• 한국초전도ㆍ저온공학회논문지
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• 제23권2호
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• pp.19-23
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• 2021

We have studied the breaking system that combines a resistive superconducting fault current limiter (SFCL) and a DC circuit breaker for DC fault current. To verify the design of the 15 kV DC SFCL, which was driven from the previous work, a 500 V DC system was built and a scale-down SFCL were manufactured. The manufactured SFCL module was designed as a bifilar coil which is a structure that minimizes inductive reactance. The manufactured SFCL module has been experiment to verify characteristics of the current-limiting performance in the DC 500 V system. Also, the manufactured FCL module was combined with the DC circuit breaker to be experimented to analyze the breaking performance. As a result of the experiment, when SFCL was combined to the DC circuit breaker, the energy dissipation received by the DC circuit breaker was reduced by up to 84% compared to when the DC circuit breaker operates alone. We are preparing methods and experiments for the optimal method for much higher performance as a future work.

• 전기학회논문지
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• 제66권11호
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• pp.1575-1583
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• 2017

With the development of DC distribution, DC circuit breaker is required to ensure the stability of the DC grid. Unlike a mechanical circuit breaker that blocks after several tens of milliseconds, a DC SSCB(Solid-State Circuit Breaker) can break the fault well within 1 [ms], so it can prevent the damage of accident. However, the previous DC SSCB requires a lot of switching elements for charging commutation capacitors, and the control is complicated. Therefore, this paper proposes a new DC SSCB suitable for DC grid. The proposed DC SSCB is simple to control for charging commutation capacitors, and it can perform the rapid breaking and operating duty of reclosing and rebreaking. The proposed DC SSCB was designed to 380 [V] and 5 [kW] class which is suitable for residential DC distribution, and the operating characteristics of the proposed DC SSCB were verified by simulations and experiments. It is anticipated that the proposed DC SSCB may be utilized to design and realize DC grid system.

• 한국초전도ㆍ저온공학회논문지
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• 제18권4호
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• pp.30-34
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• 2016

In this study, a SFCL-combined DC circuit breaker system was proposed by applying the current-limiting technology for DC circuit breaking. The SFCL-combined circuit breaker system consists of a mechanical DC circuit breaker combined with superconductors. To ensure the reliable structure and operation of the SFCL-combined circuit breaker system, a simulation grid was designed using the EMTDC/PSCAD program, and simulation was conducted. The results showed that the SFCL-combined DC circuit breaker system with superconductors limited the maximum fault current by 37%. In addition, the burden on the DC circuit breaker was decreased by 87%.

• 전력전자학회논문지
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• 제17권4호
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• pp.368-376
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• 2012

According to developed distributed generators, Solid State Circuit Breaker(SSCB) is essential for high power quality of DC Grid. In this paper, a simple and new structure of DC SSCB with a fast circuit breaker and fault current limiter is proposed. It can help to choice low specification of elements because of the limiting of fault current and achieve economic efficiency for minimizing auxiliary SCRs. Also all of SCRs have little switching loss because they operate under ZVS and ZCS. Through simulations and experiments of short-circuit fault, the performance characteristic of proposed circuit is verified and a guideline is so suggested that the DC SSCB is applied for a different DC grid using formulas.

• 전력전자학회논문지
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• 제25권6호
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• pp.503-510
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• 2020

The importance of DC breakers as key protection equipment is increasing in accordance with growing concerns on MVDC distribution network systems without DC/AC conversion. Different from the situation in AC systems, no natural zero-crossing point exists in DC systems. Thus, DC breaker technology is more difficult than AC breaker technology. The solutions for DC breakers can be divided into three types: mechanical, power electronics, and hybrid. In this study, the operating principles of several topologies of hybrid circuit breakers and that of the proposed DC breaker are analyzed and simulated by sorting two types. The breakers are compared in terms of the type and number of semiconductors, volume, power loss, auxiliary components, isolation, and other aspects. The advantages and disadvantages of the breakers are also analyzed.

• 전력전자학회논문지
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• 제17권1호
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• pp.21-26
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• 2012

In recent years, DC distribution systems are becoming hot issue due to the increase in digital loads and DC generation systems according to the expansion of renewable energy technologies. However, removing the fault current in DC grids is comparably difficult since the current in DC grids has no zero-crossing point like in AC grids. Thus, developing dedicated DC circuit breakers for DC grids is necessary to get safety for people and electrical facilities. This paper proposes magnet arc extinguishing method to develop a 300[$V_{DC}$]/10[A] DC circuit breaker. The performance of the proposed DC circuit breaker was verified by an experimental circuit breaker test system built in this research.

• 전기학회논문지
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• 제65권12호
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• pp.2109-2112
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• 2016

The rate of rise of the fault current in DC grids is very high compared to AC grids because of the low line impedance of DC lines. In AC grids the arc of the circuit breaker under current interruption is extinguished by the zero current crossing which is provided naturally by the system. In DC grids the zero current crossing must be provided by the circuit breaker itself. Unlike AC girds, the magnetic energy of DC grids is stored in the system inductance. The DC circuit breaker must dissipate the stored energy. In addition the DC breaker must withstand the residual overvoltage after the current interruption. The main contents of this paper are to ${\cdot}$ Explain the theoretical background for the design of DC circuit breaker. ${\cdot}$ Develop the simulation model in PSIM of the real scaled DC circuit breaker for 1,800V DC railway. ${\cdot}$ Suggest design guidelines for the DC circuit breaker based on the experimental work, simulations and design process.

• Journal of Power Electronics
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• 제17권1호
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• pp.272-281
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• 2017

The DC circuit breaker is essential for supplying stable DC power with the advent of DC transmission/distribution and sensitive loads. Compared with mechanical circuit breakers, which must interrupt a very large fault current due to their slow breaking capability, a solid-state circuit breaker (SSCB) can quickly break a fault current almost within 1 [ms]. Thus, it can reduce the damage of an accident a lot more than mechanical circuit breakers. However, previous DC SSCBs cannot perform the operating duty, and are not economical because many SCR are required. Therefore, this paper proposes a new DC SSCB suitable for DC grids. It has a low semiconductor conduction loss, quick reclosing and rebreaking capabilities. As a result, it can perform the operating duties of reclosing and rebreaking. The proposed DC SSCB is designed and implemented so that it is suitable for home dc distribution at a rated power of 5 [kW] and a voltage of 380 [V]. The operating characteristics are confirmed by simulation and experimental results. In addition, this paper suggests design guidelines so that it can be applied to other DC grids. It is anticipated that the proposed DC SSCB may be utilized to design and realize many DC grid systems.

• 전기학회논문지
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• 제68권1호
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• pp.215-219
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• 2019

Development of DC interruption technology is being studied actively for enhanced DC grid reliability and stability. In this study, coil type superconductor DC circuit breaker was proposed as DC interruption. It is integration technology that combined current-limiting technique using superconductor and cut-off technique using mechanical DC circuit breaker. Superconductor was applied to the coil type. In simulation, Mayr arc model was applied to realize the arc characteristic in the mechanical DC circuit breaker. PSCAD/EMTDC had used to model and perform the simulation. To find out the protection range of coil type superconductor DCCB, the working operation have analyzed based on the rated voltage of DCCB. The results confirmed that, according to apply the limiting device, the protection range was increased in twice. Therefore, the probability of failure of interruption has lowered significantly.

• 한국전자통신학회논문지
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• 제15권6호
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• pp.1069-1074
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• 2020

DC에는 전류 영점이 없기 때문에 DC 차단기의 차단 동작시 아크가 발생한다. 이때 발생하는 아크의 크기에 따라 회로 차단기의 열화 또는 그리드에 치명적인 사고를 발생시킬 수 있다. 따라서 HVDC의 상용화에 있어서 DC차단기의 차단 성능의 안정성 확보는 대단히 중요한 부분이다. 본 연구에서는 DC 차단기의 성능과 신뢰성을 향상시키기 위해 초전도체가 적용된 LC 차단기를 제안하였다. 초전도 LC 차단기는 기존 LC 차단기의 인덕터에 초전도 코일을 적용한 구조로 되어있다. 초기 고장 전류를 제한하는 것 외에도 고장 발생시 안정적인 전류 0점을 생성한다. 이를 확인하기 위해 EMTDC / PSCAD 프로그램을 통해 시뮬레이션을 수행하였다. 또한 초전도 LC 차단기는 일반 코일이 적용된 LC 차단기와의 동작 특성을 비교하였다. 그 결과 초전도 코일이있는 LC 회로 차단기는 일반 코일이있는 LC 회로 차단기에 비해 초기 고장 전류를 약 12kA 더 제한하는 것으로 나타났다. 이러한 결과를 통해서 DC 차단기의 아크 소화 시간을 약 0.16 초 단축시킬 수 있었고, 이를 통해 회로 차단기의 전기적 부담이 줄어드는 것을 확인할 수 있었다.