• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1100-1109
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• 2006

In this study, two different technologies which can measure temperature simultaneously at many points are introduced. One is to use a thermal sensor cable that is comprised of addressable thermal sensors connected in parallel within a single cable. The other is to use an optic fiber with Distributed Temperature Sensing (DTS) system. The difference between two technologies can be summarized as follows. A thermal sensor cable has a concept of 'point sensing' that can measure temperature at accurate position of a thermal sensor. So the accuracy and resolution of temperature measurement are up to the ability of the thermal sensor. Whereas optic fiber sensor has a concept of 'distributed sensing' because temperature is measured by ratio of Stokes and anti-Stokes component intensities of Raman backscatter that is generated when laser pulse travels along an optic fiber. It's resolution is determined by measuring distance, measuring time and spatial resolution. The purpose of this study is that application targets of two temperature measurement techniques are checked in technical and economical phases by examining the strength and weakness of them. Considering the functions and characteristics of two techniques, the thermal sensor cable will be suitable to apply to the assessment of groundwater flow, geothermal distribution and grouting efficiency within 300m distance. It is expected that the optic fiber sensor can be widely utilized at various fields (for example: pipe line inspection, tunnel fire detection, power line monitoring etc.) which need an information of temperature distribution over relatively long distance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.179-184
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• 2016

The usual way used by electric power stations to deliver high levels of generated power is via 6.6kV XLPE (or CV) cables. Depending on the manufacturing technique, installation environment, and usage conditions, the deterioration processes of the power cables start from the instant of operation. Cable junctions may break down in three years from the start of operation due to the manufacturing or construction defects. Otherwise they should be in good working order for 20-30 years. When the cable system (the cable itself and cable junctions combined) deteriorates, fire accidents happen due to the dielectric breakdowns. We have invented a device to monitor the deteriorating status of cables at Korean Western Power Co. Ltd. located in Taean, Chungcheongnam-do province. In this paper, we introduce the device hardware. Using the device, we have measured the insulation resistance and humidity in the sheath of the cables. We present, in analysed results, the effect of humidity on insulation resistance in cable sheaths.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.243-248
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• 2017

This study used general carbon fibers(CF), which can be utilized for a low voltage cable screen, as well as metal-coated carbon fibers(MCF) to make cables and analyzed the properties of electromagnetic effectiveness. Both braid CF and MCF cables with 3,000 strands, 16 spindles, and braid density of 90% or over were adopted. The tape-type MCF specimens were spread into a tape(width: 15mm) using a hot melt to make a cable. The shield effectiveness was measured up to the 1GHz range in accordance with IEC 62153-4-6; braid shielded cables featured a superior shielding effect at 63dB than tape-type shielded cables. That was because the tape-type shielded cable has relatively more gaps and holes between carbon fibers than the braid type, resulting in a more inflow or emission of electromagnetic waves. In the case of braid cables, the characteristics of their electromagnetic waves were enhanced, with higher spindles and higher conductivity of carbon fibers. The shield effectiveness of the MCF shielded cable, however, was lower than that of tin-coated one.

• Fire Science and Engineering
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• v.30 no.5
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• pp.116-123
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• 2016

The quantitative risk assessment methods for thermal failure in targets were studied using fire modeling. To this end, Fire Dynamics Simulator (FDS), as a representative fire model, was used and the probabilities related to thermal damage to an electrical cable were evaluated according to the change in fire area inside a specific compartment. 'The maximum probability of exceeding the damage thresholds' adopted in a conservative point of view and 'the probability of failure' including the time to damage were compared. The probability of failure suggested in the present study could evaluate the quantitative fire risk more realistically, compared to the maximum probability of exceeding the damage thresholds with the assumption that thermal damage occurred the instant the target reached its minimum failure criteria in terms of the surface temperature and heat flux.

• Congress of the korean instutite of fire investigation
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• 2010.12a
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• pp.63-79
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• 2010

It is found to the arc trace on the junction termination of 345kV cable. According to the analysis of the cable material is judged to be good. Manufacturing and design problems are not considered. In construction defects, it was estimated to the low level of insulation oil. In the majority of the arc trace appeared XLPE is found. However, there is no Soots mark, yellow band has not been confirmed, not associated with a radial arc of the spider leg is not evidence. In other opinions, void, contamination or jut are not found on the inside of XLPE. Thus, by the attachment of the impurities in surface of XLPE insulation is judged to the breakdown.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.88-94
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• 2018

This study examined the safety of a cable stayed bridge caused by damage to the cable system. Many cable-supported bridges, including cable-stayed bridges and suspension bridges, have been constructed on the Korean peninsula. This requires efficient maintenance and management because this structure has complex structural components and systems. This large structure also often faces risks either from manmade causes or natural phenomena. In 2015, the cables on one cable-stayed bridge in South Korea was struck by lightning, which led to a fire on the cables. These cables were damaged, which put the bridge at risk. This bridge was back in use after a few weeks of investigations and replacements of the cables but this was done at enormous social and economic expense. After this event, risk-based management for infrastructure is required by public demand. Therefore, this study examined the risks on the cable system due to potential damage. In this paper, a one cable-stayed bridge in South Korea was selected and its safety was investigated based on the damage scenarios of cable system for efficient and prompt management, and to support decision making. FEM analysis was conducted to evaluate the safety of the bridges after damage to the cable system.

• Structural Engineering and Mechanics
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• v.92 no.1
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• pp.53-64
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• 2024

This paper presents an innovative theoretical and numerical model to predict the lateral-torsional buckling (LTB) of simply supported steel I-beams with external prestressed tendons. The model incorporates an updated prestressing force, accounting for thermal effects and various external loadings. Critical multipliers are determined by solving an eigenvalue problem derived from applying Galërkin's approach to a set of nonlinear equilibrium equations. Validation is carried out through Finite Element Method (FEM) simulations, incorporating a new expression for an equivalent thermal expansion coefficient for the beam-tendon system, addressing both mechanical and thermal deformations. The primary aim is to estimate critical conditions considering material property degradation due to fire. The present results are generally in good agreement with those provided by the literature.

• Journal of the Korean Society of Safety
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• v.32 no.6
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• pp.22-28
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• 2017

According to the National Fire Data System (NFDS), more than 5,000 vehicle fires have occurred every year for the last 10 years. Vehicle fires are primarily caused by mechanical (breaking system and engine), electrical (wiring and battery), and chemical (oil and fuel gas leakage) problems. The electrical factor has increased with the installation of driver convenience equipment. For example, today, the black box is widely used to provide video data recording of motor vehicle accidents. The black box consists of a front camera, rear camera, and wires. The black box wires are directly connected to the junction box or fuse box from the start battery that operates to provide normal on power supplying for engine stop. It is extremely dangerous when the wires short circuit due to insulation aging, mechanical and electrical stress, etc. In this study, the black box wiring fire risk have been analyzed and investigated when the steady state and abnormal operations, and under the following conditions: wiring arrangements with a high temperature condition, insulation aging, poor contact, and short circuits. The results showed that black box wiring short circuits had a higher fire risk than the other fire hazard elements. To prevent fire hazards caused by black box wiring, the black boxes must be installed by qualified service personnel. Do not modify the wiring, remove the fuse and secure the wiring using cable ties or insulation tape.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.189-195
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• 2017

The only method used in the power stations in order to deliver generated electric power is 6 kV XLPE (or CV) single core cables. Among many kinds of accidents happening in the power stations, the outbreak of fire due to the deterioration of live cables causes enormous socioeconomic losses. From the installation of the cables, the management and diagnose should be thoroughly made. Even though it differs depending on the installations and usage conditions, the cross-sectional area of cables is in shortage. The excessive allowable temperature caused from the current causes the deterioration of cables. In order to prevent an unexpected breakdown of live cables, we have invented a device to monitor and diagnose the status of cables. We have installed our device in the Korea Western Power Co., Ltd.. In this paper, we present our research results in situ that we have obtained by measuring the temperature of sheath, changing with the surrounding circumstances, especially ambient temperatures. We also show our study results of characteristics for temperature of sheath surface and load current at the ambient temperatures of $40^{\circ}C-10^{\circ}C$.

• Fire Science and Engineering
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• v.17 no.4
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• pp.36-41
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• 2003

This experimental study shows the combustion characteristics for each coating thickness of water and oil paint which are used as fire retardant paints that prevent fire propagation through cables in underground culverts and trays. To evaluate combustion characteristics, smoke density(ASTM E 662) and Limited Oxygen Index(ASTM D 2863) experiment method was used. As the results of this study, the combustion characteristics of fire retardant paints produced the following : (a) The molt suitable coating thickness of fire retardant paint was 1.5∼2.0 mm in water paint and 0.2 mm in oil paint. (b) Flaming method in experiments of smoke density were found to be higher than Non-flaming method. (c) Water paint has the fire retardant effect and characteristics better than oil paint in measurement results of smoke density and oxygen index. (d) The oxygen index of water and oil fire retardant was able to know that it was satisfied a standard (30 or above).