• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.281-283
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• 1999

A novel prototype of an inductive superconducting fault current limiter with an iron core and an air sap was fabricated and tested. If its impedance is not high enough to limit the fault current, then destructive damage occurs in the power system. We attained a magnetic saturation under the higher current by introducing an air gap in the three-legged magnetic core. The fault current was successfully limited to two times as much as the nominal current without high fault current within 1/4 cycles at a 60 Hz source having an effective voltage of 70V.

• ETRI Journal
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• v.31 no.2
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• pp.209-214
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• 2009

In this paper, we propose a novel test methodology for the detection of catastrophic and parametric faults present in analog very large scale integration circuits. An automatic test pattern generation algorithm is proposed to generate piece-wise linear (PWL) stimulus using wavelets and a genetic algorithm. The PWL stimulus generated by the test algorithm is used as a test stimulus to the circuit under test. Faults are injected to the circuit under test and the wavelet coefficients obtained from the output response of the circuit. These coefficients are used to train the neural network for fault detection. The proposed method is validated with two IEEE benchmark circuits, namely, an operational amplifier and a state variable filter. This method gives 100% fault coverage for both catastrophic and parametric faults in these circuits.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.451-465
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• 2008

The DC over current relay(76i) and the DC under voltage relay(mid-point relay, 80A) used mainly with DC protective relay system of DC electric railway in Korea, But the DC fault selective relay(50F) is applying to recently mainly. In this study, simulation to compare 76i/80A and 50F in the methods of protection and the operational characteristics were executed through verifying a calculation of short circuit current and using PSCAD/EMTDC transition program. As a result of this study, it was proved that while 80A runs in relation to the scale of fault resistance, 50F runs regardless of the scale of fault resistance or the length of rail.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.637-650
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• 2007

A new on-line fault detection and isolation(FDI) scheme has been proposed for engines using an adaptive neural network classifier; this paper investigates the robustness of this scheme by evaluating in a wide range of operational modes. The neural classifier is made adaptive to cope with the significant parameter uncertainty, disturbances, and environmental changes. The developed scheme is capable of diagnosing faults in the on-line mode and can be directly implemented in an on-board diagnosis system(hardware). The robustness of the FDI for the closed-loop system with crankshaft speed feedback is investigated by testing it for a wide range of operational modes, including robustness against fixed and sinusoidal throttle angle inputs, change in load, change in an engine parameter, and all changes occurring simultaneously. The evaluations are performed using a mean value engine model(MVEM), which is a widely used benchmark model for engine control system and FDI system design. The simulation results confirm the robustness of the proposed method for various uncertainties and disturbances.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2888-2898
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• 2021

Vital area identification (VAI) is an essential procedure for the design of physical protection systems (PPSs) for nuclear power plants (NPPs). The purpose of PPS design is to protect vital areas. VAI has been improved continuously to overcome the shortcomings of previous VAI generations. In first-generation VAI, a sabotage fault tree was developed directly without reusing probabilistic safety assessment (PSA) results or information. In second-generation VAI, VAI model was constructed from all PSA event trees and fault trees. While in third-generation VAI, it was developed from the simplified PSA event trees and fault trees. While VAIs have been performed for NPPs in full-power operations, VAI for NPPs in low-power and shutdown (LPSD) operations has not been studied and performed, even though NPPs in LPSD operations are very vulnerable to sabotage due to the very crowded nature of NPP maintenance. This study is the first to research and apply VAI to LPSD operation of NPP. Here, the third-generation VAI method for full-power operation of NPP was adapted to the VAI of LPSD operation. In this study, LPSD VAI for a few plant operational states (POSs) was performed. Furthermore, the operation strategy of vital areas for both full-power and LPSD operations was discussed. The LPSD VAI method discussed in this paper can be easily applied to all POSs. The method and insights in this study can be important for future LPSD VAI that reflects various LPSD operational states. Regulatory bodies and electric utilities can take advantage of this LPSD VAI method.

• Structural Monitoring and Maintenance
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• v.5 no.1
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• pp.51-65
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• 2018

A number of sensing techniques have been implemented for detecting defects in civil infrastructures instead of onsite human inspections in structural health monitoring. However, the issue of faults in sensors has not received much attention. This issue may lead to incorrect interpretation of data and false alarms. To overcome these challenges, this article presents a deep learning-based method with a new architecture of Stateful Long Short Term Memory Neural Networks (S-LSTM NN) for detecting sensor fault without going into details of the fault features. As LSTMs are capable of learning data features automatically, and the proposed method works without an accurate mathematical model. The detection of four types of sensor faults are studied in this paper. Non-stationary acceleration responses of a three-span continuous bridge when under operational conditions are studied. A deep network model is applied to the measured bridge data with estimation to detect the sensor fault. Another set of sensor output data is used to supervise the network parameters and backpropagation algorithm to fine tune the parameters to establish a deep self-coding network model. The response residuals between the true value and the predicted value of the deep S-LSTM network was statistically analyzed to determine the fault threshold of sensor. Experimental study with a cable-stayed bridge further indicated that the proposed method is robust in the detection of the sensor fault.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.38-42
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• 2019

To protect the power systems from fault current, the rated protective equipment should be installed. However growth of power system scale and concentration of loads caused the large fault current in power transmission system and distribution system. And capacities of installed protective equipment have been exceeded the due to increase of fault current. This increase is not temporary phenomenon but will be steadily as long as the industry develops. The power system need a counter measurement for safety, so superconducting fault current limiter (SFCL) has been received attention as an effective solutions to reduce the fault current. For the above reasons various type SFCL is studied recently. In this paper, the operational characteristics and power burden of trigger type SFCL is studied. The trigger type SFCL has been used for real system research in many countries. And another trigger type SFCL (double quench trigger type SFCL) is also studied. For this paper, short circuit test is performed.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.40-44
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• 2001

Recently. the high-tc superconducting fault col-rent limiters (SFCL) are studied worldwide to be classified as a resistive type or an inductive type such as a magnetic shielding type and a inductive type. The high-tc SFCL wish an open core belongs to the magnetic shielding type SFCL. Unlike conventional magnetic shielding type SFCLS it uses the open core to reduce the mechanical vibrations and installation space, The high-tc SFCL with an open core was designed and manufactured by stacking three BSCCO 2212 tubes. It was tested in the maximum source voltage of 400 Vrms. The results such as the reduction of fault current and impedance of the SFCL are described in this paper. The results show that the fault current in the source voltage of 400 Vrms was reduced to be about 123 Apeak. about 3.9 times greater than the normal state current. Also, the impedance of the high-tc SFCL was about 9${\Omega}$ about 9 times greater than the normal state impedance. The impedance of the SFCL appears just after the fault, and its size is dependent on the source voltage. From the impedance, the inductance of the SFCL was calculated.

• Journal of Information Technology Applications and Management
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• v.11 no.4
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• pp.87-94
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• 2004

The software reliability growth model(SRGM) has been developed in order to estimate such reliability measures as remaining fault number, failure rate and reliability for the developing stage software. Almost of them assumed that the faults detected during testing were evetually removed. Namely, they have studied SRGM based on the assumption that the faults detected during testing were perfectly removed. The fault removing efficiency. however. IS imperfect and it is widely known as so in general. It is very difficult to remove detected fault perfectly because the fault detecting is not easy and new error may be introduced during debugging and correcting. Therefore, the fault detecting efficiency may influence the SRGM or cost of developing software. It is a very useful measure for the developing software. much helpful for the developer to evaluate the debugging efficiency, and, moreover, help to additional workloads necessary. Therefore. it is very important to evaluate the effect of imperfect dubugging in point of SRGM and cost. and may influence the optimal release time and operational budget. I extent and study the generally used reliability and cost models to the imperfect debugging range in this paper.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.11
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• pp.619-623
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• 2004

We proposed the bridge type superconducting fault current limiter(SFCL) using switching operation of high-Tc superconducting(HTSC) thin film. The proposed bridge type SFCL consists of HTSC thin film, a diode bridge and a dc reactor. The controller for the operation of an interrupter is required in the conventional bridge type SFCL to prevent the continuous increase of fault current after a fault happens. On the other hand, the proposed bridge type SFCL can limit the fault current without the interrupter and the controller for its operation by the resistance generated when the gradually increased fault current exceeds HTSC thin film's critical current. We calculated the time when the gradually increased fault current started to be limited by the resistance generated in HTSC thin film after a fault happened and confirmed that it could be dependent on the amplitude of source voltage. The experimental results well agreed with the calculated ones from simulation.