• Title/Summary/Keyword: Finite fault

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Sensitivity Analysis of Finite Fault Model in Stochastic Ground Motion Simulations (추계학적 지진동 모사에서 유한단층 모델의 민감도 분석)

  • Lee, Sang-Hyun;Rhie, Junkee
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.3
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    • pp.159-164
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    • 2024
  • Recent earthquakes in Korea, like Gyeongju and Pohang, have highlighted the need for accurate seismic hazard assessment. The lack of substantial ground motion data necessitates stochastic simulation methods, traditionally used with a simplistic point-source assumption. However, as earthquake magnitude increases, the influence of finite faults grows, demanding the adoption of finite faults in simulations for accurate ground motion estimates. We analyzed variations in simulated ground motions with and without the finite fault method for earthquakes with magnitude (Mw) ranging from 5.0 to 7.0, comparing pseudo-spectral acceleration. We also studied how slip distribution and hypocenter location affect simulations for a virtual earthquake that mimics the Gyeongju earthquake with Mw 5.4. Our findings reveal that finite fault effects become significant at magnitudes above Mw 5.8, particularly at high frequencies. Notably, near the hypocenter, the virtual earthquake's ground motion significantly changes using a finite fault model, especially with heterogeneous slip distribution. Therefore, applying finite fault models is crucial for simulating ground motions of large earthquakes (Mw ≥ 5.8 magnitude). Moreover, for accurate simulations of actual earthquakes with complex rupture processes having strong localized slips, incorporating finite faults is essential even for more minor earthquakes.

A Fault Detection Isolation and Compensation Scheme using Finite-time Fault Detection Observers (유한시간 수렴 고장검출관측자를 이용한 고장검출식별 및 보상기법)

  • Lee, Kee-Sang
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.9
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    • pp.1802-1808
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    • 2009
  • A fault detection observer with finite time convergence characteristics(FT_FDO) is proposed and applied to a fault detection isolation system for a dynamic control system. The FT_FDO is a kind of dual state-observer scheme that provides with the state estimates insensitive to a specified fault and the corresponding fault estimate. The state estimates are processed to get the residual that will be logically compared with other residuals to detect and isolate the fault of interest, and the fault estimate may be used for fault compensation. The FDIS employing the FT_FDOs can be considered to be a multiple observer schemes(MOS) in which FT_FDOs are parallelly driven to generate a set of residuals to be compared each other. Due to the finite time convergence characteristics of the FT_FDO, the predetermined detection delay can be considered in the design stage of FDIS so that any fault of interest can be detected and identified in that time. It evidently resolves a well known difficulty of threshold selection owing to the transient responses of the fault detection observers(FDO) employed in FDIS. An FDIS is constructed for instruments(2-sensor, 1-actuator) in an inverted pendulum control system, and simulations are performed to show the performance of the FDIS and fault tolerant control system.

Calculation of Distributed Magnetic Flux Density under the Stator-Turn Fault Condition

  • Kim, Kyung-Tae;Hur, Jin;Kim, Byeong-Woo
    • Journal of Power Electronics
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    • v.13 no.4
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    • pp.552-557
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    • 2013
  • This paper proposed an analytical model for the distributed magnetic field analysis of interior permanent magnet-type blush-less direct current motors under the stator-turn fault condition using the winding function theory. Stator-turn faults cause significant changes in electric and magnetic characteristic. Therefore, many studies on stator-turn faults have been performed by simulation of the finite element method because of its non-linear characteristic. However, this is difficult to apply to on-line fault detection systems because the processing time of the finite element method is very long. Fault-tolerant control systems require diagnostic methods that have simple processing systems and can produce accurate information. Thus analytical modeling of a stator-turn fault has been performed using the winding function theory, and the distributed magnetic characteristics have been analyzed under the fault condition. The proposed analytical model was verified using the finite element method.

The effect of pile cap stiffness on the seismic response of soil-pile-structure systems under near-fault ground motions

  • Abbasi, Saeed;Ardakani, Alireza;Yakhchalian, Mansoor
    • Earthquakes and Structures
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    • v.20 no.1
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    • pp.87-96
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    • 2021
  • Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to investigate the effect of pile cap stiffness on the seismic response of soil-pile-structure systems under near-fault ground motions. The Von Wolffersdorff hypoplastic model with the intergranular strain concept is applied for modeling of granular soil (sand) and the behavior of structure is considered to be non-linear. Eight fault-normal near-field ground motion records, recorded on rock, are applied to the model. The numerical method developed is verified by comparing the results with an experimental test (shaking table test) for a soil-pile-structure system. The results, obtained from finite element modeling under near-fault ground motions, show that when the value of cap stiffness increases, the drift ratio of the structure decreases, whereas the pile relative displacement increases. Also, the residual deformations in the piles are due to the non-linear behavior of soil around the piles.

Fault-Tolerant Control for 5L-HNPC Inverter-Fed Induction Motor Drives with Finite Control Set Model Predictive Control Based on Hierarchical Optimization

  • Li, Chunjie;Wang, Guifeng;Li, Fei;Li, Hongmei;Xia, Zhenglong;Liu, Zhan
    • Journal of Power Electronics
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    • v.19 no.4
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    • pp.989-999
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    • 2019
  • This paper proposes a fault-tolerant control strategy with finite control set model predictive control (FCS-MPC) based on hierarchical optimization for five-level H-bridge neutral-point-clamped (5L-HNPC) inverter-fed induction motor drives. Fault-tolerant operation is analyzed, and the fault-tolerant control algorithm is improved. Adopting FCS-MPC based on hierarchical optimization, where the voltage is used as the controlled objective, called model predictive voltage control (MPVC), the postfault controller is simplified as a two layer control. The first layer is the voltage jump limit, and the second layer is the voltage following control, which adopts the optimal control strategy to ensure the current following performance and uniqueness of the optimal solution. Finally, simulation and experimental results verify that 5L-HNPC inverter-fed induction motor drives have strong fault tolerant capability and that the FCS-MPVC based on hierarchical optimization is feasible.

Dynamic Analysis Algorithm of Irreversible Demagnetization of IPM-type Brushless DC Motor by Stator Turn Fault (고정자 절연파괴 고장에 의한 매입형 영구자석 BLDC 모터의 불가역 감자에 대한 동적해석 알고리즘)

  • Lee, Yoon-Seok;Kim, Kyung-Tae;Hur, Jin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.12
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    • pp.1661-1667
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    • 2013
  • This paper studies the dynamic irreversible demagnetization characteristics of an interior permanent magnet (PM) brushless DC motor with a stator turn fault. A new algorithm, which is a finite element method (FEM) combined with a line voltage equation of the motor, is developed to analyze irreversible demagnetization under dynamic and transient states and considers a stator turn fault. The input current, circulating current, magnetic distribution characteristics, and operating property of the PM, including the irreversible demagnetization in the fault state, are analyzed using this algorithm by considering the magnetic saturation effect. The feasibility of the proposed method confirmed from the analysis results is verified via an experiment. Through this fault analysis, we can accurately check the fault phenomena of a PM motor against the demagnetization fault for fault prevention.

Experimental and numerical studies on mechanical behavior of buried pipelines crossing faults

  • Zhang, Dan F.;Bie, Xue M.;Zeng, Xi;Lei, Zhen;Du, Guo F.
    • Structural Engineering and Mechanics
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    • v.75 no.1
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    • pp.71-86
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    • 2020
  • This paper presents a study on the mechanical behavior of buried pipelines crossing faults using experimental and numerical methods. A self-made soil-box was used to simulate normal fault, strike-slip fault and oblique slip fault. The effects of some important parameters, including the displacement and type of fault, the buried depth and the diameter of pipe, on the deformation modes and axial strain distribution of the buried pipelines crossing faults was studied in the experiment. Furthermore, a finite element analysis (FEA) model of spring boundary was developed to investigate the performance of the buried pipelines crossing faults, and FEA results were compared with experimental results. It is found that the axial strain distribution of those buried pipelines crossing the normal fault and the oblique fault is asymmetrical along the fault plane and that of buried pipelines crossing the strike-slip fault is approximately symmetrical. Additionally, the axial peak strain appears near both sides of the fault and increases with increasing fault displacement. Moreover, the axial strain of the pipeline decreases with decreasing buried depth or increasing ratios of pipe diameter to pipe wall thickness. Compared with the normal fault and the strike-slip fault, the oblique fault is the most harmful to pipelines. Based on the accuracy of the model, the regression equations of the axial distance from the peak axial strain position of the pipeline to the fault under the effects of buried depth, pipe diameter, wall thickness and fault displacement were given.

The Study on Current Limiting Characteristic Analysis of Magnetic Shielding Type Fault Current Limiter

  • Lee, Jae;Lim, Sung-Hun;Kang, Hyeon-Gon;Ko, Seok-Cheol;Han, Byoung-Sung
    • Progress in Superconductivity
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    • v.3 no.2
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    • pp.235-240
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    • 2002
  • In this paper, we investigated the current limiting characteristic in the magnetic shielding type fault current limiter(MSFCL). The circuit analysis was executed by using finite differential method(FDM). This paper suggests that the current limiting performance can be achieved in two ways (resistive and inductive one), according to design parameter. By comparing current limiting characteristics in two ways and surveying the important parameters which determine the operational way after fault occurs in the design of MSFCL, it is shown that the magnetic shielding type fault current limiter can be operated in either resistive or inductive way.

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Development of the Global Tsunami Prediction System using the Finite Fault Model and the Cyclic Boundary Condition (유한 단층 모델 및 순환 경계조건을 이용한 전지구 지진해일 예측 시스템 개발)

  • Lee, Jun-Whan;Park, Eun Hee;Park, Sun-Cheon;Woo, Seung-Buhm
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.27 no.6
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    • pp.391-405
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    • 2015
  • A global tsunami prediction system was suggested for a distant tsunami using a finite fault model and a cyclic boundary condition. The possibility of the suggested system as a distant tsunami response system was checked by applying it into the case of 2014 Chile tsunami. A comparison between the numerical results(tsunami height and arrival time) with different conditions (boundary condition, governing equation, grid size and fault model) and measured data (DART buoy, tide station) showed the importance of the finite fault model and the cyclic boundary condition.

The Study of Designing the Parameters of DC Reactor for Inductive Superconducting Fault Current Limiter By Using Finite Element Method (유한요소법을 이용한 유도형 고온 초전도 한류기용 DC Reactor의 설계 파라미터 결정법에 관한 연구)

  • 김용구;강형구;김태중;윤용수;고태국
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2002.02a
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    • pp.326-329
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    • 2002
  • The dc reactor type superconducting fault current limiter is composed of a power converter, magnetic core reactors and a do reactor that is a superconducting coil. When a fault occurs, the dc reactor maintains the stability of system by limiting its fault current. In this study, we focus on the design of the dc reactor using FEM(Finite Element Method). In order to design it, various elements should be considered such as magnetic field intensity, Lorentz's force, its inductance and so forth. Firstly, we forecast the values of those elements from the simulation of FEM and then measured with a copper wire magnet. Finally, verify the reliability of this FEM method by comparing with two results.

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