• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.103-104
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• 2006

Since the first proposition of IEC61850 object model at 1993, many questions about making a seamless model have been issued. the reason which they have worry about is that the functions of the equipment are supposed to be changed properly and new equipment and scheme are need to be introduced according to user's application. To handle those issues, TC57 which is a IEC committee for power control and communication has continuously updated the object model. Nowadays along with the new object model involving power quality, distribution resource and wind power, the committee has a plan to announce the revision of IEC61850-7-4. In the study, authors will present the prediction and diagnosis object models for transformer. Transformer models for protection and control have already been dealt with in the international standard but the models for prediction and diagnosis have never mentioned until now. Designing the prediction and diagnosis functions with the existing IEC61850-7-4, it'll be shown what is a proper object model for prediction and diagnosis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.445-447
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• 1997

In this paper a remote monitoring and control system using Modem for UPS (Uninterruptible Power Supply) is proposed. The conventional remote monitoring system for UPS is used to local remote monitoring system by RS232 or RS485 communication code. But recently. the system is changed to wide remote monitoring and control system using Modem for quick analysis of errors, correction of errors, report of errors and other user-friendly functions. In this study, we designed and develope system which is able to control UPS an monitor errors, statuses, actual values transmitted from UPSs of each site.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1374-1375
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• 2008

본 논문은 3상 일괄형 GIS의 부분방전 진단을 위해 새롭게 개발한 진단 알고리즘에 관한 것이다. 진단 알고리즘 개발을 위해, 먼저 실시간 부분방전 데이터를 행벡터 및 열벡터로 구성하고 각각의 벡터에서 통계 특징량 및 질감 특징량을 추출하였다. 다음으로 이들 특징량을 GA-NN(Genetic Algorithm - Neural Network) 학습에 적용하여 진단 알고리즘을 구성하였다. 또한 진단 알고리즘의 위상독립성은 부분방전 신호의 위상변화에 관계없이 진단결과가 일치하는 것을 확인함으로써 검증하였다. 개발한 진단알고리즘의 실증 평가를 위해, 부분방전이 발생되고 있는 국내 3상 일괄형 GIS 변전소에 적용하였다. 적용 결과, 위상에 관계없이 부분방전 발생원을 정확히 진단함을 확인하였고, 이를 통해 개발 알고리즘의 우수성을 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.369-371
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• 1999

A torque ripple minimization technique is proposed for high power induction motors driven by 3-level inverters with switching frequency of inverter switching elements limited around 500Hz level. It is noted that conventional DTC algorithms with torque ripple minimization scheme are devised for applications with relatively high switching frequency above 2-3kHz. A new DTC algorithm, especially for low switching frequency inverter system, illustrates relatively reduced torque ripple characteristics all over the operating speed region. Simulation results show effectiveness of the proposed control algorithm, and associated experimental works will be presented in the final paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.381-383
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• 1999

In this paper a remote monitoring and control system using SNMP(Simple Network Management Protocol) for UPS (Uninterruptible Power Supply) systems is proposed. The local remote system by RS-232 or RS-485 communication code or the wide remote system by modems is used for conventional remote monitoring & control system for UPSs. But recently because of communication cost and long distance the system is changed to remote control systems through internet and information communication network. And serial communication method by RS-232 or RS-485 is used between agent and UPSs. In this study. we designed and developed the system which is able to control UPSs and to monitor errors. statuses and actual values transmitted from UPS through internet.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2048-2050
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• 1998

An uninterruptible power supply(UPS) with parallel operation is used to increase the power capacity of the system or to secure higher reliability at critical loads. In the parallel operating system composed of the multiple UPSs, load-sharing, i.e. current balance control between them is key technique. Because of its low impedance and quick response characteristics, inverter output current changes very rapidly and thereby easily researches an overload condition. The difference between total load current divided by number of operating inverters and its own current is detected as unbalanced current. Then frequency and voltage are controlled to minimize the active component and the reactive component. A good performance of the proposed load-sharing technique is verified by experiments in the parallel operating system with two 40kVA UPSs.

• 대한조선학회논문집
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• 제49권6호
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• pp.484-490
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• 2012

Experiments of circulating water channel and two dimensional numerical simulations were performed to investigate the fluctuating characteristics of pressure in moonpool. Based on the quasi-two dimensional characteristics of pressure fluctuations disclosed by the spatial cross-correlations, the numerical results showed qualitatively good agreement with experimental data. Proper orthogonal decomposition was employed to the spatial distributions of pressure fluctuations in order to find the first and second modes of fluctuations. The first mode of pressure fluctuations showed that the fluctuating characteristics of pressure were related to the behaviors of vortical structures. The velocity fluctuations were conditionally averaged to make clear that the coherent structures were responsible for the pressure fluctuations in moonpool.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.351-353
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• 1999

In this paper, electric field analysis of 170kV class GCB is carried out. Considering the movement of arcing contacts during circuit interruption, electric field analysis between moving and fixed contacts is performed with changing the stroke length. From analysis results, electric field stresses are high at stationary arcing contact, moving arcing contact and varies at changing nozzle shapes. Specially, the stationary arcing contact shape has an significant effect on the capacitive small current interruption and the reduction of the electric field stress at this area is important. Varying the shape of stationary arcing contact, electric field analysis is carried out and the optimal shpae of the fixed arcing contact where the electric field stress is low is designed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.89-91
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• 1999

The performance of circuit interruption of $SF_6$ puffer cylinder type gas circuit breaker(GCB) has been evaluated from the results of electrical insulation strength which is depend on material property, such as $SF_6$ gas density in circuit breaker tank. In order to determine circuit breaker dimension in the safety criteria. electrical field analysis has been done by finite element method. Gas density of concerned area in the circuit breaker has been calculated. In order to predict small current break performance, Electrical field analysis result must be calculated based the results of density from cold flow dynamics. The proposed method has been carried out and evaluated for 362kV class high voltage GIS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.953-955
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• 2004

This paper describes the information transmission method using communication networks between Remote Terminal Unit(RTU) and Protection and Control system(PCU) of the direct current switchgear for Light Railway Vehicle, and also represents the test result, which carried out in the laboratory. In this test, transmission signal waveform, polling time, response time and request/response frame were measured between RTU and PCU. The field test including the measurements of analog signal and status of the digital logic operation of PCU will be conducted in near future.