety and mass transportation. Recently, effects on the railway structures due to expansion of newly constructed road, construction of subway, city gas pipeline, communication network, electric power network and construction of other railway underground crossing in accordance with urban planning and organization has influenced safe operation of trains. Accordingly, standard for selection of construction method that will enable construction of more economical and rational subway underground crossing structures by preventing problems occurring at the time of above construction works and accidents in safe operation of trains due to construction in advance is definitively necessary. Although there are numerous construction methods that can be applied at the time of construction of railway underground crossing, there are much difficulties in selection of appropriate construction method that considers characteristics of each construction method on non-excavation type construction method, train operation plan of number of operational routes and on-site circumstances. Therefore, this research aims to present rational standard for selection of construction method for such, and standard for slowdown speed and interception of train when passing the areas of slowdown in sectors under construction.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.257-262
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• 2003

Now, the population and economical power is deeply concentrated to Seoul-metropolitan region, therefoere the provinces is so lagging behind and the country cannot get balance development. And, like metropolitan region, the more outer the living area of local wide-area city is spreading, the more serious wide-region transportation problems are. But the railroads near wide-area city fun seldom commuter train, so they cannot absorb the transportation demand of wide-area city metropolitan region. To solve above transportation problem, local wide- area cities try to make a subway or a light rail transit. But it is so difficult because the limit of public finance and original small capacity of light rail. In the paper, I propose 'Local city wide-area electric railways' system of the consortium of 'Local wide-city and province transportation union', Korean National Railroad (KNR) and local capital. A 'Local wide-city and province transportation union' operates commuter railways directly using the facilities of KNR, and local capital invests to the stations of above railways system. Therefore the commuter railway system around local wide-city region will be constructed quickly and the stations will be the strong point of local development and investment.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1370-1376
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• 2008

The structure of railroad or subway is that low fare transportation system of the large traffic volume. Like this structure is subjected to the cyclic load of moving vehicle. Consequently the result of the settlement analysis or plastic deformation prediction of railroad bed could be used as an important factor in safety of the railroad. The results of cyclic triaxial test were used in the numerical analysis of power model which Li and Selig(1994) developed. The soil samples were obtained from the construction site of railroad. Cyclic triaxial test was conducted with the variation of the magnitude of cyclic load and soil types. The large magnitude of plastic deformation in the railroad bed is caused of structure failure of the railroad.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1607-1609
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• 2005

This paper presents capability calculation methods for regenerative inverter in DC electrified transit system. The proposed method uses a train performance and power simulation tool to calculate the regenerative power generated in the DC substation and decide the capability of regenerative inverter. The capability of regenerative inverters for Seoul subway line 5, 6, 7, and 8 has been calculated.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.767-775
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• 2005

Power Supply System for electric railways is diversified with technical development and is required high technologies. especially, recently there is required many research and development for earthing to ensure safety of people and protection of installations. Generally, leakage resistance is high between rail and ground at tunnel section of subway. because of short circuit of feeding line, earthing interference by transient overvoltage between signals and communication system, and insulation failure, it can damage to human and equipments To minimize these obstacles, earthing equipment is installed at underground section of railway, but it brings about problems in accordance with operate each earthing system to be not enough required protection provisions for electrified railways. This paper proposes effective earthing method to be concerned about installation cost and maintenance. The validity of the proposed earth method is verified by simulation results at underground section of railways.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1159-1162
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• 1998

The induced voltage of underground pipelines caused by the stray current not only do harm to workers and instruments. but also cause big accident such as gas explosion. The AC stray current is mainly produced by the grounding system of the 22.9kV distribution power system and the DC stray current is mainly produced by the subway system. The mechanism of AC and DC induction, stray current failure examples of domestic and foreign countries and the countermeasure of the AC and DC induction are described.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.197-202
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• 2023

This paper presents the design method and electrical characteristics of a high-efficiency power amplifier for a 50 Watts class repeater applied to a 5G system and used in in-building, subway, and tunnel. GaN was used for the termination transistor of the power amplifier designed here, and intermodulation signals were removed using DPD to satisfy linearity. In addition, in order to handle various requirements such as amplifier gain control and alarm processing required in the 5G system, the microprocessor is designed to exist inside the power amplifier. The amplifier manufactured to confirm the electrical performance of the power amplifier satisfying these conditions satisfied 46.5 dBm and the overall efficiency of the amplifier was 37%, and it was confirmed that it satisfied various alarm conditions and electrical characteristics required by telecommunication companies.