• Earthquakes and Structures
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• v.5 no.2
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• pp.129-142
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• 2013

Linear and nonlinear time history analyses have been becoming more common in seismic analysis and design of structures with advances in computer technology and earthquake engineering. One of the most important issues for such analyses is the selection of appropriate acceleration time histories and matching these histories to a code design acceleration spectrum. In literature, there are three sources of acceleration time histories: artificial records, synthetic records obtained from seismological models and accelerograms recorded in real earthquakes. Because of the increase of the number of strong ground motion database, using and scaling real earthquake records for seismic analysis has been becoming one of the most popular research issues in earthquake engineering. In general, two methods are used for scaling actual earthquake records: scaling in time domain and frequency domain. The objective of this study is twofold: the first is to discuss and summarize basic methodologies and criteria for selecting and scaling ground motion time histories. The second is to analyze scaling results of time domain method according to ASCE 7-05 and Eurocode 8 (1998-1:2004) criteria. Differences between time domain method and frequency domain method are mentioned briefly. The time domain scaling procedure is utilized to scale the available real records obtained from near fault motions and far fault motions to match the proposed elastic design acceleration spectrum given in the Eurocode 8. Why the time domain method is preferred in this study is stated. The best fitted ground motion time histories are selected and these histories are analyzed according to Eurocode 8 (1998-1:2004) and ASCE 7-05 criteria. Also, characteristics of both near fault ground motions and far fault ground motions are presented by the help of figures. Hence, we can compare the effects of near fault ground motions on structures with far fault ground motions' effects.

• Structural Engineering and Mechanics
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• v.34 no.6
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• pp.755-778
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• 2010

Near-fault ground motion with directivity or fling effects is significantly influenced by the rupture mechanism and substantially different from ordinary records. This class of ground motion has large amplitude and long period, exhibits unusual response spectra shapes, possesses high PGV/PGA and PGD/PGA ratios and is best characterized in the velocity and the displacement time-histories. Such ground motion is also characterized by its energy being contained in a single or very few pulses, thus capable of causing severe damage to the structures. This paper investigates the characteristics of near-fault pulse-like ground motions and their implications on the structural responses using new proposed measures, such as, the effective frequency range, the energy rate (in time and frequency domains) and the damage indices. The paper develops also simple mathematical expressions for modeling this class of ground motion and the associated structural responses, thus eliminating numerical integration of the equations of motion. An optimization technique is also developed by using energy concepts and damage indices for modeling this class of ground motion for inelastic structures at sites having limited earthquake data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.184-189
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• 2022

In this paper, the fault current limiting operations of three-phase transformer type superconducting fault current limiter (SFCL) using double quench, which consisted of E-I iron core with three legs wound by primary and secondary windings and two superconducting modules (SCMs), were analyzed according to three-phase ground fault types. To verify the effective operation of the three-phase transformer type SFCL using double quench, the test circuit for three-phase ground faults was constructed, and the fault current tests were carried out. Through analysis on the fault current test results, the different fault current limiting characteristics of three-phase transformer type SFCL using double quench from three-phase transformer type SFCL using three SCMs were discussed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.10
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• pp.550-555
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• 2004

Fault section isolation and service restoration are very important for function of DAS. In Japan, a progressive protection method is used for the line to ground fault section isolation and service restoration. But the progressive protection method has a drawback that the customer will experience outage time and that the rate in use of the feeder is not over 50%. This paper presents a new Service Restoration Algorithm which is for the line to ground fault section isolation and service restoration method for a ungrounded distribution system. If the proposed algorithm is used, the rate in use of the feeder can improve than before because a distribution system can change multi connection of feeder and the customer's outage time can be reduced. The proposed algorithm has been successfully tested in a distribution system.

• Progress in Superconductivity
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• v.1 no.1
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• pp.73-80
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• 1999

We investigated the current limiting characteristics of resistive and inductive SFCLs with 100 $\Omega$ of impedance for line-to-ground faults in the 154 kV transmission system. The fault simulation at the phase angles $0^{\circ}$, $^45{\circ}$, and $90^{\circ}$ showed that the resistive SFCL limits the fault current less than 17 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppresses the current below 14 kA, but with 5 kA of DC component which decreases to zero in 5 cycles. We concluded that the inductive SFCL has higher performance in current limiting effect, but the resistive SFCL was better from the viewpoint of less DC components.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.435-454
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• 2007

In this study, we demonstrated the characteristics of the near-fault ground motion thatwas not considered in the domestic seismic design code and how the effect of the near-fault ground motion affects the response of cable-stayed bridges. Afterselecting the actual measurement records of the typical near- and far-fault ground motion, the characteristics of ground motion is analyzed using the elastic and inelastic response spectrum. Analyzing the response regarding the earthquake's characteristics on cable-stayed bridges by the typical three-type cable-stayed bridges and the actual cable-stayed bridge, the characteristics of responses about main members are compared and analyzed. Moreover,reliability analysis is accomplished using the results of the seismic response analysis, and the seismic safety of the cable-stayed bridges is evaluated quantitatively as a reliability index and probability of failure. According to the results of the response spectrum, the earthquake response analysis and the reliability analysis, because the effect of the near fault ground motion against the response of cable-stayed bridges is different from the effect of the existing far-fault ground motion, it should be considered as an important factor when designing cable-stayed bridges.

• Journal of the Korean Society of Safety
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• v.22 no.6
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• pp.41-45
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• 2007

Short circuit and ground fault account for the primary causes of electrical fires. In this research, real-scale experiments were conducted to assess the possibility of electrical fires due to these causes. The experiment conditions were identical with an actual fire accident, in which the power cable was supported by an iron fence. The purposes of this research are to investigate the short circuit caused by wire cutting, the conductivity of the iron fence depending on its coating conditions, and the ground fault of one wire or two wires in an effort to reconstruct the fire accident. The test results show that, owing to the instant operation of circuit breaker in the moment of short circuit or ground fault, the generated ignition energy is far less than necessary to start an ignition. Therefore it is concluded that electrical fire is highly unlikely if the electric system is protected by a circuit breaker with normal functions.

• Earthquakes and Structures
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• v.13 no.2
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• pp.211-220
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• 2017

Observations from past strong earthquakes revealed that near-fault ground motions could lead to the failure, or even collapse of electricity transmission towers which are vital components of an overhead electric power delivery system. For assessing the performance and robustness, a high-fidelity three-dimension finite element model of a long span transmission tower-line system is established with the consideration of geometric nonlinearity and material nonlinearity. In the numerical model, the Tian-Ma-Qu material model is utilized to capture the nonlinear behaviours of structural members, and the cumulative damage D is defined as an index to identify the failure of members. Consequently, incremental dynamic analyses (IDAs) are conducted to study the collapse fragility, damage positions, collapse margin ratio (CMR) and dynamic robustness of the transmission towers by using twenty near-fault ground motions selected from PEER. Based on the bending and shear deformation of structures, the collapse mechanism of electricity transmission towers subjected to Chi-Chi earthquake is investigated. This research can serve as a reference for the performance of large span transmission tower line system subjected to near-fault ground motions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.69-76
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• 2003

Near-field ground motions exhibit special characteristics that are different from ordinary far-field ground motions. This paper first briefly examines the characteristics of near-field ground motions associated with fault directivity and fling-step effects. Then evaluation of near-field ground motions by inelatstic response spectrum analysis is performed and analyzed. As a result, ductility demand in near-field ground motions is larger in hanging wall than in foot wall in long period regions. Also in long period regions ductility demand in soil site is larger than that in rock site.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.8-8
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• 2010

In this paper, the limiting characteristics of the fault current in a power system with a superconducting fault current limiter(SFCL) applied into neutral line of main transformer in a distribution power line were analyzed. The SFCL applied into the neutral line of main transformer power system can limit the unsymmetrical fault current from the single-line ground fault or the double-line ground fault. In addition, it could be decreased a number of SFCL and a load. This method could be expected to reduction of a power loss in the neutral line, because of a neutral line current is zero in ordinary times.