• 전기학회논문지
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• 제62권8호
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• pp.1163-1168
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• 2013

The maximum allowable value of loop impedance($Z_s$) to secure the operation of overcurrent protective devices and the safety for indirect contact is a very important in TN-C-S system. The loop impedance is divided into inner loop impedance which consumer can adjust and external loop impedance($Z_e$) which only electric operator can adjust. Thus, an external loop impedance which limits to less than a certain value is a very important factor for human body protection against electric shock in TN-C-S system. The concept of loop impedance($Z_s$) is recently introduced to the domestic, the study about external loop impedance is yet insufficient. However, the study about the reference impedance as specified by the IEC 60725 standard to improve the quality and reliability of the power supply is being made. In this paper, reference value of external loop impedance($Z_e$) to meet domestic environment will be proposed by the nationwide measurement and statistical analysis.

• 한국안전학회지
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• 제29권5호
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• pp.116-122
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• 2014

Assessment of setting process of concrete is important as it provides useful information to schedule concreting work in construction site. Electrical impedance measurement method, which utilizes the change of electrical resistance of concrete, has been applied to assess setting process of cement-based materials. However, the applicability of the method has been demonstrated only for cement paste and mortar. The main purpose of this research is to develop the electrical impedance based setting process assessment for concrete. To this end, electrical impedance response model for concrete should be developed in advance since it is essential to estimate the electrical resistance of concrete from measured impedance response. The electrical resistance of concrete is a key parameter for the setting process assessment. In this study electrical impedance responses of the concrete in setting process are measured and analyzed. Thereby, an electrical impedance response model of the liquid state concrete is developed and schematically validated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.2174_2175
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• 2009

This Paper present about loop impedance characteristic based on korea internal electrical environment. Analysis parameters were touch voltage, electrical shock current and human body resistance. Result, For protect of electrical shock must measuring of loop impedance. And current capacity & loop impedance are must important parameters.

• Smart Structures and Systems
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• 제22권1호
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• pp.1-11
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• 2018

This study presents early crack detection of steel fiber-reinforced concrete (SFRC) under varying temperature and humidity conditions using an instantaneous electrical impedance acquisition system. SFRC has the self-sensing capability of electrical impedance without sensor installation thanks to the conductivity of embedded steel fibers, making it possible to effectively monitor cracks initiated in SFRC. However, the electrical impedance is often sensitively changed by environmental effects such as temperature and humidity variations. Thus, the extraction of only crack-induced feature from the measured impedance responses is a crucial issue for the purpose of structural health monitoring. In this study, the instantaneous electrical impedance acquisition system incorporated with SFRC is developed. Then, temperature, humidity and crack initiation effects on the impedance responses are experimentally investigated. Based on the impedance signal pattern observation, it is turned out that the temperature effect is more predominant than the crack initiation and humidity effects. Various crack steps are generated through bending tests, and the corresponding impedance damage indices are extracted by compensating the dominant temperature effect. The test results reveal that propagated cracks as well as early cracks are successfully detected under temperature and humidity variations.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.167-173
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• 2011

This paper presents a method for the development of the impedance locus to test the dynamic characteristics of protective relays. Specifically, using the proposed method, the impedance locus can comprise three impedance points, and the speed of impedance trajectory can be adjusted by frequency deviation. This paper is divided into two main sections. The first section deals with the configuration of impedance locus with voltage magnitude, total impedance magnitude, and impedance angle. The second section discusses the control of the locus speed with the means of the deviation between two frequencies. The proposed method is applied to two machine equivalent systems with offline simulation (i.e., PSCAD) and real-time simulation (i.e., real-time simulation environment) to demonstrate its effectiveness.

• 한국전기전자재료학회논문지
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• 제25권5호
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• pp.372-376
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• 2012

This study focused on the performance characteristics of solar cell using the impedance technique. We measured an impedance according to frequency from 1 Hz until 1 MHz. It could know that the impedance was decreased according to the frequency increases in solar cell. The impedance of single crystal solar cell was 0.61 ${\Omega}$ at 1 Hz, and kept almost settled value to $1{\times}10^2$ Hz. However, the impedance of polycrystal solar cell was $7{\times}10^3{\Omega}$ at 1 Hz.

• 전기학회논문지
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• 제56권6호
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• pp.1087-1091
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• 2007

Exact impedance modeling of the electrode/electrolyte interface is important in bio-signal sensing electrode development. Therefore, the investigation of the equivalent circuit models for the interface has been pursued for a long time by several researchers. Previous circuit models fit the experimental results in limited conditions such as frequency range, type of electrode, or electrolyte. This paper describes a new electrical circuit model and its capability of fitting the experimental results. The proposed model consists of three resistors and two constant phase elements. Electrochemical impedance spectroscopy was used to characterize the interface for Au, Pt, and stainless steel electrode in 0.9% NaCl solution. Both the proposed model and the previous model were applied to fit the measured impedance results for comparison. The proposed model fits the experimental data more accurately than other models especially at the low frequency range, and it enables us to predict the impedance at very low frequency range, including DC, using the proposed model.

• 전기학회논문지
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• 제62권5호
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• pp.612-619
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• 2013

This paper proposes an early diagnosis technique for the stator-turn fault (STF) in an interior permanent magnet (IPM)-type brushless DC (BLDC) motor using the impedance parameter. We have analyzed the varying characteristics owing to the STF through various experiments and the finite element method (FEM). As a result, we have presented a simple method for fault detection. This technique can be applied without requiring a fast Fourier transform (FFT) and the calculation of the negative-sequence impedance. The fault detection system works on the basis of the comparison the measured impedance with the database impedance. The variations in the characteristics owing to the STF as well as the proposed technique have been verified through the simulation and experiment.

• Journal of Power Electronics
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• 제16권3호
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• pp.1163-1175
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• 2016

In recent years, microgrids have been the focus of considerable attention in distributed energy distribution. Microgrids contain a large number of power electronic devices that can potentially cause negative impedance instability. Harmonic impedance is an important tool to analyze stability and power quality of microgrids. Harmonic impedance can also be used in harmonic source localization. Precise measurement of microgrid impedance and analysis of system stability with impedances are essential to increase stability. In this study, we introduce a new square wave current injection method for impedance measurement and stability analysis. First, three stability criteria based on impedance parameters are presented. Then, we present a new impedance measurement method for microgrids based on square wave current injection. By injecting an unbalanced line-to-line current between two lines of the AC system, the method determines all impedance information in the traditional synchronous reference frame d-q model. Finally, the microgrid impedances of each part and the overall microgrid are calculated to verify the measurement results. In the experiments, a simulation model of a three-phase AC microgrid is developed using PSCAD, and the AC system harmonic impedance measuring device is developed.

• 대한토목학회논문집
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• 제40권2호
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• pp.183-189
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• 2020

이 논문은 인장 응력, 주변 온도 및 인가 주파수에 대한 강선의 전기적 임피던스 민감도에 관한 실험적 조사이다. 다양한 응력 수준 및 온도에 대해서, 강선의 전기적 임피던스가 자가진단 시스템에서 측정되었다. 세 가지 경우의 실험이 다양한 온도 조건, 응력 수준 및 적용 주파수에 대해서 수행되었다. 주어진 주파수에서 온도가 상승하고 응력이 감소하면 강선의 전기 임피던스가 증가한다. 실험 결과는 전기적 임피던스와 온도 사이의 상관관계가 모든 응력 수준에서 선형 관계임을 보여준다. 온도에 대한 임피던스의 감도는 응력보다 훨씬 높다는 점이 주목 된다.