• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권6호
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• pp.431-440
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• 2000

This paper analyses the dynamic performance of HVDC System connected to a weak AC system for various exciter characteristics of synchronous machines connected at the converter bus. Conventionally capacitors are used to supply reactive power requirement at a strong converter bus. But the installation of synchronous machine is essential in a isolated weak network to re-start after a shutdown of HVDC and to increase system strength. The dynamic performance of a synchronous machine depends on the characteristics depends of its exciter. In this paper, several exciter types are used to investigate their effect on the dynamic performance of the HVDC system and modifications to standard exciter topologies are suggested to mitigate observed problems.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권9호
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• pp.562-568
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• 2004

The frequency and phase angle of the utility voltage are important in many industrial systems. In the three-phase system, they can be easily known by using the utility voltage vector. However, in the case of single phase system, there are some difficulties in detecting the information of utility voltage. In conventional system, the zero-crossing detection method is widely used, but could not obtain the information of utility voltage instantaneously. In this paper, the new digital PLL control using virtual two phase detector is proposed with a detailed analysis of single-phase digital PLL control for utility connected systems. The experimental results under various utility conditions are presented and demonstrate an excellent phase tracking capability in the single-phase grid-connected operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.612-614
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• 2005

국내 배전계통에 90년대 중반이후 초기에 도입된 외국산 및 국산 폴리머애자를 현장에서 발취하여 특성을 평가하였다. 외관 관찰, 하우징의 발수성 및 경도, 전기적 특성, 하우징 재질의 변화특성 둥을 시험 평가하였다. 평가 결과 하우징은 발수성이 상실되었으며 표면에 열화가 진행되었다. 그러나 애자의 성능은 양호한 것으로 나타났다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.97-98
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• 2006

디지털 보호계전기의 성능 검증은 정특성 성능 검증, 동 특성 성능 검증, 내 환경 성능 검증으로 나누어진다. 이 중 동특성 성능 검증에 대한 중요성이 증가하고 있으나, 실시간 디지털 시뮬레이터에 대한 접근의 어려움으로 인해서 해당 기술의 보급이 용이하지 않았다. 전력연구원에서는 이러한 점을 해결하고 관련 기술의 보급을 위해서 디지털 보호계전기 동특성 성능 검증의 기반을 마련하였으며, 이 기반은 성능 검증을 위한 계통 모델과 성능 검증 절차서로 각각 구성되어 있다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권4호
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• pp.174-179
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• 2002

In this paper, the modified simulation algorithms of the Auto Transformer (AT) feeding electric train system were proposed. To obtain terminal voltage of train by using equivalent circuit or the AT feeding system, the iterative method is proposed for which determine the train voltages. The train voltages are iteratively calculated from the system voltage drop and line impedance. In the carte study, the proposed method is verified from actual operation data of the Kwa-Chon line. Also it is verified that the proposed method can be extent to the multi-train simulation tool. The terminal voltage of the multi-train can be calculated by using superposition principle and it is easily applied to the proposed method. Therefore, the proposed method can be a solution for the complexity of the circuit analysis in the existing methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.319-321
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• 2001

When the fault occurred at distribution system, the restoration was late. There are 2 reasons The one is the error of fault location the other is multiple possible candidates of fault location. This paper presents two of new techniques for diagnosing fault regions. The proposed diagnosis scheme is capable of accurately identifying the location of fault upon its occurrence. based on the integration of information available from protective devices and measured load current change at the substation. In this paper expert system for real fault region is presented using these facts. Testing of the developed system using EMTP Simulation Model has demonstrated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 전문대학교육위원
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• pp.68-71
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• 2004

Frequency is an important operating parameter of a power system. Electric power systems sustain transient frequency swings whenever the balance between generation and load does not no longer hold. To cope with this Constraints, it requires an accurate and high speedy frequency deviation estimation technique and suitable adjustment to obtain the power system energy balance. This paper describes the design, computational aspects and implementation of an iterative technique for measuring power system. The rate change of the phase angle is used for estimation. To confirm the validity of the proposed algorithm, the simulation studies carried out on a typical 154[KV] double T/L system by using EMTP software. Some test results are presented in the paper.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1488-1495
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• 2002

The response time represents how fast a system responds to a given disturbance at the system boundary. Flow restricting devices for controlling transients can result in a decrease in the peakm pressure, but may change response time. Response lag in a hydraulic system leads to inefficient working cycle and operator discomfort. The experiments were conducted in order to get information on the parameters which exert appreciable influence on the response time. The experimental apparatu including a hydraulic actuator, orifice and a hydraulic pump was an idealization of a bucket hydraulic shifting system. Experimental results show that the response time depends on operating pressure and flow rate. The effects of orifice type and size on the response time are quantified.

• 대한기계학회논문집B
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• 제31권4호
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• pp.330-334
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• 2007

The objective of this study was to investigate the effecs of fouling mitigation for ceramic ball in cooling water system experimentally. The devices filled with ceramic balls were connected to the bypass line of the heat exchanging system. Cooling water in the heat exchanging system was artificial water. To visualize the formation of fouling on the heat transfer surface a number of images were obtained using a CCD camera with real-time microscopy. Fouling resistances and overall heat transfer coefficients were measured in order to analyze fouling mitigation effects. We found that the ceramic ball devices for artificial water reduced the formation of fouling compared to the no-mitigation devices.

• 대한기계학회논문집B
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• 제20권2호
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• pp.680-688
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• 1996

In this paper, the unsteady state calculational model is proposed for the thermal stratification analysis in the feedwater line of the PWR plant. By defining dimensionless parameters in the two-dimensional polar coordinate system and applying SIMPLE algorithm, the temperature and flow profiles due to the thermal stratification are obtained. Base on the fact that the most significant condition occurs when the fluid temperature difference between the piping ends reaches as high as 166.deg. C, the present result shows that max. Dimensionless temperature difference of 0.6 (about l00.deg. C) obtained between hot and cold sections of pipe wall at dimensionless time 47.0.