• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.455-457
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• 2004

An accurate digital distance relaying algorithm which is immune to reactance effect of the fault resistance and the load current for phase-to-phase short fault in 765kV untransposed transmission lines is proposed. The algorithm can estimate adaptively the impedance to a fault point independent of the fault resistance. To compensate the magnitude and phase of the apparent impedance, this algorithm uses the angle of an impedance deviation vector. The impedance correction algorithm for phase-to-phase short fault uses a voltage equation at fault point to compensate the fault current at fault point. A series of tests using EMTP output data in a 765kv untransposed transmission lines have proved the accuracy and effectiveness of the proposed algorithm.

• 한국음향학회지
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• 제13권2호
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• pp.23-29
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• 1994

본 논문에서는 원통형 압전 진동체에 대한 수중 방사 임피던스를 유한 배플 구조에서의 측정 결과와 무한 배플 구조에서의 이론 결과를 비교하여 방사 임피던스에 대한 배플의 영향을 규명하였다. 배플의 길이가 증가할수록 방사 임피던스의 측정치는 무한 배플에서의 이론치에 접하하며, 배플의 영항은 방사저항에서 보다 방사 리액턴스에서 더 지배적 임을 보인다. 따라서 음향 변환기의 설계시 무한 배플 구조에서의 방사 임피던스 이론 결과를 적용하기 위해서는 배플길이에 따른 임피던스의 보상이 수행되어야 한다.

• 한국콘텐츠학회논문지
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• 제20권8호
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• pp.653-665
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• 2020

추천 에이전트의 활용이 활발해지면서 사용자에게 내부 논리를 설명할 수 없던 블랙박스 문제를 해결하는 방법으로 '설명 기능'이 주목을 받고 있다. 본 연구는 '설명 기능'의 유무에 따른 사용자 경험을 살펴보는 것에서 한 걸음 더 나아가 설명 방식과 상세도에 따라 어떠한 영향이 있는지 살펴보고자 한다. 설명 방식은 '에이전트가 특정 행동을 한 이유'를 설명하는 why 방식과 '특정 행동을 하지 않는 이유'를 설명하는 why not 방식으로 구분하였으며 상세도 조건은 상세도 높음/상세도 낮음으로 구분하였다. 연구 결과 why 설명 방식이 사용자의 투명성, 신뢰도, 만족도, 재사용 행동 의도에 긍정적인 영향을 주는 것을 발견하였으며, 상세도가 높을수록 심리적 반발에 대한 인식이 높아진다는 것을 확인하였다. 또한, 설명 방식과 상세도는 상호작용을 통해 '설명' 인식에 영향을 주었으며, 만족도와 추천 수용 의도에 영향을 준다는 경향성이 발견되었다. 본 연구는 사용자 경험에 긍정적인 영향을 주는 설명 방식과 적절한 상세도에 대해서 시사점을 제시하였으며, 설명 방식과 상세도의 상호작용을 통해 사용자 경험에 영향을 준다는 연구 결과를 통해, 추천 에이전트 맥락에서 설명 기능의 방식과 상세도를 결정하기 위해서는 세심한 주의가 필요하다는 제안을 하였다.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2083-2088
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• 2015

The transient characteristics of the tri-axial High Temperature Superconducting (HTS) power cable are different from those of a conventional power cable depending on whether the cable is under a steady or transient state due to the quench. Verification using simulation tools is required to confirm both the characteristics of the cable and the effect of the cable when it is applied to a real utility. However, a component for the cable has not been provided in simulation tools; thus the RTDS-based model component of the tri-axial HTS power cable was developed, and a simulation was performed under the transient state. The considered properties of model component include resistance, reactance and temperature. Simulation results indicate the variation of HTS power cable condition. The results are used for the transient characteristic analysis and stability verification of the tri-axial HTS power cable. In the future, the RTDS-based model component of the cable will be used to implement the hardware-in-the-loop simulation with a protection device.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.259-261
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• 2000

UPFC(Unified Power Flow Controller) consists of two voltage sourced converter(VSC)s inserted into AC system through series and parallel coupling transformer, where two VSCs are linked by capacitor at DC-side. Since VSC acts as an AC voltage source behind a reactance, where both magnitude and phase angle of the source are controllable, UPFC can be represented by the equation related to input-output relation of two VSCs. Voltage control of DC-link capacitor provides the path of real power flow between two VSCs. While UPFC is controlled for maintaining the given reference value in steady state, it should be controlled for damping power oscillation in dynamics. For such a control objective, the control strategy based on the energy function was proposed and has been shown to be effect and robust for damping power oscillation of power system. In this paper, UPFC model based on the VSC was analysed and applied to power-flow control and stability analysis. The control strategy based on the energy function is adopted for damping power oscillation of power system. The effectiveness of proposed control strategy was verified by simulation study

• 한국통신학회논문지
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• 제15권1호
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• pp.71-79
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• 1990

逆바이어스 電壓變化에 따라 終端된 바랙터 리액턴스 變化로부터 發生되는 反射波의 連續的인 位相變化를 擴張시키기 위하여 인덕터와 바랙터를 直列로 連結시킨 回路와 하이브리드 링이 結合된 아나로그 移相器를 動作周波數 10GHz에서 設計하였으며, 分散特性 및 不連續 影響을 考慮하여 마이크로 스트립線路로 製作하였다. 實驗結果, 逆바이어스電壓을 20V가지 變化시킴에 따라 位相은 $52.34^{\circ}$에서 $235.01^{\circ}$까지 變化되므로서 $180^{\circ}$이상의 位相變化를 얻을 수 있었으며, 傳送 損失은 -3.6~14.3dB 및 Return loss는 -16~-18dB(1.37 < VSWR < 2.3)을 나타내었다.

• 대한전기학회논문지
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• 제45권2호
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• pp.301-309
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• 1996

This paper estimates the electric field effect near 765[kV] AC double transmission line with numerical data. The induced voltage and current of a human and car under who kinds of phase arrangement are calculated when each of two objects is insulated or grounded. When the calculated results of the low-reactance and superposition phase arrangement are compared, it is proved that the induced voltage and current of the former are about 30 [%] smaller than that of the latter. The induced current of a human and car are less than 0.5[mA] which is about 10[%] less than that of the American National Standard Code. Also the induced voltage and current of dead lines by other live lines are calculated. Finally the effective number and position of shield wires to reduce the field in ground level are considered. charge simulation method and surface charge method are used to simulate the 2 or 3 dimensional transmission line model respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.809-811
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• 2004

A 1MW class superconductng synchronous motor is designed considering several conditions such as superconducting wire length, machine efficiency and size. As the machine is larger and larger, the superconducting machine shows the advantages more and more over the conventional machines. Although the advantages at 1MW rating are not so great, the design approach to get an appropriate result would be very helpful for larger superconducting synchronous machine design. Major design concerns are focused on reducing expensive Bi-2223 HTS(High Temperature Superconducting) wire which is used for superconducting field coil carrying the rating current around 30K($-243^{\circ}C$) while the machine efficiency is higher than conventional motors or generators with the same rating. Furthermore, some iron cored structure is considered to reduce the HTS wire requirement without bad effect on machine performances such as sinusoidal armature voltage waveform, synchronous reactance and so on.

• Advances in Energy Research
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• 제3권2호
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• pp.81-95
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• 2015

Microgrid, which can be considered as an integration of various dispersed resources (DRs), is characterized by number of DRs interfaced through the power electronics converters. The microgrid comprising these DRs is often operated in an islanded mode. To minimize the cost, reduce complexity and increase reliability, it is preferred to avoid any communication channel between them. Consequently, the droop control method is traditionally adopted to distribute active and reactive power among the DRs operating in parallel. However, the accuracy of distribution of active and reactive power among the DRs controlled by the conventional droop control approach is highly dependent on the value of line impedance, R/X i.e., resistance to reactance ratio of the line, voltage setting of inverters etc. The limitations of the conventional droop control approach are demonstrated and a modified droop control approach to reduce the effect of impedance mis-match and improve the time response is proposed. The error in reactive power sharing is minimized by inserting virtual impedance in line with the inverters to remove the mis-match in impedance. The improved time response is achieved by modifying the real-power frequency droop using arctan function. Simulations results are presented to validate the effectiveness of the control approach.

• 조명전기설비학회논문지
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• 제16권3호
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• pp.84-92
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• 2002

저압간선의 굵기는 계통의 전압강하, 간선의 포설조건별 온도 보정계수를 적용한 허용 전류 및 간션의 임피 던스 값에 따라 결정된다. 따라서, 간선의 허용전류 값올 결정하기 위하여 간선의 포셜조건에 따른 적정 보정계 수가 적용되어야 하며, 저압간선의 정확한 임피던스 값을 분석하기 위하여 간선의 종류, 간선의 규격, 포셜조건 에 따른 온도, 표피효과 및 근접 효과 둥이 고려되어야 한다. 본 연구는 저압계통의 전압강하를 고려한 간선의 굵기 산정에 대한 체계적인 설계 흐름도를 제시 하였으며, 일반적인 계산 방식에 비하여 오차가 적은 계수로서 저압간선 굵기 선정 설계 실무에 적용할 수 있는 계산 방식을 연구하였다.