• Title/Summary/Keyword: cable failure

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A Study of Efficient Algorithm for Survivable Network Design with Conduit (관로가 있는 생존가능망 설계에 관한 효율적인 알고리즘 연구)

  • Kang, Hyo-Kwan;Han, Chi-Geun
    • The KIPS Transactions:PartC
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    • v.8C no.5
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    • pp.629-636
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    • 2001
  • Network is changed from voice-based network into multimedia-based network by development of communication technology and multimedia service. We need a large bandwidth for multimedia service. The optical fiber is a more suitable medium than existing copper-based cable for large bandwidth. But, it is so expensive than copper-based cable. So, Minimizing total cost becomes a more important concept. In order to construct a minimum cost network, we have to consider existing conduits in network. On the other hand, optical fiber network allows that larger amount of traffic can be transmitted than copper-based network does. However, a failure of a node or link can make a serious damage to the network service. Thus, we have to get multiple paths to support continuous service even if a loss of failure occurs in some point of the network. The network survivability problem is to design the network that can provide reliable service to customers anytime with minimum total cost. In an existing solution of the network survivability problem with conduits, a conduit is considered only one time. But, the conduit is reusable if the network satisfies the required survivability. Proposed algorithm can more effectively considered already existed conduit. Network survivability and edge cost is predetermined. The proposed algorithm finds the best solution by conduit sharing within the limits of network survivability. According to the simulation result, the proposed method can decrease 7% of total cost than an existing method by effective conduits adaption.

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Experimental and Analytical Studies on the Non-Linear behaviors of Pre-Stressed Steel H-Beams (프리스트레스트 H형강 거더의 비선형 거동에 대한 실험적 및 이론적 연구)

  • Kim, Moon-Young;Kim, Nak-Kyung;Oh, Yong-Hwan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.32 no.6
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    • pp.359-366
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    • 2019
  • Experimental and analytical studies on the behavioral characteristics of a pre-stressed (PS) steel girder are conducted to investigate the effects of deviators on the non-linear inelastic properties of the PS system. In this regard, 4 test specimens consisting of a steel H-beam, a straight cable with eccentricity, anchorages, and deviators are built and failure tests are performed under two-point loading. In addition, in-plane elastic deformation theories for the PS system without a deviator, and with three deviators at regular intervals are analytically formulated and solved using a symbolic calculation technique. To verify the validity of the experimental and the proposed analytical theories, the results obtained using FEM models composed of beam elements, rigid beam elements, and truss cable elements, are compared to the experimental results and the analytical solutions. As a result, it is determined that externally installed un-bonded deviators inhibit flexural deformation of the deformed beam to such an extent that their elastic stiffness, and failure strength are significantly improved compared to those of the PS system without deviators.

GEOTECHNICAL DESIGNS OF THE SHIP IMPACT PROTECTION SYSTEM FOR INCHEON BRIDGE

  • Choi, Sung-Min;Oh, Seung-Tak;Park, Sang-Il;Kim, Sung-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09c
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    • pp.72-77
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    • 2010
  • The Incheon Bridge, which was opened to the traffic in October 2009, is an 18.4 km long sea-crossing bridge connecting the Incheon International Airport with the expressway networks around the Seoul metropolitan area by way of Songdo District of Incheon City. This bridge is an integration of several special featured bridges and the major part of the bridge consists of cable-stayed spans. This marine cable-stayed bridge has a main span of 800 m wide to cross the vessel navigation channel in and out of the Incheon Port. In waterways where ship collision is anticipated, bridges shall be designed to resist ship impact forces, and/or, adequately protected by ship impact protection (SIP) systems. For the Incheon Bridge, large diameter circular dolphins as SIP were made at 44 locations of the both side of the main span around the piers of the cable-stayed bridge span. This world's largest dolphin-type SIP system protects the bridge against the collision with 100,000 DWT tanker navigating the channel with speed of 10 knots. Diameter of the dolphin is up to 25 m. Vessel collision risk was assessed by probability based analysis with AASHTO Method-II. The annual frequency of bridge collapse through the risk analysis for 71,370 cases of the impact scenario was less than $0.5{\times}10^{-4}$ and satisfies design requirements. The dolphin is the circular sheet pile structure filled with crushed rock and closed at the top with a robust concrete cap. The structural design was performed with numerical analyses of which constitutional model was verified by the physical model experiment using the geo-centrifugal testing equipment. 3D non-linear finite element models were used to analyze the structural response and energy-dissipating capability of dolphins which were deeply embedded in the seabed. The dolphin structure secures external stability and internal stability for ordinary loads such as wave and current pressure. Considering failure mechanism, stability assessment was performed for the strength limit state and service limit state of the dolphins. The friction angle of the crushed stone as a filling material was reduced to $38^{\circ}$ considering the possibility of contracting behavior as the impact.

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Performance Analysis of the Powerline Communication for Condition Monitoring System of an MW Class Offshore Wind Turbine's Nacelle (MW급 해상풍력발전기 나셀의 상태 감시를 위한 전력선 통신 성능 분석)

  • Sohn, Kyung-Rak;Kim, Kyoung-Hwa;Jeong, Seong-Uk;Nam, Seung-Yun;Kim, Hyun-Sik
    • Journal of Navigation and Port Research
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    • v.40 no.3
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    • pp.159-164
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    • 2016
  • The goal of this study is to implement a communication system that can monitor the status of the nacelle using the power cable itself, without the dedicated communication lines such as an UTP cable and optical fiber for the offshore wind turbine. An inductive coupling powerline communication system for a MW class offshore wind turbine was proposed and its communication performance was demonstrated. The inductive couplers was designed for operation at up to 500 A using a ferrite composite materials. Field test was carried out on the wind farms of Jeju island. Using the iperf communication test program, we have obtained more than 15 Mbps data transmission rate through the 100 m power cable that was installed between the nacelle and the bottom of the power converter. In the data transmission stability test for a week, there was no failure ever. The minimum transmission rate was 15 Mbps and the average data rate was about 20 Mbps. Next, we have installed an infrared camera inside the nacelle in order to measure the temperature distribution and variation of the nacelle. The real-time thermal image taken by the camera was successfully sent to the monitoring system without error.

Mechanical Properties and Statistical Evaluation of EPR According to the Accelerated Degradation (EPR의 가속 열화에 의한 기계적 특성 및 통계적 평가)

  • Kim, Ji-Yeon;Yang, Jong-Suk;Lee, Gil-Soo;Seong, Baek-Yong;Bang, Jeong-Hwan;Park, Dae-Hee
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.8
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    • pp.501-507
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    • 2015
  • In this paper, EPR (ethylene propylene rubber) insulation material was accelerated degradation test at $121^{\circ}C$, $136^{\circ}C$, $151^{\circ}C$, and experiment the typical EAB (elongation at break) at mechanical characteristics analysis. It is shown that the failure-time at the point of 50% of the initial value of Elongation rate to obtain the activation energy. The failure-time was shown each 5,219 hr, 3,165 hr, and 668 hr at three temperatures. In order to derive the activation energy, Arrhenius methodology was applied. Also, we got the Arrhenius plot from three accelerated temperatures. The activation energy values got 0.98 eV from EAB test. The experimental data were evaluated for estimating the probability density, and the suitable distribution by using statistical program MINITAB. It is shown that EAB data by the acceleration thermal degradation is most suitable for the Weibull distribution.

Aero-elastic response of transmission line system subjected to downburst wind: Validation of numerical model using experimental data

  • Elawady, Amal;Aboshosha, Haitham;El Damatty, Ashraf
    • Wind and Structures
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    • v.27 no.2
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    • pp.71-88
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    • 2018
  • At the University of Western Ontario (UWO), numerical tools represented in semi-closed form solution for the conductors and finite element modeling of the lattice tower were developed and utilized significantly to assess the behavior of transmission lines under downburst wind fields. Although these tools were validated against other finite element analyses, it is essential to validate the findings of those tools using experimental data. This paper reports the first aeroelastic test for a multi-span transmission line under simulated downburst. The test has been conducted at the three-dimensional wind testing facility, the WindEEE dome, located at the UWO. The experiment considers various downburst locations with respect to the transmission line system. Responses obtained from the experiment are analyzed in the current study to identify the critical downburst locations causing maximum internal forces in the structure (i.e., potential failure modes), which are compared with the failure modes obtained from the numerical tools. In addition, a quantitative comparison between the measured critical responses obtained from the experiment with critical responses obtained from the numerical tools is also conducted. The study shows a very good agreement between the critical configurations of the downburst obtained from the experiment compared to those predicted previously by different numerical studies. In addition, the structural responses obtained from the experiment and those obtained from the numerical tools are in a good agreement where a maximum difference of 16% is found for the mean responses and 25% for the peak responses.

Analysis of fault current in offshore wind farm ccording to the grid connection method (해상풍력 발전단지의 전력망 연계방식에 따른 고장전류 분석)

  • Ahn, Jin-Hong;Kim, Eel-Hwan
    • Journal of IKEEE
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    • v.24 no.3
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    • pp.691-698
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    • 2020
  • The installation cost or the magnitude of the fault current varies depending on the grid connection method of the offshore wind farm. Therefore, there is a need for an efficient power grid connection method considering the capacity and location of the complex. In particular, most power cables in offshore wind farms use 3-core considering cost and efficiency. In the event of a failure such as a short circuit, the entire cable must be replaced, which can lead to significant losses in terms of cost, considering repair costs and turbine downtime. Therefore, in this paper, a radial, ring, and molding method is introduced into a 100 MW wind farm to be installed at Jeju offshore, and a three-phase short circuit failure is performed using a PSCAD/EMTDC program to perform computer analysis. I would like to propose a suitable power grid connection method.

A Study on the Safety Assessment and Damage Pattern of Water Purifier Compressors (정수기용 압축기의 안전성 평가 및 소손 패턴 분석에 관한 연구)

  • Choi, Chung-Seog
    • Journal of the Korean Society of Safety
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    • v.28 no.2
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    • pp.21-25
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    • 2013
  • The purpose of this study is to provide basic data for the safety assessment of a water purifier when water leaks due to inappropriate maintenance and the examination of the cause of accidents related to the leak. Due to its inspection and management by non-specialists, if a leak occurs in a water purifier with the water level controller being inclined, it may result in the failure of the compressor, power supply line, PCB, etc. The analysis of the thermal diffusion pattern of water purifier compressors using a thermal image camera shows that its maximum temperature was approximately $80^{\circ}C$. In addition, its operating current was a maximum of 13 A and the system's operating current was approximately 1.7 A after the compressor was charged. It was found that the housing type power cable cover of the compressor had the effect of preventing electric shock but has poor flame resistance. Furthermore, the performance of the overload protector, PTC relays, etc., was excellent but they have potential for problems as metallic terminals were exposed, resulting in the potential of a safety related accident. The terminals and their surface damaged by the tracking showed a trace of carbonization and the resistance between terminals was measured to be approximately $8{\Omega}$. In addition, while the tracking was proceeding, the fuse and circuit breaker installed for system protection did not operate.

Radiation Measurement of a Operational CANDU Reactor Fuel Handling Machine using Semiconductor Sensors (ICCAS 2003)

  • Lee, Nam-Ho;Kim, Seung-Ho;Kim, Yang-Mo
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.1220-1224
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    • 2003
  • In this paper, we measured the radiation dose of a fuel handling machine of the CANDU type Wolsong nuclear reactor directly during operation, in spite of the high radiation level. In this paper we will describe the sensor development, measurement techniques, and results of our study. For this study, we used specially developed semiconductor sensors and matching dosimetry techniques for the mixed radiation field. MOSFET dosimeters with a thin oxide, that are tuned to a high dose, were used to measure the ionizing radiation dose. Silicon diode dosimeters with an optimum area to thickness ratio were used for the radiation damage measurements. The sensors are able to distinguish neutrons from gamma/X-rays. To measure the radiation dose, electronic sensor modules were installed on two locations of the fuel handling machine. The measurements were performed throughout one reactor maintenance cycle. The resultant annual cumulative dose of gamma/X-rays on the two spots of the fuel handling machine were 18.47 Mrad and 76.50 Mrad, and those of the neutrons were 17.51 krad and 60.67 krad. The measured radiation level is high enough to degrade certain cable insulation materials that may result in electrical insulation failure.

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Study of Injection Molding Process of Shift Lever Using Injection Molding Analysis (사출성형해석을 통한 자동차 레버쉬프트의 사출공정에 관한 연구)

  • Park, Chul-Woo;Lee, Boo-Youn;Lee, Sang-Min
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.6
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    • pp.7-13
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    • 2015
  • The production processes were reviewed through the injection analysis of the shift lever as a core component of an auto lever installed in the automatic transmission of cars. The injection analysis was carried out for the shift lever and rod among the components in a shift lever module. The shift lever and rod are designed for injection molding with the insertion of a tube, a pin cable plate, and a steel rod for securing the strength of the product. The charging time, failure of injection molding, weld line, air trap, and deformation were reviewed according to this insert. Analyses on various gate positions were carried out for reviewing the cultivation and deformation of fiber around major components, such as the generation section of manipulation feeling and assembly section, so that optimal gate conditions might be reviewed and reflected in the mold design. Finally, we plan to compare the analysis results with the production of trial products.