• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.4
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• pp.161-166
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• 1999

We have performed an EMTDC simulation for the current limiting effects of a superconducting fault current limiter (SFCL). The fault currents in the 154 kV transmission line between the arbitrary S1 and S2 substations increased up to 39 kA during the single and double line-to-ground faults, respectively. The SFCL in the transmission line is sufficient.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.211-217
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• 2016

Most nuclear power plants now utilize solid grounded low voltage systems. For safety and reliability reasons, the low voltage (LV) high resistance grounding (HRG) system is also increasingly used in the pulp and paper, petroleum and chemical, and semiconductor industries. Fault detection is easiest and fastest with a solidly grounded system. However, a solidly grounded system has many limitations such as severe fault damage, poor reliability on essential circuits, and electrical noise caused by the high magnitude of ground fault currents. This paper will briefly address the strengths and weaknesses of LV grounding systems. An example of a low voltage HRG system in the LV system of a nuclear power plant will be presented. The HRG system is highly recommended for LV systems of nuclear power plants if sufficient considerations are provided to prevent nuisance tripping of ground fault relays and to avoid the deterioration of system reliability.

• Steel and Composite Structures
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• v.32 no.1
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• pp.91-110
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• 2019

In the present study, the effects of six different ground motion scaling methods on inelastic response of nonlinear steel moment frames (SMFs) are studied. The frames were designed using energy-based PBPD approach with the design concept using pre-selected target drift and yield mechanism as performance limit state. Two target spectrums are considered: maximum credible earthquake spectrum (MCE) and design response spectrum (DRS). In order to investigate the effects of ground motion scaling methods on the response of the structures, totally 3216 nonlinear models including three frames with 4, 8 and 16 stories are designed using PBPD approach and then they are subjected to ensembles of ground motions including 42 far-fault and 90 near-fault pulse-type records which were scaled using the six different scaling methods in accordance to the two aforementioned target spectrums. The distributions of maximum inter-story drift over the height of the structures are computed and compared. Finally, the efficiency and reliability of each ground motion scaling method to estimate the maximum nonlinear inter-story drift of special steel moment frames designed by energy-based PBPD approach are statistically investigated, and the most suitable scaling methods with the lowest dispersion for two groups of earthquake ground motions are introduced.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.285-287
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• 2007

This paper describes that the effect on the other system is generated by the single line to ground fault of the underground transmission systems and distribution systems established the common ground in trefoil. Each system is modeled by EMTP/ATPDraw and the system carry out simulations according to the various values of common ground to analyse. In this study, the result of analysis based on simulation suggests protection method and ground system of each system.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.3
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• pp.226-232
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• 2002

This paper explains a technique to improve the fault coverage of oscillation-test [1-5] for linear analog circuits. The transient behavior of the virtual ground is monitored during oscillation to extract information of the circuit. The limitation of the oscillation-test is analyzed, and an efficient signature analysis technique is proposed to maximize the fault coverage. The experimental result proves that the parametric fault coverage can be significantly increased by the proposed technique.

• Earthquakes and Structures
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• v.22 no.1
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• pp.53-64
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• 2022

This study proposes an intelligent semi-active isolation system combining a variable-stiffness control device and ground motion characteristic prediction. To determine the optimal control parameter in real-time, a genetic algorithm (GA)-fuzzy control law was developed in this study. Data on various types of ground motions were collected, and the ground motion characteristics were quantified to derive a near-fault (NF) characteristic ratio by employing an on-site earthquake early warning system. On the basis of the peak ground acceleration (PGA) and the derived NF ratio, a fuzzy inference system (FIS) was developed. The control parameters were optimized using a GA. To support continuity under near-fault and far-field ground motions, the optimal control parameter was linked with the predicted PGA and NF ratio through the FIS. The GA-fuzzy law was then compared with other control laws to verify its effectiveness. The results revealed that the GA-fuzzy control law could reliably predict different ground motion characteristics for real-time control because of the high sensitivity of its control parameter to the ground motion characteristics. Even under near-fault and far-field ground motions, the GA-fuzzy control law outperformed the FPEEA control law in terms of controlling the isolation layer displacement and the superstructure acceleration.

• Journal of the Korea Society for Simulation
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• v.20 no.3
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• pp.59-67
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• 2011

This paper proposes a model to analyze the fault factors of air-to-ground weapon delivery utilizing software fault localization methods. In the previous study, to figure out the factors to affect the accuracy of air-to-ground weapon delivery, the FBEL (Factor-based Error Localization) method had been proposed and the fault factors were analyzed based on the method. But in the study, the correlation between weapon delivery accuracy and the fault factors could not be revealed because the firing accuracy among several factors was fixed. In this paper we propose a more precise fault analysis model driven through a study of the correlation among the fault factors of weapon delivery, and a method to estimate the possibility of faults with the limited number of test cases utilizing the model. The effectiveness of proposed method is verified through the simulation utilizing real delivery data. and weapons delivery testing in the evaluation of which element affecting the accuracy of analysis that was available to be used successfully.

• Proceedings of the KIEE Conference
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• summer
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• pp.619-621
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• 2004

This paper presents the rapid and accurate algorithm for fault discrimination in transmission lines. When faults occur in transmission lines, fault discrimination is very important. If high impedance faults occur in transmission lines, it cannot be detected by overcurrent relays. The method using current and voltage cannot discriminate high impedance fault. Because of this reason this paper uses voltage and zero sequence current, and the proposed algorithm uses fuzzy logic method. This algorithm uses voltage and zero sequence current per period in case of faults. Single line ground fault and three-phase fault can be detective using voltage. Two-line ground fault and line to line fault and high impedance can be detected using zero sequence current. To prove the performance of the algorithm, it test algorithm with signal obtained from ATPDraw simulation.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.451-458
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• 2008

The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.105-112
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• 2001

The purpose of this study is to assess the stability of tunnel for a high speed railway crossing the fault zone. The area where the tunnel crossed the fault zone can be unstable during construction and operation. Geotechnical investigations have been conducted to determine an optimum excavation method by obtaining the material properties around the fault zone and to check the stability of the tunnel. For the numerical analysis, the FLAC, numerical analysis code based on finite difference method, was utilized to analyze the behavior of the fault at three points having typical ground conditions. Based on the results of numerical analysis, the combinations of compaction grouting and LW grouting were determined as suitable methods for pre-excavation Improvement of the ground surrounding the tunnel opening. In conclusion, the stability of the tunnel construction for the high speed railway within the fault zone may be obtained by adopting the optimum excavation method and the reinforcement method. The numerical analysis based on FLAC program contains errors caused by assumptions used in numerical analysis, therefore constant monitoring with respect to the change of ground condition and groundwater is highly recommended to minimize the numerical error and the possibility of damage to tunnel.