• 전기학회논문지
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• 제61권7호
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• pp.937-943
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• 2012

Most of faults occurred in transmission lines are single-phase to ground faults and transient faults. Single-phase auto reclosing is an appropriate scheme to maintain the system stability and restore the system effectively when those faults are occurred. In single-phase auto reclosing scheme, the secondary arc is generated after faulted phase is tripped to eliminate the fault and it is sustained by the capacitive and inductive coupling to the healthy phases. It is important to reclose the faulted phase after fully extinction of secondary arc because of the damage applied to system. Therefore, it is necessary to research on the detection of secondary arc extinction to ensure high success rate of reclosing. In this step, firstly, the accurate modelling of secondary arc should be performed. In this paper, the modelling of secondary arc is performed by using EMTP-RV and the simulation results show that the implemented model is correct and effective.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 전기설비
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• pp.53-54
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• 2006

본 논문에서는 유도전동기의 고정자권선 고장진단을 목적으로 이상적인 전동기의 전류신호와 실시간으로 운전하고 있는 전동기 전류신호를 Park's Vector에 각각 적용시켜 Park's Vector 패턴을 만들고 패턴 피크값의 기준치와 측정치의 편차를 이용하여 오차치를 벗어날 때 고장으로 진단하는 Park's Vector 패턴의 피크값을 이용한 고정자권선의 고장진단을 시도하였다. 숙달된 작업자가 Park's Vector패턴을 보고 고장을 분석해야 했던 방법과는 달리 패턴을 비교하지 않고도 자동으로 고장을 진단하고 경보해주는 진단 방법을 제시하였다. 실제 전류분석 및 진단을 위해 상용 프로그램인 LabVIEW를 이용하였다.

• 한국정밀공학회지
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• 제20권3호
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• pp.82-88
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• 2003

The nondestructive internal quality evaluation of agricultural products has been strongly required from the needs for individual inspection. Recently, the ultrasonic wave has been considered as a solution fur this problem, and an ultrasonic system was constructed for the ultrasonic NDE of fruits and vegetables in our previous work. In this paper, the practical applicability of our ultrasonic system is tested fur the inspection of internal defects (central cavity) in Atlantic potato. Sound speed and RMS of transmitted ultrasonic wave signal were measured and classification algorithm using 2 dimensional stochastic analysis. was presented. Experimental results showed greater value of sound speed and RMS (root mean square) of transmitted signal in normal samples than in abnormal samples with cavity. Also a stochastic method to distinguish normal and abnormal showed fault detection rate less than 5%.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 추계학술대회
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• pp.200-201
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• 2010

본 논문에서는 매트릭스 컨버터(matrix converter)의 스위치 개방사고를 감지하는 기법을 제안한다. 매트릭스 컨버터는 크게 두 가지의 형태로 구현할 수 있는데 그 중 간접 매트릭스 컨버터(indirect matrix converter) 구조에서의 개방사고를 살펴보기로 한다. 제안된 고장진단 기법은 측정된 각 상의 전류를 기반으로 만들어진 패턴과 비교하여 고장상태를 판단하고 고장 스위치의 위치를 판별한다. 시뮬레이션을 통해 제안한 개방사고 고장진단 기법의 타당성을 검증한다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2000년도 제13회 춘계학술대회 및 임시총회 학술발표 논문집
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• pp.324-327
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• 2000

본 논문에서는 LAN 상에서의 장애 검출과 장애를 유발시킨 호스트에 대한 위치 확인을 통하여 보다 효율적인 네트워크 장애 관리가 이루어질 수 있도록 하기 위한 알고리즘을 제시하고 있다. LAN 상에서의 주된 장애로 충돌율에 의한 네트워크 지연 장애를 들 수 있다. 따라서 패킷 충돌 감지를 통하여 네트워크 지연을 감지하고 이를 통하여 브로드캐스트, 멀티캐스트, 에러 발생 패킷 등을 분석하여 충돌율을 많이 발생시킨 호스트를 찾는다. 패킷을 많이 발생시킨 호스트에 대하여 RMON2를 이용하여 응용 프로토콜의 종류를 파악하고 이에 대한 내용을 관리자에게 통보함으로써 네트워크 장애 관리를 효율적으로 수행할 수 있다.

• Geosciences Journal
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• 제22권6호
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• pp.891-902
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• 2018

Techniques for more reliable detection of 3D subsurface flow paths are highly important for most water-related geotechnical projects. In this case study, a magnetometric resistivity method with a new approach and state-of-the-art technology ("Willowstick survey") was applied to the testbed dam (YD dam) site, and its applicability was validated by geotechnical investigation techniques including borehole drilling and sampling, Lugeon test, flow direction and velocity test, and seismic tomography. In addition to the magnetometric survey, a 3D electrical resistivity survey was performed independently and the results were compared and discussed. The electrical resistivity survey was effective in detecting groundwater levels, but it was limited in mapping leakage paths. On the other hand, the Willowstick magnetometric survey effectively detected geologic weaknesses (e.g., fault fracture) and potential leakage paths of the dam site foundation rocks. The results of this research are expected to be effective for water infrastructures where leakage is an important issue.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.97-104
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• 2008

Most of engine control systems for helicopter turboshaft engines are equipped with dual sensors. For the system with dual redundancy, analytic methods are used to detect faults based on the system dynamical model. Helicopter engine dynamics are affected by aerodynamic torque induced from the dynamics of the main rotor. In this paper an engine model including the rotor dynamics is constructed for the T700-GE-700 turboshaft engine powering UH-60 helicopter. The singular value decomposition(SVD) method is applied to the developed model in order to detect sensor faults. The SVD method which do not need an additional computation to generate residual uses the characteristics that the system outputs in direction of the left singular vector if an input is applied in direction of the right singular vector. Simulations show that the SVD method works well in detecting and isolating the sensor faults.

• 산업경영시스템학회지
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• 제36권1호
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• pp.78-85
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• 2013

Since the basic built-in-test, prognostic health management (PHM) has evolved into more sophisticated and complex systems with advanced warning and failure detection devices. Aerospace and military systems, manufacturing equipment, structural monitoring, automotive electronic systems and telecommunication systems are examples of fields in which PHM has been fully utilized. Nowadays, the automotive electronic system has become more sophisticated and increasingly dependent on accurate sensors and reliable microprocessors to perform vehicle control functions which help to detect faults and to predict the remaining useful life of automotive parts. As the complication of automotive system increases, the need for intelligent PHM becomes more significant. Given enormous potential to be developed lays ahead, this paper presents findings and discussions on the trends of automotive PHM research with the expectation to offer opportunity for further improving the current technologies and methods to be applied into more advanced applications.

• International Journal of Internet, Broadcasting and Communication
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• 제11권1호
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• pp.47-53
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• 2019

The idea of ensemble learning is to train multiple models, each with the objective to predict or classify a set of results. Most of the errors from a model's learning are from three main factors: variance, noise, and bias. By using ensemble methods, we're able to increase the stability of the final model and reduce the errors mentioned previously. By combining many models, we're able to reduce the variance, even when they are individually not great. In this paper we propose an ensemble model and applied it to classification problem. In iris, Pima indian diabeit and semiconductor fault detection problem, proposed model classifies well compared to traditional single classifier that is logistic regression, SVM and random forest.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.416-417
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• 2019

In this paper, an effective power flow control strategy (PFCS) based on the centralized control approach and a DC-link (DCV) restoration algorithm for DC microgrid (DCMG) are presented. By investigating the statuses of system power units, eleven operating modes are given to ensure the system power balance under various conditions. To avoid the system power imbalance caused by the delay of grid fault detection, a reliable DCV restoration algorithm is proposed. In the proposed scheme, when an abnormal variation of the DCV is detected, the battery instantly starts a local emergency control mode to restore the DCV to the nominal value regardless of the control mode from the central controller. The simulations and experiments are carried out to prove the effectiveness of the PFCS and the proposed DCV restoration algorithm.