• Journal of the Korean Society of Safety
• /
• v.33 no.2
• /
• pp.21-27
• /
• 2018

The expansion and stable operation of electric power facilities are important factors with development of industrial facilities in modern society. In high-voltage equipment such as GIS, the insulation characteristics may be deterioated by environment-friendly gas adaption and miniaturization. There is also the possibility of accidents due to insulation breakdown due to the deterioration of power facilities. Therefore, it is necessary to extend the diagnosis system to continuously monitor the danger signals of these power equipment and to prevent accidents. Most of the internal defects in the GIS system are conductive particles, floating electrode defects, protrusion defects, and the like. In this case, a partial discharge phenomenon is accompanied. These partial discharge signals occur irregularly and various noise signals are included in the field, so it is difficult to evaluate the reliability in the development of the diagnostic system. In this paper, a study was made on equipment capable of generating a partial discharge simulated signal that can be adjusted in size and frequency to be applied to a diagnostic device by electromagnetic wave detection method. The PD simulated pulse generator consists of a user interface module, a high-voltage charging module, a pulse forming circuit, a voltage sensor and an embedded controller. In order to simulate the partial discharge phenomenon similar to the actual GIS, a discharge cell was designed and fabricated. The application of the prototype pulse generator to the commercialized PD diagnosis module confirmed that it can be used to evaluate the performance of the diagnostic device. It can be used for the development of GIS diagnosis system and performance verification for reliability evaluation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.2
• /
• pp.266-271
• /
• 2014

The Electromagnetic Interference(EMI) generating from corona discharge of transformer area can interference the digital Instrument and Control(I&C) systems located nearby transformers. When the potential gradient of the electric field around the conductor is high enough to form a conductive region but not high enough to cause electrical breakdown to nearby objects, the EMI of corona discharge emits with the conducted and radiated noise and it interferences the signals of the I&C systems. Since digital I&C systems have an efficiency and competitive price, the analog I&C systems have been upgraded and displaced with the digital I&C systems but which have less EMI Immunity. There was no assessment to I&C systems by EMI generating corona discharge nearby transformers. When the safety-related I&C systems are installed in plants, the verification of equipment EMI should be done not in site-specific test but in test facilities. There are the need to do the site-specific EMI evaluation of corona discharge nearby transformers. This paper assesses the margin between plant emission limits and the highest composite plant emission of corona. When the non safety-related I&C systems are placed in transformer area, it suggests the appropriate radiated susceptibility level to EMI of corona discharge.

• Journal of the Korean Society of Safety
• /
• v.5 no.2
• /
• pp.32-39
• /
• 1990

The ${\gamma}$-Fe$_2$O$_3$ compounds were oxidized in the furance after gas detecting sensor made molding as the Fe$_3$O$_4$ the synthesized Fe$_3$O$_4$, by ferrous sulfate and sodium hydroxide. Their sensities on carbon monoxide, ethyl alcohol and L. P. G. were measured at various temperatures, respectively. And then their electrical resistivities, thermal properties (D.T.A. ＆ T.G.A.), were examined about their having an effet on the gas-sensing in company with the effect of pure ${\gamma}$-Fe$_2$O$_3$ and the detecting sensor ${\gamma}$-Fe$_2$O$_3$, which reacts with $K_2$CO$_3$ in the hydrothermal coundition, and the electrical conductive mechanism was reflected simultaneously. It was observed that the electrical conductivities and response ratios showed highest value at the endothermic temperature part, 300~35$0^{\circ}C$ of D.T.A.―curve. Consequently, the response ratios and response times of the hydrothermal detecting sensor were higher than that of pure detecting sensor, the specific surface areas were the highest at the endothermic range of D.T.A.-curve. These response ratios of detecting sensor for $K_2$CO$_3$, process at hydrothermal condition on carbon monoxide appeared higher than that on ethyl alcohol and in case of L.P.G. last.

• Fire Science and Engineering
• /
• v.30 no.4
• /
• pp.73-81
• /
• 2016

A self-regulating heating cable is an electrical heating element by flowing an electric current between parallel conductors filled with an extruded semi-conductive polymer. Self-regulating heating cables are used mainly for frost protection purposes because the construction is convenient and the price is low. On the other hand, structural problems with imperfections of the insulation can cause a fire despite their usefulness. This paper deduced a direct method to derive the cause by investigating the scene of a fire due to a self-regulating heating cable and analyzed the basic problem using fault tree analysis. In this paper, the actual fire scene was a cold storage warehouse, and fire investigation was conducted. After investigating the fire scene and fault tree analysis, the cause of the fire could be attributed to dielectric breakdown of the self-regulating heating cable. This paper could be utilized in the fire safety activities and similar fire investigations.

• Nuclear Engineering and Technology
• /
• v.48 no.4
• /
• pp.932-940
• /
• 2016

Pool boiling heat transfer of water saturated at atmospheric pressure was investigated experimentally on Cu surfaces with high-temperature, thermally-conductive, microporous coatings (HTCMC). The coatings were created by sintering Cu powders on Cu surfaces in a nitrogen gas environment. A parametric study of the effects of particle size and coating thickness was conducted using three average particle sizes (APSs) of $10{\mu}m$, $25{\mu}m$, and $67{\mu}m$ and various coating thicknesses. It was found that nucleate boiling heat transfer (NBHT) and critical heat flux (CHF) were enhanced significantly for sintered microporous coatings. This is believed to have resulted from the random porous structures that appear to include reentrant type cavities. The maximum NBHT coefficient was measured to be approximately $400kW/m^2k$ with APS $67{\mu}m$ and $296{\mu}m$ coating thicknesses. This value is approximately eight times higher than that of a plain Cu surface. The maximum CHF observed was $2.1MW/m^2$ at APS $67{\mu}m$ and $428{\mu}m$ coating thicknesses, which is approximately double the CHF of a plain Cu surface. The enhancement of NBHT and CHF appeared to increase as the particle size increased in the tested range. However, two larger particle sizes ($25{\mu}m$ and $67{\mu}m$) showed a similar level of enhancement.

• Carbon letters
• /
• v.21
• /
• pp.61-67
• /
• 2017

We report the use of carrot, a new and inexpensive biomaterial source, for preparing high quality carbon dots (CDs) instead of semi-conductive quantum dots for bioimaging application. The as-derived CDs possessing down and up-conversion photoluminescence features were obtained from carrot juice by commonly used hydrothermal treatment. The corresponding physiochemical and optical properties were investigated by electron microscopy, fluorescent spectrometry, and other spectroscopic methods. The surfaces of obtained CDs were highly covered with hydroxyl groups and nitrogen groups without further modification. The quantum yield of as-obtained CDs was as high as 5.16%. The cell viability of HaCaT cells against a purified CD aqueous solution was higher than 85% even at higher concentration ($700{\mu}g\;mL^{-1}$) after 24 h incubation. Finally, CD cultured cells exhibited distinguished blue, green, and red colors, respectively, during in vitro imaging when excited by three wavelength lasers under a confocal microscope. Offering excellent optical properties, biocompatibility, low cytotoxicity, and good cellular imaging capability, the carrot juice derived CDs are a promising candidate for biomedical applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2002.05a
• /
• pp.529-534
• /
• 2002

It was recommended for all ship engaged in international voyages to carry the dedicated Digital Selective Calling receiver, DSC equipment, VHF transceiver, etc according to Global Maritime Distress & Safety System. Also International Maritime Organization recommended for navigation and communication equipments to applicate the EMC regulations, therefore most of electronic equipments using in the vessel to be faced with problems to cope with new regulations. This study has applied and analyzed the EMC for an equipment integrated with Ch.70 dedicated DSC receiver, DSC equipment, VHF transceiver and groped for solutions to cope with. The test has applied the electromagnetic interference such as the measurement for unwanted emissions from conductive & radio emission and the electromagnetic susceptibility such as the immunity from voltage, frequency variation and electro static discharge, hence comes to be understand the problems related with the power and the earth.

• Journal of Sensor Science and Technology
• /
• v.27 no.6
• /
• pp.397-402
• /
• 2018

Proper seat design is critical to the safety, comfort, and ergonomics of automotive driver's seats. To ensure effective seat design, quantitative methods should be used to evaluate the characteristics of automotive seats. This paper presents a system that is capable of simultaneously monitoring body pressure distribution and surface deformation in a textile material. In this study, a textile-based capacitive sensor was used to detect the body pressure distribution in an automotive seat. In addition, a strain gauge sensor was used to detect the degree of curvature deformation due to high-pressure points. The textile-based capacitive sensor was fabricated from the conductive fabric and a polyurethane insulator with a high signal-to-noise ratio. The strain gauge sensor was attached on the guiding film to maximize the effect of its deformation due to bending. Ten pressure sensors were placed symmetrically in the hip area and six strain gauge sensors were distributed on both sides of the seat cushion. A readout circuit monitored the absolute and relative values from the sensors in realtime, and the results were displayed as a color map. Moreover, we verified the proposed system for quantifying the body pressure and fabric deformation by studying 18 participants who performed three predefined postures. The proposed system showed desirable results and is expected to improve seat safety and comfort when applied to the design of various seat types. Moreover, the proposed system will provide analytical criteria in the design and durability testing of automotive seats.

• Journal of Sensor Science and Technology
• /
• v.30 no.4
• /
• pp.255-260
• /
• 2021

We studied electrochemical sensors using printed carbon nanotube (CNT) film on a polyethylene terephthalate (PET) substrate. Multiwalled CNT films were printed on a PET substrate to study its feasibility as hazardous and noxious substances (HNS) detection sensor. The printed CNT film (PCF) with a 50 ㎛ thickness exhibited a specific resistance of 230 ohm. To determine the optimum sensor structure, a resistance-type PCF sensor (R-type PCF sensor) and a conductive-type PCF sensor (C-type PCF sensor) were fabricated and compared using diluted NH₃ droplets with various concentrations. The response magnitude, response time, sensitivity, linearity, and limit of detection (LOD) were compared, and it was concluded that the C-type PCF sensor exhibited superior performance. By applying a C-Type PCF sensor, we confirmed the detection performance of 12 types of floating HNS and the response of the sensor with selectivity according to the degree of polarity.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.1
• /
• pp.99-104
• /
• 2014

In this paper, Fire resistance test was carried out in accordance with the change of the insulation conditions on the exposed side and unexposed side of the coaming to obtain optimal insulation conditions for class H-120 insulation in connection with specimen-1 of the preceding paper for the evaluation of fireproof performance for fire dampers according to hydrocarbon fire conditions. As a test result, specimen-2(88 mm, $171^{\circ}C$) was satisfied class H-120 insulation, but specimen-3(76 mm, $181^{\circ}C$) was exceeded thermal insulation acceptance criteria at 110 minutes, therefor, specimen-2(88 mm) is optimal insulation conditions as possible lightweight than specimen-1. Test result comparison, we concluded that temperature rising of the coaming insulation surface was influenced by conductive heat from the bulkhead, and coaming surface was influenced by radiant heat from blade & coaming.