• Proceedings of the KSR Conference
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• 2001.10a
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• pp.343-349
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• 2001

In this study we examined the method to estimate numerically the amount of the regenerated power and the excess regenerated power produced in the DC electric power supply system for the urban light rail transit system. And their economic feasibilities are also studied. For this study DC electric power supply system is simulated and the numerical analysis of the regenerated power and the excess regenerated power are conducted. The study result on the sample system shows that the facility to consume the excess regenerated power or the inverting equipment to reuse the excess regenerated power in the electric substation is feasible economically.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.412-417
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• 2004

In urban rail transit systems, ground faults in the DC traction power supply system are currently detected by the potential relay, 64P. Though it detects the fault it cannot identify the faulted region and therefore the faulted region could not be isolated properly. Therefore it could cause a power loss of the trains running on the healthy regions and the safety of the passengers in the trains could be affected adversely. Two new ground fault protective relay schemes that can identify the faulted region are presented in this paper. A current limiting device, called Device X, is newly introduced in both system, which enables large amount of ground fault current flow upon the positive line to ground fault. One type of the relaying schemes is called directional and differential ground fault protective relay which uses the current differential scheme in detecting the fault and uses the permissive signal from neighboring substation to identify the faulted region correctly. The other is called ground over current protective relay. It is similar to the ordinary over current relay but it measures the ground current at the device X not at the power feeding line, and it compares the current variation value to the ground current in Device X to identify the correct faulted line. Though both type of the relays have pros and cons and can identify the faulted region correctly, the ground over current protective relaying scheme has more advantages than the other.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4112-4118
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• 2011

Electrical Railroads provide electric power, which can operate vehicles, via feeder wires. And the supplied current returns to the transformer substation through lines and ground net. The return current, related to signal, power and power line, and track circuit systems, is one of the most important component in the electric railway. Therefore, to prevent system faults and breakdown according to unbalance and overcurrent of the return current, various and detailed analyses for the return current are needed. In the paper, we present measurement and analysis manners in real environment and evaluate its safety. For analysis, we utilize the measured values of return currents measured in track circuits in electric railway. we expect that this research plays a key role to the related fields.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1432-1438
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• 2011

This paper presents the simulation of traction power supply system for the evaluation of voltage drop in Kyungbu high speed line. This simulation is performed in circumstance of extended feeding through vicinity substation. Extended feeding should be considered from design of system. Therefore, voltage drop at extended feeding must be accepted against regulation. In this paper, voltage drop is evaluated under condition of extended feeding targeting section from Shinchungju and Pyungtaek S/S.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.216-218
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• 2017

The imbalance at the 3-phase side at the railway power supply substation has been a well-known issue. Due to the difference in status of loads at each phase at any given moment, it is difficult to maintain the balance in the 2-phase side of the transformer. Consequently, the 3-phase side also presents a certain level of imbalance as well. A co-phase power supply was proposed as a solution. The real application of such system is gradually expanding, proving the effectiveness of the system. In this paper, the application of the single phase D-Q rotating frame theory was applied to the control of the co-phase power supply system. In addition, the power stack of the system was composed of MMC valves, which offers superior operational characteristics. The effectiveness of the system was verified with a real-time simulation, and the results are presented.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.495-504
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• 2009

As the Reliability Centered Maintenance(RCM) is being studied, maintenance tasks can be performed effectively through the Risk Priority Number(RPN) evaluation about the components in the system. The RPN is usually calculated through arithmetical operations of three values, Severity, Occurrence, and Detection for each facility. This RPN provides information that includes risk level of the facility and the priority order of maintenance tasks for facility. However, if there is no sufficient historical failure data, it is difficult to calculate the RPN. In this case, historical failure data from other sources can be used and apply this data to korean railway system. In this paper, it is proposed that a new methodology to model the failure rate as a fuzzy membership function. This method is based on failure data from other sources by means of the fuzzy theory and the expert opinion system. And considering assessment tendency of each expert, distortions that happened when the failure rate of facilities is estimated were minimized. This results determine Occurrence values of facilities. Taking advantage of this result., the RPN can be calculated with Severity and Detection of facilities by using the fuzzy operation. The proposed method is applied the rail-way power substation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1053-1058
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• 2013

Because of computational burden and complex topology of substation, a transmission overload relief using circuit-breaker switching was very complex and difficult. However, a on-line algorithm for reducing the overloads in transmission lines has made progress due to the advance of IT technology. This paper describes the methodology for alleviating the overloads in transmission lines by circuit-breaker switching. First, the severe contingency lists and substations were selected from the results of contingency analysis. Then the switch combinations are determined using circuit-breakers of the selected substation. The topology changes are limited to equipment outage, bus split, island split, bus merge and island merge. Finally, the fast screening and full analysis methods are used to analyze the overload in transmission lines. To verify the performance of the proposed methodology, we performed a comprehensive test for both test system and large-scale power systems. The results of these tests showed that the proposed methodology can accurately alleviate the overloads in transmission lines from online data and can be applied to on-line applications.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.816-823
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• 2007

Electric car tract plays the role of supply high electric power to the electric car from the substation by using Pantograph of the electric car. It is always exposed to the external atmosphere, which results in quite substantial fluctuations in current and voltage during operation of electric car. This generates possibility of occurrence of accident at all times. Since range of wiring metallic globe installed on the catenary cannot achieve complete electrical contact, accidents are occurring due to circulating current caused by arc caused by incomplete contact due to occurrence of hairline fracture of Pantograph due to pressure or vibration of wiring. Furthermore, rapid increase in the operational current due to increase in the operational frequency of the electric car is causing erosion and short circuit of the metallic globe at the contact points. This study on arc is generated as current transmitted out of the substation courses through power line or wiring metallic globe other than the main circuit as the current is being collected at the electric car through feeder and feeder divergence device. Accordingly, since heat generated by the arc becomes the cause for generation of circulating current due to melting of metal or softening of metal due to increase in temperature accompanying increase in contact resistance, this research shall describe causes and measures against occurrence of circulation current.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.406-410
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• 2009

Power facilities of urban rail transit substation is deterioration, and endurance limitation is coming, so urban rail transit facilities should take any necessary measure for maintenance and repair. In this paper proposes online monitoring system using the wireless communications for the urban rail transit. This system is constructed various departments; such as sensor, measurement, data communication, host computer, and power departments. It is designed to collect and save AI (Analog Input) information of the power facilities, and to analyze and display them. As a result, it is possible to prevent from any unexpected power cuts and monitor my abnormalities in real time, and to collect accumulated data for creating a better management system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1810-1817
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• 2015

The railway vehicle has an auxiliary power unit for supplying power to the associated electronic control devices and passenger service unit. Typically, input voltage from the catenary for rolling stock is highly fluctuating according to the substation capacity, vehicle propulsion and regeneration. Especially, the frost and freezing on contact wire in winter can cause a blackout inside vehicle, and also brings about electronic components damaging and the system down. To prevent this problem, a large filter and capacitor is used. But this is not a perfect solution, because it is increasing weight of the unit. In this paper, a new algorithm is proposed to suppress the disturbance without adding devices. Simulation and experimental results show that the proposed algorithm has performance to suppress the disturbance at the sudden input voltage variations.