• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.299-300
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• 2019

본 논문에서는 MVDC(Medium-Voltage DC) 차단기의 성능평가를 수행하기 위해 사용되는 단락 시험 설비의 새로운 구조를 제시한다. 단락 시험 설비는 직류 고전압과 고전류를 발생시키고 이러한 조건에서 차단기의 개폐 성능을 검증한다. 고전압과 고전류를 단일 회로로 합성하는 구조의 경우, 단락 시험 설비의 규모와 전력용량이 매우 크다. 제시하는 단락 시험 설비는 별개의 회로인 고전류원과 고전압원으로 구성된다. 각 회로에서 직류 고전압과 고전류를 발생시켜 단락 시험을 수행하는 구조이다. 제시하는 단락 시험 설비의 구조와 동작 원리를 설명하고 시뮬레이션 분석을 통하여 그 성능을 검증하였다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.7
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• pp.297-305
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• 2006

This paper summarizes a development of visualization software for protective engineering in low-voltage power systems. The study is concentrated on the following aspects. First, a software engineering method is applied for designing the object-oriented program. The design and implementation of a Graphic User Interface(GUI) and its integration to a power system framework are developed using object-oriented programming(OOP) in Visual C++. Second, we develop the short circuit analysis module that oriented a low-voltage power system. It is possible to calculate a peak, symmetrical RMS, DC component and asymmetrical fault currents for each time. And it is the first software that can calculate the fault current for single branch of three-phase system. The calculation accuracy is compared with commercial software, and the libraries of low-voltage components are served for convenience use. Third, protective engineering functions are equipped. It is possible to automatically select the circuit breaker which based on the user input characteristics and the fault current calculation and examine the protective coordination. Through the case study, we verified that the developed software can be effectively used to examine the protective engineering in low-voltage power systems.

• Journal of the Korean Society of Safety
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• v.25 no.5
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• pp.15-21
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• 2010

Regenerative Energy Storage System(ESS) is a system that saves regenerative energy which generated instantly in the regenerative braking of Electric Multiple Unit(EMU) and disappear, and reuse the stored energy when EMU is in powering. Such system related to a research field of renewable energy which emerged concerning climate change and high oil prices. In the case of existing domestic rolling stock, about 25% to 30% of generated regenerative energy is restored to power source and is regarded as direct factor of raising catenary voltage. Such rapid change of catenary voltage is a cause of the failure of EMU's electronic equipment and lowering its reliability and is also a cause of train's fault occurred by tripping circuit breaker. In this paper, we intend to investigate the effect on blending characteristics of electric-braking and pneumatic-braking whether the regenerative energy storage system is used or not in urban transit DC 1,500V feeding system, while trains run. And we also intend to investigate its effect on stabilization of the blending, fluctuation of catenary voltage and various electric equipments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.8
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• pp.39-47
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• 2011

The motion of a conductive spherical particle under uniform electric field is investigated in order to find a suitable method for removing the conducting solid impurities contained in liquid plastic. When the positive dc voltage applied to the upper electrode, the vertical up-and-down motion of a charged particle by electrostatic force is observed by a charge-coupled device (CCD) camera or a high-speed video camera. The experimental data of the static threshold voltage by which the particle starts to move toward the counter electrode in air or silicone oil are in good agreement with theoretical value. When the applied voltage is larger than the static threshold voltage, the particle motion pattern in silicone oil consists of four stages: upward motion, stopping at the upper electrode, downward motion and stopping at the lower electrode. The stopping motion on the electrode is thought to be caused by the liquid flow accompanied by the particle motion. The particle charge calculated by integrating the pulse current, which is generated by the charge exchange between the electrode and the particle, is approximately 0.1~0.25 times of the theoretical value. This study is expected to help understand the electric properties of microparticles in oil circuit breaker (OCB) and oil transformer and improve their performance and longevity.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.54-59
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• 2023

In this paper, we analyze experimental results by applying the PHILS model to a lab-scale superconducting current limiter system for its actual application in medium-voltage direct current (MVDC) systems. Superconducting current limiters exhibit effective current-limiting performance in circuit breaker operations, particularly in limiting large fault currents within a short period, addressing the challenges posed by the increasing use of renewable energy and the integration of DC medium-voltage distribution systems. The development of such superconducting current limiters faces various technical and cost disadvantages, especially when applying a medium-voltage 35kV level system, which is intended for future introduction. The proven lab-scale superconducting current limiter system and the PHILS model are combined and integrated into the actual system. Our plan involves analyzing the limiter's performance, assessing its impact on the system, and preparing for its application in future medium-voltage systems. Utilizing RTDS, a simulation was conducted by connecting actual scaled-down equipment and systems, with the analysis results presented.