• 한국초전도ㆍ저온공학회논문지
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• 제16권3호
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• pp.10-14
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• 2014

Due to continuous increase of electric power consumption, couple of resolutions for improving accuracy in power system like line separation are being studied. The increase of the power demand can cause problems such as supply difficulties of the electricity and broadband outages, failure, etc. When a fault occurs in the power system, a fault current also increases. Fault current creates problems like reduction of lifespan and failure on the power system. In order to resolve these problems, the reduction of initial fault current using the characteristics of superconducting element was applied to fault current limiter. We applied the system to high speed fault current limiter. We found that the superconducting element effectively reduced initial fault current and the fault current was limited by changing operation of high speed interrupter.

• 한국전자파학회논문지
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• 제14권6호
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• pp.625-629
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• 2003

GaAs PIN 다이오드를 이용하여 저손실 고출력 MMIC 리미터를 설계하고 제작하였다. 고전력 수용 능력을 증가시키기 위하여 새로운 GaAs PIN 다이오드 에피구조를 제안하였다. 2종류의 리미터 회로를 설계하고 그리미팅 전력을 측정하였다. 측정결과에서 리미팅 전력은 설계회로 토폴로지에 따라 달라졌다. 제작된 2단 리미터의 리미팅 전력은 14 ㎓에서 각각 17 ㏈m과 23 ㏈m으로 측정되었다.

• 한국전자파학회논문지
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• 제23권7호
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• pp.791-796
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• 2012

RF 리미터(limiter)는 원하지 않는 신호로부터 수신단을 보호하기 위해 사용되는 소자로서, 임계값 이상의 모든 입력신호에 대해 일정한 출력을 제공한다. 다이오드를 사용하는 RF 리미터는 작은 신호는 통과시키는 반면, 어떤 임계값 이상의 신호는 감쇄시켜서 전달한다. 현대의 레이더 시스템에서 수신기를 보호하기 위해 사용되는 RF 리미터는 새로운 간섭 위협이나 복잡한 전자파 환경의 도전으로부터 극복할 수 있는 절대 필요한 역할을 수행한다. 본 논문은 고출력 RF 리미터를 구현하기 위해 PIN 다이오드와 Limit 다이오드의 조합으로 구성된 회로를 제안한다. PIN 다이오드는 스위치의 격리도(isolation) 특성을 이용하는 것과 같이 다이오드의 격리도 특성을 이용하는 개념을 적용한다. S-대역에서 200 us 펄스폭을 갖는 2 kW RF 리미터를 개발하였다. 그 측정 결과는 예측한 값과 잘 일치함을 알 수 있다.

• 한국전자파학회논문지
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• 제23권9호
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• pp.1065-1072
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• 2012

본 논문에서는 레이다 시스템의 수신단의 도파관 리미터와 대역 통과 여파기를 하나의 소자로 구현하는 방법을 제시하고자 한다. 먼저 대역 통과 여파 특성을 갖는 아이리스 구조를 제안하고 PIN 다이오드를 연결하여 도파관에 입사되는 전력의 크기에 따른 PIN 다이오드 바이어스 동작 특성에 따라서 각각 여파기와 리미터로 동작하는 구조를 설계하였다. 제작된 구조는 낮은 전력의 마이크로파가 입사하는 경우, 10 GHz에서 -0.7 dB의 삽입 손실을 갖는 통과 대역을 형성하는 여파기로, 높은 전력의 마이크로파가 입사하는 경우 대략 25 dB의 분리도를 갖는 리미터로 동작한다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.43-46
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• 2003

The dc reactor type high-Tc superconducting fault current limiter(SFCL) is composed of three parts, a power converter, a magnetic core reactor(MCR) and a dc reactor. This study concerned with the power converter of the DC reactor type high-Tc SFCL. The rectifying devices which power converter of 6.6kV/200A SFCL consists of have to endure high voltage. We propose the dual mode power converter to reduce the voltage which each rectifying device endures. In the single phase the experiment and simulation of dual mode power converter and the simulation of power converter with one bridge rectifier are performed. The current of each system with different power converter has a same tendency and the voltage which rectifying device of dual mode power converter endures is reduced in half by comparison with that of power converter with one bridge rectifier. We found dual mode power converter can be applied to SFCL.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.334-336
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• 2002

This study is concerned with the operation algorithm and power switch drive circuit for DC Reactor Type High-Tc Superconducting Fault Current Limiter (SFCL). In the case of SFCL, Power switching operation algorithm are very important problem. So, this driving will determine the performance of SFCL. In this paper, we provide a simple algorithm and easy drive circuit. Through experiment we found that ideal is right.

• 한국전기전자재료학회논문지
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• 제23권1호
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• pp.42-47
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• 2010

The power burden of high-$T_c$ superconducting (HTSC) elements comprising superconducting fault current limiter (SFCL) using magnetic coupling of shunt reactors was analyzed. The magnetically coupled shunt reactors play a role in distributing the even power burden between HTSC elements comprising the SFCL, which contributes to the effective current limiting and recovery characteristics of the SFCL. It was confirmed through the comparative analysis on the SFCLs with both the magnetically coupled and the magnetically uncoupled shunt reactors that the magnetically coupled shunt reactors could improve the SFCL's performance by equalizing the power burden of HTSC elements.

• 전기학회논문지
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• 제63권6호
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• pp.764-769
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• 2014

This paper describes sheath voltage limiter(SVL) transient characteristics by switching overvoltage considering single point bonding in underground transmission cables. The crossbonding system is generally used for grounding methods of underground transmission system. However, the single point bonding system is used in selective area which is difficult to consist of crossbonding major section. The sheath voltage limiters are connected between joints in the single point bonding. Specially, the high overvoltage might be generated in that section as well as the aging of sheath voltage limiter might be progressed by various electrical stress including lightning overvoltage, switching overvoltage and power frequency overvoltage. Therefore, in this paper, the switching overvoltage characteristics in underground cables are firstly analysed using EMTP simulation. Then, the switching overvoltage of sheath voltage limiter is also studied in single point bonding. Finally, the reduction method of sheath voltage limiter switching overvoltage is proposed by various simulation studies including circuit breaker operating order.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.141-144
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• 2015

The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.322-325
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• 2002

In this paper, the power-linking device connecting the high-Tc super-conducting(HTS) coil to the power system in the DC reactor type three-phase high-Tc superconducting fault current limiter (SFCL) has been designed. This design was triggered from the concept that the magnetic energy could be exchanged into the electrical energy each other. Ferromagnetic material is used as the path of magnetic flux. The device mentioned above was named Magnetic Core Reactor(MCR). MCR was designed to minimize the voltage drop caused by copper loss. The current density of the conductor was 1.3 A/mm$^2$ and % voltage drop was 2%.