• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.105-108
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• 2000

The fundamental characteristics of the cavity-backed slot antenna at 2.45 GHz are analyzed with the method of moment for the use of a part of rectenna element. The proposed antenna has a rectangular-narrow slot on the upper surface and a feed post and a parasitic post inside of the cavity. The interior posts are perpendicular to the slot surface in order that the microwave circuits can be attached to the bottom of the cavity. Theoretical results shows that the maximum return loss of 50 dB at the input terminal of the antenna is achieved.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1589-1590
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• 2015

전기철도차량에 전기를 공급하는 가공 전차선로 시스템은 커티너리(catenary) 방식과 강체가선 방식으로 구분 할 수 있으며 강체가선 방식은 DC 급전구간에서 주로 사용하고 있는 T-bar 시스템과 AC 급전구간에서 주로 사용하는 R-bar 시스템으로 구분 할 수 있다. 최근 국내환경에 적합한 고속용 R-bar 시스템의 개발을 진행하고 있으며 여기에 필요한 브래킷 지지 및 절연용 장간애자와 동상구분을 위한 절연구분장치 개발을 진행하고 있다. 따라서 국내에 수입하여 적용하고 있는 저속, 고속 R-bar 시스템용 장간애자 및 절연구분장치의 성능기준을 확인하고 개발에 필요한 성능기준을 검토 적용하여 고속 R-bar 시스템용 장간애자 및 절연구분장치 개발을 진행할 예정이다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.485-490
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• 2012

Nowadays, in metropolitan railroad, DC feeding system is being generally applied. In order to reduce damage of electro-chemical corrosion caused by stray current and leakage current, in DC feeding system, rail is used as negative-polarity return conductor for traction load current. However, it has problem of rail potential increase and there are no adequate measures to prevent it in domestic. The rise of rail potential leads to damage for human and equipments. To solve the problems, this paper presents fundamental theory and related standards about rail potential increase. And then, we analyzed field testing data and simulated a variety of operations by using PSCAD/EMTDC as an analysis program of power system. In addition, this paper suggests rail potential limit device and addresses how to the device. To verify the effect, simulation of DC feeding system before and after the application of the device is carried out in various cases.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1479-1484
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• 2014

This paper deals with regenerative energy in railway system which one of the largest customer in terms of load capability. Unlike the other loads of power system, loads of railway systems change in time and space. It has a characteristic amount of generating regenerative energy by frequent starting and braking in railway system. Therefore, it is expected higher utilization in railway system than the other systems. The purpose of DC power supply simulation is analyzing backed energy, regenerative energy by each railway vehicle and substation. In this paper, regenerative energy utilization are analyzed using DC power supply simulation and it is performed changing major influence on the design such as the number of installing absorber, internal resistance value, no-load voltage value at substation or operating parameters at regenerative energy utilization. After simulating, results are compared and analyzed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.7
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• pp.1013-1018
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• 2014

This paper described the development of equalizing spacer for minimization of voltage drop according to DC feeder extension. Power consumption is increased as shorter interval of train driving time and transportation capacity increase in urban subway. Therefore we investigated voltage drop of catenary at a point in case of traction driving of a train in parallel to the DC power supply system. Based on it's result, equalizing spacer is designed and fabrication to minimize the voltage drop in accordance with the power supply line arranged in three rows, and then its performance was confirmed that the stress distribution of main body and the distributed load are satisfied through the body structure modeling.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1108-1114
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• 2016

The cause of failure in the AT feeding system is divided into grounding, short-circuit of feeding circuit and internal faults of the railway substation. Since the fault current is very high, real-time current is detected and the failure must be immediately removed. In this paper, a new DC offset elimination filter that can remove component to decrease in the form of exponential function using low-pass filter was proposed in order to extract the fundamental wave from distorted fault current. In order to confirm the performance of the proposed filter method, AT feeder system was modelled by simulation tool and simulations were performed under various conditions such as fault location, fault resistance and fault voltage phase angle in case of trolley-rail short-circuit fault. When applying the proposed DC-offset removal method, it can be seen that the phase delay and gain error did not appear.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.10
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• pp.563-570
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• 2003

When a fault occurs on railway feeders it is very important to detect the fault to protect trains and facilities. Because a DC railway system has low feeder voltage, The fault current can be smaller than the current of load starting. So it is important to discriminate between the small fault current and the load starting current. The load starting current increases step by step but the fault current increases at one time. So the type of $\Delta$I/ relay(50F) was developed using the different characteristics between the load starting current and the fault current. The load starting current increases step by step so the time constant of each step is much smaller than that of the fault current. First, to detect faults in DC railway systems, an algorithm using the time constant calculated by the method of least squares is presented in this paper. If a fault occurs on DC railway systems it is necessary to find a fault location to repair the faulted system as soon as possible. The second aim of the paper is to calculate the accurate fault location using Kirchhoff's voltage law.

• 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.12
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• pp.1964-1969
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• 2012

This paper presents to verify the selective grounding fault protective relaying technique for the ungrounded DC traction power supply system. This system selectively blocks fault section when grounding fault occurred. In order to perform this verification, field test facilities have been installed on Oesam substation and Worldcup-Stadium substation, and field test process has been suggested. Also, selective grounding fault protective relaying components and rail voltage reduction device have been tested with the various trial examinations. In order to compare and evaluate performance of the selective grounding fault protective relaying function, field test system was modeled and the system fault simulation results were compared and evaluated with the field test result. Performance of selective grounding fault protective relaying function was evaluated with the above-mentioned process, and the fact that the system recognizes fault section irrespective of insulation between rail and ground and fault resistance from grounding fault.

• 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.