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A simplified model of corona discharge on overhead wire has been proposed for propagating surge computations using the finite-difference time-domain method. The radial progression of corona streamers from the wire is represented as the radial expansion of cylindrical conducting region whose conductivity is several tens of microsiemens per meter. Two wire radii are considered: 5 and 2 mm, in order to simulate two experimental configurations by Noda. The critical electric field on the surface of a 5-mm radius wire for corona initiation is set to E_0 = 1.8 or 2.9 MV/m. For a 2-mm radius wire, it is set to E _0 = 2.2 MV/m. The critical background electric field necessary for streamer propagation is set to Ecp = 0.5 MV/m for positive voltage application, and Ecn = 1.5 MV/m for negative voltage application. The computed waveform of radial current (including both conduction and displacement currents) agrees well with the corresponding measured waveform. Also, the computed relation between the total charge (charge residing on the wire and emanated corona charge) and applied voltage ( qV curve) agrees well with the corresponding measured one, except for relatively low applied voltages. Additionally, the increase of coupling between the energized wire and another one nearby due to corona discharge is well reproduced. [ABSTRACT FROM PUBLISHER]

This paper presents calculations of lightning transient potential rises in grounding systems. A partial element equivalent circuit (PEEC) method, adopting a modified image method, is employed in this paper. The modified image method in this paper has two options either including or neglecting images of conduction currents along conductors for calculating series impedances. The effect of retardation in the PEEC method is also investigated. Comparisons of simulation results by the proposed method with those by the method of moments, the finite-difference time-domain method, and experimental results collected from the literature show that the PEEC method with the modified image method is quite effective in the evaluation of transient potential rise in a grounding system. [ABSTRACT FROM PUBLISHER]

The transient distribution of heat generated in a 16‐layer carbon fiber‐reinforced plastic (CFRP) panel, in which a lightning current with a magnitude of 3 kA, a rise time of 6.4 µs, and a time to half‐peak value of 69 µs is injected, has been computed. Each layer of the CFRP panel has a fiber axis direction of 45, 90, −45, or 0° and, therefore, has anisotropic electrical and thermal conductivities. This multilayer CFRP panel has been represented with a conductivity matrix consisting of off‐diagonal elements in the finite‐difference time domain (FDTD) simulation. The heat is computed, on the basis of FDTD‐computed conduction current densities, using a discretized heat equation. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Archorn voltages of a simulated 500-kV twin-circuit line, in the case of one-phase back-flashover due to lightning to a tower top, are analyzed by the thin-wire time-domain analysis (TWTDA) code. Prior to this analysis, a recently proposed fiashover model is incorporated into TWTDA. It becomes clear that the archorn voltages of the other two phases show a quite similar time-varying characteristic after one-phase back-flashover. An EMTP simulation is also carried out, The archorn voltages computed by the electromagnetic transients program (EMTP) agree well with those computed by TWTDA before the back-flashover on one phase. On the other hand, during about 1 μs after the one-phase back-flashover, the archorn voltages of the other two phases computed by EMTP deviate much from those computed by TWTDA. Particularly in the case of the middle- or the lower-phase back-flashover, the deviation is noticeable. The reason for this discrepancy is discussed. [ABSTRACT FROM AUTHOR]

This paper develops a shunt admittance formula of an overhead conductor above snow by adopting the Hertz vector. Based on the formula, the effect of snow on the wave propagation characteristics of the conductor is investigated. The admittance is increased by the snow. The difference from the case of no snow becomes smaller as the frequency becomes higher, because the permittivity of the snow reaches unity as the frequency increases. The effect of snow on the attenuation constant increases and that on the propagation velocity and characteristic impedance decreases, as the frequency increases. The difference from the no-snow case in the attenuation constant, the velocity, and the step response of wave deformation increases as the snow depth, the density, and the temperature increase. The characteristic impedance depends on the snow depth but not on the density and the temperature. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 26–33, 2001 [ABSTRACT FROM AUTHOR]

Discusses the use of a two-conductor model for lightning surge calculation. Role of lightning surge analysis in the insulation design of substations and transmission lines; Representation of a double-circuit line by a two-conductor circuit in the proposed method; Reduction of the computing time and memory requirement.

With the progress of cable manufacturing technology in recent years, pipe-type cables have become increasingly popular. A POP cable consists of three-phase coaxial cables placed in a steel pipe. It has good insulation withstand strength and induction shielding characteristics. However, the centers of the three cables and the pipe are arranged eccentrically and admittance and impedance characteristics are considerably complicated, making it difficult to analyze its propagation characteristics. This paper proposes a new fast and accurate digital computer program to calculate the propagation characteristics of POP cable.

Lithium plating can cause capacity fade and thermal runaway safety issues in lithium-ion batteries. Therefore, accurately detecting the amount of lithium plating on the surface of the battery's negative electrode is crucial for battery safety. This is especially crucial in high-energy-density applications such as battery energy storage systems or in electric vehicles (EVs). Early detection of lithium plating is crucial for evaluation of reliability and longevity. It also serves as a method for early diagnostics in practical industrial applications or infrastructure, such as EV transportation. This can enhance its impact on customers. This study validates the effectiveness of titration gas chromatography (TGC) technology in quantitatively detecting lithium plating on graphite negative electrodes in lithium-ion batteries. The results show that it can detect a minimum of 2.4 μmol of metallic lithium. Compared with the heating direct current resistance and reference electrode methods, which can be used to perform only qualitative dendrite detection, TGC has a wider range of detection. Compared with the nuclear magnetic resonance (NMR) method with higher quantitative detection accuracy, the maximum difference between the detection results of the two methods was only 7.2%, but the TGC method had lower cost and higher implementation convenience. In summary, among various dendrite detection methods, the TGC method can not only realize the effective quantitative detection of lithium plating, but also comprehensively consider its detection range, implementation convenience, cost, and detection accuracy, indicating that it is suitable for engineering applications and has the prospect of realizing large-scale quantitative detection of lithium plating in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

SUMMARY: The voltage variation in a remote system is large when the system is connected by long‐distance AC cables due to the cable capacitance. In Japan, the longest 54‐km 66‐kV AC submarine cable interconnection between the Kyushu mainland and Goto Islands was commissioned in 2005. It was requested to mitigate the voltage variation caused by switching off and on one circuit of the two circuits in the AC cables when a fault occurs. Since the conventional voltage control methods such as transformer tap changer or shunt capacitor and reactor banks are not sufficient because of their slow response time, a static var compensator (SVC) was installed on the Goto Islands. In such an application, an SVC control method should be developed so as not to override the existing voltage control systems. This paper describes the SVC control method developed for the Goto Islands AC interconnection project, which can be applied to similar situations. The effectiveness of the control method was verified by the results of effective value simulation and of field testing, which was implemented before the SVC was commissioned in 2007. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(3): 19–30, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com). DOI 10.1002/eej.22337 [ABSTRACT FROM AUTHOR]

The basic and qualitative characteristics of the proximity effect in comparison with the skin effect on multiconductors are investigated based on finite-difference time-domain simulations to find equivalent/approximate geometrical parameters by which a transient can be calculated by existing electromagnetic transients-type simulation tools. The proximity effect appears very different depending on the current directions on the conductors, and is cancelled out in the center conductor on a three-conductor system. A filament current assumption results in a quite different current distribution from that considering the conductor volume. Based on the investigation and the IEC formula, an approximate formula of the conductor impedance considering the proximity and skin effects is proposed. The validity of the proposed formula is confirmed by calculated results of the impedance compared with the IEC formula, and of an intersheath mode transient in comparison with a field test result. The formula makes it possible to calculate a transient with the proximity effect by the EMTP. [ABSTRACT FROM AUTHOR]

The electric field in and around a 2.6-m-long substation arrester, on which a 1 MV lightning impulse is imposed, has been analyzed using the finite-difference time-domain (FDTD) method. The arrester is represented as a combination of 10 mm × 10 mm × 10 mm cubic cells, each of which has a nonlinear resistivity (or conductivity) in each of the x-, y-, and z-directions, dependent on the electric field in each direction. This simple representation requires no iterative procedure, and is suitable and useful for the FDTD simulation of an overvoltage-imposed arrester. The transient electric field in and around the overvoltage-imposed arrester, and the spatial distributions of vertical and radial electric fields along the surface of the arrester are shown. The influence of a shield ring is also shown. [ABSTRACT FROM PUBLISHER]

An improved representation of a straight thin wire for a 3-D finite-difference time-domain simulation has been applied to the transient analysis of a straight thin wire in a lossy medium, and its validity has been shown. In this representation, a straight wire having a specified radius is simulated by a straight wire having the equivalent radius 0.199Δs, where Δs is the lateral side length of cubic cells employed, embedded in an artificial parallelepiped medium having modified conductivity (only if it is in a lossy medium), modified relative permittivity, and modified relative permeability. Also, the equivalent radius of a staircase-approximated oblique wire in air has been evaluated, and its thin-wire representation has been discussed. [ABSTRACT FROM AUTHOR]

In this paper, a simplified model of corona discharge for the finite-difference time-domain (FDTD) computations has been applied to analysis of transient voltages at the tower of a transmission line caused by direct lightning strikes to an upper phase conductor. In the simulations, three 40-m towers, separated by 300 m, with one overhead ground wire and three phase conductors are employed. Corona is assumed to occur only on the upper phase conductor struck by lightning. The progression of corona streamers from the conductor is represented as the radial expansion of cylindrical conducting region around the conductor. The reduction of transient-voltage peak due to corona is not very significant, so that the voltage at the nearest tower exceeds the insulation level of 66/77 kV power line considered in this paper. For a 10-kA peak current, the upper-phase-conductor voltage peaks are reduced by 26% and 21% for a positive stroke with 1-μs- and 3-μs-risetime currents, respectively, and those for negative-stroke case are reduced by 18% and 13%, respectively. For a 20-kA peak current, the corresponding upper-phase-voltage peaks are reduced by 32% and 25% for the positive-stroke case, and those for the negative-stroke case are reduced by 22% and 15%. [ABSTRACT FROM AUTHOR]

The wave propagation characteristics on an overhead conductor in a high-frequency band were investigated based on the Wise's earth-return admittance and modified Pollaczek's (accurate) earth-return impedance in a previous paper. In this paper, the characteristics are studied using the numerical electromagnetic code (NEC), which is based on the method of moments in the frequency domain. Results computed using NEC show quite similar characteristics to those described in the previous paper, i.e., a transition between transverse electromagnetic and transverse magnetic propagation called Sommerfeld–Goubau propagation. Thus, the mode transition has been confirmed. Also, observation indicates that Wise's admittance and an accurate impedance (transmission line approach) are applicable to investigating high-frequency wave propagation on an overhead horizontal conductor, as Kikuchi pointed out. [ABSTRACT FROM PUBLISHER]

The equivalent radius of a thin wire, which is represented by forcing the tangential electric field along the wire axis to zero in a three-dimensional finite-difference time-domain simulation, has been evaluated on the basis of a surge or characteristic impedance of a perfectly conducting horizontal wire above a perfectly conducting ground. It is 0.199Δs, where Δs is the lateral side length of cubic cells employed, and is smaller than the equivalent radii, 0.230Δs and 0.208Δs, estimated by Noda and Yokoyama (2002) and by Railton et al. (2006), respectively. Further, the thin wire representation of Railton et al. with this equivalent radius, which embeds a wire having the equivalent radius in an artificial parallelepiped medium having modified relative permittivity and permeability, has been proposed, and its validity has been tested for a horizontal wire and a vertical wire. [ABSTRACT FROM PUBLISHER]

In this paper, a procedure for computing transient electromagnetic fields with the constrained interpolation profile (CIP) method in the two-dimensional (2-D) cylindrical coordinate system has been derived. Then, it has been applied to analyzing electromagnetic pulses produced by a current wave propagating upward along a vertical lightning return-stroke channel. CIP-computed waveforms agree well with corresponding waveforms computed using analytical expression of Uman et al. or the finite-difference time-domain method. [ABSTRACT FROM AUTHOR]

Highlights: [•] Validity of Ala et al.’s soil-ionization model is tested against several electrodes. [•] Values of adjustable constants for this model are determined. [•] Progressions of soil ionization around grounding electrodes are visualized. [ABSTRACT FROM AUTHOR]

In this paper, a procedure for computing electromagnetic fields with the transmission-line-modeling (TLM) method in the two-dimensional (2-D) cylindrical coordinate system has been derived. Then, it has been applied to analyzing electromagnetic pulses produced by a current wave propagating upward along a vertical lightning return-stroke channel. TLM-computed waveforms agree well with corresponding waveforms computed using analytical expression of Uman et al.and the finite-difference time-domain method. [ABSTRACT FROM PUBLISHER]

In this paper, a simplified model of corona discharge for the finite-difference time-domain (FDTD) computations has been applied to analysis of lightning-induced voltages at different points along a 5-mm radius, 1-km long single overhead wire taking into account corona space charge around the wire. Both perfectly conducting and lossy ground cases were considered. FDTD computations were performed using a 3-D nonuniform grid. The progression of corona streamers from the wire is represented as the radial expansion of cylindrical weakly conducting (40 μS/m) region around the wire. The magnitudes of FDTD-computed lightning-induced voltages in the presence of corona discharge are larger than those computed without considering corona. The observed trend is in agreement with that reported by Nucci et al. and by Dragan et al ., although the increase predicted by our full-wave model (up to 5% and 9% for negative and positive lightning return strokes, respectively) is less significant than in their studies (up to a factor of 2) based on the distributed-circuit model with sources specified using the electromagnetic field theory. The disparity is likely to be related to the use of different charge-voltage diagrams, explicitly assumed by Nucci et al. and Dragan et al . and resulting from our FDTD model with corona in the present study. When corona is considered, there is a tendency for induced-voltage rise time to increase. It appears that the distributed impedance discontinuity, associated with the corona development on the wire, is the primary reason for higher induced-voltage peaks and longer voltage rise times, compared to the case without corona. [ABSTRACT FROM PUBLISHER]

We have shown that finite-difference time-domain (FDTD) electromagnetic computations for a conductor system having a radius smaller than 0.15Δr or larger than 0.65Δr (Δr is the lateral side length of cells employed), modeled using arbitrary-radius-wire representations proposed so far with a time increment determined from the upper limit of Courant's stability condition, result in numerical instability. A primary factor causing this numerical instability is that the speed of waves propagating in the radial direction from the wire in the immediate vicinity of the wire exceeds the speed of light, and therefore, Courant's condition is not satisfied there. It is further shown that for these cases, the arbitrary-radius-wire representation can be improved by modifying the material parameters for the axial field components closest to the wire as well as those for the radial electric and circulating magnetic field components. The improved wire representation is effective in representing a wire whose radius ranges from 0.0001Δr to 0.9Δr. [ABSTRACT FROM AUTHOR]

This paper has investigated the nonuniform characteristics of a counterpoise based on the frequency-dependence of R, L, C, and G and propagation parameters identified from measured results of transient voltages and currents on the counter- poise. It becomes clear that the characteristic impedance is significantly length-dependent (i.e non-uniform, at a high frequency). As the frequency tends to infinity, the maximum value of the characteristic impedance is almost the same irrespective of its geometry, physical constants and soil conditions. However, the characteristic impedance at a section near to source end is far smaller than that near to the remote end. The apparent series impedance increases and the admittance decreases for a counterpoise section farther to the source end. The propagation constant shows less noticeable nonuniformity than that for the characteristic impedance. [ABSTRACT FROM AUTHOR]

Transient responses of a horizontal grounding electrode in three different arrangements of a current lead wire and a voltage reference wire are calculated using the finite-difference time-domain (FDTD) method for solving Maxwell's equations. The test arrangement does not significantly influence the transient response of the horizontal grounding electrode. The transient response calculated using the electromagnetic transients program (EMTP) for Sunde's equivalent circuit agrees reasonably well with the corresponding response calculated using the FDTD method, except for the initial rising portion of the voltage at the close end (to the excitation point) of the horizontal grounding electrode. The EMTP-calculated response for an equivalent circuit, modified to improve this discrepancy, agrees better with the corresponding FDTD-calculated response. [ABSTRACT FROM AUTHOR]

This paper has derived an impedance formula for conductor's semiconducting layer based on a conventional circuit theory. The formula is confirmed to be identical to an accurate one derived by solving Maxwell's equation. A wave-propagation characteristic and a transient voltage on a cable having the semiconducting layer on the conductor's surface are evaluated by applying the derived formula, and are compared with those on a cable with no semiconducting layer. The semiconducting layer increases the conductor impedance, and thus, the attenuation constant is increased, and the propagation velocity and the characteristic impedance are decreased for a coaxial mode by the semiconducting layer, hut the inter-phase mode of propagation is not affected. A transient voltage is attenuated more and its oscillating period becomes greater than those on a cable with no semiconducting layer. The effect of the semiconducting layer impedance on the wave-propagation characteristic and the transient voltage is rather minor when the layer thickness is small and the resistivity is high, and the semiconducting layer effect is dominated by its admittance. [ABSTRACT FROM AUTHOR]

Many failures of wind turbine blades and electrical equipment due to powerful lightning strikes have occurred. The lightning-induced wind turbine failures that have occurred in recent years can be classified into two main categories. The first is a mechanical component failure. The second is a failure or malfunction of electric or electronic equipment inside or around the wind turbine due to an increase in the potential of the wind turbine grounding system or the electromagnetic induction caused by the lightning strike. In the latter case, the equipment often fails owing to the increase in the potential of the grounding system, the method of suppressing the potential rise by laying a grounding wire vertically or horizontally to the wind turbine foundation is adopted. We propose an empirical expression for the effective length of counterpoises connected to a large grounding electrode such as a wind turbine foundation, and verify the expression using finite-difference time-domain (FDTD) method. [ABSTRACT FROM AUTHOR]

An estimation method of equivalent circuit parameters for rechargeable batteries that follows Artificial Neural Network (ANN) logic is proposed in this paper. The capability of the nonlinear analysis of the ANN is suitable for estimating the parameters that are nonlinearly involved in the complex circuit equation. The parameters have to be obtained from the complex internal impedances, which are measured in a wide frequency range. The accuracy is improved by dividing this wide range into a low-frequency and a high-frequency region. These regions are strongly related to the capacity fade and the maximum chargeable/dischargeable current, respectively. The improved method will determine the optimal frequency region for three different rechargeable batteries, which are composed of Li-Ion, Pb and Ni-MH. The accuracy of the proposed method is confirmed by a comparison with the measured results obtained using a conventional frequency domain method. For obtaining the real-time diagnostics of the battery, an improved dual ANN system, which employs unequal sampling, is proposed to obtain the circuit parameters. The deterioration of a battery can be detected from the estimated parameters, which can help in further investigations that aim to develop diagnostic models for the embedded circuit in industrial applications. [ABSTRACT FROM AUTHOR]

For finite‐difference time‐domain (FDTD) simulations, Ala et al. (2008) proposed a simplified engineering soil ionization model on the basis of the dynamic soil‐resistivity model of Liew and Darveniza (1974), and tested its validity against experiments on a 0.61‐m single vertical grounding conductor. In the model, the resistivity of each soil‐representing cell is controlled by the instantaneous value of the electric field there and time. In this article, to test the validity of this model, it was applied to FDTD simulations of the surge responses of different grounding electrodes: an 8.1‐m single horizontal grounding cylindrical electrode buried at a depth of 1 m in a homogeneous soil, and a 1.5‐m single vertical grounding cylindrical electrode in a homogeneous soil. The FDTD‐computed responses agree reasonably well with the corresponding ones measured by Sekioka et al. (1998) and Asaoka et al. (2005). Also, influences of ground‐surface soil ionization, direction‐dependent or direction‐independent resistivity, and three parameters (ionization constant, deionization constant, and critical electric field) of the model were investigated. Surface ionization has a non‐negligible influence only on a short grounding electrode buried in a relatively high‐resistivity soil. Direction‐dependent resistivity yields a little higher voltage and an acute ionization zone near the tip of electrode. Both ionization constant and critical electric field have significant effects: the voltage generated decreases with decreasing ionization constant and/or critical electric field. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

A model of a vertical conductor for a circuit analysis is proposed based on calculation results by the Finite-Difference Time-Domain (FDTD) method. The model expresses a frequency-dependent effect of a vertical conductor. In addition, differences in its propagation characteristics of the upward and downward traveling waves are taken into consideration. An experiment is carried out using a reduced-size wind turbine tower model. The simulation results by Electromagnetic Transients Program (EMTP) accurately reproduce the experimental results. [ABSTRACT FROM AUTHOR]

Surge propagation on nonuniform conductors has been investigated on the basis of finite-difference time-domain (FDTD) simulations. It has been confirmed that an inclined conductor above the earth is represented following the image theory based on transverse electromagnetic (TEM) wave propagation by two angled (nonparallel) conductors in a free space. Nonparallel conductor systems above the earth show a wave propagation characteristic quite different from that of the TEM mode, and thus steady-state and transient phenomena on the nonparallel conductors cannot be appropriately analyzed by a circuit theory and by simulation tools such as the EMTP based on the circuit theory. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Carson's, Pollaczek's, Wise's, and Sunde's earth-return impedances of an overhead line have been examined, and errors involved in the formulas are explained. Modified Pollaczek's and Carson's/Sunde's formulas are described. Wave propagation characteristics on a multiconductor in a high-frequency region are evaluated by adopting the modified earth-return impedance and Wise's earth-return admittance. Sommerfeld–Goubau propagation in a high-frequency region, which shows transition between transverse electromagnetic and transverse magnetic propagation, has been confirmed in the calculated results which agree with those predicted by Kikuchi for a single conductor. On a multiconductor system, it is found that the aerial mode also shows Sommerfeld–Goubau propagation when the separation between conductors is large and the earth resistivity is high. [ABSTRACT FROM AUTHOR]

In this paper, a numerical procedure for computing electric and magnetic fields in a three-dimensional space using the constrained interpolation profile (CIP) method is presented. Then, this method is applied to computing electric and magnetic fields, which are generated by a current wave propagating upward along a vertical lightning return-stroke channel. The lightning return-stroke channel is modeled by a phased-current-source array. The spatial and temporal distribution of the lightning return-stroke channel or phase-current-source array is represented by a new simple mathematical function of height, time and channel-base current. [ABSTRACT FROM AUTHOR]

In this paper, we have applied the transmission-line modeling (TLM) method to analyzing transient responses of grounding electrodes and lightning-induced voltages on an overhead wire. In either analysis, a lossy ground was considered. TLM-computed responses agree reasonably well with the corresponding measured and finite-difference-time-domain-computed responses. This fact shows that the TLM method is effective and useful in analyzing lightning electromagnetic pulses and lightning-associated transient phenomena. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the application of the partial element equivalent circuit (PEEC) method in the time and frequency domains for calculating tower surge responses and insulator voltages of an actual transmission tower, and transient performance of grounding systems. Neglecting of electromagnetic retardation effect in the PEEC method in the time domain is proposed to increase efficiency of the method. Incorporation of nonlinear elements such as a flashover model and a soil ionization model with the PEEC method in the time domain is presented. Moreover, an effective way to increase the efficiency of the method in terms of computation time, which consists of the appropriate combination of the PEEC method and the transmission line theory, is proposed. The transmission line model is adapted to combine with the method for reducing elements in the PEEC method. Comparisons of the simulation results by the proposed methods in the time and frequency domains with other numerical methods and with available experimental data show satisfactory agreement. [Copyright &y& Elsevier]

This paper investigates numerical instability issues in the mutual impedance formula between an overhead conductor and a buried conductor proposed by Pollaczek with special reference to the integrand of Pollaczek's infinite integral. The integrand shows a negative real part and positive imaginary part at a high frequency, which result in negative resistance and inductance. The reason for this is the assumption of TEM-mode propagation in Pollaczek's formula as is well known. The fact suggests that numerical instability of the infinite integral is caused by incorrect integrand in a high-frequency region. Based on the observations, the applicable limit of Pollacezk's formula is analytically derived. Finally, a simple closed-form formula is developed, which approximates Pollaczek's formula with satisfactory accuracy. [ABSTRACT FROM AUTHOR]