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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]

A model expressing beams, pillars, and electrical wiring in a building for lightning surge simulation by circuit analysis method is proposed in this paper. The proposed model expresses the self‐surge impedance of the electrical wiring as a function of the distance between conductors and the radius of the electrical wiring. The mutual impedance is expressed by the distance between the surfaces of a structure and a nearby wire instead of the distance between the conductor centers. In the case of two conductors having far different radii in proximity, the distribution of electromagnetic fields around the two conductors is similar in horizontal and vertical arrangements. Thus, the electrical wiring nearby pillars can be treated as a horizontal conductor. The circuit analysis results show that the voltage difference generated between the structure and the electrical wiring is calculated more precisely by the proposed model than by the conventional model. [ABSTRACT FROM AUTHOR]

When lightning strikes an apartment building, transient voltages are generated or induced in electrical and telecommunication wires in the building. The transient voltages may cause malfunctions or failures of electronic or telecommunication appliances. Therefore, it is necessary to know the spatial distribution of voltage, generated by typical lightning, in the building. Although there are several works studying lightning‐generated voltages in buildings, they do not consider the presence of concrete that accommodates steel structures. In this paper, lightning‐induced voltages between wires in a simplified apartment building struck by lightning are computed using the finite‐difference time‐domain (FDTD) method, taking into account the presence of reinforced concrete. On the basis of the computed results, the effect of the presence of concrete is discussed. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

We have shown that finite-difference time-domain (FDTD) electromagnetic computations for a conductor system having a radius smaller than 0.15[DELTA]r or larger than 0.65[DELTA]r ([DELTA]r 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 0.0001[DELTA]r to 0.9[DELTA]r. Index Terms--Electromagnetic fields, finite-difference time-do-main (FDTD) methods, transient analysis, wire.

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 counterpoise. 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. Index Terms--Admittance, distributed-line, grounding electrode, impedance, nonuniform line, numerical identification.

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. Index Terms--Electromagnetic transient analysis, equivalent circuits, finite difference methods, grounding electrodes.

An equivalent radius of a thin wire in a lossy medium, represented by the finite-difference time-domain method, is derived using the concept that was proposed to derive an equivalent radius of a thin wire in air. Then, a simple technique to specify an arbitrary radius of a thin wire in a lossy medium is proposed. The proposed technique does not employ locally fine or nonuniform subgrids, but is based on an orthogonal and uniform-spacing Cartesian grid. The validity of the proposed technique is investigated in a transient state, as well as in a quasisteady state, and shown to be satisfactory. Index Terms--Finite-difference time-domain (FDTD), grounding electrode, grounding resistance, thin wire.

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, but 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. Index Terms--Cable, impedance, semiconducting layer, transient, wave propagation.

This paper has proposed an impedance formula of pipe enclosed and tunnel-installed cables of which the thickness of the pipe and tunnel wall is finite. Thus, it is composed of a two-layered conductor (i.e., the first medium is the finite thickness pipe or the finite thickness tunnel wall, and the second medium is the outer conductor to infinite). The impedance by the formula developed in the paper shows a quite different characteristic from that calculated by an existing impedance formula which was derived from the assumption of an infinitely thick pipe. Wave propagation and transient voltage characteristics are investigated using the proposed formula, and a difference from those by the existing formula is made clear. The proposed impedance formula has made it possible a detailed and more accurate analysis of wave propagation and transient overvoltage characteristics on pipe-enclosed and tunnel-installed cables. Index Terms--Impedance, pipe-enclosed cable, transient, tunnel installed cable, wave propagation.

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 flashover 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 [micro]s 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. Index Terms--Back-flashover, electromagnetic transients program (EMTP), lightning surge, numerical electromagnetic field analysis.

This paper discusses the back-flashover (BFO) phenomena in a high-voltage (HV) vertical double-circuit transmission line by means of numerical simulations. The single- and multiphase BFOs are analyzed considering 24 cases of AC-voltage angles and nonlinear characteristic of flashovers, taking advantage of the circuit analysis method in time domain. The models used in circuit analysis are the TEM-delay model, which can take into account the non-TEM characteristics of tower and line, and the conventional models. Prior to the BFO analysis, the characteristics of circuit models are compared and discussed with the numerical electromagnetic analysis results. In BFO analysis, it is clarified that the occurrence probability of the multiphase BFO is heavily depending on the bias AC-voltages. The relation of measured BFO phases and AC-voltages are well explained by the TEM-delay model with the valid lightning current magnitude. The conventional circuit models could have underestimated the occurrence of BFOs in HV transmission lines. The analysis and discussions shown in this paper can be utilized for advanced evaluation of lightning performance of transmission lines that considers the seriousness of lightning accidents. [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]

When lightning strikes a transmission tower or overhead line, the lightning current generates a spherically expanding electromagnetic field. The propagation mode of an expanding electromagnetic wave is different from that of a transverse electromagnetic (TEM) wave, which is applied to the modeling of transmission lines. This paper presents an equivalent circuit model of an overhead transmission line that considers the TEM‐mode formation delay. The TEM‐mode formation delay is approximately represented by the first‐order delay functions in surge impedances and time delays in the mutual coupling from one line to the others. The proposed circuit model of the overhead line is introduced to the Alternative Transients Program version of Electromagnetic Transients Program using the MODELS language through a formulation in the phase domain based on Dommel's method. The results of the proposed model are validated through a comparison with the results of a three‐dimensional numerical electromagnetic analysis. Furthermore, the effect of the delay of the TEM‐mode formation on the voltages across the insulator strings of a lightning‐struck tower is described by referencing a previous experimental study conducted using an actual 500 kV transmission tower. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The electromagnetic fields, which are produced by lightning currents flowing into a transmission tower and into overhead ground wires, spherically expand with time, and propagate as non-transverse electromagnetic (TEM) waves at least within the round trip time of the traveling wave along the tower. In this paper, a distributed-parameter line model of a vertical double-circuit transmission tower with an overhead line struck by lightning is composed considering the non-TEM characteristics. The surge impedances of the tower, ground wires, and phase conductors increase with time and reach their TEM-mode or steady state values with time constants determined from the configuration. In addition, the significant wave attenuation along the tower is included in the circuit model according to the propagation characteristic determined by the tower configuration. The virtual inductive grounding impedance or damping circuits for approximately representing the wave attenuation is no longer needed. The proposed model is applied to four types of transmission towers. Waveforms of voltages across insulator strings computed by the finite-difference time-domain method, which are regarded as the reference, are well reproduced by the proposed model. Computation efficiency is drastically improved by the proposed model comparing to the numerical electromagnetic field analysis. [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]

This paper proposes a circuit model of a lightning strike to a tall grounded object. The model can consider the direction-dependent attenuation characteristic of current propagating along with a tall grounded object as well as frequency-dependent characteristics of lightning channel and tower impedances, in contrast to the conventional lossless transmission line representations. Hence, the model removes the use of an unrealistic high grounding impedance for approximately expressing the significant current attenuation propagating upward along with the tall object. Measured lightning currents at a height of about 500 m of the 634-m-high Tokyo Skytree are accurately reproduced with the proposed model, which assumes a constant lightning channel impedance with a current source that generates a current waveform decaying with time, or a frequency (time) dependent lightning channel impedance with a step-like voltage source. The proposed model can also be used for lightning electromagnetic pulse calculations. [ABSTRACT FROM AUTHOR]

Lightning electromagnetic pulse (LEMP) waveforms associated with lightning strikes to the 634-m high Tokyo Skytree are calculated by the finite-difference time-domain (FDTD) method in the two-dimensional (2-D) cylindrical coordinate. The three-dimensional (3-D) tortuous lightning channel and the tall strike object are represented by an “equivalent vertical” phased-current-source array. The current propagation speed along the equivalent vertical lighting channel is determined in two steps: first, the channel is projected on a plane including the strike object and a field observation point, and then it is converted into the straight vertical channel right above the strike object. Thus, the height-dependent lightning-current propagation speed along the equivalent channel depends on the direction of the observation point. The proposed method greatly reduces computational resources required for calculating LEMPs without deteriorating accuracy since it allows the use of the 2-D FDTD method. LEMP waveforms measured at a horizontal distance of 27, 57, and 101 km (in different directions) from the strike object are accurately reproduced by the proposed method. The results clarified that the lower region of the tortuous lightning has a large influence on the wavefront of the LEMPs at a horizontal distance ranging from 20 to 100 km from the strike point. [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]

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]

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]

Transient characteristic of power system apparatus in a high-frequency region should be modeled with stray capacitors. Pi-type circuit is commonly used to represent the stray capacitors between terminals and those to the ground. A modeling method for the pi-type circuit with unsymmetrical stray capacitances to ground is proposed in this paper. To obtain the unsymmetrical stray capacitances to ground, a couple of differential-mode measurements are interchangeably applied. The parameters of the pi-type circuit can be determined by the measurements with a common-mode measurement. A nonlinear least-squares method is used to estimate the capacitances. The method is applied to compose an equivalent circuit of a miniature circuit breaker (MCB), which has unsymmetrical stray capacitances to ground. The application is not only for the MCB but also for a scaled model of a high-voltage circuit breaker. A gas-filled arrester is used as a voltage sensor for the test because the voltage across the stray capacitor cannot be directly measured due to the input capacitance of a voltage probe. A transient response of the MCB with the gas-filled arresters is numerically simulated to show the usefulness of the equivalent circuit. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

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]

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]

SUMMARY In this paper, representations of a perfectly conducting thin wire and an imperfectly conducting medium in the transmission line modeling (TLM) calculation are briefly explained. Then, the method is applied to analyzing surge responses of a vertical parallelepiped grounding electrode and a square-loop grounding electrode. Surge responses calculated using the TLM method agree reasonably well with the corresponding responses measured and calculated using the finite-difference time-domain method. It is probably the first time that surge responses of grounding electrodes have been analyzed reasonably accurately using the TLM method. [ABSTRACT FROM AUTHOR]

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]

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]