• 한국안전학회지
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• 제33권3호
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• pp.21-26
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• 2018

Approximately 20% of the total fire is electrical fire, and electrical energy is a potential source of heat. Large-scale fault currents that occur during a line ground fault flow into electric utility poles, electric power equipment, or electric appliances of the customer, and cause simultaneous electrical fire. In this paper, we investigated the possibility of fire through the change of fault current flowing in faulty and sound feeder in case of 1 line ground fault in 22.9 kV distribution line. We propose a fire investigation analysis method for simultaneous multiple electrical fire such as evidence analysis method, and fault current occurrence confirmation method in case of fire accident by analyzing the fault current occurring in the ground fault in the distribution line using EMTP, electric power system analysis program.

• 설비공학논문집
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• 제27권11호
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• pp.587-595
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• 2015

In this study, fault symptoms were simulated and analyzed for a single-effect absorption chiller. The fault patterns of fault detection parameters were tabulated using the fault symptom simulation results. Fault detection and diagnosis by a process history-based method were performed for the in-situ experiment of a single-effect absorption chiller. Simulated fault modes for the in-situ experimental study are the decreases in cooling water and chilled water mass flow rates. Five no-fault reference models for fault detection of a single-effect absorption chiller were developed using fault-free steady-state data. A sensitivity analysis of fault detection using the normalized distance method was carried out with respect to fault progress. When mass flow rates of the cooling and chilled water decrease by more than 19.3% and 17.8%, respectively, the fault can be detected using the normalized distance method, and COP reductions are 6.8% and 4.7%, respectively, compared with normal operation performance. The pattern recognition method for fault diagnosis of a single-effect absorption chiller was found to indicate each failure mode accurately.

• 한국정밀공학회지
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• 제22권10호
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• pp.80-89
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• 2005

In this paper, time-frequency analysis using wavelet packet transform and advanced-MDSA (Multiple Dimensional Spectral Analysis) which based on wavelet packet transform is applied fur fault source identification and diagnosis of early detection of fault non-stationary sound/vibration signals. This method is analyzing the signal in the plane of instantaneous time and instantaneous frequency. The results of ordinary coherence function, which obtained by wavelet packet analysis, showed the possibility of early fault detection by analysis at the instantaneous time. So, by checking the coherence function trend, it is possible to detect which signal contains the major fault signal and to know how much the system is damaged. Finally, It is impossible to monitor the system is damaged or undamaged by using conventional method, because crest factor is almost constant under the range of magnitude of fault signal as its approach to normal signal. However instantaneous coherence function showed that a little change of fault signal is possible to monitor the system condition. And it is possible to predict the maintenance time by condition based maintenance for any stationary or non-stationary signals.

• 한국멀티미디어학회논문지
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• 제16권1호
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• pp.87-99
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• 2013

IT융합 응용 기술의 발전으로 스마트 디바이스들의 활용이 증대되고 있고 지불결제 시스템에서도 스마트 IC카드의 사용이 급증하고 있다. 또한 무선 이동통신기술과 멀티미디어 처리 기술의 발전에 따라 언제 어디서나 IC카드 지불결제 시스템의 사용이 요구되고 있다. 이에 IC카드 지불결제 시스템의 보안성(security) 역시 중요한 이슈로 떠오르고 있다. IC카드 지불결제 시스템들과 같은 정보 시스템의 보안성을 평가하기 위한 여러 가지 결함 분석 기법들이 있다. 그러나 IT융합 응용 기술이 확대 발전함에 따라 정보 시스템의 종류와 특성이 다양해지면서 단지 하나의 시스템 보안성 평가 방법으로는 적절한 분석이 이루어 질 수 없다. 따라서 본 논문에서는 IC카드 지불결제 시스템의 보안성을 평가하기 위해서 두 가지 중요 결함 분석 기법인 결함 트리 분석(Fault Tree Analysis; FTA) 기법과 치명도(Criticality)기반의 고장모드별 영향 분석(Fault Modes and Effect Analysis/Criticality; FMEA/C)기법을 통합하여 사용함으로서 IC카드 지불결제 시스템의 결함 분석을 수행하여 보안성을 평가하고 개선하는 방법을 제안한다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.522-532
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• 2017

In this study, we propose a fault analysis method for a power distribution grid with PCS-based DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.

• Journal of Power Electronics
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• 제16권3호
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• pp.1097-1109
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• 2016

Fault detection and isolation are related to system monitoring, identifying when a fault has occurred, and determining the type of fault and its location. Fault detection is utilized to determine whether a problem has occurred within a certain channel or area of operation. Fault detection and diagnosis have become increasingly important for many technical processes in the development of safe and efficient advanced systems for supervision. This paper presents an integrated technique for fault diagnosis and classification for open- and short-circuit faults in three-phase inverter circuits. Discrete wavelet transform and principal component analysis are utilized to detect the discontinuity in currents caused by a fault. The features of fault diagnosis are then extracted. A fault dictionary is used to acquire details about transistor faults and the corresponding fault identification. Fault classification is performed with a fuzzy logic system and relevance vector machine (RVM). The proposed model is incorporated with a set of optimization techniques, namely, evolutionary particle swarm optimization (EPSO) and cuckoo search optimization (CSO), to improve fault detection. The combination of optimization techniques with classification techniques is analyzed. Experimental results confirm that the combination of CSO with RVM yields better results than the combinations of CSO with fuzzy logic system, EPSO with RVM, and EPSO with fuzzy logic system.

• 한국지형학회지
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• 제25권3호
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• pp.89-103
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• 2018

This study presents results of analysis on fault-related landforms and the Quaternary fluvial landforms, which are important evidences for active faulting by identifying surface deformation, around the Ulsan Fault Zone. In addition, this study suggests lineament map and inferred active fault-line map based on analyzing linearity and continuity of these landforms and by compiling location information of existing active faults. We convince that quantitative tectonic-geomorphological analysis are an effective method for active faults tracking, in particular, considering the conditions of relatively low seismicity and surface ruptured-events in the Korean Peninsula compared to plate boundary active areas. However, research on active fault in South Korea is just an infant stage since the 1990s and requires accumulation of research achievements on development and application of various fault analysis techniques, analysing and standardizing linear structures.

• 전력전자학회논문지
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• 제4권1호
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• pp.35-42
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• 1999

본 논문에서는 전력계통 고장해석 교육 및 훈련을 위한 대화식 컴퓨터 소프트웨어를 개발하였다. 개발된 소프트웨어는 고장해석에 대한 손쉬운 이해 및 소프트웨어의 사용자 편의를 증가시키기 위하여 윈도우, 그래픽 아이콘, 다양한 그래픽 출력 기능 등을 포함하고 있다. 특히, 대화식 기능을 부가함으로서 사용자가 다양한 사고 조건에서 고장해석을 모의할 수 있도록 하였다. 이러한 기능을 통하여 사용자는 전력계통 고장해석의 기본 개념 및 사고로 인한 계통의 영향에 대한 이해를 손쉽게 습득할 수 있다. 제안된 소프트웨어는 16모선 전력계통을 통하여 사례연구를 수행함으로 전력계통 고장해석의 교육 및 훈련에 유용한 기능들을 갖추고 있음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.274-275
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• 2011

Fault current problems is considered a serious issue in the power system because large fault currents not only cause many side effects to the equipments of power system but also lead to severe problems, such as blackouts. This paper deals with the structural analysis and 3-phase fault current stability of the future Seoul metropolitan power system. The simulation composition and analysis are performed with the 4th KEPCO power supply planning data using PSS/e. Through the results of the simulations, it can be observed that the future Seoul metropolitan system results in a fault current which exceeds the circuit breaker (CB) rate. This unremovable fault current can cause critical damage to power system. To resolve the problem, the algorithm for the application of Voltage Sourced Converter Back-to-Back High Voltage Direct Current (VSC BTB HVDC) is being proposed. where the most suitable location for solving fault current problem in Seoul metropolitan area is being implemented.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.702-705
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• 1996

Recently, induction motors are used more widely because of their low cost and simple structure. Therefore, the importance of fault detection and isolation of induction motors significantly increases. In most case the line current is used for fault detection and isolation. But in case that an induction motor has an inverter for control, it distorts the information of faulty state included in the line current. This paper proposes a new method for fault detection and isolation of induction motors that is speed controlled by the inverter using frequency analysis of the reference current instead of the line current for fault detection and isolation.