• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.2
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• pp.80-86
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• 2004

During magnetic inrush or over-excitation, saturation of the core in a transformer draws a large exciting current, which can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. The relay calculates core-loss current from the induced voltage and the core-loss resistance; the relay calculates the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss and the magnetizing currents from the conventional differential current. Comparison study with the conventional differential relay with harmonic blocking is also shown. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1667-1669
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• 2001

The clack of Insulator, which results from internal or external surges such as electrical, mechanical, and thermal stress, might cause ground fault and a power failure without proper repairs. In order to minimize losses caused by a short-term or long-term power failure, it is necessary to detect the deteriorated insulator as early as possible. To do so, we will develop a new device, which can detect and trace an deteriorated insulator by monitoring its physical change the variation of frequency spectrum. This device will do so by finding a Periodic wave sharp (120 Hz), a peculiar wave generated by defused electricity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1154-1157
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• 2004

During normal machine operation, partial discharge(PD) measurements were performed with turbine generator analyzer(TGA) in imitation stator winding of high voltage motors. The motor was energized to 4.47kV, 6.67, respectively. Applied voltage to Imitation winding was used two voltage level, 4.47[KV]and 6.67[KV]. Motors having imitation stator winding were installed with 80pF capacitive couplers at the terminal box Case of PD Pattern regarding applied voltage phase angel, the PD patterns were displayed two dimensional and three dimensional. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). As the result, we could discrimidate using TGA the difference of internal and surface discharge for imitation stator winding. We have used the other technique, in order to feature extraction of faulty signals on stator winding, Daubechies Discrete wavelet transform and Harmonics analysis(FFT) about faulty signals.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.121-124
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• 2003

This paper shows shear wave behavior of CFRP(carton fiber reinforced plastics) composite laminates as a polar grid form to evaluate vibration pattern of ultrasonic transducers, which gives measured modelling fundamental contents of nondestructive evaluation. This modelling decomposes the transmission of a linearly polarized wave into orthogonal components through each ply of a laminate. It is found that a high probability shows between the model and measurement system in characterizing lay up of CFRP composite laminates. Also evaluating quantitatively the defects in CFRP laminates who found to be possible of normalized frequency obtained from 2D-FFT technique based on C-scan method. Thus, the technique is proven to be one of the useful means to evaluate any internal defect in CFRP composite laminates.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.552-553
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• 2012

현재의 발전소 내부에 가동 중인 열교환기 배관 라인의 Clinker Monitoring System은 초고온의 열교환기 내부의 벽면 및 배관라인의 클링커 상태를 감시하는 시스템을 요구하고 있다. 이러한 열교환기 내부의 상태를 감시하기 위하여 초고온에 견딜 수 있고 회전이 가능한 장치를 열교환기 내부에 투입하여 회전 가능한 장치를 통하여 원격으로 영상을 전송하도록 하여 클링커 상태를 영상으로 모니터링 하여 열교환기 내부의 상태를 감시 관찰 분석할 수 있는 시스템을 구성하였다. 본 논문에서는 발전설비의 열교환기 내부의 클링커 상태를 모니터링 할 수 있도록 회전 가능한 렌즈 튜브와 보호용 냉각 시스템을 추가된 통합 모니터링 시스템을 제기하고자 한다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1263-1270
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• 2000

The operation frequency of High-speed Communication System becomes very fast with the advanced technology of VLSI chips and system implementation. There may exist various types of noise sources degrading the signal integrity in this system. The present main system is made of backplane, so faults can be brought whenever a board is removed, replaced or added. This backplane boards testing is a very important process to verify the operation of system. firstly, we model the effects of the internal noises in the High-speed Communication System to the signal line and propose a new design method to minimize these effects. For the design methodology, we derive the characterization value for each mode land them construct the optimal simulation model. We compare the result of own proposing method with that fo the existing methods, through simulation and show that the quality of High-speed Communication System is significantly enhanced. Secondary our proposing BIST for the Backplane Boards Testing is designed to guarantee that there is no fault in the high-speed communication system.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.249-251
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• 2001

The two fuzzy criteria to distinguish the internal fault from the inrush for the power transformer protection have been identified. They are based on the terminal voltage, fundamental and second harmonic component of differential current. A systemetic way to determine the associated fuzzy membership function is also proposed.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.47-50
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• 2001

Presently the Korean grounding system uses TN system, multi-grounding method with TT independent grounding method. Nevertheless TN system can't exist with TT system in the technological terms. If they coexist, it causes ground-fault circuit not to operate, and brings about different electrical potential rise by customer system. It brings about serious problems for safety. This paper aims for improving method of grounding system based on the technical analysis on instances in foreign countries and Korea. Almost standards and construction manner were apt to be internationalized after WTO/TBT agreement was concluded. The internal grounding systems should meet the international criteria and reliability for safety, and be provided with technologically impeccable standards.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.747-748
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• 2006

본 연구에서는 전력계통에서 발생되는 surge나 고장전류에 의해서 변압기의 1차측 코일에 유도되는 전자력의 크기를 유한요소 전자계해석 프로그램(FLUX2D)을 이용하여 해석하였다. 400kVA, 6600/220(V) 단상내철형 변압기의 권선간 전자력계산을 축대칭FEM을 이용하여 각방향의 전자력을 분석하였다. 누설자속분포, 전류유입시 권선 상호간에 작용하는 힘의 변화와 힘의 분포, 전류유입시 권선 상호간에 작용하는 힘의 변화와 힘의 분포, 변압기 내부권선의 정상시와 고장전류시의 전자계비교를 전자계해석을 통하여 변압기에 미치는 영향을 해석하였다. 변압기에 대전류가 유입되는 경우의 전자력 분석결과는 변압기의 절연설계 및 단락기계력에 대한 프레임 구조 설계를 위한 자료로 활용된다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.368-372
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• 2014

The most widely used scheme for detecting loss of excitation on generator is used to sense apparent impedance from generator terminals. This paper presents loss of excitation algorithm using DFT filter based negative offset mho elements for generator field protection. It's algorithm includes two negative mho characteristics looking in the generator. The generator control system was modeled by PSCAD/EMTDC software, and then the proposed algorithm was tested by the collecting relaying signals from selected the generator model. From simulation results, the loss of excitation algorithm can be used to field protection for generator.