• 대한전기학회논문지:전력기술부문A
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• 제53권7호
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• pp.397-404
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• 2004

This paper describes a study of transient characteristics in 765kV untransposed transmission lines. As the 765(kV) system can carry bulk power, some severe fault on the system nay cause large system disturbance. The large shunt capacitance and small resistance of 765kv transmission line make various difficulties for its protection. These problems including current difference between sending and receiving terminals on normal power flow, low order harmonic current component in fault current and current transformer saturation due to the long DC time constant of the circuit etc. must be investigated and solved. The analysis of transient characteristics at sending terminal has been carried out for the single phase to ground fault and 3-phase short fault, etc. The load current, charging current in normal condition and line flows, fault current, THD(Total Harmonic Distortion) of harmonics, time constants have been analysed for the 765kV untransposed transmission line systems.

• 조명전기설비학회논문지
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• 제23권7호
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• pp.20-28
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• 2009

This paper presents the design of zero current switching ZCS pulse frequency modulation type DC-DC converter for magnetron power supply. A magnetron serving as the microwave source in a microwave oven is driven by a switch mode power supply (SMPS). SMPSs have the advantages of improved efficiency, reduced size and weight, regulation and the ability to operate directly from the converter DC bus. The demands of the load system and the design of the power supply required to produce constant power at 4[kV]. A magnetron power supply requires the ability to limit the load current under short circuit conditions. The current source series resonant converter is a circuit configuration which can achieve this. The main features of the proposed converter are an inherent protection against a short circuit at the output, a high voltage gain and zero current switching over a large range of output power. These characteristics make it a viable choice for the implementation of a high voltage magnetron power supply.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2568-2571
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• 2002

A LCD backlight inverter control IC based on the piezoelectric transformer (PZT) for Cold Cathode Fluorescent Lamp (CCFL) lighting is proposed. It is indeed a variable frequency, variable duty (VFVD) controller having dual feedback control loops for achieving both the regulation of lamp current and the maximum efficiency. The PWM controller regulates the lamp current, while the PLL controller tunes the operating frequency to the frequency that the efficiency of the combined LC-PZT resonator becomes maximum. The mixed PLL/PWM control technique lets the backlight inverter operate at the maximum efficiency in spite of the variation of component and environment. The controller features include a protection for an open or broken lamps, and an open lamp regulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.479-481
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• 2001

Traditionally, instrument transformer of the ferromagnetic core type have been used for measuring current in GIS(Gas Insulated Switchgear). Recently, with the introduction of digital technology at the protection relay or measurement device level, the use of new current sensor can be foreseen. Current measurement by means of Rogowski coil is just one illustration of this. This paper describes the progress of development of Rogowski-coil type CT for application in 170kV GIS.

• 대한전기학회논문지:전력기술부문A
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• 제52권11호
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• pp.647-654
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• 2003

As electrical power system has become complicated and enlarged to cope with the increasing electric demand, it has to be expected that higher speed, higher reliability, higher function and higher arithmetic ability in protective relay should be realized. Therefore, in this papers, by hardware design and implementation used DMA controller that transfer blocks of data to any location in the memory map without interfering with CPU operation, CPU utilization is increased effectively, as a result it made possible to implement multi-function digital protective relay which has high trust and high function of protection as well as control and metering for power transformers using single processor(DSP).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.503-505
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• 1995

The surge arrester plays a vital role in the protection of substation against transient overvoltages resulting from lightning surges and system switching operations. The proper selection and application of the surge arrester is an integral part of the process of substation equipment insulation level selection. The paper outlines the basic consideration in modeling the lightning stroke, the surge arrester, and the system to be protected. The paper discusses the results of various cases simulated using the alternative transient computer program to evaluate the separation effects.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(5)
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• pp.245-248
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• 2001

This paper is indicating the problems, which are the conduction loss on the high frequency transformer, the protection of rectification diode as the snubber loss and the stress of switching main devices, as be made high current and high speed in the phase-shift switching full-bridge DC-DC converter is used the power supply’s main circuit of high capacity. To improve those problems, in this paper, it is proposed that is the resonant circuit auxiliary can be reduced conduction losses and stabilized output control. And, it is constructed prototype of the power supply as the result of computer simulations.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1997년도 추계학술발표회논문집
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• pp.74-77
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• 1997

As underground distribution systems to be operated in downtown have more merits than overhead distribution system, underground distribution systems are being increased. But when pad-mounted transformers have troubles, reptures and fires can be occurred. We think that this makes accidents and power failures of bulidings and generates malaise and a great economic loss. In order to increase the reliability of pad-mounted transformers, we have investigated transformers and understood their failure mechani는. Therefore, we would have objectives and necessities of this study to improve quality and operating condition and install switches to be able to check and maintain transformers and optimize protection devices and increase cooling effect in pad-mounted transformers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1266-1268
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• 2004

This is a thesis that a quarter-brick size of 100W class open-frame type on board power module comprising telecommunication application is reported. The input voltage is established between 36 and 75 in range in order for power module to be utilized for the telecommunication application, and output were set at 3.3V and 30A. A number of parts used for transformer, inductor, and hit sink are composed of PCB in order for DC-DC converter to be lowered below 8 mm. A constant current control circuit was annexed to the system as well as basic protection prototypes such as over-voltage, over-current, and over-temperature were well considered to enhance more credibility, and were tested. As a result, high circuit performance and credibility turned out to be significant.

• Journal of Power Electronics
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• 제10권2호
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• pp.125-131
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• 2010

Switched-resonator converters are a new family of soft switching DC-DC converters where the energy is transferred via a resonator. This paper introduces some isolated topologies of this family. The achieved advantages include, load independent soft-switching, self short-circuit protection, and optimization capability due to topology variety. Compared to conventional series-resonant converters, outstanding advantages such as a smaller fewer number of switches and diodes, a smaller transformer, and lower current stresses are achieved. A general synthesis scheme, functional topologies, and essential relations are included. Experimental results from a laboratory prototype confirm the presented theoretical analysis.