• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.250-254
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• 2016

Currently, power conversion system which converts AC to DC Power is applied in domestic urban railway. The diode rectifier is used in most of them. However the diode rectifier can not control the output voltage and can not regenerate power as well. On the other hand, PWM (pulse width modulation) converter using IGBT (isolated gate bipolar transistor) can control output voltage, allowing it to reduce the output voltage drop. Moreover the Bi-directional conduction regenerates power which does not require additional device for power regeneration control. This paper compared the simulation results for the DC power supply system on both the diode rectifier and the PWM converter. Under the same load condition, simulation circuit for each power supply system was constructed with the PSIM (performance simulation and modeling tool) software. The load condition was set according to the resistance value of the currently operating impedance of light rail line, and the line impedance was set according to the distance of each substations. The train was set using a passive resistor. PI (proportional integral) controller was applied to regulate the output voltage. PSIM simulation was conducted to verify that the PWM Converter was more efficient than the diode rectifier in DC Traction power supply system.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.185-189
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• 2008

D.C. traction systems can cause stray currents which could adversely affect both the railway concerned and outside installations, when the return circuit is not sufficiently insulated versus earth. As experience for several decades has not shown evident corrosion effects from a.c. traction systems and actual investigations are not completed, stary currents flowing from a d.c. traction system is issued. D.C. traction systems can cause stray currents can be corrosion and subsequent damage of metallic structures, where stray currents leave the metallic structures. There is also the risk of overheating, arcing and fire and subsequent danger to persons and equipment. Any provision employed to control the effects of stray currents be checked, verified and validated. Direct measurement of stray current is difficult and a provision employed to control the effects of stray currents is proposed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.9
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• pp.427-433
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• 2005

In DC tracking power supply system, ground faults are currently detected by the potential relay, 64P. Though 64P relay detects ground fault, it cannot Identify the faulted region which causes long traffic delays and safety problem to passengers. Two new ground fault protective relay schemes that can identify the faulted region are presented in this paper. One is bus differential protective relay and the other is ground overcurrent protective relay. Both type of relays is similar in principle to the ordinary bus differential protective relay and the ground overcurrent relay used in other power system. In DC traction power supply system, since it is ungrounded, ground fault current is not big enough to operate those relays. To solve the problem, a current control 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. Algorithms for these relays are developed and their validity are verified by EMTP simulation.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.212-214
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• 2007

Regenerative energy which is generated during brake periods of DC traction might cause malfunction or destruction of rectifier or any other power conversion devices caused the increment of DC line voltage. Regenerative energy storage system using super-capacitor is one of the method to control the DC line voltage safely. And super-capacitor is very important device as energy storage device. Therefore, In this paper, we designed the regenerative energy storage system using super-capacitor and propose the method about predicting the lifetime of super-capacitor established in storage system. According to the this research, we can estimate the proper replacement moment for the existed super-capacitor due to the safety of the system. And improve the reliability of regenerative energy storage system using super-capacitor.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.12
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• pp.529-535
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• 2006

In DC tracking power supply system, ground faults are currently detected by the potential relay, 64P. Though 64P relay detects ground fault, it cannot identify the faulted region which causes long traffic delays and safety problem to passengers. A new ground fault protective relay scheme, ${\Delta}I$ ground fault protective relay, that can identify the faulted region is presented in this paper. In ${\Delta}I$ ground fault protective relaying scheme, ground fault is detected by 59, overvoltage relay, which operates ground switch installed between the negative bus and the ground. It preliminarily chooses the faulted feeder after comparing the current increases among feeders and trips the corresponding feeder breaker. After some time delay, it then recloses the breaker if it finds the preselected feeder is not the actual faulted feeder. Whether or not the preselected feeder is the actual faulted feeder is determined by checking the breaker trip status in the neighboring substation in the direction of the tripped breaker. If the corresponding breaker in the neighboring substation is also tripped, it finally judges the preselected feeder is actually a faulted feeder. Otherwise it recloses the tripped breaker. Its algorithms is presented and verified by EMTP simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.1056-1060
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• 2012

Online monitoring system is becoming an essential element of railway traction system for utilized to condition based malignance management and various techniques currently employed in railway traction system. Among the various techniques, it is efficient to detect partial discharge signals by electromagnetic wave detection in order to detect insulation fault of rectifier. Although VHF (Very High Frequency), UHF (Ultra High Frequency) sensors were adopted to detect partial discharge of power facilities, due to characteristics of urban railway, excessive noise occurs from 500 MHz to 1.5 GHz on UHF bandwidth. In this paper a new measurement system able to monitoring the conditions of power facilities on DC substation in metro was studied and set up. The system uses UHF sensors to measure the partial discharge of the rectifier due to electric faulting and dielectric breakdown. Comparison and estimation for performance of SHF sensor which had devised to detect partial discharge signal of urban railway rectifier has conducted. In order to estimate performance of SHF sensor, we have compared the sensor with existing UHF sensor on sensitivity upon frequency bandwidth generated by pulse generator, and also we have verified performance of the SHF sensor by detection results of partial discharge signal from urban railway rectifier.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.247-251
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• 2006

The traction DC feeder cable is one of the key devices for the safety operation of subway system, but for low voltage DC feeder cable (<3000 V) for subway, little attention has been paid by investigators on its online monitoring technology. With an introduction of cable laying and operation environment for the cable, this paper investigated the on-line monitoring technology of 1500 V DC feeder cable of subway. Firstly, in the text, the fault model of 1500 V DC cable was proposed based on the analysis of the fault type of the DC feeder cable, and then put forward synthetically on-line monitoring discharge signal and DC leakage current signal to assess DC feeder cable insulating state. The results of laboratory experiment prove that the proposed methods are feasible and can be implemented on-line monitor on DC feeder cable of subway.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.335-342
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• 2001

The problems in the loadflow study of the fixed voltage DC traction power supply system including the regeneration power is analyzed. And the computer algorithm to avoid the problem is developed. A computer program using the developed algorithm was developed. A test run of the computer program is conducted and the result shows the algorithm and the program developed is very effective for the loadflow study of the system including the regeneration power.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.322-328
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• 2001

In the electric railway systems, it is very important that we should design the system configuration, location and power capacity of substation. This paper presents the results of system configuration and system design of the DC traction power supply for the test line of Light Rail Vehicle. The voltage fluctuation of train and the power capacity of substation are calculated by computer simulation using the nodal equation, K.C.L／K.V.L, Ohm's law and superposition theory.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.548-551
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• 2000

The battery charger for high speed trail car is very important power source for the purpose of safty and system stability. it provides control power of VVVF, CVCF, DC/DC converter and inverter for traction motor. This paper included power circuit of the ZVZCS type battery charger for high speed trail car and battery included power circuit of the ZVZCS type battery charger for high speed trail car and inverter for traction motor. This paper included power circuit of the ZVZCS type battery charger for high speed trail car an battery charging algorithm. Also the optimum parallel operation of 50Kw battery charger for high speed trail car and charging control method of Ni-Cd battery illustrates validity and effectiveness through the experiments.