• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.988-990
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• 1999

Using neural network approach, the diagnosis of faults in industrial process that requires observing multiple data simultaneously are studied in this paper. Two-stage diagnosis is proposed as the basic structure. The first stage detects the dynamic trend of each measurements and the second stage diagnosis the faults. This paper makes up for the disadvantage of neural about unknown faults. The potential of this approach is demonstrated in simulation using a model of tank reactor.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1216-1221
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• 1990

An algorithm for multiple fault diagnosis of linear dynamic systems is proposed. The algorithm is constructed by using of the geometric approach based on observation that, when the number of faulty units of the system is known, the set of faulty units can be differentiated from other sets by checking linear varieties in the measurement data space. It is further shown that the system with t number of faults can be diagnosed within (t+1) sample-time units if the input-output measurements are rich and that the algorithm can be used for diagnosis even when the number of faults is not known in advance.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.12
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• pp.1687-1696
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• 1995

An integrated fault diagnosis system for heterogeneous manufacturing environments is developed. This system has a contrast with existing diagnosis systems in the respect that they are mostly for diagnosing faults on individual machines. In addition to the usual (e.g., audio, electrical) diagnostic signals, the characteristics of products from the machines are considered as the unifying diagnostic parameters among heterogeneous machines in the diagnosis. The system is composed of a knowledge representation scheme and a diagnostic query processing mechanism. Its knowledge representation scheme allows the diagnostic knowledges from heterogeneous unit diagnostic systems to be uniformly expressed in terms of the causal relations among relevant data items. It is flexible in the sense that causes for one relation can be effects for another may be reflected on our knowledge representation scheme. The diagnosis mechanism is based on a probabilistic inferencing method. This probablistic diagnosis mechanism provides more general diagnosis than existing ones in that it accommodates multiple causes and takes complication among causes into account. These scheme and mechanism are applied to a typical example to demonstrate how our system works.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10B
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• pp.841-848
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• 2004

In case of failure in the IP network services should be provided via a backup path which fully meets QoS requirements. In this regard, we in this paper suggest simple-PFC(5-PFC) to restore single link failure, iterative-PFC(i-PFC) for multiple link failures, and fault_node Avoidance-PFC(a-PFC) for failures of nodes such as routers. Taking the minimum cost rerouting problem into account, we compare and analyze performance of those three mechanisms carrying out Direct_destination Rerouting(DR).

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.12
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• pp.555-560
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• 2006

As it has been reported that more than 60% of transmission line faults occurs due to lightning strokes, lighting is one of concerned issues in electric power utility company. Most of transmission line is double circuit in Korea. Double circuit outages account for 33.7 percent of total lightning faults from 1996 to 2004. Even though transmission fault might be cleared shortly by protective system, it could deteriorate the power quality accompanied with sag or flicker. Moreover, double circuit fault may lead to more aggravated situation, for instance, blackout. To Protect transmission lines from lightning stroke, reduction of tower footing resistance, multiple ground wires and unbalanced insulation in double circuit lines have been adopted. In this paper, we would like to introduce insulation design standards for lightning protection of Korea Electric Power Corporation.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.3-5
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• 2001

When a fault occurs on distribution network. blackout region may happen, then it should be restored as fast as possible to minimize interruption of electric service. In this paper. A near optimal method to restore distribution network is proposed. For an optimal restoration, the number or switching operations must be minimized. The proposed method generates a general restoration plan for any distribution network fault and designed to reduce switching operations considering available load transfers. In this method overall process time can reduce with heuristic rules, which make a reduction of search space before restoration process. To achieve a near optimal solution, multiple load transfer algorithm is proposed too.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.410-413
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• 1998

A passive approach for enhancing fault detection and isolation performance of multiple observer based fault detection isolation schemes(FDIS) is proposed. The FDIS has a hierarchical framework to perform detection and isolation of faults of interest, and diagnosis of process faults. The decision unit comprises of a rule base and fuzzy inference engine and removes some difficulties of conventional decision unit which includes crisp logic and threshold values. Emphasis is placed on the design and evaluation methods of the diagnostic rule base. The suggested scheme is applied for the FDIS design for a DC motor driven centrifugal pump system.

• Journal of the Korea Society for Simulation
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• v.12 no.2
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• pp.55-62
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• 2003

The explosive Increase of wireless networks and the advancement of mobile devices lead to the expansion of mobile environment. In accordance with the development of mobile environment, the need to use mobile database is increased sharply, and also it accompanies the related problems. The current mobile database system is based on the centralized method from which a synchronized server manages multiple mobile database management system to synchronize. From this mobile system architecture, several kinds of problems can be detected such as the management of synchronization issues between mobile databases and the transaction management issues. Furthermore, the current mobile database management system does not consider any solution on the fault tolerance. To solve those problems, this paper proposes the mobile agent-based mobile database management system. The proposed system provide high confidence and efficiency by enhancing the network efficiency and fault tolerance through the mobile grouping.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9B
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• pp.791-798
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• 2004

In case of failure in the IP network, services should be provided via a backup path which fully meets QoS requirements. In this regard, we in this paper suggest simple-PFC(s-PFC) to restore single link failure, iterative-PFC(i-PFC) for multiple link failures, and fault_node Avoidance-PFC(a-PFC) for failures of nodes such as routers. Taking the minimum cost rerouting problem into account, we compare and analyze performance of those three mechanisms carrying out Direct-destination Rerouting(DR).

• Journal of Power Electronics
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• v.16 no.1
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• pp.340-350
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• 2016

A cascaded hybrid multilevel inverter including a reconfiguration technique for low voltage dc distribution applications is proposed in this paper. A PWM generation fault detection and reconfiguration paradigm after an inverter cell fault are developed by using only a single-chip controller. The proposed PWM technique is also modified to reduce switching losses. In addition, the proposed topology can reduce the number of required power switches compared to the conventional cascaded multilevel inverter. The proposed technique is validated by using a 3-kVA prototype. The switching losses of the proposed multilevel inverter are also investigated. The experimental results show that the proposed hybrid inverter can improve system efficiency, reliability and cost effectiveness. The efficiency of proposed system is 97.45% under the tested conditions. The proposed hybrid inverter topology is a promising method for low voltage dc distribution and can be applied for the multiple loads which are required in a data center or telecommunication building.