• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.43 no.7
• /
• pp.1050-1060
• /
• 1994

This paper is a study on the computer simulation of the characteristics of the superconducting fault current limiter. Input variable parameters are apparent power, load resistance value, line resistance value and so on. Initial fault current 2 times larger than the trigger current is required to reduce the switching time of SFCL. The propagation velocity increases abruptly, the transport current is several times larger than the ciritical current. In this paper, the switching time is calculated to be 323$\mu$ sec, and the initial fault current is 19 times larger than the critical current. Because the trigger coils are bifilar winding, they have little impedance in superconducting state. After fault occurred, the limiting coil acts as a superconducting reactor and the trigger coils quench at a critical current. Without the SFCL in the circuit, fault current after the load impedence is shorted might be increased to 1100A. The fault current is, therefore, successfully limited by the superconducting limiting coil to 100A determined by the coil inductance.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.94-97
• /
• 1998

The conceptual design of integrated three phase superconducting fault current limiter (SFCL) is presented. And through simulation of power system where this SFCL is installed, the characteristics of this SFCL is analyzed. It is like three-phase transformer. So it has the same characteristics with inductive single phase SFCL. But it has more merits than single phase SFCL. Differently to single phase SFCL, integrated three phase SFCL induces impedance at all phase by any single phase fault to protect the power system more safely.

• Proceedings of the IEEK Conference
• /
• 2007.07a
• /
• pp.461-462
• /
• 2007

DC Arc is an electric discharge which is occurred in two oppolsite electrode when system operating with DC current appliance. In this paper, DC arc detection system is designed for the display of DC arc fault current which is occurred in the local electric network with DC Power. This DC arc is one of the main causes of electric fire of dc system. Arc fault in electrical network has the characteristics of low current, high impedance and low frequency. DC Arc current detection device is designed for the display of arc fault current which has the modified arc characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.426-432
• /
• 2017

An experimental and numerical study on shock attenuation in a solid by a subminiature flyer impact was conducted to determine the performance of a subminiature exploding foil initiator such as, flyer velocity and impulse loading. The obtained attenuation pattern shows the possibility to determine the critical flyer velocity for initiating the miniaturized pyrotechnic unit by figuring out shock intensity and duration according to flight characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11a
• /
• pp.513-516
• /
• 2001

In this study, the properties of MCMB anode Mixed with KCF were evaluated. KCF material was used as not only conducting agent but also active material. The Electric conductivity of MCMB and KCF were 23.7S/cm and 45.8S/cm. Characteristics of anode with different KCF contents were the best effect at 2wt%. The 1st Ah efficiency of cells were increased with increment of KCF contents. The internal resistance and the rate capability were 1.59Ω and 135mAh/g at 2C. The discharge capacity was gradually faded with the charge-discharge cycling to about 50th cycles.

• Electrical & Electronic Materials
• /
• v.8 no.6
• /
• pp.787-794
• /
• 1995

To improvement the magnetic and frequency properties of YIG(Yttrium-Iron Garnet) in microwave region, it is investigated that the effect of $Al^{3+}$ ions on magnetic and frequency characteristics of YIG, using samples of basic YIG composition( $Y_{3}$F $e_{5}$ $O_{l2}$) added with A1$_{2}$ $O_{3}$ from 0 to 2.5 [mol%]. The measurment is conducted mainly for the structural properties and magnetical properties. The structural properties is measured using SEM(Scanning Electro Microscope), EDX(Energy-dispersive X-ray spectrometer) and XRD(X-ray diffraction equipment). The magnetical properties is measured with B-H curve tracer and impedance analyzer. As a result, it is confin-ned that the effect of eddy current loss is minimized while maintaining high saturation flux density of YIG, when YIG is added with 0.5 [mol%] of A1$_{2}$ $O_{3}$.>.>.

• Electrical & Electronic Materials
• /
• v.9 no.1
• /
• pp.51-58
• /
• 1996

This report describes thick traveling-wave electrode formation and microwave transmission characteristics of the fabricated electrodes. Effective refractive indices of the microwave in the 5 micron CPW type traveling-wave electrodes is around 2.45 according to the results of time domain S parameter measurements. The bandwidth of the electrodes is about 10 GHz and could be extended to 15 GHz through optimization of the process. The developed process technique that enables plating of micropatterns upto 20 micron can be applied to broadband optical intensity modulators.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.1347-1349
• /
• 2003

PV array, which is generally installed in the outside, has the possibility to be damaged by high voltage doc to lightning. Because the surge characteristic of PV array has not been fully identified yet, there is the very important issue whether PV array should be connected with ground or not. In this paper, a basic model of PV array is provided considering solar cell's barrier capacitance and ground capacitance for analysis of surge characteristics.

• Journal of Sensor Science and Technology
• /
• v.5 no.3
• /
• pp.33-40
• /
• 1996

$(Ba_{0.5}\;Ca_{0.5})TiO_{3}$ humidity-sensitive devices were fabricated by a solid reaction method, and their electrical properties were investigated. The specimens exhibited good humidity sensitivity, in which the impedance changes linearly. It is shown that electrical conduction with moisture adsorption is dominated by the ions through characteristics of charging and discharing current, and electrical conductivity increases as rasing the temperature and relative humidity. It is realized that relative permittivity increases and activation energy decreases with increasing relative humidity.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.2
• /
• pp.363-369
• /
• 2017

This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.