• ETRI Journal
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• 제31권2호
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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.

• 전기학회논문지
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• 제66권3호
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• pp.599-604
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• 2017

Nowadays reactance method is being used as a technique for fault location in parallel feeding AC traction power system. However, implementation of this method requires a large number of field tests(ground fault) which is a huge burden on the operators. This paper presents a new estimation technique using quadratic interpolation to reduce number of times for field test and improves the accuracy of fault location. To verify a new technique, we solve AT feeding circuit and model it using PSCAD/EMTDC. Finally this paper conducts a comparative analysis of usefulness between a new technique and real field data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.315-317
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• 2003

Power system is becoming more and more complex and large. And power consumption increases rapidly according to the industry development. There is an ample possibility for a fault in proportion to these facts. Therefore power system engineer is requested to abilities, fault analysis and fault prevent. This paper handling result data by Object Oriented Database(OODB) because OODB has advantages abut flexibleness and recycling. Besides this paper presents fault analysis program by Graphic User Interface(GUI) to understand easily program using method.

• Journal of Information Processing Systems
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• 제16권4호
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• pp.870-881
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• 2020

Because SCADA monitoring data of wind turbines are large and fast changing, the unbalanced proportion of data in various working conditions makes it difficult to process fault feature data. The existing methods mainly introduce new and non-repeating instances by interpolating adjacent minority samples. In order to overcome the shortcomings of these methods which does not consider boundary conditions in balancing data, an improved over-sampling balancing algorithm SC-SMOTE (safe circle synthetic minority oversampling technology) is proposed to optimize data sets. Then, for the balanced data sets, a fault diagnosis method based on improved k-nearest neighbors (kNN) classification for wind turbine blade icing is adopted. Compared with the SMOTE algorithm, the experimental results show that the method is effective in the diagnosis of fan blade icing fault and improves the accuracy of diagnosis.

• 전력전자학회논문지
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• 제26권1호
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• pp.32-37
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• 2021

This study proposes a DC series arc fault detector using a frequency analysis method called the discrete wavelet transform (DWT), in which the processing speed of the DWT algorithm is improved effectively. The processing time can be shortened because of the time characteristic of the DWT result. The performance of the developed DC series arc fault detector for a large photovoltaic system is verified with various DC series arc generation conditions. Successful DC series arc detection and improved calculation time were both demonstrated through the measured actual arc experimental result.

• 한국가스학회지
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• 제5권2호
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• pp.1-8
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• 2001

공정의 위험성 평가를 위한 이상트리 작성은 많은 시간과 인력을 요하는 작업으로 대규모 화학공장에 적용하기가 매우 힘들다. 본 연구에서는 화학공정의 이상트리 합성을 위해 장치에서 발생할 수 있는 공정변수의 이탈 및 장치이상에 대한 원인-결과 관계를 나타내는데 필요한 객체지향 지식기반의 프레임워크를 제안하였다. 이상에 대한 원인을 탐색하기 위하여 장치의 객체지향 모델링과 장치간의 연결관계를 이용하여 이탈을 전파하고 이를 통해 이상트리를 합성하였다. 제안된 방법론을 질산 냉각 공정에 적용하여 그 유효성을 검증하였다.

• 한국화재소방학회논문지
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• 제31권6호
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• pp.67-73
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• 2017

항공기 정비 격납고는 고가의 항공기를 보관하거나 정비, 점검등을 하는 건축물로 화재발생 빈도는 낮지만 화재발생 시 인적, 물적 피해가 매우 클 수 있다. 따라서 본 연구에서는 Fault tree를 이용하여 현재 운용중인 항공기 정비 격납고 소화시스템의 화재 안전성에 대한 정성적 분석을 시행하고, 도출된 기본사상에 대한 고장률 자료를 활용하여 정량적 분석을 실시한 후 정상사상의 발생 확률에 대한 Minimal cut set의 중요도를 분석하였다. Minimal cut set에 의한 정성적 분석결과 항공기 격납고 포헤드 소화시스템의 화재제어 실패로 대형화재로 확대될 수 있는 사고경로는 14개라는 것을 알 수 있었다. 또한 정량적인 분석 결과 대형화재로 확대될 확률은 $2.08{\times}E-05/day$이며, Minimal cut set의 중요도 분석 결과 화재 발생 시 4개의 Minimal cut set 즉, 구역별 화재 감지기 및 포헤드 동작과 항공기 날개 및 Fire plume에 의한 소화약제 차단이 동일하게 24.95%로 대형화재로 확대될 가능성의 대부분을 차지하였으며, 항공기 정비 격납고의 포헤드 소화시스템은 항공기 날개 하부화재에 대한 적응성이 없어 개선이 필요한 것으로 Fault tree를 이용하여 처음 확인하였다.

• 한국지반환경공학회 논문집
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• 제24권12호
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• pp.53-60
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• 2023

최근들어 고속철도 및 도로 설계속도 향상과 더불어 터널건설공사가 차지하는 비중이 비례하여 높아지고 있다. 특히, 우리 나라 지형특성인 산악지가 많으므로 장대터널공사가 급증하고 있다. 이와같이 터널 장대화 추세로 단층대 구간을 회피하여 터널 설계 및 시공이 어려운 것이 현실이고 산악지에 터널건설은 설계 시에도 지반조사가 지형조건상 어려운 경우가 많아서 정밀한 지반 조사가 어렵고 이로 인하여 터널시공 중에 터널 주변 지반에 풍화 취약구간인 단층대들이 존재하는 경우에는 단층대 분포와 강도특성, 지하수 분포범위에 따라 굴착 중 터널 안정성에 직접적인 영향을 주게된다. 특히 본 연구대상 터널과 같이 터널 천정부에 일정 간격 이격되어 터널 상부에 단층대가 분포하고 있어 설계 시 지반조사에서 파악이 안된 경우에는 굴착 시간이 경과 후 터널바닥부 변형이 발생하게 되어 막장면 관찰을 통해 변위 발생 여부를 분석하는데는 한계가 있다. 따라서 유사사례 분석을 통해 변형 등이 발생하였을 때 적절한 보강방안에 대한 분석이 필요하다.

• 대한전기학회논문지:전력기술부문A
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• 제54권9호
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• pp.427-433
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• 2005

In DC tracking power supply system, ground faults are currently detected by the potential relay, 64P. Though 64P relay detects ground fault, it cannot Identify the faulted region which causes long traffic delays and safety problem to passengers. Two new ground fault protective relay schemes that can identify the faulted region are presented in this paper. One is bus differential protective relay and the other is ground overcurrent protective relay. Both type of relays is similar in principle to the ordinary bus differential protective relay and the ground overcurrent relay used in other power system. In DC traction power supply system, since it is ungrounded, ground fault current is not big enough to operate those relays. To solve the problem, a current control device, called device 'X', is newly introduced in both system, which enables large amount of ground fault current flow upon the positive line to ground fault. Algorithms for these relays are developed and their validity are verified by EMTP simulation.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.659-663
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• 2012

The application of large power transformer into a power distribution system was inevitable due to the increase of power demand and distributed generation. However, the decrease of the power transformer's impedance caused the short-circuit current of the power distribution system to be increase thus, the higher short-circuit current exceeded the cut-off ratings of the protective devices such as circuit breaker. To solve these problems, several countermeasures have been proposed to protect the power system effectively from higher fault current and the superconducting fault current limiter (SFCL) has been expected to be the promising countermeasure. In spite of excellent current limiting performances of the SFCL, on the other hand, the efforts to apply the SFCL into power system has been delayed due to both the limited spaces for the SFCL's installation and its long recovery time after the fault removal. In order to solve these problems, a hybrid SFCL, which can perform either first half cycle limiting of first half cycle non-limiting operation, has been developed by corporation of LSIS (LS Industrial System) and KEPCO (Korea Electric Power Corporation). In this paper, we tried to requirements hybrid SFCL by PSCAD/EMTDC. Simulation results of our analysis of the hybrid SFCL is that its accompanied the characteristics both the limit the fault current and quick recovery caused by the less impact from superconductor.