• Journal of electromagnetic engineering and science
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• v.5 no.1
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• pp.14-20
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• 2005

In this paper, a technique is presented for broadbanding the bow-tie slot antenna fed by a CPW(coplanar waveguide). The bandwidth performance of existing bow-tie slot designs is greatly enhanced by optimizing the slot shape and properly adjusting the characteristic impedance of the coplanar waveguide feeding the slot. To connect the 50-ohm input coaxial line to the CPW feed line, a linear taper in the CPW is employed. The designed antenna shows a 3.5 $\~$ 10.0 GHz impedance bandwidth, a 3.5 $\~$ 6.0 GHz pattern bandwidth, and a 5.5 $\~$ 7.5 dBi gain over 3.5 $\~$ 6.0 GHz. Above 6.0 GHz, the antenna radiation pattern appreciably deviates from the typical dipolar pattern.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.375-380
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• 2004

This paper presents the basic quench protection idea for the HTS(High-Temperature Superconducting) cable. In Korea power system, the transfer capability of transmission line is limited by the voltage stability, and HTS cable could be one of the countermeasure to solve the transfer limit as its higher current capacity and lower impedance[1]. However, the quench characteristic of HTS cable makes HTS cable to loss its superconductivity, and therefore change the impedance of the line and power system operating condition dramatically. This pheonominum threats not only HTS cable safety but also power system security, therefore a proper protection scheme and security control counterplan have to be established before HTS cable implementation. In this paper, the quench characteristics of HTS cable for the fault current based on heat balance equation was established and a proper protection method by FCL(Fault Current Limiter) was suggested.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.2
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• pp.41-48
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• 1997

Nowadays, EMI emission characteristics, which causes harmful effect on power distribution system and other equipments, have been studied in field of Power electronics, vigoriously. So, in this paper, the conducted EMI emission is measured and compared for 3-phase diode rectifier and PWM converter according to switching frequency variation and current control method change using LISN(Line Impedance Stabilization Network) and spectrum analyzer.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2546-2548
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• 1999

This paper describes characteristics of independent load sharing of parallel UPS systems and proposes a method of control which does not require control interconnections at each UPS system and compensates for line impedance. Simulation results of a two-module UPS system with different power latins and line impedance have demonstrated the feasibility of the proposed control scheme in load sharing.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1373-1375
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• 1999

High impedance fault (HIF) is defined as fault the general overcurrent relay can not detect or interrupt. Especially when HIF occur in residential areas, energized high voltage conductor results in fire hazard, equiment damage or personal threat. This paper proposes the model of HIF in transmission line using the ZnO arrester and resistance to be implemented within EMTP. Wavelet transform is efficient and useful for the detection of HIF in power system, because it uses variable windows according to frequency. HIF detection method using wavelet transform can distinguish HIF from similar phenomena like arcfurance load, capacitor bank switching and line switching.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.260-264
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• 2003

In this paper, a $\lambda/4$ hairpin resonator is proposed to reduce the size of planar resonators for a LTCC MLC bandpass filter. The $\lambda/4$ hairpin resonator operates as stepped impedance resonator (SIR) without changing the width of the planar resonator. It is composed of two sections those are parallel coupled line and transmission line. The characteristic impedance of two sections is different each other. The design formulas of the bandpass filter using the coupling element at the arbitrary position are derived from even and odd-mode analysis. The formulas can take account of the arbitrary coupling of lumped ana/or distributed resonators. The advantage of this filter is its abilities to change freely the coupling structure between two resonators. Experimental bandpass filters for 2.4GHz Band are implemented and their performances are shown.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.4
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• pp.399-404
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• 1987

By using the principles of the three line coupled, the equivalent admittance parameters of the band-stop filter of the three line two port spurline for MIC are derived. The frequency and in/output impedance characteristics of the filter were studied. One-section spurline bandstop filter with their stopband cented near 4GHz have been fabricated and tested. The results show good agreement between the theoretical centre frequency and the experimental results.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.319-322
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• 2002

Distance relay is operated in calculating line impedance. It can be worked accurately in overhead line. However, power cables or combined transmission lines need compensation for calculated impedance because cable systems have sheaths, grounding wires and sheath voltage limiters(SVLs) Neuro-fuzzy can be viewed either as a fuzay system, a neural network or fuzzy neural network and it can estimate the location of the fault accurately. In this paper, fault section and fault location can be classified and estimated in neuro- fuzzy inference system and neural network.

• ETRI Journal
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• v.27 no.6
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• pp.677-684
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• 2005

A phased array antenna was fabricated using four-element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a $Ba_{0.6}Sr_{0.4}TiO_3(BST)/MgO$ structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance-matching-part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this techniqueadapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X-band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by $15^{\circ}$ in either direction.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.305-307
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• 2003

This paper presents an apparent impedance calculation procedure for distance relaying of transmission line involving FACTS (Flexible AC Transmission System) devices, particularly the UPFC (Unified Power Flow Controller), between Kangjin and Jangheung in Korea. With the changes of UPFC's parameters, the measurement and protective range (trip boundaries) of the adaptive distance relay can also be changed. So, it is the most important part in the field of system protection to analyze the operating characteristic of relaying system. The presence of UPFC significantly affects the trip boundaries which are also adversely affected by fault resistance combined with remote end infeed. This paper presents the apparent impedance calculations and the distance relay setting characteristics for faults involving the UPFC in the KEPCO system.