• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 심포지엄 논문집 정보 및 제어부문
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• pp.16-18
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• 2004

The flexible AC transmissions system (FACTS) is the underpinning concept upon which are based promising means to avoid effectively power flow bottlenecks and ways to extend the loadability of existing power transmission networks. This paper proposes a method by which the optimal locations of the FACTS to be installed in power system under cost function. The optimal solution of this type of problem requires large scale nonlinear optimization techniques. We used Lagrange multipliers to solve a nonlinear equation with equality and ineaquality constraints. Case studies on the standard IEEE 14 bus system show that the method can be implemented successfully and that it is effective for determining the optimal location of the FACTS.

• 대한지구과학교육학회지
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• 제6권2호
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• pp.101-111
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• 2013

The purpose of this study was to investigate the characteristics and proprieties of the granite observing results in the 4th grades elementary students' scientific inquiry activities. For this, the 4th, 94 students participated in granite observing activity which had objects to collecting applicable scientific facts for the distinguishing granite among the volcanic rocks. Following are the study results. First, the 829s of total results (879s) were admitted as the facts, but the rest, 50s were not the facts but the inference results. Second, the 542s results which were related to the shape, weigh, size, smell, sound, and touch (feeling) containing glittering of the rock specimen were the useless for the inquiry objects. And only the 85s results were the scientific facts which were deserved the admitting propriety for the inquiry objects. Third, the 185s results which were targeting to the particles (minerals) on the rock specimen were the admitting facts, but the 163s facts which were related to color, size and shape of the particles were deserved as admitting propriety for the inquiry objects. Consequently, the focusing on the proprieties of the granite observing results in the elementary students' scientific inquiry activities, only the 248 results (28.2%) of the total 879s were the admitting proprieties as the meaningful scientific facts in the scientific inquiry activities.

• East Asian mathematical journal
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• 제35권4호
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• pp.467-488
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• 2019

The purpose of this study is to analyze multiplication facts(1st and 0th multiplication) in elementary mathematics. In the 2015 revised curriculum, students learn multiplication and multiplication facts in the 2nd grade. Many teachers experience difficulties in organizing the multiplication problem situation in multiplication facts(1st and 0th multiplication). This study aims to consider the causes of these difficulties and devise teaching methods. The method of this study is a comparative and analytic method. In order to compare textbooks, we select the Korean elementary mathematics textbooks(1st curriculum~2015 revised curriculum) and the six foreign elementary mathematics textbooks(Taiwan, Japan, Finland, Unites States, Hongkong, Singapore). As a result, the multiplication problem situation and the multiplication model assume the same bundle and bundle model. Also, we must consider the teaching timing of multiplication facts(1st and 0th multiplication) and the use of commutative law. In this study, we proposed a multiplication teaching scheme in consideration of the multiplication problem situation and teaching model, teaching period and commutative law etc.. to teach multiplication facts(1st and 0th multiplication) in elementary mathematics.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.129-136
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• 2006

This paper proposes a probabilistic evaluation for the transient stability of electrical power systems incorporating FACTS devices. The uncertainties of the fault location and relay operation time play important keys in power system instability evaluation. The TCSC and SVC are employed for the reduction of system instability probability. This method is demonstrated by the WSCC test system and the results are compared with and without FACTS by means of Monte Carlo simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.22-24
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• 2000

As a competition is introduced in the electricity supply industry, a congestion problem arises in the transmission network. The congestion causes the transmission cost to increase. One way to decrease the congestion cost is to control the transmission flow through the installation of FACTS(Flexible AC Transmission system). This paper deals with the optimal site of the FACTS for reducing the congestion cost using a shadow price which is one of the economic signals for the systems. Test results show that the site of the FACTS(UPFC) is optimal to minimize the congestion cost by the proposed algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.31-33
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• 2000

This paper discusses the operational characteristic analysis of distance relay depending on the power system parameters in transmission line including FACTS devices. Distance relay requires protective coordination because the FACTS devices change power system parameters to increase power transmission capacity. In this paper, the dynamic operational characteristics of distance relay are analyed for the effect of fault resistance and operation mode of FACTS devices according to the installed points of these devices.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.159-160
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• 2006

This paper discusses sensitivity analysis for determining adequate locations of series-type FACTS devices. The main objective of FACTS reinforcement is to alleviate line over-loadings against violation of thermal limits after disturbances. This paper, to obtain the information concerning series-type FACTS locations, proposes a formulation for the sensitivity of the PI (Performance Index) with respect to the variation of the branch parameters, and applies to 5-bus test system to show the effectiveness of the sensitivity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전력기술부문
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• pp.258-260
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• 2006

비수도권과 수도권의 수급 불균형 해소를 위한 6개의 북상선로에 흐르는 융통조류량의 한계값이 경제성 평가의 한 기준이 될 수 있다. 본 논문에서는 수도권 융통전력 한계를 고려한 제약급전사례의 검토 결과를 이용하여 FACTS 투입에 따른 증대된 융통전력한계를 바탕으로 FACTS 투입에 따른 혼잡비용측면에서 운전이익을 평가하는 방법을 논한다. 즉, F-V 해석결과를 이용하여, 수도권 융통전력 한계값을 결정하고 좀 더 정확한 운전이익 계산하기 위하여 결정된 한계값을 P-POOL 프로그램을 이용하여 혼잡비용 경감 효과를 확인할 수 있는 모의 방법을 확립한다. 확립된 방안은 계획계통을 이용해 검증하고, 최종적으로 FACTS 투입량과 투입후보지에 대한 융통전력 한계 측면에서의 경제성 평가한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.15-17
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• 2004

The flexible AC transmissions system (FACTS) is the underpinning concept upon which are based promising means to avoid effectively power flow bottlenecks and ways to extend the loadability of existing power transmission networks. This paper proposes a method by which the optimal locations of the FACTS to be installed in power system under cost function. The optimal solution of this type of problem requires large scale nonlinear optimisation techniques. We used Lagrange multipliers to solve a nonlinear equation with equality and ineaquality constraints. Case studies on the standard IEEE 14 bus system show that the method can be implemented successfully and that it is effective for determining the optimal location of the FACTS

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.837-846
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• 2004

This paper presents a screening technique for greatly reducing the computation involved in determining the optimal location and types of Flexible AC Transmission System (FACTS) devices in a large power system. The first-order sensitivities of the generation cost for various FACTS devices are derived. This technique requires solving only one optimal power flow (OPF) to obtain sensitivities with respect to FACTS device control variables for every transmission line To implement a sensitivity-based screening technique, we used a new UPFC model, which consists of an ideal transformer with a complex turns ratio and a variable shunt admittance. A S-bus system based on the IEEE 14-bus system was used to illustrate the technique.