• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.253-254
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• 2020

High Voltage Direct Current (HVDC) 시스템은 고압 직류송전을 위한 시스템이다. 고압 직류 송전을 위해서는 전력변환기가 교류전력을 직류전력으로 변환해주어야 하는데, 최근에는 모듈형 멀티레벨 컨버터(Modular Multilevel Converter, MMC)가 많이 적용되고 있다. MMC는 다수의 서브모듈이 직렬로 구성되어 있으며 DC-link단에 대용량 커패시터가 없다. MMC의 심각한 사고 중에 하나는 DC측 전력케이블의 단락사고로 시스템에 따라서 수십 kA 정도의 사고전류가 AC측 CB(Circuit Breaker)가 열리기 전까지 수십 ms에서 수백 ms동안 흐른다. 만약 하프브릿지 회로의 서브모듈로 구성된 컨버터에 별도 보호장치가 없으면 단락전류는 서브모듈의 하단 다이오드를 통해서 흐르게 되어 소손되게 된다. 이를 방지하기 위해 단락전류를 바이패스(by-pass) 시키기 위한 별도의 사이리스터를 추가하는데 이 기기의 사양은 DC 단락 전류를 충분히 견딜 수 있어야 한다. 본 논문에서는 사이리스터의 서지 전류 내력을 평가하기 위해 사양을 분석하고 시뮬레이션과 실험을 통해서 검증하였다.

• Fire Science and Engineering
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• v.30 no.5
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• pp.67-73
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• 2016

This paper examined the structure, fire resistance of brass fittings type CSST employed in gas appliances and the reliability verification. Brass fittings of type CSST consisted of cladding, tubing, nut, clamp ring, socket, and ball valve. The applicable JIA standard regulates the maximum working pressure to be 4.2 kPa, which is the highest pressure of the relevant standards and the KS D 3625 stipulates the maximum pressure to be 3.24 kPa. With a normal product, the average resistance within the confidence interval was found to be $7.36m{\Omega}$. The average resistance within the confidence interval was $6.67m{\Omega}$ after the fire resistance tests. The analysis indicated that the AD was 1.584 and the standard deviation was 0.3972 with respect of a normal product. Compared to the normal product, however, the damaged product after the fire resistance test showed better features, such as an AD of 1.145 and a standard deviation of 0.2467. Moreover, the average resistance of the normal product was $7.359m{\Omega}$ and the standard deviation in histogram analysis was 0.3972. The average resistance of the damaged product after the fire resistance test in the histogram was $6.67m{\Omega}$ and the standard deviation was 0.2467.

• Fire Science and Engineering
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• v.33 no.4
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• pp.59-69
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• 2019

The present article relates to an experimental study on fire risks due to overcharge and external heat of ESS lithium battery. According to the experimental results of overcharge, ignition occurred as combustible gas and smoke was slowly increased after occurrence of venting, and an explosive combustion form accompanied by flame eruption and sparks was displayed as charged energy is rapidly discharged in an instant. On the other hand, according to the experimental results of external heat, as a tremendous amount of combustible gas and smoke was ignited following being discharged after occurrence of vent, the charged energy itself was rapidly reduced due to the discharged energy so that a passive combustion form was observed when compared with overcharge after occurrence of flames. According the analysis results of fire damage characteristics, differences between external heat (External flame) could be found through visual and X-ray inspections. Namely, while inside electrode plate was completely destroyed and perforation of the electrode plate was observed in the case of overcharge, fire damage of the electrode plate was not severe maintaining the form in the case of external heat.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.21-25
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• 2013

The purpose of this study is to provide basic data for the safety assessment of a water purifier when water leaks due to inappropriate maintenance and the examination of the cause of accidents related to the leak. Due to its inspection and management by non-specialists, if a leak occurs in a water purifier with the water level controller being inclined, it may result in the failure of the compressor, power supply line, PCB, etc. The analysis of the thermal diffusion pattern of water purifier compressors using a thermal image camera shows that its maximum temperature was approximately $80^{\circ}C$. In addition, its operating current was a maximum of 13 A and the system's operating current was approximately 1.7 A after the compressor was charged. It was found that the housing type power cable cover of the compressor had the effect of preventing electric shock but has poor flame resistance. Furthermore, the performance of the overload protector, PTC relays, etc., was excellent but they have potential for problems as metallic terminals were exposed, resulting in the potential of a safety related accident. The terminals and their surface damaged by the tracking showed a trace of carbonization and the resistance between terminals was measured to be approximately $8{\Omega}$. In addition, while the tracking was proceeding, the fuse and circuit breaker installed for system protection did not operate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.583-593
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• 2018

Lightning causes physical damage to aircraft, such as melting, burning and arcing, and magnetic field that occurs on the aircraft's outer body during the penetration of a lightning stroke causes voltage and current transients in the electronics and wiring within the aircraft. This effect will cause induced lightning strikes in the aircraft's internal airborne electronic systems, preventing safe flight. This paper introduces protection circuit design techniques, and the test results that meet the requirements for certification of criteria.

• Fire Science and Engineering
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• v.18 no.4
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• pp.72-77
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• 2004

In this paper, we studied on the short-circuit process, surface structure, and component variation of vinyl cords. In the results of high speed imaging system (HSIS) analysis, as soon as wire covering was damaged by heat, the conductor of wire came in contact with the other conduct of wire, and the short-circuit occurred. Stereomicroscope and SEM analysis indicated that the source part of wire showed V-type form. The molten beads of load part were bigger than those of source part. In the results of EDX analysis, Cu and O were detected in the source part, whereas covering material (Cl, Ca), Cu and O were detected in the load part. The results will help us to find out the cause of electrical fire.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.305-309
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• 2009

This paper operate with variable line impedance equipment consist of resister and reactor, when connect to 3phase induce motor present solve problem appear grid interconnection before/after about voltage transient of pv inverter through test and analysis solve problem.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.4
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• pp.100-110
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• 1995

This paper aims at reviewing the possibility of application over normal or abnormal, detection used by AE, and the characteristics of grinding processes. In this study, when WA-vitri-fied ' resinoid bond grinding wheels:36 kinds of grinding wheel and grinding depth were tuned at the surface grinding, the zone of AE signal generation is theoretically modelled and reviewed by grinding processes. The variation of grinding resistance( F$n^{9}$ $F_{t}$) and AE signal is detected in-process by the use of AE measuring system. The tests are carried out in accordance with grain size and grade of grinding wheels, and work-pieces-STD11 and STD61. According to the experiment's results, the following can be expected;as grinding time passes by, the relation of grinding depth and quantity of AE signal, observing on AE signal and grinding burn suggest the characteristics of grinding processes and evalution on the possibility of control of grinding machine, and monitoring abnormal conditions.e, and monitoring abnormal conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.71-77
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• 2010

Protection against lightning surge is an essential part of almost any electrical and electronic equipment today. Metal Oxide Varistor(MOV) is the single most important component in the overwhelming majority of the Surge Protective Devices(SPD) designated to provide such protection. In this paperr various types of MOV based SPD are inspected and experiments are carried out on the side effects of the low Measured Limiting Voltage(MLV) characteristics. Experiment results show that a lower MLV could cause a higher Temporary Overvoltage(TOV)-induced SPD failure rate in the field, and SPD are more likely to be victims rather than protectors in a TOV scenario. This means that from a safety perspective, the SPD should be specified with higher TOV withstand capability(UT) and faster SPD disconnector.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.64-65
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• 2014

신재생에너지원의 급속한 보급, 고신뢰 및 고효율 전원망에 대한 고객의 요구, 디지털부하의 급증 등 기술적 사회적 환경의 변화에 따라 직류배전망에 대한 관심이 높아지고 있다. 이에 따라 직류배전망의 안전성에 대한 문제도 지속적으로 제기되고 있다. 특히 지락, 단락사고, 절연고장, 낙뢰, 아크, 전식 등으로부터 인체 감전과 기기의 소손, 정지 또는 오동작이 발생될 수 있으며 이로 인해 심각한 문제를 야기될 수 있다. 국제표준 IEC 60364에서는 전기설비에 따른 접지시스템을 TT, TN 및 IT접지의 3가지로 분류하고 있다. TN접지방식은 전원선과 설비외함의 노출 도전부를 보호도체를 사용하여 공통으로 접지하는 계통을 말한다. 따라서, 전원선이 외함에 접촉되거나 인체의 감전에 의한 누전사고가 발생하였을 때 전원선 전체를 통하여 흐르는 전류의 차이를 검출함으로서 사고전류의 검출이 즉각 이루어 질 수 있다. 교류계통에서는 영상전류검출기에 의하여 누설전류의 검출이 가능하지만 직류계통에서는 영상전류검출기를 사용할 수 없으므로 새로운 방식의 누전검출장치의 개발이 요구된다. 또한 감전 사고는 인체의 사고와 설비의 사고 두 가지로 구별되며, 효율적인 전력운영과 안전을 위하여 두가지 사고에 대해 통합적으로 구분 동작이 가능한 누설전류 검출기 개발이 요구된다. 본 연구에서는 TN접지계통에서 직류누설전류 검출이 가능한 홀 센서(HCT)를 사용하여 인체 및 설비의 누설전류 패턴에 따라 구분 동작이 가능한 직류용 누설전류 검출기 개발에 관한 연구를 수행하였다.