• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.929-940
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• 2006

Early detection and diagnosis of incipient induction machine faults increases machinery availability, reduces consequential damage, and improves operational efficiency. However, fault detection using analytical methods is not always possible because it requires perfect knowledge of a process model. This paper proposes a neural network based expert system for diagnosing problems with induction motors using vibration analysis. The short-time Fourier transform (STFT) is used to process the quasi-steady vibration signals, and the neural network is trained and tested using the vibration spectra. The efficiency of the developed neural network expert system is evaluated. The results show that a neural network expert system can be developed based on vibration measurements acquired on-line from the machine.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.516-518
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• 1995

This paper presents an integrated fault diagnosis expert system for power systems. The proposed system diagnoses various faults occurred in both substations and transmission lines even in the case that substation fault is spreaded over the network. To cope with this problem, A meta-inference method is proposed. This scheme shares same the data structure with the pre-developed intelligent operational aid expert system installed in a practical sub-control center, without modification. This advanced integrated diagnosis system is developed using a low cost personal computer owing to the special modular programming technique. Case studies show a promising possibility of the proposed method.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.43-45
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• 2008

In this paper, the operational characteristics of SFCL with magnetically coupled two coils were modeled and simulated by PSCAD/EMTDC. The dependence of the line voltage sag on the resistance of superconducting element during the fault period was analyzed. Through the analysis for the winding direction of two coils, the line voltage sag in case of the additive polarity winding was observed to be more improved compared to the case of the subtractive polarity winding.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.281-283
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• 2008

The superconducting fault current limiter (SFCL) using magnetic coupling of two coils with series connection, which was suggested by us, has the merit to increase the operational current and the limiting impedance of the SFCL through the adjustment of the inductance ratio and the winding direction of two coils. In addition, the recovery characteristics of the SFCL is affected by the winding direction of two coils as well as two coils' inductance ratio. In this paper, the fault current limiting and recovery characteristics of a SFCL using magnetic coupling of two coils with series connection were analyzed. Through the analysis based on the experimental results, the recovery characteristics and the current limiting characteristics of the SFCL were confirmed to be improved more in case of the additive polarity winding.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집
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• pp.57-60
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• 2004

본 논문은 전원단과 부하단사이에 GTO 사이리스터 브리지가 설치된 단상 DC 리액터타입을 적용한 고온초전도 사고전류제한기 동작특성에 대해 분석하였다. GTO 사이리스터 브리지가 설치된 DC 리액터 타입 FCL(Fault Current Limiter)은 평상시에 초전도코일에 전기에너지를 저장한다. 전원단의 사고로 인해 전력 공급이 중단되었을 경우 FCL은 부하에 저장된 에너지를 공급할 수 있을 뿐 아니라 부하단 사고로 인한 사고전류 제한기능을 수행하게 되는데 이와 같은 동작은 GTO 사이리스터를 제어함으로서 가능해진다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.337-340
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• 2003

This paper describes the operational characteristics of protection algorithm applied in distributed generations(DG) for faults occurred in the interconnected distribution networks. The DG can be Influenced by abnormal grid conditions such as disturbances occurring in the neighboring distribution feeders as well as the interconnected power line. Particularly, in case of the fault happening in the neighboring distribution feeders emanated from the substation to which DG is connected, the protective devices in the DG might mis-operate. The mis-operation of protective devices can be varied by the fault conditions. The simulation results for Hoenggye substation model composed of five feeders using PSCAD/EMTDC showed that the number of mis-operation of protective devices applied in DG is about 0.66 times per one year.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기설비전문위원
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• pp.210-212
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• 2004

본 논문은 전원단과 부하단사이에 GTO 사이리스터 브리지가 설치된 단상 DC 리액터타입을 적용한 고온초전도 사고전류제한기 동작특성에 대해 분석하였다. GTO 사이리스터 브리지가 설치된 DC 리액터 타입 FCL(Fault Current Limiter)은 평상시에 초전도코일에 전기에너지를 저장한다. 전원단의 사고로 인해 전력공급이 중단되었을 경우 FCL은 부하에 저장된 에너지를 공급할 수 있을 뿐 아니라 부하단 사고로 인한 사고전류 제한기능을 수행하게 되는데 이와 같은 동작은 GTO 사이리스터를 제어함으로서 가능해진다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.97-99
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• 2001

본 논문은 전원단과 부하단사이에 GTO 사이리스터 브리지가 설치된 단상 DC 리액터타입을 적용한 고온초전도 사고전류제한기 동작특성에 대해 분석하였다. GTO 사이리스터 브리지가 설치된 DC 리액터 타입 FCL(FAULT CURRENT LIMITER)은 평상시에 초전도코일에 전기에너지를 저장한다. 전원단의 사고로 인해 전력공급이 중단되었을 경우 FCL은 부하에 저장된 에너지를 공급할 수 있을 뿐 아니라 부하단 사고로 인한 사고전류 제한기능을 수행하게 되는데 이와 같은 동작은 GTO 사이리스터를 제어함으로서 가능해진다.

• 품질경영학회지
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• 제39권2호
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• pp.170-178
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• 2011

In general, a software fault detection phenonenon is described by a software reliability model based on a nonhomogeneous Poisson process(NHPP). In this paper, we propose a software reliability growth model considering the differences of the software environments in both the testing phase and the operational phase. Also, we consider the problem of determining the optimal release time and the optimal warranty period that minimize the total expected software cost which takes account of periodic software maintenance(e.g. patch, update, etc). Finally, we analyze the sensitivity of the optimal release time and warranty period based on the fault data observed in the actual testing process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.633-635
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• 2004

The current limiting characteristics of the flux-lock type superconducting fault current limiters(SFCLs) were investigated. The flux-lock type SFCL consists of a flux-lock reactor and high-T_c superconducting (HTSC) element. In this SFCL the initial limiting current level can be controlled by adjusting the inductances of two coils. In this paper, the operational characteristics of the flux-lock type SPCL were analyzed and the current Limiting characteristics of it were investigated through the experiments.