• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.74_76
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• 2009

This paper presents a discrete wavelet analysis based algorithm to address the fault impedance calculation under transient state in radial power distribution networks. The fault impedances have been derived under different fault conditions. Furthermore, a recursive fault distance estimation method is proposed utilizing the measured fault impedance and power line parameters. The proposed scheme can resolve the errors caused by the non-homogeneous power lines, the presence of lateral loads since, the fault impedance will always be updated with the recursive form. For the verification of the proposed scheme, a filed test has been peformed with varying fault resistances in the 22.9(kV) radial system. Power meters and fault locators were installed at the substation. It was figured out that the performance of the discrete wavelet and the recursive scheme are very good even for high fault resistance condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 B
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• pp.542-544
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• 1997

The analysis of distribution line faults is essential to the proper protections in the power system. A high impedance fault does not make enough current to cause conventional protective devices. In this paper, Fractal dimensions are estimated for distinction between normal status and fault status in the power system. Application of the concepts of the fractal geometry to analyze chaotic properties of high impedance fault current was described. In addition, to analyze variation of fault current and normal current on phase plane, embedding state variables are reconstructed from 1 dimensional time series.

• 한국지능시스템학회논문지
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• 제9권5호
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• pp.545-549
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• 1999

Previous studies on high impedance faults assumed that the erratic behavior of fault current would be random. 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 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. In addition qualitative analysis such a s phase planes Poincare maps obtained from fault currents indicate that the irregular behavior is described by strange attractor.

• 한국초전도ㆍ저온공학회논문지
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• 제16권2호
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• pp.59-63
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• 2014

HTS power cable bypass the fault current through the former to protect superconducting tapes. On the other hand, the fault current limiting (FCL) power cable can be considered to mitigate the fault current using its increased inductance and resistance. Using the increased resistance of the cable is similar to the conventional resistive fault current limiter. In case of HTS power cable, the magnetic field of HTS power cable is mostly shielded by the induced current on the shield layer during normal operation. However, quench occurs at the shield layer and its current is kept below its critical current at the fault condition. Consequently, the magnetic field starts to spread out and it generates additional inductive impedance of the cable. The inductive impedance can be enhanced more by installing materials of high magnetic susceptibility around the HTS power cable. It is a concept of SFCL power cable. In this paper, a sample SFCL power cable is suggested and experimental results are presented to investigate the effect of iron cover on the impedance generation. The tests results are analyzed to verify the generation of the inductive and resistive impedance. The analysis results suggest the possible applications of the SFCL power cable to reduce the fault current in a real grid.

• 대한전기학회논문지:전력기술부문A
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• 제51권8호
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• pp.371-378
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• 2002

This paper presents the rapid and accurate algorithm for fault detection and location estimation in the transmission line. This algorithm uses wavelet transform for fault detection and harmonics elimination and utilizes least square error method for fault impedance estimation. Wavelet transform decomposes fault signals into high frequence component Dl and low frequence component A3. The former is used for fault phase detection and fault types classification and the latter is used for harmonics elimination. After fault detection, an adaptive data window technique using LSE estimates fault impedance. It can find a optimal data window length and estimate fault impedance rapidly, because it changes the length according to the fault disturbance. To prove the performance of the algorithm, the authors test relaying signals obtained from EMTP simulation. Test results show that the proposed algorithm estimates fault location within a half cycle after fault irrelevant to fault types and various fault conditions.

• 한국초전도ㆍ저온공학회논문지
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• 제22권1호
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• pp.7-11
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• 2020

As demand for electricity in urban areas increases, it is necessary to improve electric power stability by interconnecting neighboring substations and high temperature superconductor (HTS) power cables are considered as a promising option due to its large power capacity. However, the interconnection of substations reduces grid impedance and expected fault current is over 45 kA, which exceeds the capacity of a circuit breaker in Korean grid. To reduce the fault current below 45 kA, a HTS power cable having a fault current limiting (FCL) function is considered by as a feasible solution for the interconnection of substations. In this study, a FCL HTS power cable of 600 MVA/154 kV, transmission level class, is considered to reduce the fault current from 63 kA to less than 45 kA by generating an impedance over 1 Ωwhen the fault current is induced. For the thermal design of FCL HTS power cable, a parametric study is conducted to meet a required temperature limit and impedance by modifying the cable core from usual HTS power cables which are designed to bypass the fault current through cable former. The analysis results give a minimum cable length and an area of stainless steel former to suppress the temperature of cable below a design limit.

• 대한전기학회논문지:전력기술부문A
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• 제51권5호
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• pp.209-216
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• 2002

Recently, there is greater demand for stable supply of electric power as higher level of our living. It becomes the important problem that the cause of fault in power system is found out in early stage, if once it occurs. In this respect, accurate classification of arcing faults in power systems is vitally important. This paper presents a new classification method for arcing faults in power system. To obtain data of various faults including high impedance fault(HIF) and low impedance fault(LIF), HIF model with the ZnO arrester is adopted and implemented within the overall transmission system model based on the electromagnetic transients program(EMTP). Results of phase plane trajectory if Clarke modal transformation using postfault current and voltage are utilized to classify types of arcing faults. The performance of the proposed method is tested on a typical 154 kV korean transmission system under various fault conditions. As can be seen from results, phase plane trajectory of postfault current should be combined with that of o component from Clarke modal transformation to give reliability of clear fault classification. Thus the proposed method can classify arcing faults including LIFs and HIFs accurately in power systems.

• 대한전기학회논문지:전력기술부문A
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• 제49권10호
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• pp.473-478
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• 2000

A more reliable algorithm for detecting a high impedance fault (HIF) requires voltage and current at the relaying point containing information of HIF characteristics including buildup/shoulder as well as nonlinearity/asymmetry. This paper presents a modeling method of an HIF in a distribution system. In order to do this, the proposed method uses two series time-varying resistances (TVRs) controlled by Transient Analysis of Control Systems (TACS) in EMTP. One TVR is employed for nonlinearity/asymmetry and then the other TVR for buildup/shoulder. The proposed method is implemented in EMTP and thus the voltage and current at the relaying point can be obtained.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.465-467
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• 1995

High impedance fault can not be easily detected by conventional method. But if it would not be detected and cleared quickly, it can result in fires, and electric shock. In this paper, ANN, which has learning capability, is used for high impedance fault detection. The potential of the neural network approach is demonstrated by simulation using KEPCO's measured data. Among ANN models used in this paper, CPN shows better result than BPN in respect of convergence and reliability.

• 한국전자통신학회논문지
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• 제6권3호
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• pp.411-416
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• 2011

배전계통에서 고임피던스 고장(HIF : High Impedance Fault) 판단의 신뢰성을 높이기 위해서는 무엇보다도 HIF의 특징을 정확히 나타낼 수 있는 HIF 모델을 얻는 것이 중요하다. 따라서 본 연구에서는 아크모델을 기반으로 하는 수개의 HIF 모델들을 검토하여 그 특징들을 비교, 분석한다. 또한, 직접 적분법을 적용하여 HIF 특징을 가지는 아크모델을 구현하는 방법론을 연구한다.