• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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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.

• Proceedings of the KSME Conference
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• 2008.11a
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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.

• Journal of the Korean Society of Safety
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• v.27 no.3
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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.

• Journal of the Korean Society of Safety
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• v.24 no.2
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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.

• Fire Science and Engineering
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• v.22 no.4
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• pp.54-60
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• 2008

In this study, damage characteristics of MCCB and terminal block due to poor contact were analyzed, and various poor contact detection techniques were suggested. Firstly, the detection techniques using thermocouple and infrared thermal camera were analyzed respectively. Also, thermo-cap during poor contact detected abnormal status effectively by changing its color, and the detection system using an odor detector and odor capsules was analyzed. Lastly, poor contact detection screw was made using characteristics of fusible alloy, and we applied the poor contact detection screw to terminal block. The above methods could prevent electrical fire caused by poor contact effectively if they are used properly.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2007.11a
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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.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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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.

• Fire Science and Engineering
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• v.29 no.5
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• pp.57-66
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• 2015

This thesis is based on a research to investigate the electrical fire risk due to the single and composite cause in a terminal block. This paper analyzed the thermal characteristics depending on the screw torque change and contact resistance change to measure the fire risk due to the poor contact from single cause first. To measure the fire risk due to the composite cause, the acceleration tracking depending on the contact resistance change was experimented to check the correlation of poor contact and tracking to fire. The experiment result showed that the thermal characteristics were clearer as the screw torque in poor contact status and magnitude of contact resistance increased and that the thermal characteristics of terminal block depending on the contact resistance change was more reliable than the thermal characteristics depending on the screw torque change. Moreover, the terminal block poor contact and tracking were correlated in the case of the composite cause, and when two composite causes were interacted, the electrical fire risk was higher than the single cause.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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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.