• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.26-26
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• 2010

Line to ground faults or lightning strikes in electrical power systems produce high frequency overvoltages. With this reason, a wide band analysis of the ground impedance is necessary. In the paper, design of a wideband ground impedance meter which can measure the ground impedance in ranges from 65 Hz to 1.5 MHz is described. Also, a noise elimination method by a digital band-pass filter during measurement is proposed. The maximum measurement error of the meter is estimated 3 % in full ranges.

• Proceedings of the KSR Conference
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.329-334
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• 2001

This paper presents exact autotransformer-fed AC electric railroad system modeling using constant current mode. The theory is based on the solution of algebraic. The proposed modeling is considered the line self-impedances and mutual-impedances. Besides, the load modeling improved results are obtained as application to the proposed constant current mode. In the analysis on AT-fed AC electric railroad system circuit, a generalized analysis method using the loop equation on a case by case. the simulation objectives are to calculate the catenary and rail voltages with respect to ground, as the train moves along a section of line between two adjacent ATs. The model contains assumptions regarding the representation of the autotransformer, the impedance of the track/catenary system, and the grounding arrangements, which all effect the accuracy of the result. The modeling results seem very reasonable. It is established that techniques for the AC electric railroad system modeling and analysis.

• Proceedings of the KSR Conference
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.704-711
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• 2000

This study is carried out using a circuit model approach. First, the self and shunt impedances of all the conductors in the rail system and the mutual impedances between different conductors are computed. Then, a circuit representing the both rail systems at interfaces including the rails, feeders, protection wires, contact wires, ground wires is built. Auto-transformers in the system are also represented in the circuit model. The circuit model is then 1]recessed using a circuit solver based on a double-elimination method. Several different scenarios are analyzed, including the load conditions and a few fault conditions with different fault locations. The effect of the buried ground wires is also analyzed by comparing the results with and without the presence of the ground wires. The analysis procedure presented in the paper demonstrated an accurate way of computing fault current distribution and EMC at interfaces between both systems. The results presented in the paper can be used as a reference for estimating interference levels in similar rail systems.

• Proceedings of the KIEE Conference
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• 대한전기학회 2004년도 추계학술대회 논문집 전기설비전문위원
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• pp.127-133
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• 2004

접지도체의 굵기를 결정하는 국외 규격은 재료의 특성값인 물리적 정수까지 적용하여 광범위하게 적용할 수 있는 반면 수식이 복잡한 문제점이 있고 JIS와 국내규격은 수식은 간단하나 제약조건이 많은 문제점이 있다. 또한, 접지도체의 접속방법에 따라 최대허용온도가 다르게 적용되므로 접지도체 굵기 산정 방식이 복잡하고 적용 방법이 상이하여 시공현장에서 엔지니어들이 적용하는데 많은 어려움이 있다. 따라서, 본 논문에서는 새로운 접지도체 굵기 산정방식을 제시하고 접속방법에 따른 접지도체 굵기 산정 간이식을 제시한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제61권6호
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• pp.910-915
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• 2012

In this paper we propose multi-grounded neutral design method which was considered of transferred transient overvoltage when line to neutral fault occurs. Specially, In order to confirm the actual transient overvoltage magnitude which occurs on neutral line, we considered some screening(shielding) effects. The screening coefficient was deducted from field test results and calculation in a distribution line which is identical with an actual power line. The purpose of this paper is to attempt to suggest the guidance for grounding skystem design considering limitation of overvoltage for LV side in IEC 61936. The result is based on EMTP simulation and real field faults situation in distribution lines.

• Proceedings of the KIEE Conference
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2106-2107
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• 2008

이 논문은 국내 저압접지방식의 현장적용화를 위한 실증시험장 구축과 실증시험의 검증을 위한 시뮬레이션 환경 구축에 관한 논문이다. 외함접지방식에 의존하고 있는 국내 저압접지방식은 IEC에서 제안하고 있는 접지방식에 비하여 낙후되어 있고, 이에 대한 증거로서 선진국에 비하여 십수배에 달하는 감전사고 발생을 들 수 있다. 이러한 국내 실정을 극복하고자, IEC저압접지방식에 대한 실증시험장 구축을 목적하고 있으며, 그에 대한 일환으로 실증시험 검증용 시뮬레이션 환경 구축을 수행하고 있다. 본 논문은 TN-S 방식의 접지방식으로 구성된 배전계통을 PSCAD/EMTDC를 이용하여 모델링하고, 도체-외함-접지의 동시지락을 모의함으로서 외함도체의 전위상승과 감전사고의 발생 가능성을 모의하였다.

• Journal of Ocean Engineering and Technology
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• 제18권1호
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• pp.41-46
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• 2004

This paper describes a study on the tearing damage of a ship's bottom plating, during a grounding. It is widely known that different scaling laws are applied for bodies undergoing simultaneous plastic flow and crack propagation in the deformation of plate tearing. Specifically, the basic scaling law is not followed for the fracture. In this study, in order to verify the problem, plate cutting experiments for geometrically similar models have been performed. From the experimental results, it has been observed that the cutting forces and energy for the larger models are significantly lower than those of the smaller models. A simplified analytical method for the estimation of tearing is proposed, based on the experiments. It has been observed that the results of the present formula are highly correlated with the experiments.

• Corrosion Science and Technology
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• 제6권2호
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• pp.77-81
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• 2007

Fault current can be discharged from power transmission tower due to lightning or inadvertent contact of crane, etc. Pipelines in proximity to either the source of the ground fault or the substation grounding grid may provide convenient conductive path for the fault current to travel. Inappropriate measures to the neighboring pipelines against the fault current may cause severe damages to the pipes such as coating breakdown, arc burn, puncture, loss in wall thickness, or brittle heat-affected zone. Like inductive and conductive AC coupling, steadily induced fault current right after the coating breakdown can lead to corrosion of the pipeline. In this work, some protection guidelines against fault currents used in the field have been validated through the simulation and analytical method.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.66-76
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• 2017

This paper is concerned with investigating the plastic material properties of steel plate formed by line heating method, and is aimed at implementing more rational design considering the accidental limit states such as collision or grounding. For the present study, line heating test for marine grade steel plate has been carried out with varying plate thickness and heating speed, and then microscopic examination and tensile test have been carried out. From the microscopic, it is found that the grain refined zones like ferrite and pearlite are formed all around the heat affected zone. From the tensile test results, it is seen that yield strength, tensile strength, fracture strain, hardening exponent and strength coefficient vary with plate thickness and heat input quantity. The formulae relating the material properties and heat input parameter should be, therefore, derived for the design purpose considering the accidental impact loading. This paper ends with describing the extension of the present study.

• Journal of Industrial Technology
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• 제27권B호
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• pp.9-14
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• 2007

In this paper, four types of igniters were modeled and their characteristics were researched. And then we analyzed and experimented the effect on the control IC operation in this system. Due to the high ignition voltage, the DC power line on control IC is contaminated with the impulsive noise voltage. So the control IC operation is stopped. Therefore we have found that contamination of DC power noise is reduced by shielding, grounding pattern, and filtering method. We showed that the experimental results are agreed with the theoritical value obtained by the four types of ignitor models.