• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.5
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• pp.209-216
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• 2002

Recently, there is greater demand for stable supply of electric power as higher level of our living. It becomes the important problem that the cause of fault in power system is found out in early stage, if once it occurs. In this respect, accurate classification of arcing faults in power systems is vitally important. This paper presents a new classification method for arcing faults in power system. To obtain data of various faults including high impedance fault(HIF) and low impedance fault(LIF), HIF model with the ZnO arrester is adopted and implemented within the overall transmission system model based on the electromagnetic transients program(EMTP). Results of phase plane trajectory if Clarke modal transformation using postfault current and voltage are utilized to classify types of arcing faults. The performance of the proposed method is tested on a typical 154 kV korean transmission system under various fault conditions. As can be seen from results, phase plane trajectory of postfault current should be combined with that of o component from Clarke modal transformation to give reliability of clear fault classification. Thus the proposed method can classify arcing faults including LIFs and HIFs accurately in power systems.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.34-36
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• 2006

In this paper, we will treat the diagnosis problem to accurately determine fault types. The judgement of fault types is accomplished by observing the cluster newly formed with faults and clustering the input current waveforms to intrinsically show the conditions with the dignet that is a clustering algorithm. The types of input current waveforms are, however, constrained during normal operation, though it considers the load character. In case of faults. new clusters are generated outside the clusters. which appear during normal operation, because the input current waveforms of the induction motor are generated by the type which is not observed in case of faults. The diagnosis about the types of faults is essential to building a fault tree about the induction motor, and it removes the causes of the faults using a fuzzy logic. We, first, constitute a fault tree, which connects with the parts and the entire system of the induction motor, and investigate fault modes which can be generated from the fault tree and the relationship of the cause and the effect of each part (of the motor). Also, we distinguish the faults of each part by means of inducing the said of fuzzy relation equations encapsulating the relationship of the fault modes and each part.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1532-1537
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• 2009

Nowadays the diversity and large-capacity of electric appliances are strong effect on electrical fires augment in an alarming way. But, as the inactive response characteristics of the existing RCD (Residual Current protective Device) used on low voltage power distribution lines, so control of overload and electric short circuit faults, major causes of electrical fires, are not enough. Therefore this paper is confirmed the unreliability of the existing RCD by electrical faults simulation and is proposed a auxiliary trip device of RCD by using a high precision current sensor (namely, reed switch) for the prevention of electrical disasters in low voltage power distribution lines caused by overload or electric short circuit faults. The sensitive reed switch in the proposed ATD (auxiliary trip device) exactly detects the increased magnetic flux with the overload or the short current caused by a number of electrical faults, and then rapidly cuts off the existing RCD. The proposed auxiliary trip device of RCD is confirmed the excellent characteristics in response velocity and accuracy in comparison with the conventional circuit breaker through various operation performance analysis. The proposed ATD can also prevent electrical disaster, like as electrical fires, which resulted from the malfunction and inactive response characteristics of the existing RCD.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.589-599
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• 2004

Most models assume the complete debugging environments by requiring a complete software correction in quantitative evaluation of software reliability. But, in many case, new faults are involved in debugging works, for complete software correction is impossible. In this paper, software growth model is proposed about incomplete debugging environments by considering the possibility of new faults involvements, and software faults occurrence status are also mentioned about NHPP by considering software faults under software operation environments and native faults owing to the randomly involved faults in operation before test. While, effective quantitative measurements are derived in software reliability evaluation, applied results are suggested by using actual data, and fitnesswith existing models are also compared and analyzed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.2
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• pp.61-66
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• 2005

This paper presents a refined protection algorithm of the unfused 22.9kV shunt capacitor banks in grounded wye connection to improve the existing algorithm using the voltage difference method. It is difficult to detect ground faults with arc near the input points or ground faults near the grounding point by the existing algorithm using only the voltage balanced relay. This paper shows that ground faults with arc near the input point can be detected by harmonics analysis of the differential voltage and that it has no impact of harmonics out of nonlinear loads which have the quantitative influence on capacitor banks. Thus the proposed method using harmonics analysis can be a proper detection method. In case of ground faults near the grounding point, an OVGR is being added recently and its validity is verified in this paper. The proposed method is applied to a 22.9kV example system and is verified that the proposed algorithm can detect clearly faults which are not easy to detect by the existing method.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.10
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• pp.29-38
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• 1999

This paper presents a new algorithm RICP(Redundancy Identification using Critical-pair Paths) to identify untestable faults in combinational logic circuits. In a combinational logic circuit, untestable faults occurred by redundancy of circuits. The redundancy of a circuit can be detected by analyzing areas of fanout stem and reconvergent gates. The untestable faults are identified by analyzing stem area using Critical-Pair path which is an extended concept of critical path. It is showed that RICP is better than FIRE(Fault Independent REdundancy identification) algorithm in efficiency. The performance of both algorithms was compared using ISCAS85 bench mark testing circuits.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.50-57
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• 2010

Various installation faults may lie in fasteners in the construction of a direct-fixation track by the top-down method. At an extreme, they may cause excessive interaction between the train and track, compromise the running safety of the train, and cause damage to the track components. Therefore, the faults need to be kept within the allowable level through an investigation of their effects on the interactions between the train and track. In this study, the vertical dynamic stiffness of fasteners in installation faults was measured based on the dynamic stiffness test by means of an experimental apparatus that was devised to feasibly reproduce gap faults. This study proposes an effective analytical model for a train-track interaction system in which most elements, except the nonlinear wheel-rail contact and some components that behave bi-linearly, exhibit linear behavior. To investigate the effect of the behavior of fasteners in gap faults in a direct-fixation track on the vehicle and track, vehicle-track interaction analyses were carried out, targeting key review parameters such as the wheel load reduction factor, vertical rail displacement, rail bending stress, and mean stress of the elastomer. From the results, it was noted that the gap faults in the concrete bearing surface of a direct-fixation track need to be limited for the sake of the long-term durability of the elastomer than for the running safety of the train or the structural safety of the track.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.71-79
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• 2000

The original March algorithms cannot detect CMOS ADOFs(Address Decoder Open Faults) which requires separate deterministic test patterns. Modified March algorithm using DOF(Degree of Freedom) was suggested to detect these faults in addition to conventional stuck faults. This paper augments the modified march test to further capture NPSFs(Neighborhood Pattern Sensitive Faults). Complete CA(Cellular Automata) is used for address generation and Rl-LFSRs(Randomly Inversed LFSRs) for data generation. A new modified March algorithm can detect SAF, CF, TF, CMOS ADOFs, and part of NPSFs. Time complexity of this algorithm is still O(n).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.868-877
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• 2006

Sensor network applications need synchronized time to the highest degree such as object tracking, consistent state updates, duplicate detection, and temporal order delivery. In addition, reliability issues and fault tolerance in sophisticated sensor networks have become a critical area of research today. In this paper, we proposed a fault tolerant clock management scheme in sensor networks considering two cases of fault model such as network faults and clock faults. The proposed scheme restricts the propagation of synchronization error when there are clock faults of nodes such as rapid fluctuation, severe changes in drift rate, and so on. In addition, it handles topology changes. Simulation results show that the proposed method has about $1.5{\sim}2.0$ times better performance than TPSN in the presence of faults.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1095-1106
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• 2005

Recently, the conventional controller of machine-tool has been increasingly replaced by the PC-based open architecture controller, which is independent of the CNC vendor and on which it is possible to implement user-defined application programs. This paper proposes CNC­implemented fault diagnosis and web-based remote services for machine-tool with open architecture CNC. The faults of CNC machine-tool are defined as the operational faults occupied by over $70{\%}$ of all faults. The operational faults are unpredictable as they occur without any warning. Two diagnostic models, the switching function and the step switching function, were proposed in order to diagnose faults efficiently. The faults were automatically diagnosed through the fault diagnosis system using the two diagnostic models. A suitable interface environment between CNC and developed application modules was constructed for the internal function of CNC. In addition, a suitable web environment was constructed for remote services. The web service functions, such as remote monitoring and remote control, were implemented, and their operability was tested through the web. The results obtained through this research could be a model of fault diagnosis and remote servicing for machine-tool with open architecture CNC.