The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightn... more The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightning surges is very important for the rational design of those circuits in substation. In this paper, experiences of surge phenomena on low-voltage control circuit are presented. Then, some examples are shown to explain mechanism of induced voltages into low voltage control circuit and modeling of grounding mesh and low-voltage control circuit.
The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightn... more The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightning surges is very important for the rational design of those circuits in substation. In this paper, experiences of surge phenomena on low-voltage control circuit are presented. Then, some examples are shown to explain mechanism of induced voltages into low voltage control circuit and modeling
In this letter, we have demonstrated a simple method to evaluate the resistivity and relative per... more In this letter, we have demonstrated a simple method to evaluate the resistivity and relative permittivity of a lossy medium. The method comprises two parts: the first one is to measure the frequency characteristic of impedance between two parallel electrodes having a lossy medium inside, and the second one is to calculate the resistivity and relative permittivity of the medium, in terms of the resistance and capacitance between the electrodes, from the measured frequency characteristic of impedance.
The Electro Magnetic Transients Program (EMTP) is originated from the Ph. D. thesis of H. W. Domm... more The Electro Magnetic Transients Program (EMTP) is originated from the Ph. D. thesis of H. W. Dommel supervised by Prof. Prinz in 1962 at the Technical University of Munick. This article describes why and how the EMTP was developed in the Bonneville Power Administration, US Department of Interia (Department of Energy since 1978). Also some stories behind the EMTP in the early stage of its development are described, as the author being involved in a transient simulation since 1965 and being one of original EMTP developers.
Two estimation methods for a backward impedance of a power distribution system are proposed in th... more Two estimation methods for a backward impedance of a power distribution system are proposed in this paper. A frequency response of a transient current flowing into a capacitor, which connected to a distribution line, has information of the backward impedance. The impedance is obtained from an attenuation constant and a resonance frequency determined by the capacitance and the impedance of power distribution system. These parameters are stably obtained from a frequency response of the transient current using a least square method. The accuracy of the method heavily depends on the origin on the time-axis for Fourier transform. Additional time-origin estimation is required for an accurate estimation of the backward impedance. The second method estimates the backward impedance using two transient current waveforms obtained by connecting alternately different capacitors to a distribution line. The backward impedance can be represented as a function of the frequency responses of these current. This method is suitable for an automatic measurement of the backward impedance because the method is independent from the time-origin. The proposed methods are applicable to an estimation of a harmonic current of the distribution system. In this paper, a harmonic current flowing through a distribution wire is estimated from the estimated backward impedance and the measured results of harmonic voltages obtained by an instrument developed by the authors.
Ecti Con2010 the 2010 Ecti International Confernce on Electrical Engineering Electronics Computer Telecommunications and Information Technology, 2010
ABSTRACT This paper presents the application of a partial element equivalent circuit (PEEC) metho... more ABSTRACT This paper presents the application of a partial element equivalent circuit (PEEC) method neglecting retardation in the time domain for calculating tower surge responses and insulator voltages of an actual transmission tower, and transient performance of grounding electrodes. A comparison of the simulation results by the PEEC method in the time domain with simulation results calculated by a full-wave PEEC method in the frequency domain and experimental data shows satisfactory agreement not only for amplitudes but also for waveshapes.
Impedance of cylindrical specimens of a soil having three different lengths is measured at freque... more Impedance of cylindrical specimens of a soil having three different lengths is measured at frequencies ranging from 40Hz to 40MHz using two parallel electrodes in order to estimate and remove the effect of the contact impedance. Both conductivity and relative permittivity of the tested soil increase with increasing the moisture ratio. The conductivity of the soil having a moisture ratio of 5% is almost constant (about 3mS/m) at frequencies lower than 10MHz, and increases with increasing frequency beyond 10MHz. The relative permittivity of the same soil decreases with increasing frequency up to 10MHz, at which it is 7.
IEEE Transactions on Power Apparatus and Systems, 1980
Wave propagation characteristics of a single-core coaxial cable and a pipe enclosed cable are pre... more Wave propagation characteristics of a single-core coaxial cable and a pipe enclosed cable are presented in this paper. For any underground cables, there exists a propagation mode of which the attenuation is very large and the velocity is very low. In the pipe enclosed cable case, propagati on modes within the pipe are almost the same whether the pipe thickness
The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightn... more The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightning surges is very important for the rational design of those circuits in substation. In this paper, experiences of surge phenomena on low-voltage control circuit are presented. Then, some examples are shown to explain mechanism of induced voltages into low voltage control circuit and modeling of grounding mesh and low-voltage control circuit.
The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightn... more The study of surge voltage levels induced in low- voltage control or monitoring circuit by lightning surges is very important for the rational design of those circuits in substation. In this paper, experiences of surge phenomena on low-voltage control circuit are presented. Then, some examples are shown to explain mechanism of induced voltages into low voltage control circuit and modeling
In this letter, we have demonstrated a simple method to evaluate the resistivity and relative per... more In this letter, we have demonstrated a simple method to evaluate the resistivity and relative permittivity of a lossy medium. The method comprises two parts: the first one is to measure the frequency characteristic of impedance between two parallel electrodes having a lossy medium inside, and the second one is to calculate the resistivity and relative permittivity of the medium, in terms of the resistance and capacitance between the electrodes, from the measured frequency characteristic of impedance.
The Electro Magnetic Transients Program (EMTP) is originated from the Ph. D. thesis of H. W. Domm... more The Electro Magnetic Transients Program (EMTP) is originated from the Ph. D. thesis of H. W. Dommel supervised by Prof. Prinz in 1962 at the Technical University of Munick. This article describes why and how the EMTP was developed in the Bonneville Power Administration, US Department of Interia (Department of Energy since 1978). Also some stories behind the EMTP in the early stage of its development are described, as the author being involved in a transient simulation since 1965 and being one of original EMTP developers.
Two estimation methods for a backward impedance of a power distribution system are proposed in th... more Two estimation methods for a backward impedance of a power distribution system are proposed in this paper. A frequency response of a transient current flowing into a capacitor, which connected to a distribution line, has information of the backward impedance. The impedance is obtained from an attenuation constant and a resonance frequency determined by the capacitance and the impedance of power distribution system. These parameters are stably obtained from a frequency response of the transient current using a least square method. The accuracy of the method heavily depends on the origin on the time-axis for Fourier transform. Additional time-origin estimation is required for an accurate estimation of the backward impedance. The second method estimates the backward impedance using two transient current waveforms obtained by connecting alternately different capacitors to a distribution line. The backward impedance can be represented as a function of the frequency responses of these current. This method is suitable for an automatic measurement of the backward impedance because the method is independent from the time-origin. The proposed methods are applicable to an estimation of a harmonic current of the distribution system. In this paper, a harmonic current flowing through a distribution wire is estimated from the estimated backward impedance and the measured results of harmonic voltages obtained by an instrument developed by the authors.
Ecti Con2010 the 2010 Ecti International Confernce on Electrical Engineering Electronics Computer Telecommunications and Information Technology, 2010
ABSTRACT This paper presents the application of a partial element equivalent circuit (PEEC) metho... more ABSTRACT This paper presents the application of a partial element equivalent circuit (PEEC) method neglecting retardation in the time domain for calculating tower surge responses and insulator voltages of an actual transmission tower, and transient performance of grounding electrodes. A comparison of the simulation results by the PEEC method in the time domain with simulation results calculated by a full-wave PEEC method in the frequency domain and experimental data shows satisfactory agreement not only for amplitudes but also for waveshapes.
Impedance of cylindrical specimens of a soil having three different lengths is measured at freque... more Impedance of cylindrical specimens of a soil having three different lengths is measured at frequencies ranging from 40Hz to 40MHz using two parallel electrodes in order to estimate and remove the effect of the contact impedance. Both conductivity and relative permittivity of the tested soil increase with increasing the moisture ratio. The conductivity of the soil having a moisture ratio of 5% is almost constant (about 3mS/m) at frequencies lower than 10MHz, and increases with increasing frequency beyond 10MHz. The relative permittivity of the same soil decreases with increasing frequency up to 10MHz, at which it is 7.
IEEE Transactions on Power Apparatus and Systems, 1980
Wave propagation characteristics of a single-core coaxial cable and a pipe enclosed cable are pre... more Wave propagation characteristics of a single-core coaxial cable and a pipe enclosed cable are presented in this paper. For any underground cables, there exists a propagation mode of which the attenuation is very large and the velocity is very low. In the pipe enclosed cable case, propagati on modes within the pipe are almost the same whether the pipe thickness
Uploads
Papers by Akihiro Ametani