• 전기학회논문지
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• 제57권4호
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• pp.560-566
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• 2008

Today, as the power trades between generation companies and power customer are liberalized, the uncertainty level of operated power system is rapidly increased. Therefore, transmission operators as decision makers for transmission expansion are required to establish a deliberate investment plan for effective operations of transmission facilities considering forecasted conditions of power system. This paper proposes the methodology for the optimal solution of transmission expansion in deregulated power system. The paper obtains the expected value of transmission congestion cost for various scenarios by using occurrence probability. In addition, the paper assumes that increasing rates of loads are the probability distribution and indicates the location of expanded transmission line, the time for transmission expansion with the minimum cost for the future by performing the Montecarlo simulation. To minimize the investment risk as the variance of the congestion cost, Mean-Variance Markowitz portfolio theory is applied to the optimization model by the penalty factor of the variance. By the case study, the optimal solution for transmission expansion plan considering the feature of market participants is obtained.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2106-2117
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• 2017

An effective statistical feature extraction approach of data sampling of fault in the combined transmission system is presented in this paper. The proposed algorithm leads to high accuracy at minimum cost to predict fault location and fault type classification. This algorithm requires impedance measurement data from one end of the transmission line. Modal decomposition is used to extract positive sequence impedance. Then, the fault signal is decomposed by using discrete wavelet transform. Statistical sampling is used to extract appropriate fault features as benchmark of decomposed signal to train classifier. Support Vector Machine (SVM) is used to illustrate the performance of statistical sampling performance. The overall time of sampling is not exceeding 1 1/4 cycles, taking into account the interval time. The proposed method takes two steps of sampling. The first step takes 3/4 cycle of during-fault and the second step takes 1/4 cycle of post fault impedance. The interval time between the two steps is assumed to be 1/4 cycle. Extensive studies using MATLAB software show accurate fault location estimation and fault type classification of the proposed method. The classifier result is presented and compared with well-established travelling wave methods and the performance of the algorithms are analyzed and discussed.

• 한국광학회지
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• 제17권2호
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• pp.120-126
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• 2006

격자 구조형 평면도파로와 원통형 광섬유로 구성된 격자구조형 광섬유 결합기(GAFC)를 제안하였고, 그 최적 전력결합 특성을 종방향 모드 전송선로이론(L-MTLT)에 기초하여 분석하였다. 또한, 격자 구조형 평면도파로에서 입사된 광신호가 단일 모드 광섬유로 결합되기 위한 새로운 최적 조건들을 제시하였다. 수치해석 결과 GAFCs에서 최적 전력결합 특성은 기존에 널리 사용하는 위상정합 조건이 아닌 새로운 조건(즉, 정확한 모드의 최소간격 조건)에서 나타났다.

• 한국정보통신학회논문지
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• 제6권5호
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• pp.724-730
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• 2002

디지털 통신시스템에서는 인접채널에 대한 간섭을 최대한 줄이기 위하여 필연적으로 선형 전력증폭기가 요구된다. 선형 전력증폭기는 매우 다양하며, 그 중에서도 전방제환 전력증폭기는 구조상 광 대역이면서 선형화 정도가 매우 우수하기 때문에 많이 이용된다. 전방궤환 전력증폭기는 지연 선로의 손실로 인하여 전체효율이 감소한다. 본 논문에서는 이러한 지연 선로를 손실이 매우 작은 지연 여파기를 사용함으로써 효율과 선형성을 동시에 개선하였다. 측정 결과, ACLR이 약 17.43(dB) 개선되었으며, 이것은 지연 여파기를 사용함으로써 3.44(dB) 더 개선되었음을 나타낸다.

• Journal of electromagnetic engineering and science
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• 제4권4호
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• pp.150-155
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• 2004

Universal design equations are presented for the H-plane T-junction power divider with a circular conducting post in a rectangular waveguide. For a given operating frequency and power split ratio, the post offset from the T-junction center line, the distance between the post and the waveguide wall, and the post diameter can be adjusted to obtain a minimum reflection at the input waveguide. Optimum values of the post offset are given in terms of the normalized frequency and the power split ratio. Corresponding values of the post diameter and the distance of the post from the waveguide wall are given in terms of the normalized frequency and the post offset.

• 한국통신학회논문지
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• 제19권4호
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• pp.691-700
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• 1994

본 논문에서는 전력선을 이용한 조광용 전자식 안정기의 원격 제어신호 전송 방식을 고안하였다. 기존의 방식은 상측파기 완전히 전단된 두개의 신호가 N 주기의 간격으로 전송하는 방식이며, 제안된 방식은 다른 상측파 내의 임의의 명령에 따라 일정 위상에서 파가 절단된 신호를 전송하는 방식이다. 이 방식은 파형을 절단하는데서 오는 전송전력의 손실을 최소한으로 줄일 수 있다. 구현에 있어서 파형의 절단 위치 결정과 수신신호 위상을 결정하기 위한 타이머가 필요하기 때문에 타이머가 내장된 마이크로프로세소를 이용해 정확한 위상 계산을 하도록 했다. 결과적으로 전력선을 이용한 전자식 안정기의 원격 제어신호의 전송기법에 있어서 기존의 방식보다 전력전송 효율이 좋은 원격 제어기를 구현하였고 그특성을 측정하였다.

• 한국통신학회논문지
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• 제17권10호
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• pp.1074-1080
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• 1992

새로운 (5.8)블록 2진 선로부호를 제안하였다. 제안된 선로부호 MB58은 무직류(DC-free)성질 및 유한 연속장(runlength limited) 성질을 만족할 뿐만아니라, 대역폭이 나이퀴스트 주파수로 제한되므로 대역폭 효율이 개선된다. 또한 이 부호는 memoryless 부호이고, 오류 발생을 검출해 낼 수 있는 장점이 있으며 복호규칙이 간단하다. 제안된 선로부호에 대한 전력스펙트럼에서 DC(f=0)및 나이퀴스트 주파수(f=1/2Ts)에서 전력 영점이 존재함을 시뮬레이션을 통해 확인하였으며 눈 모양의 시뮬레이션을 통해 눈이 충분히 크게 됨을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 논문집 센서 박막재료연구회 및 광주 전남지부
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• pp.41-41
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• 2008

Al-doped ZnO (AZO) thin films have been fabricated by vertical in-line dc magnetron sputtering for transparent conducting oxides (TCOs) applications. The effects of substrate temperature and dc power on the characteristics of AZO thin films are investigated and also optimized the process conditions to get the best electrical and optical properties. The fabricated thin films show a good electrical and optical uniformity within ${\pm}5%$ over the whole area of substrate ($200mm\;{\times}\;200mm$) ; the minimum resistivity of $8\;{\times}\;10^{-4}\;{\Omega}cm$ and the average transmittance of 90% within the visible wavelength range. We have found that the band gap ($E_g$) increases with increasing substrate temperature and dc power, whereas the crystallinity is getting improved with increasing substrate temperature. The binding energy of Zn $2p_{3/2}$ and O 1s is observed to decrease as the substrate temperature increases.

• 전기학회논문지
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• 제64권12호
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• pp.1673-1678
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• 2015

This paper describes magnetic field on power cable in underground transmission systems. Based on specification which is being used in domestic power utility, magnetic field was analyzed in accordance with line arrangement, line burial depth and phase spacing. Magnetic field magnitude and its trend were understood in each circuit type such as double circuits, triple circuits and quadruple circuits of underground transmission systems. In addition, magnetic field was analyzed according to phase arrangement changing in each circuit. Finally, the proper phase arrangement configuration type was suggested by the evaluation of analysis result. Magnetic field was calculated by using Biot-Savart's law. According to the evaluated magnetic fields based on phase layout configuration in each circuit, it figured out that each of magnetic fields was different. As a result, this paper proposes a proper phase layout configuration for generating minimum magnetic field. It is evaluated that the phase layout configuration in each circuit proposed in this paper can be used at actual underground transmission systems.

• Industrial Engineering and Management Systems
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• 제6권1호
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• pp.22-27
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• 2007

This paper describes the optimization of maintenance workforce scheduling at Afam power station in Nigeria. The objective is to determine the optimum schedule to satisfy growing maintenance labour requirements with minimum cost and highest efficiency. Three alternative maintenance workforce schedules are compared. The first alternative is to continue with the traditional five-day workweek schedule currently being practiced by Afam power station maintenance line. The second alternative is to switch to a seven-day workweek schedule for the morning shift only. The third alternative is to use a seven-day workweek schedule for all three work shifts. The third alternative is chosen, as it is expected to save 11% of the maintenance labour cost.