• Smart Structures and Systems
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• v.20 no.1
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• pp.43-52
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• 2017

Structural health monitoring has drawn great attention in the field of civil engineering in past two decades. These structural health monitoring methods evaluate structural integrity through high-quality sensor measurements of structures. Due to electronic deterioration or aging problems, sensors may yield biased signals. Therefore, the objective of this study is to develop a fault detection method that identifies malfunctioning sensors in a sensor network. This method exploits the autoregressive modeling technique to generate a bank of Kalman estimators, and the faulty sensors are then recognized by comparing the measurements with these estimated signals. Three types of faults are considered in this study including the additive, multiplicative, and slowly drifting faults. To assess the effectiveness of detecting faulty sensors, a numerical example is provided, while an experimental investigation with faults added artificially is studied. As a result, the proposed method is capable of determining the faulty occurrences and types.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.257-258
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• 2011

This paper describes a new method for the seamless operation mode transfer of a PCS with minimized voltage disturbance. The proposed method provides reduced STS turn off time after line fault and smooth mode change between current and voltage control of the PCS. The usefulness of the method is verified through simulations with the consideration of the time delay in detecting a line fault and SCR turn-off time.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1850-1851
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• 2011

The faults of a electric motor cause to rise the maintenance and repair cost and to reduce the reliability of the electric power system. In this paper, the auto fault detection system for a induction motor is developed using the torque signal spectrum analysis. The spectrum of motor torque signal is used for finding a bearing fault feature frequency. A threshold value, for detecting the motor bearing fault is set by the difference of torque signal spectrum(FFT signal) between normal condition and faulted condition of the motor.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.4
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• pp.18-23
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• 2011

Generally, the digital circuit card can be tested by automatic test equipment using LASAR(Logic Automated Stimulus and Response). This paper proposes the ROM data extracting algorithm which can test the digital circuit card that consists usually ROMs. We are implemented of the proposed fault detecting program by LabWindow/CVI 8.5 and the digital automatic test instrument with NI-VXI(National Instrument - Versa Bus Modular Europe eXtentions for Instrumentation) card. We also make an interface circuit board connecting the digital test instrument and the digital circuit card. It shows the good performance of getting the data from ROMs.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.10
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• pp.473-478
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• 2000

A more reliable algorithm for detecting a high impedance fault (HIF) requires voltage and current at the relaying point containing information of HIF characteristics including buildup/shoulder as well as nonlinearity/asymmetry. This paper presents a modeling method of an HIF in a distribution system. In order to do this, the proposed method uses two series time-varying resistances (TVRs) controlled by Transient Analysis of Control Systems (TACS) in EMTP. One TVR is employed for nonlinearity/asymmetry and then the other TVR for buildup/shoulder. The proposed method is implemented in EMTP and thus the voltage and current at the relaying point can be obtained.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.59-62
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• 1992

Power system fault transient signals are highly distorted due to the presence of high frequency components in the voltage and current signals and an exponentially decaying dc-offset component in the current signals. Modern protective relays have to make reliable fast decisions about the nature of a fault in the presence of such transients. To use a dc-offset removing filter makes relay algorithms much fast and reliable for detecting a fault. In this paper, several dc-offset removing filters are described, and characteristics of them are compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1127-1132
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• 2000

Impulsive acoustic and vibration signals within rotating machinery are often induced by irregular impacting. The detection of these impulses can be useful for fault diagnosis purposes. Recently there has been an increasing trend towards the use of higher order statistics for fault detection within mechanical systems based on the observation that impulsive signals tend to increase the kurtosis values. This paper considers the use of the third and fourth order Wigner moment spectra, called the Wigner bi- and tri- spectra receptively, for analysing such signals. Expressions for the auto-and cross-terms in these distributions are presented and discussed. It is shown that the Wigner trispectrum is a more suitable analysis tool and it performance is compared to its second order counterpart for detecting impulsive signals. These methods are also applied to measured data sets from an industrial gearbox.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.11
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• pp.569-574
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• 2001

In this paper, we described the new IEC method with fuzzy theory for detecting abnormal causes within transformer. The proposed technique presented the solution of limitation in case of lying nearly boundary conditions and not having codes for measured gas values in IEC code. Also, we proved the confidence of diagnosed results in the use of the gases values in real fault transformers.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.113-115
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• 1999

A more reliable relaying algorithm for detecting a high impedance fault (HIF) requires fault currents at the relaying point containing information of various HIF characteristics as well as load conditions. As HIF characteristics, there are buildup, shoulder, nonlinearity and asymmetry. This paper presents a modeling method of a HIF in a distribution system using EMTP. In order to represent HIF characteristics, the proposed method uses two time-varying resistances. The first TVR models nonlinearity and asymmetry using voltage as the input. The second TVR models buildup and shoulder using time information as the input. The proposed method is implemented in EMTP.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.88-88
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• 2000

As more and more critical commercial applications move on the Internet, providing highly available servers becomes increasingly important. One of the advantages of a clustered system is that it has hardware and software redundancy. High availability can be provided by detecting node or daemon failure and reconfiguring the system appropriately so that the workload can be taken over bi the remaining nodes in the cluster. This paper presents how to provide the guaranteeing high availability of clustering web server. The load balancer becomes a single failure point of the whole system. In order to prevent the failure of the load balancer, we setup a backup server using heartbeat, fake, mon, and checkpointing fault-tolerance method. For high availability of file servers in the cluster, we setup coda file system. Coda is a advanced network fault-tolerance distributed file system.