• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2206-2207
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• 2008

본 논문에서는 분전반에서의 화재 위험 요소와 화재위험 요소에 대한 현장 실태조사 결과를 분석하였다. 분전반에서의 화재 위험 요소는 크게 전기적 요인, 환경적 요인, 물리적 요인으로 나눌 수 있으며 전기적 요인으로는 단락, 과부하(과전류), 접촉불량, 전류 불평형 등이 있으며 환경적 요인으로는 수분(염분 등), 먼지(분진, 목분, 철분 등), 온도(고온) 등에 의한 절연파괴, 기기 손상, 오동작 등이 있다. 물리적 요인으로는 기계적인 진동이나 충격 등에 의한 전기적 접속부의 이완에 의한 발열 등을 들 수 있다. 이러한 화재 위험 요인에 대하여 현장실태조사를 실시한 결과, 일부 분전반에서 내부에 먼지 등 이물질이 차단기, 전선, 단자대 등의 표면에 부착되어 있음을 확인할 수 있었으며 수분이나 염분 등의 영향으로 전극간 절연물 표면의 열화로 화재가 발생할 가능성이 있다. 또한, 적외선 열화상 분석결과, 일부 차단기 단자에서 국부 발열이 관측되었으며, 부하 분담의 불평형에 의한 발열도 확인되었다. 이러한 위험요인에 의한 화재 예방을 위하여 규정된 전선 굵기의 사용과 적정 체결압력의 확보, 상간 전류 불평형을 줄이기 위한 부하 분담의 조정이 필요하다. 향후, 분전반에서의 전기화재, 감전사고 등 전기재해의 예방을 위하여 지속적이고 체계적인 유지관리는 물론 사고 발생 전에 이상 징후를 사전에 감지하여 조치를 취할 수 있도록 하는 기술의 개발과 현장 적용이 요구된다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.349-358
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• 2019

This paper aimed at collecting sensor signals to extract characteristic parameter of the rotor. A vibration test rig has been developed to perform model tests. Signal characteristics were analyzed when driving normally. Envelope FFT Analysis is used to extract vibration components caused by periodic impacts from other vibration factors. Signal analysis was performed when load changes were given to speed sensors and vibration test rigs that show low frequency characteristics of the rotor and signal analysis according to rotational speed. The acceleration signal measured in the bearing housing has a small amplitude and produces only the rotational frequency component and harmonic component of the motor. As the number of rotations increases, the amplitude of acceleration can be seen. As the rotational speed increases, it can be seen that there is a difference in the shape of the original data and compared with the acceleration FFT graph, it can be seen that the noise is strong at low frequencies and the corresponding rotational frequency components are clearly represented. It can be seen that changing the load does not increase the main rotational frequency component.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.4
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• pp.21-28
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• 1986

Conversion of anaerobic mesophilic digestion to thermophilic range has been investigated using a synthetic sludge. When temperature was raised at a rate of 2, 1, and $0.5^{\circ}C$ per day with continuous feeding, a lower reaction rate was observed with a high rate of temperature change. Although methane fermentation ceased completely for an digesters at thermophilic temperature, acid fermentation continued. Methane fermentation was never achieved even with neutralization during 6 months of resting. The methane formers were completely inactivated by the temperature shock and accumulation of volatile acids due to continuous feeding, while the acid formers lost biological activity quickly, but gradually acclimated to a high temperature. When temperature was raised without feeding, successful thermophilic digestion was achieved with 1 day of resting at thermophilic temperature at a rate of $1^{\circ}C$ per day, and also achieved with 20 days of resting at a direct increase. Conversion to a thermophilic range is easily achieved with resting. A short period of resting is required at a low rate of temperature increase, while a long period of resting enough to balance methane formers with acid fermers makes a conversion possile when temperature is raised at a high rate. Soured thermophilic digesters were recovered after seeding of mesophilic sludges, and sludge seeding could be a good method of start-up, conversion, or recovery of a thermophilic digester. Significant amount of thermophiles seemed to be present in the mesophilic digesters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.494-500
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• 2019

The purpose of this study was to determine a method to prevent damage during the transfer of loading through optimal design of loading transfer software for an ammunition-carrying armored vehicle. Typically, an ammunition carrier armored car is equipped with an automated charge transfer system. The load is intermittently damaged during the loading of the cargo, and this needs to be improved. The following improvements and verification tests were carried out. As impact speed increased, the loading speed was reduced 60%, and a special fixture utilizing a force gauge was developed and tested. If the maximum current of 11A for the servo controller is output when the load of the conveyor is generated by interference inside the loading tube, there is a possibility of charge breakage. If the maximum current is low, the load cannot be loaded. In the loading test for the ammunition carrier armored car with the actual charge, the improved design was found to be valid, as the load was not damaged and occurred nominally.

• Journal of Environmental Science International
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• v.2 no.4
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• pp.325-330
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• 1993

A number of experiments were conducted in order to investigate the organic removal efficiency and biomass characteristics according to the organic shock loading rate in a fluidized bed biofilm reactor. At the operation conditions of HRT, 8.44 hour, superficial upflow velocity, 0.9 cm/sec and temperature, 22$\pm$$1^{\circ}C$, the removal efficiency of SCOD was founded to be 96.5, 92 and 90 % with the organic shock loading rate of 3.5, 10.8 and 33 kgCOD/m$^3$ㆍday, respectively. Within the F/M ratio ranged 0.4 to 2.0 kgCOD/kgVSSㆍday, the SCOD removal efficiency was shown as 90% at F/M ratio of 2.0 kgCOD/kgVSSㆍday, but the TCOD removal efficiency was 72 % at F/M ratio of 1.8 kgCOD/kgVSSㆍday. The average biomass concentrations were 7800, 14950 and 27532 mg/l on the organic shock loading rate of 3.5, 10.8 and 33 kgCOD/$\textrm{m}^3$ㆍday, respectively. This result was agreed with the fact that more biomass could be produced at high concentration of substrate, but some biomass was detached at the onset of shock and easily acclimated at the shock condition.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.603-605
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• 2005

전력수요의 증대에 따른 계동모의 확장에 따라 관련기기는 초고압 및 대용량화 추세에 있다. 이러한 관련기기들 중에서도 특히 154/22.9kV 전력용 변압기는 고장시 수용가의 정전범위가 방대하고 변압기 내부 고장의 복구비용 또한 막대하므로 경제적 손실은 물론 사회적 영향도 크다. 우리나라에서는 1980년 초기부터 154/22.9kV 전력용 변압기의 고장이 급증하였으며, 이러한 원인은 주로 직전접지 방식을 채택하고 있는 한전 계통에서 배전선의 지락고장에 의한 지락고장 전류가 변압기 중성점을 통하여 변압기에 충격을 가함으로써 변압기 권선 단락 절연파괴 및 ULTC 고장 등이 발생하는 것으로 밝혀졌다. 따라서 한전에서는 변압기 중성점으로 흐르는 지락고장전류의 저감을 위해 변압기 중성점 접지 리액터(NGR: Neutral Ground Reactor)를 설치하여 운전하고 있으며, 결과 변압기 고장이 크게 감소하였다. 그러나 모선 절체시 변압기 1, 2차측 차단기 Trip 고장이 발생하였으며, 고장 발생 원인은 NGR 보호계전기 59GT 계전기의 오동작에 의한 86T Lock Out 계전기 동자으로 변압기 1, 2차측 차단기 Trip 고장이 발생한 것으로 추정된다. 따라서 본 논문에서는 무부하 모선 차단시 59GT 계전기에 나타나는 이상 전압을 EMTP (electro-magnetic transient program)를 이용하여 분석하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.3
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• pp.161-171
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• 2010

As embedded systems adopt monolithic kernels, NAND flash memory is used for swap space of virtual memory systems. While flash memory has the advantages of low-power consumption, shock-resistance and non-volatility, it requires garbage collections due to its erase-before-write characteristic. The efficiency of garbage collection scheme largely affects the performance of flash memory. This paper proposes a novel garbage collection technique which exploits data redundancy between the main memory and flash memory in flash memory-based virtual memory systems. The proposed scheme takes the locality of data into consideration to minimize the garbage collection overhead. Experimental results demonstrate that the proposed garbage collection scheme improves performance by 37% on average compared to previous schemes.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.469-472
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• 2008

As recycled fine aggregate manufacturing technology with exceeding in economical efficiency, reduction efficiency of environmental load and quality improvement effect of recycled fine aggregate, it is to develop dry manufacturing system composed specific gravity separator of high-speed rotation impact type and centrifugal Force Powder Collector, etc. in this study. And it is to verify performance with evaluating quality of recycled fine aggregate. In consequence, it is identify that performance improvement effect of recycled fine aggregate by crushing recycled fine aggregate according to high-speed rotation impact, separating and collecting powder and minuteness dust according to centrifugal Force and mass defect, separating and reclaiming minuteness sand to mass defect.

• Journal of the Korean Magnetics Society
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• v.9 no.1
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• pp.64-70
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• 1999

The inrush current of transformer can flow when the overvoltage caused by surge or external faults is applied. In this paper, an algorithm for the calculation of this inruch current is proposed. The capacitances of windings are precalculated by using 3 dimensional FEM and are appended to circuit of the transformer. And transient characteristics of the transformer are analyzed by axisymmetric FEM which is coupled magnetic field of transformer and circuit of transformer. When a transformer encounters abnormal voltage, using the proposed method, internal magnetic field of transformer, voltages and currents of windings are calculated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.794-797
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• 2005

The automatic load transfer switch (ALTS), a kind of electric power switch, typically automatically transfers electrical loads from a normal electrical power source to an emergency electrical power source upon reduction or loss of normal power source voltage. It can also automatically re-transfer the load to the normal power source when the normal voltage has been restored within acceptable limits. The transfer operation of ALTS is accomplished by a spring-driven linkage mechanism. In order to control or delay the transfer switching time, the ALTS studied in this paper uses the superposed leaf springs, which are subjected to impact leadings in contacting with electrical contacts. Therefore, to confirm whether the springs has enough mechanical endurance in ALTS, we build a finite element model of the superposed lear springs using LS-DYNA and perform the impact and fatigue analysis.