• Journal of Aerospace System Engineering
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• v.14 no.6
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• pp.74-78
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• 2020

The cooler driver electronics (CDE) for maintaining a low temperature of a satellite payload IR sensor has a compressor with a pulsation current load when in operation. This pulsation current creates a large voltage fluctuation and may negatively affect both the load and regulated bus stability. Thus, a CDE power conditioning system has a battery for use as a buffer that is connected in front of the CDE load line. In this system, a battery charger limiter circuit is required to protect from an over-charge of the battery and power to the load. In this study, an optimal design and parameter selection were developed and simulated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.4
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• pp.593-597
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• 2019

We proposed a current Interruption type DC superconducting circuit breaker(I-DC SCB), a protection device that combines the current limiting technology of a superconductor with the cut-off technology of circuit breaker. Unlike existing protective devices, the current I-DC SCB is a device that combines two protection functions, notably improving failure probability and operational reliability. It is also applicable to all DC systems, such as HV, MV, and LVDC, due to the ease in capacity increase. The 100 kV I-DC SCB was designed after taking into account the actual power system conditions, followed by an analysis of the transient characteristics and the breaking range of the limiter. The results of the analysis showed that the I-DC SCB had a fault current limit of about 75% at the rated voltage, and completed the cut-off operation within about 20 ms.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.34-38
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• 2006

There are many parameters that should be considered from the viewpoint of real power system operation and planning in designing HTS power devices. Especially, in the power system with HTS-FCL(fault current limiter) and TR(transformer), there is close correlation between parameters of the HTS power devices. This paper describes some considerations in determining parameters of HTS power devices, which are related to technical and economical aspects. The main parameters in this study are the quench resistance of HTS-FCL and the % impedance of HTS-TR. The results may give basic information for developing the devices.

• Progress in Superconductivity and Cryogenics
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• v.11 no.4
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• pp.25-28
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• 2009

In order to apply superconducting electric machineries such as a Superconducting Fault Current Limiter (SFCL) to the power grid, the single module should be connected in series to have reasonable size. Superconducting tapes in the module also should be stacked to satisfy requirements such as large operation current of the power grid. This is because a single superconducting tape has restricted applicable current capacity. Moreover especially in SFCL at the fault, there should be equal voltage distribution in series-connected SFCL modules. In this paper, we investigated the voltage distribution in fault current of series-connected YBCO coated conductors (CC). Depending on characteristics of the CC samples such as critical current, even voltage distribution could be achieved or not. In addition, the effect of stacked CC on the change of voltage distribution comparing to non-stack cases in series connection was confirmed by experiments. As the CC stacked, voltage difference could be reduced.

• Progress in Superconductivity and Cryogenics
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• v.10 no.3
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• pp.9-13
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• 2008

It is very important to study the protective relaying system from the viewpoint of technical analysis to apply superconducting power devices to real power systems. In this paper, we developed Superconducting Fault Current Limiter (SFCL) analysis model using Real Time Digital Simulator(RTDS) for protective relay tests in power system with SFCLs. The RTDS model has the operation mechanism of a real SFCL system.

• Progress in Superconductivity and Cryogenics
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• v.11 no.4
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• pp.29-32
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• 2009

This paper proposes the bus-tie application scheme of 154 kV SFCL (superconducting fault current limiter) in Korean power system. The reduced amount of fault current by SFCL is different by where the SFCL is installed. Therefore the inflow ratio of fault current (IRFC) is suggested to consider the effect of an SFCL's location. The proposed scheme was applied to the Korean Power System of 2010, and fault currents were calculated and analyzed with this coefficient. Simulations show that the location with high IRFC is adequate to install SFCL but more consideration of other things is required to determine the location and capacity of SFCL.

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.39-43
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• 2010

In Korea, 22.9kV hybrid SFCL (Superconducting Fault Current Limiter) has been developed and carried out long-term field tests in Gochagn power test center of KEPCO through DAPAS program. The SFCL will be installed at a distribution line of Icheon substation in Korea. For the successful application, we have to design the specifications considering real power system operation. This paper proposes a concept of the operating current based rms value for the protection coordination with protective delays and studies a proper range of the current in Korean distribution power system.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.69-74
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• 2023

The paper presents the results investigating the effect of aircraft engine impact location on the intended function evaluation results of spent nuclear fuel transport cask. As a result of the investigation, it is found that the structural integrity is maintained as the maximum accumulated equivalent plastic strain is below the acceptable criterion regardless of the collision location. It is identified that when the aircraft engine collided with the upper part of the transport cask without considering impact limiter the containment performance is weakened compared to when the aircraft engine collided with the central part.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.2
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• pp.139-152
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• 2006

A spent fuel storage cask is required to prove the safety of a canister under a hypothetical accidental drop condition. A hypothetical accidental drop condition means that a canister is assumed to be a lee drop on to a pad of the storage cask during loading it into a storage cask. A pad of the storage cask absorbs shock to maintain the structural integrities of a canister under a hypothetical accidental drop condition. In this paper a finite element analysis for various pad structures was carried out to improve the structural integrity of a canister under a hypothetical accidental drop condition. A pad of a storage cask was designed a steel structure with concrete. The 1/4 height of a pad was modified with a structure composed of a steel and a polyurethane foam as a impact limiter. The effect of a shape of a steel structure was studied. The effects of the thickness of a steel structure and the density of a polyurethane foam was also studied.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.146-150
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• 2002

1.55${\mu}{\textrm}{m}$ PnpN optical thyristor as a smart optical switch has potential applications in advanced optical communication systems. PnpP optical thyristors operating at 1.55${\mu}{\textrm}{m}$ are proposed and fabricated for the first time. In the optical thyristors, we employ InGaAs/InP multiple quantum well (MQW) for the active n- and p-layers. The thyristors show sufficiently nonlinear s-shape I-V characteristics and spontaneous emission. In the OFF-state, the device has a high-impedance up to switching voltage of 4.03(V). On the other hand, it has low-impedance and emits spontaneous light as a light-emitting diode in the ON-state voltage of 1.77(V), and switching voltage is changed under several light input conditions. It can be used as a header processor in optical asynchronous transfer mode (ATM), as a hard limiter in optical code division multiple access (CDMA) and as a wavelength converter in optical WDM systems.