• Title, Summary, Keyword: conductive dust

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Risk of Electric Arcs by Conductive Dust Accumulated on Circuit Breaker (차단기에 누적된 도전성 분진에 의한 아크 위험성)

  • Kim, Doo Hyun;Kang, Yang Hyun;Kim, Eun Jin;Hwang, Dong Gyu
    • Journal of the Korean Society of Safety
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    • v.30 no.4
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    • pp.20-25
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    • 2015
  • In general, the causes of the electrical fire are overcurrent, short circuit, poor contact, etc. This study is aimed to recognize the risk of electric arc to prevent electrical fires due to the conductive dust accumulated on the circuit breaker. The experiment was carried out by the method that conductive metal dust collected from the field is being accumulated on the experimental electrodes with gap of 13 mm until the arc is generated. In case that arc was generated, the amount of conductive dust was measured and the thickness was calculated. This experiments was conducted by particle size. In order to distinguish particle size, mesh size(60~100, 100~150, 150~200, 200~250mesh) was classified using a sieve. As the results of experiment for each of the particle sizes, it was confirmed that there is differences in the generation of arc depending on the thickness of dust accumulated.

The Development Plan of Salt Contamination Map Using GIS (지리정보 시스템을 이용한 전국 염해 오손도 구축 방안)

  • Kang, Yeon-Woog;Kwak, Joo-Sik;Shim, Eung-Bo;Yoo, Chol-Hwan
    • Proceedings of the KIEE Conference
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    • pp.377-379
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    • 2001
  • Contamination flashover is responsible for insulator electrical failures. Particularly, in Korea, with its perennially dry spring, the first spring rain often cause serious line outages by forming a conductive liquid film on the insulator surface. Rainwater and fog are not normally conductive but unfortunately atmospheric dust deposited on the insulator surface contains soluble salts which may lead to bad condition of insulation by combining watery and salts. Transmission design engineers have used a contamination map drawn on the traditional paper map. But it is not convenient because it does not include the information of Geographic Information accurately. This paper explains the newly developed salt contamination map program using Geographic Information System, which provide accurate geographic information. The program is designed to use four parts of datum, salt contamination levels, 345kV & 154 kV transmission lines, power plants & substations and background map. The digital background map is composed of raster files, the others are done by vector map.

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Performance of carbon fiber added to anodes of conductive cement-graphite pastes used in electrochemical chloride extraction in concretes

  • Pellegrini-Cervantes, M.J.;Barrios-Durstewitz, C.P.;Nunez-Jaquez, R.E.;Baldenebro-Lopez, F.J.;Corral-Higuera, R.;Arredondo-Rea, S.P.;Rodriguez-Rodriguez, M.;Llanes-Cardenas, O.;Beltran-Chacon, R.
    • Carbon letters
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    • v.26
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    • pp.18-24
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    • 2018
  • Pollution of chloride ion-reinforced concrete can trigger active corrosion processes that reduce the useful life of structures. Multifunctional materials used as a counter-electrode by electrochemical techniques have been used to rehabilitate contaminated concrete. Cement-based pastes added to carbonaceous material, fibers or dust, have been used as an anode in the non-destructive Electrochemical Chloride Extraction (ECE) technique. We studied the performance of the addition of Carbon Fiber (CF) in a cement-graphite powder base paste used as an anode in ECE of concretes contaminated with chlorides from the preparation of the mixture. The experimental parameters were: 2.3% of free chlorides, 21 days of ECE application, a Carbon Fiber Volume Fraction (CFVF) of 0.1, 0.3, 0.6, 0.9%, a lithium borate alkaline electrolyte, a current density of $4.0A/m^2$ and a cement/graphite ratio of 1.0 for the paste. The efficiency of the ECE in the traditional technique using metal mesh as an anode was 77.6% and for CFVF of 0.9% it was 90.4%, with a tendency to increase to higher percentages of the CFVF in the conductive cement-graphite paste, keeping the pH stable and achieving a homogeneous ECE in the mass of the concrete contaminated with chlorides.

Detection of Current Signal and Thermal Characteristics of Electric Fan Operated in Various Situations (선풍기의 운전 상황별 발열특성 및 전류신호 검출)

  • Kim, Doo-Hyun;Lee, Heung-Su
    • Journal of the Korean Society of Safety
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    • v.29 no.3
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    • pp.20-27
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    • 2014
  • Cooling equipment is the frequent occurrence of fire despite the absence of the heating element. National fire statistics in 2013 show that a total of 263 fires occurred in the cooling equipment and the number of electric fan has 145 fire cases. This is accounted for 55.1% of the whole. Electric fan is the electrical appliance that the heat is generated on the winding wire and the iron core. If such characteristic is not controled properly, fire would break out at the electric fan. also there is a gap filled with an insulator between connection terminals of the capacitor in the electric fan. But in case that the gap on the capacitor is covered with some conductive material such as dust, there would be a fire as well caused by electrical heating locally. Although many studies related with those have been conducted, electric fan fire is continuously occurred. In this study, thermal characteristics and current signal in various conditions such as the heat generation of windings including iron cores of the motor and the dielectric breakdown of terminals on the capacitor connected to the motor were detected. In order to measure the maximum temperature, "third level" wind velocity button was pushed and the time selection switch to "continuation" was set. Analyzed data would be available for the fire safety of the electric fan.

Thermal Characteristic and Failure Modes and Effects Analysis for Components of Photovoltaic PCS (태양광 발전 PCS 구성부품에 대한 열적특성 및 고장모드영향분석)

  • Kim, Doo-Hyun;Kim, Sung-Chul;Kim, Yoon-Bok
    • Journal of the Korean Society of Safety
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    • v.33 no.4
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    • pp.1-7
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    • 2018
  • This paper is analyzed for the thermal characteristics(1 year) of the 6 components(DC breaker, DC filter(including capacitor and discharge resistance), IGBT(Insulated gate bipolar mode transistor), AC filter, AC breaker, etc.) of a photovoltaic power generation-based PCS(Power conditioning system) below 20 kW. Among the modules, the discharge resistance included in the DC filter indicated the highest heat at $125^{\circ}C$, and such heat resulting from the discharge resistance had an influence on the IGBT installed on the rear side the board. Therefore, risk priority through risk priority number(RPN) of FMEA(Failure modes and effects analysis) sheet is conducted for classification into top 10 %. According to thermal characteristics and FMEA, it is necessary to pay attention to not only the in-house defects found in the IGBT, but also the conductive heat caused by the discharge resistance. Since it is possible that animal, dust and others can be accumulated within the PCS, it is possible that the heat resulting from the discharge resistance may cause fire. Accordingly, there are two options that can be used: installing a heat sink while designing the discharge resistance, and designing the discharge resistance in a structure capable of avoiding heat conduction through setting a separation distance between discharge resistance and IGBT. This data can be used as the data for conducting a comparative analysis of abnormal signals in the process of developing a safety device for solar electricity-based photovoltaic power generation systems, as the data for examining the fire accidents caused by each module, and as the field data for setting component management priorities.

Examination on the Mounting Status of Cigar Lighter Receptacle for Vehicles and Analysis of its Tracking Characteristics (차량용 시가 잭의 장착 실태조사 및 트레킹 특성 분석)

  • Choi, Chung-Seog
    • Journal of the Korean Society of Safety
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    • v.24 no.4
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    • pp.28-33
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    • 2009
  • This study examined the mounting status of cigar lighter receptacles for vehicles and analyzed the tracking phenomenon that occurs when foreign material entered a cigar lighter receptacle to obtain data for the analysis of accident investigation. Regardless of the vehicle's output, cigar lighter receptacles are mounted in a vehicle horizontally, vertically, or at tilting or inclined angle. The tilting type cigar lighter receptacle is much easier to use but current leakage resulting from foreign materials (coffee, beverages, water, etc.) falling into the cigar lighter receptacle may cause a fire to start. This study used a vehicle battery (DC 12V) as a power supply for the tracking test and configured its circuit in the same way as that of an electrical device in a vehicle. The tracking phenomenon that occurred in the standby mode of the vehicle exhibited a fine flame and an irregular occurrence of smoke. While this tracking phenomenon was occurring, the leakage current and the reaching distance of the flame were measured to be approximately 930mA and $20{\sim}50cm$, respectively. It is thought that the resultant flame may ignite toluene, dust, cigarettes, etc. It was observed that as the tracking progressed, the internal metal socket melted and a hole was created, the surface of which was also severely carbonized. In addition, the electrical resistance of the carbonized conductive path was measured to be approximately $30{\Omega}$. It is thought that this much resistance may cause local heating when leakage current flows and could ignite any nearby flammable material.