• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.8
• /
• pp.426-432
• /
• 2004

This paper presents a systematic approach of measurement, modeling and analysis of grounding system impedance in the field of lightning protection system and intelligent power equipments. The measurement and analysis system of ground impedance is based on a computer aided technique. The magnitude and phase of ground impedance were determined by the novel measurement and analysis using the revised fall-of-potential method. The ground impedances of the ground rod of 50 m long are considerably dependent on the frequency. The ground impedance is mainly resistive in the frequency range of 3-20 kHz. At higher frequencies, the reactive components of the ground impedances are no longer negligible and the inductance of the ground rod was found to be the core factor deciding the ground impedance. Although the steady-state ground resistance of the ground rod of 50 m was less than that of the ground rod of 10 m, the ground impedances of the ground rod of 50 m over the frequency range of more than 60 kHz were much greater than those of the ground rod of 10 m. Furthermore, the equivalent circuit model based on the measured data was proposed. and the calculated results were in approximately agreement with the measured data.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.11
• /
• pp.717-723
• /
• 1999

The transient characteristics of grounding systems play a major role in the protection of power equipments, electronic circuits and info-communication facilities against surges which arise from lightning or ground faults. Electronic devices are very weak against lightning surges injected from grounding systems and can be damaged. The malfunction and damage of electronic circuits bring about bad operation performances, a lot of economical losses, and etc. Therefore, in order to obtain the effective protection measure of electronic devices from overvoltages and lightning surges, the analysis of the transient grounding impedances in essential. One of this work is to examine the transient behaviors of grounding impedances under steplike currents for various grounding systems. And the other of this work is to evaluate the transient behaviors of a grid with rods under impulse currents and to investigate the effect of grounding lead wire. Transient grounding impedances of a grid with rods under impulse current waves have been measured as a parameter of the length of the grounding leads. Z-t, Z-i and V-i curves of transient grounding impedance under impulse current waveforms have been measured and analyzed. It was found that the grounding impedance gives the inductive, resistive and capacitive aspects under steplike current. Transient grounding impedance characteristics were very different with shapes, geometries of ground electrodes. Also, they were dependent on the waveform and magnitude of impulse current.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.247-247
• /
• 2000

A new bioelectric impedance measurement method is proposed for the precise measurement of the bioelectric impedance. To obtain the impedance from the known applied a.c. current and the measured voltage signals, a frequency conversion circuit, like the mixer in heterodyne receivers, is introduced to reduce the frequency of the original current. It can be observed from several lines of derivation that the impedance is independent on the amplitude and phase of the mixing signals. This makes it possible to use low-speed analog-to-digital converters and thus utilize cheaper electronic parts in the implementation. The possibility of the method is shown by simulations, and a generic structure applicable to bioelectric impedance measurement devices is also proposed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.1
• /
• pp.56-62
• /
• 2010

This paper describes the analysis of loop impedance characteristics by impedance alteration of protective conductors and operating characteristics of electric leakage circuit breaker by each earth systems(TT system, TN-S system and TN-C system) in IEC 60364. As a result, loop Impedance was affected by resistance & inductance. The current& voltage characteristics about earth system were identified that the TN-S system was high fault current & low touch voltage. TN-C system was almost same the TN-S system but TT system was low fault current & high touch voltage.

• Journal of the Korean Applied Science and Technology
• /
• v.25 no.1
• /
• pp.52-57
• /
• 2008

In the present study, impedance characteristics for AgO-Zn cell at various State-of-Charge (SoC) has been studied. The impedance measurements of AgO-Zn cell at various SoC were made over the frequency range from 100kHz to 10mHz with an amplitude 5mV. The impedance parameters have been evaluated by the analysis of the data using an equivalent circuit and a Non-linear least squares (NLLS) fitting method. The total resistances reflects the SoC of the cell. This indicates that the total resistance is important parameter for predicting SoC of AgO-Zn cell.

• Corrosion Science and Technology
• /
• v.15 no.6
• /
• pp.259-264
• /
• 2016

With a specially designed electrochemical cell, the changes in impedance behavior for Inconel 600 and aluminide diffusion coatings under molten sulfate film with thermal cycles (from $800^{\circ}C$ to $350^{\circ}C$) were monitored with electrochemical impedance measurements. It was found that corrosion resistance for both materials increased with lower temperatures. At the same time, the state of molten salt was also monitored successfully by measuring the changes in impedance at high frequency, which generally represents the resistance of molten salt itself. After two thermal cycles, both Inconel 600 and aluminide diffusion coatings showed excellent corrosion resistance. The results from SEM observation and EDS analysis correlated well with the results obtained by electrochemical impedance measurements. It is concluded that electrochemical impedance is very useful for monitoring the corrosion resistance of materials under molten salt film conditions even with thermal cycles.

• Corrosion Science and Technology
• /
• v.4 no.6
• /
• pp.217-221
• /
• 2005

In the present investigation, holographic interferometry was utilized for the first time to monitor in situ the thickness of the oxide film of aluminium samples during anodization processes in boric acid solutions. The anodization process (oxidation) of the aluminium samples was carried out by the technique of the electrochemical impedance spectroscopy(EIS), in different concentrations of boric acid (0.5-5.0% $H_3BO_3$) at room temperature. In the mean time, the real-time holographic interferometry was used to measure the thickness of anodized (oxide) film of the aluminium samples in solutions. Consequently, holographic interferometry is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film of the aluminium samples can be determined without any physical contact. In addition, measurements of electrochemical values such as the alternating current (A.C) impedance(Z), the double layer capacitance($C_{dl}$), and the polarization resistance(Rp) of anodized films of aluminium samples in boric acid solutions were made by the electrochemical impedance spectroscopy(EIS). Attempts to measure electrochemical values of Z, Cdl, and Rp were not possible by holographic interferometry in boric acid especially in low concentrations of the acid. This is because of the high rate of evolutions of interferometric fringes during the anodization process of the aluminium samples in boric acid, which made measurements of Z, Cdl, and Rp are difficult.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.612-613
• /
• 2007

The line impedance is important data that are applied in all analysis fields of electric power system such as power flow, fault current, stability and relay calculation etc. Usually, the impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, the impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and earth resistances. Therefore, if there is a fault in cable system, these terms will severely be caused many errors for calculating impedance. In this paper, the line impedance is measured in a power system of underground cables, and is analyzed by a generalized circuit analysis program, EMTP(Electromagnetic Transient Program), for comparison with the measured value. These analysis results are considered to become foundation of impedance calculation for underground cables.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.1
• /
• pp.30-35
• /
• 2000

The pulsed plasma wire-plate reactor was analyzed on the basis of experiment, EMTP simulation and modelling method. Though the reactor has a non-linear impedance characteristics, we demonstrate that the reactor impedance can be approximately analyzed with the measured initial capacitance and average resistive component of flat zone. Using this modelling method, the influence of the reactor capacitance on the impedance matching between pulse generator and reactor can be investigated. From this, we found that the energy of 95% was delivered form pulse generator to reactor at the ratio of $C_r/C_p\cong 0.3,\; where\; C_p\; is\; pulse\; generator\; capacitance, C_r$ is reactor capacitance.

• Journal of the Korean Chemical Society
• /
• v.30 no.3
• /
• pp.273-281
• /
• 1986

This study is focused on the correct measurement of the equations for the determination of the impedance parameters-the differential capacity of the double layer $C_d$, solution resistance $R_Q$, transfer resitance $R_i$, and adsorption pseudcapacity $C_{\phi}$/ The application of only an imaginary part of complex function of ${\omega}$ at the sinusoidal steady state indicates the following equations of total impedance: at low frequency $|Z_{LF}|=1/{\omega}_1\;C_{\phi}\;{\sqrt{1+{{\omega}_1}^2/{\omega}^2}$, at high frequency $|Z_{HF}|={\omega}_2/({\omega}_1{\omega}_3C{\phi})({\omega}^2+{{\omega}_2}^2)\;{\sqrt{{({\omega}^2+{\omega}_2{\omega}_3)}^2+{({\omega}_2{\omega}-{\omega_3{\omega})^2}}$. The values of the total impedance of cell, phase angle, and cell current that are necessary for the calculations of impedance parameters were experimentally measured from 200 to 6000Hz for the following supporting electrolytes, 0.5M $Na_2SO_4$, 1M NaCl, 19.373% sea water, 1M HCl, 1M $KNO_3$ and for $10^{-2}M$ KI and 60mM DBNA (Di-iso-Butylnitrosoamine) in these supporting electrolytes. The derived equations in this study shows that the values of impedance parameters of $C_d,\;C_{\phi},\;R_i\;and\;R_Q\;are\;15{\sim}40\;{\mu}F/cm^2,\;162{\sim}758\;{\mu}F/cm^2\;11.5{\sim}57.6\;ohm{\cdot}cm^2\;and\;0.5{\times}10^{-2}{\sim}4.1{\times}10^{-2}\;ohm{\cdot}cm^2$ respectively.