• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.172-176
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• 2001

In this paper, a new detection algorithm of faulted voltages under the unbalanced condition and a control algorithm of the instantaneous voltage sag corrector (IVSC) are proposed. To quantify the unbalance under fault conditions, the voltages are decomposed into two balanced three-phase systems using the symmetrical components of positive and negative sequence voltages, which is defined by magnitude factor (MF) and unbalance factor (UF). New control algorithm based on MF and UF values for instantaneous voltage compensation are proposed and verified through the PSCAD/EMTDC simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.918-922
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• 1998

With the development of industry, the qualitical advancement of power is needed. Since it is placed in the end step of power system, the fault at the distribution system causes some users blackout directly. So if the fault occurs, quick restoration is very important subject and, for the reason, induction of the distribution automation system is now being progressed briskly. For the quick restoration of the faulted distribution system, the load shedding of the blackout-area must be followed, and the other problems like the shedded load, faulted voltage and the rest may cause other accident. Accordingly load shedding must be based on the precise calculation technique during the distribution system load flow(dist flow) calculation. In these days because of its superior convergence characteristic the Newton-Raphson method is most widely used. The number of buses in the distribution system amounts to thousands, and if the fault occurs at the distribution system, the speed for the dist flow calculation is to be improved to apply to the On-Line system. However, Newton-Raphson method takes much time relatively because it must calculate the Jacobian matrix and inverse matrix at every iteration, and in the case of huge load, the equation is hard to converge. In this thesis. matrix equation is used to make algebraical expression and then to solve load flow equation and to modify above defects. Then the complex matrix is divided into real part and imaginary part to keep sparcity. As a result time needed for calculation diminished. Application of mentioned algorithm to 302 bus, 700 bus, 1004 bus system led to almost identical result got by Newton-Raphson method and showed constant convergence characteristic. The effect of time reduction showed 88.2%, 86.4%, 85.1% at each case of 302 bus, 700 bus system 86.4%, and 1004 bus system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.187-194
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• 2008

Because the types and severities of most engine faults are various and complex, it is not easy that the conventional model based fault detection approach like the GPA(Gas Path Analysis) method can monitor all engine fault conditions. Therefore this study proposed newly a diagnostic algorithm for isolating and diagnosing effectively the faulted components of the smart UAV propulsion system, which has been developed by KARI(Korea Aerospace Research Institute), using the fuzzy logic and the neural network algorithms. A precise performance model should be needed to perform the model-based diagnostics. The based engine performance model was developed using SIMULINK. For the work and mass flow matching between components of the steady-state simulation, the state-flow library was applied. The proposed steady-state performance model can simulate off-design point performance at various flight conditions and part loads, and in order to evaluate the steady-state performance model their simulation results were compared with manufacturer's performance deck data. According to comparison results, it was confirm that the steady-state model well agreed with the deck data within 3% in all flight envelop. The diagnosis procedure of the proposed diagnostic system has the following steps. Firstly after obtaining database of fault patterns through performance simulation, then secondly the diagnostic system was trained by the FFBP networks. Thirdly after analyzing the trend of the measuring parameters due to fault patterns, then fourthly faulted components were isolated using the fuzzy logic. Finally magnitudes of the detected faults were obtained by the trained neural networks. Because the detected faults have almost same as degradation values of the implanted fault pattern, it was confirmed that the proposed diagnostic system can detect well the engine faults.

• 자원환경지질
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• 제23권3호
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• pp.353-358
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• 1990

This paper presents numerical experiments on migration of synthetic seismograms using by $45^{\circ}$ wave equation. The seismograms used are zero-offset seismogram (corresponding to stacked section) on point reflectors, dipping plane reflector, faulted and folded layers. The seismograms are constructed by upward continuation of seismic source wavelets, exploading on subsurface reflection interfaces, to the earth surface. The synthetic seismograms are migrated by downward continuation and imaging. The upward and downward continuations are implemented by solving the $45^{\circ}$ wave equation with the finite-difference method. Migration of the synthetic data used in this study results in relatively accurate reposition of subsurface structures while the synthetic sections are quite different from the structures.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.349-352
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• 2007

It is impossible to database(DB) the patterns of cable events and cause analysis of faulted cable because the product liability(PL) law have been enforced in Korea, since 2002. In additions, simulation and pattern of cable events are needed for DB system under accelerated deterioration. In this paper, we tested for resistance to nicking of cable below the 22.9kV class due to thermal stresses. This method of exam is following IEC 60811-3-1(Common test methods for insulating and sheathing materials of electric cables). First of all, set the cable in the thermal stress instrument, temperature changed from -20 degree to 120 degree. After thermal stress, we observed a surface crack of cable through microscope and carried out AC withstand voltage test.

• 전기학회논문지
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• 제56권6호
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• pp.993-999
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• 2007

This paper discusses the effects of CD type superconducting cable operation in 22.9kV multi neutral grounded distribution system during L-G fault and counterplans to power system protection. In case of using the 3-phase CD-type superconducting cable, the inductance of superconducting cable system would be decreased due to the current of shield part of superconducting cable, which is opposite direction and nearly equal value with respect to main superconductor. However, when the shield circuit system is operated in shorted state, shield current decreases faulted ground current and give effects to power system protection scheme. This study examines the phenomena of single line to ground fault case in above mentioned system using the EMTDC program and discusses the right operation method of superconducting shield.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.117-124
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• 2000

This paper presents the construction planning and the detail design of a 16.2 km long railroad tunnel in a mountainous area. Major design conditions for railroad are the single track, loop-typed alinement, and a maximum grade of 24.5$\textperthousand$. A underground station(double track) with a length of 1.1km is located in the middle of the line for train cross-passing. Tunnel is excavated in highly complex geological conditions including faulted areas, abandoned mine works areas, and various rock types such as sandstone, shale, limestone, and coal seam partly. Drilling and blasting method was adopted because it is more flexible than TBM(Tunnel Boring Machine) as a result of risk assessment for geological conditions in this area. Two working adits were planned to adjust the construction schedule and can be used for ventilation and maintenance in operation phase. New material and concept were introduced to the tunnel drain design. They are expected to improve tunnel drain condition and capability. Rational tunnel support design was tried to consider the various tunnel size and purpose and to use the geological investigation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.320-321
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• 2011

As the scale of industries expands, the facilities of the industrial customer become larger and more complex. When a fault occurs in the system, the circuit breakers play an important role in minimizing causalitites by quickly tripping the faulted line. Since the capacity of the receiving-end has increased in size, an examination is needed to be performed between the industrial customers and the conventional circuit breakers. The transient recovery voltage, which is the initial transient characteristics of the voltage across the breaker when tripped, is an important factor in determining the circuit breaker's performance. In this paper, a TRV analysis on the large-scale industrial customer is being performed utilizing PSCAD/EMTDC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.156-157
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• 2011

본 논문은 방사상으로 운용중인 배전계통에 1선 지락 고장시 퍼지 로직 알고리즘을 이용하여 고장구간을 판단하는 기법에 대해 제안하고 있다. 배전계통에 1선 지락 고장 발생 시 선로불평형 전류에 의해 고장구간 이후의 자동화개폐기에서 고장표시기가 오동작을 한다. 이로 인해 고장구간을 잘못 판단하여 수용가에 전력공급의 신뢰성이 줄어든다. PSCAD/EMTDC라는 전력해석용 툴을 이용하여 배전계통 모델링과 시뮬레이션을 하였고, 개폐기의 영상전류 크기를 통해 퍼지 로직이라는 인공지능기법을 이용하여 정확한 고장구간을 판단하는 기법을 제안한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1850-1851
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• 2011

The faults of a electric motor cause to rise the maintenance and repair cost and to reduce the reliability of the electric power system. In this paper, the auto fault detection system for a induction motor is developed using the torque signal spectrum analysis. The spectrum of motor torque signal is used for finding a bearing fault feature frequency. A threshold value, for detecting the motor bearing fault is set by the difference of torque signal spectrum(FFT signal) between normal condition and faulted condition of the motor.