• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.191-193
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• 2008

This paper describes a compact Iron-cored Electronic Current Transformer(ECT) based on IEC 61850. The ECT developed in this study has the feature of designing the current transformer with a compact iron-core, compensating error due to the nonlinear characteristic of Iron-core, and applying IEC 61850 9-2 for sampled value(SMV). We verify the performance of the innovative product developed in the study in KERI and test the performance of digital communication in the lab.

• Journal of computational fluids engineering
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• v.5 no.3
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• pp.40-46
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• 2000

Natural convection in a wide-gap horizontal annulus is considered, and the transition of flows from steady to oscillatory convection is investigated for the fluid with Pr=0.1. The unsteady streamfunction-vorticity equation is solved with finite difference method. As Rayleigh number is increased, the steady crescent-shaped flow bifurcates to a time-periodic flow with like-rotating eddies. And afterwards, a transition to an oscillatory multicellular flow with a counter-rotating eddy on the top of the annulus occurs. A transition from steady to an oscillatory flow occurs, but dual solutions and hysteresis phenomena are not observed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.442_443
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• 2009

A large wind farm should satisfy the requirements for a grid and accomplish the optimization of the wind farm system. In that point of view, the wind farm intertie protection system, which must consider the Fault Ride-Through (FRT) requirement for more reliable protection, should be improved. This paper proposes a modified distance relay suitable for protection of a wind farm intertie considering a FRT requirement. The frequency change is used to discriminate the intertie fault from a outside zone fault. The performance of the proposed algorithm is verified using a PSCAD/EMTDC simulator.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.342_343
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• 2009

This paper describes a compact Iron-cored Electronic Current Transformer(ECT) based on IEC 61850 9-2. The ECT developed in this study has the feature of designing the current transformer with compact iron-core, compensating error due to the nonlinear characteristic of iron-core, and applying IEC 61850 9-2 for sampled value(SMV). We test the performance of the product developed in the study in KERI, KEPRI.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.42_43
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• 2009

Ferroresonance is a resonance condition between a nonlinear iron core of a potential transformer (PT) and a capacitance. It can lead to PT voltages several times the normal equipment ratings, and cause the isolation broken and damage to equipments near the PT. This paper proposes a analysis method of PT ferroresonance in the time domain. Based on the simplified equivalent circuit, a differential equation was found and the flux was calculated when ferroresonance generates. The forced response and natural response were also analyzed. The performance of proposed analysis method was verified with the EMTP-RV generated data. The method can help analysis chaotic ferroresonance and periodic ferroresonance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.645-650
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• 2007

This paper proposes a parameter estimation technique of a power transformer. Based on the combined equation, it estimates separately the primary and secondary leakage inductances using the least square method from the instantaneous voltages and currents in the steady state. The performance of the proposed technique was investigated by varying the cut-off frequency of the filter and the number of samples per cycle. The estimated values are obtained based on the average value for 41 cycle.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.09a
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• pp.137-143
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• 1995

현 전력 시스템 및 전기 전자 시스템의 대용량 단락 설비의 대형화에 따른 부수적인 시스템 구성을 초전도체 화이버를 이용하여 전력 손실과 빠른 차 단 시간을 가지는 차단기가 절대적으로 요구되고 있으며, 본 연구는 초전도 선재가 시스템에 코일로 구성하였을 때 자체에서 흐를수 있는 전류의 양을 검출하여 수치화하여 일반적인 전류계로써의 특징과 오실로스코프의 나타난 파형으로 시스템 자체에서 발생하는 이상 현상을 검색하여 시스템의 여러가 지 현상을 파악하고 또한 폐회로를 구성하여 계기의 부하로 인한 사고를 방 지하기 위하여 내부에 환 코일을 장착하여 단선되는 것을 방지하고 일정 전 류 이상이 되면 초전도체 화이버 자체가 trigger코일로 작동하여 전체 시스 템을 보호하고 전류제한장치의 개발 초기에 적용 가능한 평가 모델을 설계 구현하였다.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.580-587
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• 1995

In order to produce the bacteriolytic enzyme, bacterial strains capable of excreting a large amount of the enzyme were screened from the coastal sea water samples in Pusan. The bacterial strain SH-1, which showed the highest activity among 43 bacteriolytic enzyme producing bacteria, was finally selected for further studies. The strain SH-1 was an endospore-forming grampositive rod, and the position of spore was paracentral. These morphological characteristics assigned the isolated strain to the morphological group I classified by Gordon. The fatty acid composition of the bacterial stain was analyzed to be consisted of branched chains of iso-Cn and anteiso-Cn. Based on the percent content of the branched chain (93.85%), the isolates could be identified as a species of Bacillus. According to the experimental results of the API system (API 50CHB & API 20E) the strain was identified as Bacillus subtilis. Numerical texonomy, in which 82 major characters were examined using several species of Bacillus as the standard bacteria, indicated that the strain SH-1 showed 90% similarity to Bacillus subtilis. Thus, the isolated strain SH-1 could be identified as Bacillus subtilis.

• Journal of the Korean Institute of Educational Facilities
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• v.11 no.1
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• pp.15-23
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• 2004

Deterioration of the educational facilities built before 1985 is a serious situation. The purpose of this study is to present the efficient remodeling method of old educational facilities. This paper, part III, presents the systemic and synthetic judgment method of deterioration grade of finished materials. Evaluation of the deterioration is carried out in every eight classrooms or building elements divided by the use. And classrooms are divided by several parts for example floor, wall and ceiling etc.. The whole deterioration of the building judges the result of every part collectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.281-284
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• 1997

In this paper, the eddy current flow meter with 4-coil group is designed and made on the basis of theory, and its characteristics is considered through dry test flow experiments. The biggest output signal varied with wave form and frequency, and 900Hz in rectangular wave, 27.12kHz in sine wave. The conductivity is bigger, the output signal is bigger and has a linearity between both relation, and also The Magnetic Reynolds Number and output characteristics. The flow faster and the output singnal is bigger.