• 전기학회논문지
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• 제65권8호
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• pp.1442-1449
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• 2016

This paper proposes a diagnosis to detecting poor contact fault and fault location. Electrical fire by poor contact fault of power cable occupied a large proportion in the total electrical installations. The proposed method has an object to prevent electrical fault in advance. But detecting poor contact fault is difficult to detect fault type and fault location by using conventional reflectometry due to faults generated intermittently and repeatedly on the time change. Therefore, in this paper poor contact fault and fault conditions were defined. System generating poor contact fault produced for the experimental setup. SSTDR and algorithm of reference signal elimination heighten performance detecting poor contact fault on live power cable. The diagnosis methods of signal process and analysis of reflected signal was proposed for detecting poor contact fault and fault location. The poor contact fault and location had been detected through proposed diagnosis methods. The fault location and error rate of detection were verified detecting accuracy by experiment results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1361-1366
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• 2008

Failure mechanism of the poor contact is analyzed on the basis of used connectors and this poor contact of connectors is reappeared by the new forced fretting wear method. As the result of failure analysis and reappearance, fretting wear and corrosion of the contact interface causes the contact resistance degradation and the poor contact of connectors. The amount of degradation depends on the fretting stroke. Changes in contact resistance of static contacts are likely to be small and gradual, while motions of contact interface may result in larger and discontinuous changes in resistance and voltage. This voltage drop by fretting motions is large enough to cause the distortion of sensor signal and mis-working of electric components.

• 한국안전학회지
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• 제27권3호
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• pp.36-41
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• 2012

Electrical Connections often cause fires due to poor contact. Occurrence rate of these fires tends to increase annually. The reason why poor contacts occur is often because it is the low mechanical pressure at the contact points. A typical connection method using mechanical pressure is a screw terminal type. This study reviewed these poor contact cases in the screw terminals. In order to get reproduction of such cases, two types of experiments were conducted. the first one was conducted under the normal contact condition, and the other one was conducted under the poor contact condition that screw terminal of breaker was loosen and did not meet the requirements of toque value. In both types of experiments, compulsory vibration was adopted as a variable to aggravate poor contacts. Each of various current values(4.5A, 9.0A, 13.5A) is input. In these experiments, relationships of a contact, electrical signal such as current and electric pulse by ZCT and thermal characteristics according to vibration effect are analyzed. The suggested data and results in this study provide the useful resources helping to investigate fires due to poor contact, and they develop the detector for poor contact and finally reduce the electrical fire occurrence rate.

• 한국안전학회지
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• 제24권2호
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• pp.30-36
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• 2009

This paper aims at the precursor analysis and DB development of electrical fires based on thermal and current signals for partial disconnection and poor contact on electric wires through experiments and simulations. Also, DB system required for developing the precursor DB with these data was studied and designed. Firstly, in case of partial disconnection, characteristics were derived and analyzed by experiment and electrical-thermal finite element method(Flux 3D) on the model wires which consist of VCTF and IV electric wires. Based on the characteristics, About 351 partial disconnection precursor patterns were generated by the thermal analysis for electric wire according to deterioration time under normal state and 200% overload state of rated current. Secondly, in order to develop poor contact precursor patterns, temperature value and the current signal were considered. In simulating the poor contact situation on connector area of MCCB, connection torque was changed. Through the experimental analysis, about 251 poor contact precursor patterns were generated. Finally, Using thermal precursor patterns obtained by partial disconnection and poor contact, electrical fire thermal precursor DB was developed.

• 한국화재소방학회논문지
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• 제22권4호
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• pp.54-60
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• 2008

본 논문에서는 MCCB 및 단자대 접속부의 접촉불량에 의한 소손특성을 분석하였으며, 발열을 감지하여 화재를 예방할 수 있는 다양한 기법들을 제시하였다. 첫째로, 열전대를 사용하는 방법과 적외선 열화상기를 사용하여 접촉불량 등의 원인에 의해서 발열을 감지하는 방법을 분석하였다. 또한, 접촉불량 발생시 변색여부로 쉽게 이상유무 판단이 가능한 서모캡의 특성을 분석하였으며, 공간 등의 제약을 덜 받으면서 접속부위에 상시 설치하고 감시할 수 있는 방식인 향 캡슐과 향 검지기를 사용하여 과열을 감지하는 시스템의 원리 및 특징을 분석하였다. 마지막으로, 가융합금의 용융특성을 응용한 접촉불량 감지나사를 제작하여 단자대에 적용 및 실험하여 성능을 검증하였다. 상기 제시된 기법들을 적절히 적용된다면 MCCB 및 단자대등의 접속부의 접촉불량에 의한 전기화재 예방에 기여할 수 있을 것으로 기대된다.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2007년도 추계학술논문발표회 논문집
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• pp.205-210
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• 2007

This study on the prevention of electric fire. Generally the electric fire is caused by break or disconnection of the power line, short circuit and poor contact, arcing fault ect. In these causes, this paper is studied on the detection of poor contact and arcing fault. The arcing fault is caused by poor contact mainly. The arcing fault can occurs a electric fire by interaction of flammable gas and materials and it can be caused of tracking and carbonization. These phenomenons is also caused of electric fire. Therefore this paper is studied on the detection of arcing fault and poor contact.

• 한국안전학회지
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• 제20권1호
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• pp.87-93
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• 2005

In this paper, we analyzed ignition characteristics of combustible material and the waveform of power dissipation, voltage and current by poor contact. And the surface structure of plug by poor contact was analyzed. In the results of experiment, the heat generated by poor contact and ignited the combustible material on power cord sets. The insulation material was molten and carbonized by the heat conduction though plug pit and voids were formed inside of insulation material. The waveform of voltage and power dissipation distorted because of a growth of oxidation by poor contact. In particular, in case that load was big load, the waveform of voltage and power dissipation severely distorted as with the passage of time. The surface of plug pin was changed from erosion mark to welding mark according to big load. The results will be applied to the cause analysis of electrical disaster.

• 조명전기설비학회논문지
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• 제29권10호
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• pp.97-103
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• 2015

This paper presents the characteristics of partial discharge and radiated electromagnetic waves in the existence of a poor contact for the insulation diagnosis of eco-friendly power equipment. AC surface discharge experiment was conducted to simulate the poor contact between a hive voltage electrode (anode) and a solid insulator in $N_2/O_2$ mixture gas under a non-uniform field. The partial discharge voltage to be measured at 0.3MPa increased with the increase of the poor contact gap and was saturated with the gap. In addition to the partial discharge characteristics, it was verified that the defect of the poor contact can be diagnosed using the radiated electromagnetic waves due to the partial discharge, which measured by a biconical EMC antenna and a spectrum analyzer.

• 한국화재소방학회논문지
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• 제29권5호
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• pp.57-66
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• 2015

본 논문은 단자대에서 단일원인 및 복합원인에 의한 전기화재위험성을 규명하기 위한 연구이다. 우선적으로 단일원인인 접촉불량에 의한 화재위험성을 측정하기 위해 조임토크변화 및 접촉저항변화에 따른 열적특성을 분석하였다. 또한, 복합원인에 의한 화재위험성을 측정하기 위해 접촉저항변화에 따른 가속트래킹 실험을 실시하여 접촉불량과 트래킹의 화재연관성을 확인하였다. 실험결과 단일원인의 경우 접촉불량상태의 조임토크 및 접촉저항 크기가 증가할수록 열적특성이 뚜렷하게 나타나는 것을 확인할 수 있었고, 접촉저항변화에 따른 열적특성이 조임토크변화에 따른 열적특성보다 그 특성이 더 잘 나타났다. 또한, 복합원인의 경우 단자대 접촉불량과 트래킹은 상호연관성을 가지고 있으며, 두 가지의 복합적인 원인이 서로 작용될 경우 기존의 단일원인의 전기화재 위험성보다 상대적인 위험성이 더욱 높게 나타나는 것으로 도출되었다.

• 조명전기설비학회논문지
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• 제29권8호
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• pp.63-69
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• 2015

This paper presents the surface flashover characteristics to simulate the poor contact between an anode and a solid dielectric in a $N_2/O_2$ mixture gas (8/2) under a non-uniform field. The surface flashover voltage of the $N_2/O_2$ mixture gas revealed the irregular tendency that was not in accordance with the Paschen's law with an increasing gap of the poor contact. In addition, the insulation performance of the $N_2/O_2$ mixture gas at 0.6MPa was comparable to that of $SF_6$ gas of 0.1MPa based on the insulation performance on the poor contact. These results are able to apply the insulation design of eco-friendly gas insulation switchgear considering the internal faults.