• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.85-91
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• 2015

전력선 통신에서 사용되는 비접촉식 커플러의 신호 전달 특성을 향상시키기 위한 비접촉식 커플러의 구조와 자기장 결합에 대한 연구를 수행하였다. 비접촉식 커플러의 결합 구조를 분석하였고, Rogowski 코일을 이용한 커플러와 자성체 코어를 이용한 커플러를 제작하여 구조에 따른 신호 전달 특성을 분석하였다. 집중 정수 소자와 임피던스 트랜스포머를 이용한 임피던스 매칭법을 제안하여 협대역과 광대역에서 신호 전달 특성을 향상시켰고 전달 신호의 크기는 대역폭과 트레이드오프가 있음을 보였다. 본 연구는 추후 부하 변동에 따른 임피던스 매칭 연구에 도움을 줄 수 있다.

• 대한전기학회논문지:전력기술부문A
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• 제54권12호
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• pp.567-572
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• 2005

This paper presents a scheme to design optimal placement of phase-shifting transformers for power system congestion problems. A good design of phase-shifting transformers placement can improve total transfer capability in interconnected systems. In order to find the optimal placement of phase-shifting transformers, the power flows of the interesting transmission lines are evaluated using sequential quadratic programming technique. This algorithm considers power balance equations and security constraints such as voltage magnitudes and transmission line capacities. The proposed scheme is tested in 10 machines 39 buses and IEEE 57 buses systems. Test result shows that the proposed method can find the optimal placement of phase-shifting transformers to solver power system congestion problems.

• 한국정보통신학회논문지
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• 제24권11호
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• pp.1484-1491
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• 2020

슬롯 선로는 슬롯을 통해 전계와 자계 신호가 전달되기 때문에 슬롯의 크기가 전력 손실에 크게 영향을 준다. 일반 적으로 슬롯 선로는 낮은 전력 손실로 동작하기 위해 상대적으로 높은 비유전율(er)의 기판에서 3GHz 이상의 높은 주파수에서 사용하게 된다. 본 논문에서는 상대적으로 낮은 비유전율(er)을 가지는 Taconic사의 TLC-30(er=3) 기판을 이용하여 중심주파수 1.85GHz에서 동작하는 슬롯 선로를 이용한 4:1 임피던스 변환기를 제안하였다. 제안된 임피던스 변환기에서의 슬롯 선로는 슬롯 선로 위에 유전체 공진기를 배치하여 슬롯 선로에서의 신호 손실을 줄였다. 비유전율(er) 38의 (Zr,Sn)TiO4을 이용하여 만든 유전체 공진기를 사용한 4:1 마이크로스트립-슬롯 선로 임피던스 변환기는 1.855GHz에서 삽입 특성(S21) -0.375dB와 반사 특성(S11) -27.6dB를 보였다. 이는 유전체 공진기를 이용하면 상대적으로 낮은 비유전율 기판과 낮은 주파수 영역에서도 안정적으로 슬롯 선로를 이용할 수 있음을 확인할 수 있었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권6호
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• pp.409-416
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• 2005

For broadband high-data-rate power line communication with the allocated frequency bandwidth from 2 to 30 MHz on medium voltage (MV) distribution power lines, a signal coupling unit is developed. The coupling unit is composed of a coupling capacitor for coupling communication signal, a drain coil, and an impedance matching part. The coupling capacitor made of ceramic capacitor is designed for transmission property of better than 1 dB in the frequency range. The drain coil is used for preventing low frequency high voltage from junction of medium voltage power line in case that a coupling capacitor is not working properly any more. Also, using ferrite core, a novel broadband impedance matching transformer is developed. A complete coupling unit with a coupling capacitor, a drain coil, and a matching transformer is housed by polymer for good isolation and distinguishing from high voltage electric facilities. Each is fabricated and its frequency behavior is tested. Finally, complete signal couplers are equipped in a MV PLC test bed and their performance are measured. The measurement shows that the coupling capacitor works excellently.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.199-201
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• 2000

This paper describes the theory and experimental result of scaled model of STATCOM. The STATCOM, a solid-state voltage source inverter coupled with a transformer, is tied to a transmission line. A STATCOM inject an almost sinusoidal current of variables magnitude, at the pont of connection. This injected current is almost in quadrature with the line voltage, thereby emulating an inductive or capacitive reactance at the point of connection with the transmission line.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.108-115
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• 2000

This paper presents the new simulation algorithms using network methods to analysis the steady-state train voltage distribution characteristics in ac auto-transformer fed railroads. In general, the supply system of railroads is composed of non-symmetrical and unbalance transmission line. Therefore, the general method using simplified old algorithms have the self-contradictory errors because the supply line of train railroads is completely unbalanced. In this paper, the simulation results of new developed algorithms is compared with those of EMTP to confirm the effectiveness.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.191-196
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• 2010

Power system restoration following a massive or complete blackout starts with energizing the primary restorative transmission system. During this primary restoration process, unexpected overvoltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. In the case of the Myanmar electric power system, there are so many wide outage experiences, including complete blackout cases, caused by 230kV line faults and so on. Consequently, Myanmar's system operators have been well trained to deal with wide blackouts. Howver, system blackout restoration has been conducted by relying on the experience of only a few specialists. So, more scientific analysis is required to meet the requirements necessary to ensure fast and reliable system restoration. This paper presents analytical results on the primary restorative transmission system of Myanmar, focusing on the problems during the early restoration process. Methodologies are presented that handle load pick-up, terminal voltage and the reactive capability limitation of black-start generators to compensate the Ferranti effect. Static and dynamic simulation with the PSSolution and EMTDC programs respectively for the six cases are performed in order to select the primary restorative transmission lines.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.822-824
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• 2005

This paper presents a scheme to solve the congestion problem using phase-shifting transformer(PST) in power systems. Available transfer capability(ATC) is an important indicator of the usable amount of transmission capacity accessible by several parties for commercial trading in power transaction activities. This paper deals with an application of optimization technique for ATC calculation. Sequential quadratic programming(SQP) is used to maximize power flow of tie line subject to security constraints such as voltage magnitude and real power flow. The proposed method is applied to 10 machines 39 buses model systems to show its effectiveness.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.118-120
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• 2016

A coplanar waveguide employing periodic 3D coupling structures (CWP3DCS) was developed for application in miniaturized on-chip passive components on silicon radio frequency integrated circuits (RFIC). The CWP3DCS showed the shortest wavelength of all silicon-based transmission line structures that have been reported to date. Using CWP3DCS, a highly miniaturized impedance transformer was fabricated on silicon substrate, and the resulting device showed good RF performance in a broad band from 4.6 GHz to 28.6 GHz. The device as was 0.04 mm² in size, which is only 0.74% of the size of the conventional transformer on silicon substrate.

• 전기학회논문지
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• 제58권5호
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• pp.879-884
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• 2009

A Method for detection of saturation of a current transformer(CT) is proposed. The algorithm is initiated when the end point of a saturation period is detected. This detection is achieved by checking the time interval between the adjacent zero-crossing points of the second derivative of the secondary current. Once the end point of the saturation period is detected, the beginning point of the corresponding saturation period is determined by backward examination of the sum of the secondary current from the end point. The performance of the algorithm was evaluated for a-g faults on a 345 kV 100km overhead transmission line. The Electromagnetic Transient Program(EMTP) was used to generate fault current signals for different fault inception angles and different remanent fluxes. The performance evaluation shows that the proposed algorithm successfully detects the saturation period even in the presence of a remanent flux.