• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2525-2527
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• 2000

The analysis of distribution line faults is essential to the proper protection of power system. A high impedance fault(HIF) dose not make enough current to cause conventional protective device operating, so it is well known that undesirable operating conditions and certain types of faults on electric distribution feeders cannot be detected by using conventional protection system. In this paper, we prove that the nature of the high impedance faults is indeed a deterministic chaos, not a random motion. Algorithms for estimating Lyapunov spectrum and the largest Lyapunov exponent are applied to various fault currents detections in order to evaluate the orbital instability peculiar to deterministic chaos dynamically, and fractal dimensions of fault currents which represent geometrical self-similarity are calculated. Wavelet transform analysis is applied the time-scale information to fault signal. Time-scale representation of high impedance faults can detect easily and localize correctly the fault waveform.

• Journal of Power Electronics
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• 제15권1호
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• pp.288-297
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• 2015

This paper presents a novel approach to diagnose interturn insulation faults in three-phase transformers that operate at different loading conditions. This approach is based on the loci of instantaneous symmetrical components and requires the measurement of three input primary winding currents and voltages to diagnose faults in the transformer. The effect of unbalance supply conditions, load variations, constructional imbalance, and measurement errors when this methodology is used is also investigated. Wing size or length determines the loading on the transformer. Wing travel and area determine the degree of severity of fault. Experimental results are presented for a 400/200 V, 7.5 kVA transformer to validate this method.

• 융합신호처리학회논문지
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• 제10권1호
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• pp.86-92
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• 2009

유도 전동기의 사용이 증가함에 따라 유도전동기의 고장은 산업 사회에 커다란 피해를 끼치게 되었다. 그렇기 때문에 유도 전동기의 고장을 찾아내는 것은 매우 중요한 문제로 부각되었다. 하지만 그 중에서도 문제점은 유도전동기의 고장은 종종 오랜 시간에 걸쳐 진행된다는 것이다. 그것은 빠른 진단이 매우 중요하다는 것을 뜻한다. 이에 대해 많은 연구가 진행되어 왔으며 가장 일반적으로 쓰이는 고장 진단 방법은 진동 센서를 이용한 전동기의 기계적 고장을 찾는 방법이다. 하지만 이 방법은 신뢰도가 높은 검증 방법임에도 불구하고 높은 시스템 가격과 활용의 어려움으로 인해 새로운 방법들이 시도가 되었다. 이 논문은 시스템을 기반으로 웨이블릿 변환을 이용한 유도전동기의 고장 진단 기술을 구현하는 것을 보여주며 윈도우즈 기반 C++을 이용하여 고장인지 아닌지를 결정하는 알고리즘으로 구성되어 있다. 전체 시스템은 전류 데이터 수집 보드와 PC를 이용한 신경망 알고리즘으로 실시간으로 수행 될 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.559-562
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• 2003

In this paper, we introduce a new method detecting thyristor faults of the power converter module in Control Rod Control System. When we control the currents in each coil of Control Rod Drive Mechanism by using the current control method, the current value can follow the current reference despite the faults like the missing phase or the diode acting. Comparing the fault current values with the normal current values, the bad transient characteristics of the abnormal current can make the operations of control rods incorrect. In this case, the information from the current trends cannot be enough to detect the fault occurrence in thyristors. Instead of the coil currents, the state of thyristors can be watched by measuring the coil voltages. In the existing system of Westinghouse type, the ripple detector takes charge of this task. But this detector has some shortcomings in the point of time for fault detection, we come to devise a new fault detection method solving the problems which belong to the ripple detector.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권6호
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• pp.321-329
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• 2002

A protection scheme for series active compensator is presented and analyzed in this paper. The proposed series active compensator operated as a high impedance K($\Omega$) to the fundamentals when short-circuit faults occur in the power distribution system, and two control strategies are proposed in this paper The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame(SRF). When the short-circuit faults occur in the power distribution system, the proposed scheme can protect the series active compensator without additional protection circuits. The validity of the Proposed Protection scheme was investigated through experimental results.

• 전기학회논문지
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• 제59권1호
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• pp.19-25
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• 2010

Most faults are single-phase-to-ground fault in ungrounded system. The fault currents of single-phase-to-ground are much smaller than detection thresholds of measurement devices, so detecting single-phase-to-ground faults is difficult and important in ungrounded system. The protection coordination method using SGR(Selective Ground Relay) and OVGR(Overvoltage Ground Relay) is generally used in ungrounded system. But this method only detects fault line and it has the possibility of malfunction. This paper proposed to advanced protection coordination method in ungrounded system. The method just using zero-sequence current can detect fault line, fault phase, fault section at terminal device. The general protection method is used to back up protection. In the case study, the proposed method has been testified in demo system by Matlab/Simulink simulations.

• 한국지능시스템학회논문지
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• 제8권5호
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• pp.72-82
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• 1998

Power transformer protective relay should block the tripping during magnetizing imrush and rapidly operate the tripping during internal faults. But traditional approaches maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmounic component. To enhance the fault detection sensitivities of conventional technuques, flux-differential current derivative curve by fuzzy theory approaches is used. This paper deals with fuzzy logic based protective relaying for power transformer. The proposed fuzzy based relaying algorithm consisits of flux-differential current derivative curve, harmonics restraint, and precentage differential characteristic curv. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.

• 전기학회논문지
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• 제57권7호
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• pp.1141-1149
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• 2008

Most faults are single-phase-to-ground fault in ungrounded system. The fault currents of single-phase-to-ground are much smaller than detection thresholds of measurement devices, so detecting single-phase-to-ground faults is difficult and important in ungrounded system. This paper proposed to a FI(Fault Indicator) generation algorithm in ungrounded system. The algorithm just using line-to-line voltage and zero-sequence current detects fault line, fault phase, fault section and FI(Fault Indicator) at terminal device, This paper also proposed to application plan for this algorithm. In the case study, the proposed algorithm has been testified in demo system by Matlab/Simulink simulations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.19-21
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• 2001

Induction motors are a critical component of many industrial machines and are frequently integrated in commercial equipment. The many economical losses and the deterioration of system reliability might be caused by the failure of induction motors in industrial field. Based on the reliability and cost competitiveness of driving system(motors), the faults detection and diagnosis of system is considered very important factors. In order to perform the faults detection and diagnosis of motors, the vibration monitoring method and motor current signature analysis (MCSA) method are emphasized. In this paper, MCSA method is used for induction motor fault diagnosis. This method analyzes the motor's supply current, since this diagnoses the motor's condition. The diagnostic system is constructed by using LabVIEW of National Instruments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.308-310
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• 2003

This paper proposes a percentage current differential relaying algorithm for bus protection with a compensation algorithm of a CT. The compensating algorithm estimates the core flux at the start of the first saturation based on the value of the third-difference of the secondary current. It calculates the core flux and compensates distorted currents in accordance with the magnetization curve. The test results indicate that the algorithm can discriminate internal faults from external faults when the CT saturates. It can improve not only stability of the relay in the case of an external fault but sensitivity of the relay in the case of an internal fault.