Transmission Line Representation Research Articles

A common framework for surface plasmon binding and voltage sensing and microscopy with transmission line representation

A common framework for surface plasmon binding and voltage sensing and microscopy with transmission line representation

Modeling Pipe to Soil Potentials From Geomagnetic Storms in Gas Pipelines in New Zealand

AbstractGas pipelines can experience elevated pipe to soil potentials (PSPs) during geomagnetic disturbances due to the induced geoelectric field. Gas pipeline operators use cathodic protection to keep PSPs between −0.85 and −1.2 V to prevent corrosion of the steel pipes and disbondment of the protective coating from the pipes. We have developed a model of the gas pipelines in the North Island of New Zealand to identify whether a hazard exists to these pipelines and how big this hazard is. We used a transmission line representation to model the pipelines and a nodal admittance matrix method to calculate the PSPs at nodes up to 5 km apart along the pipelines. We used this model to calculate PSPs resulting from an idealized 100 mVkm−1 electric field, initially to the north and east. The calculated PSPs are highest are at the ends of the pipelines in the direction of the applied electric field vector. The calculated PSP follows a characteristic curve along the length of the pipelines that matches theory, with deviations due to branchlines and changes in pipeline direction. The modeling shows that the PSP magnitudes are sensitive to the branchline coating conductance with higher coating conductances decreasing the PSPs at most locations. Enhanced PSPs produce the highest risk of disbondment and corrosion occurring, and hence this modeling provides insights into the network locations most at risk.

Current-Limiting Reactors Based Time-Domain Fault Location for High-Voltage DC Systems With Hybrid Transmission Corridors

Accurately locating the fault distance helps in the rapid restoration of the isolated line back into the system. This article proposes a novel time-domain-based algorithm to determine accurate fault location in high-voltage direct current (HVdc) systems with hybrid dc transmission corridors i.e., a combination of underground cables (UGCs) and overhead lines (OHLs). The work gives a fault location method for a two-segment and three-segment hybrid transmission corridor (HTC) and then generalizes the analysis for an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> -segment HTC. The algorithm offers flexibility to locate faults ranging from the homogeneous transmission line to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> -segment HTC. The algorithm uses a simplified unit resistance–inductance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$RL$ </tex-math></inline-formula> ) representation of transmission lines along with time-domain-based measurements i.e., terminal voltage, current, and voltage across current-limiting reactors (CLRs). Power systems computer-aided design/electromagnetic transients including dc (PSCAD/EMTDC)-based simulations are used to validate robust performance against variation of key implementation parameters like type of faults, fault resistance, fault location, sampling frequency, and white Gaussian noise (WGN) in measurement. Further, the fault location calculation is analyzed under parameter variation i.e., change in the true value of unit resistance and unit inductance of line or cable and the true value of dc link capacitance.

A modified implementation of the Folded Line Equivalent transmission line model in the Alternative Transient Program

This paper proposes a modified implementation of the Folded Line Equivalent transmission line model to represent three-phase transmission lines. The Folded line equivalent decomposes a line into its open circuit and short circuit contributions. We propose an alternative orthogonal matrix to transform single-phase transmission line parameters, voltages, and currents to the Folded Line Equivalent domain. Because the proposed matrix is orthogonal, it can directly represent bidirectional transformations using circuit components in simulation software, such as the ATP-EMTP. First, the circuit implementation of Clarke’s matrix decouples a three-phase transmission line into its modes. Then, the circuit implementation of the proposed matrix decouples each mode into its open circuit and short circuit contributions. This paper proves that the proposed approach outputs similar results as those obtained by the Universal Line Model and the JMarti model in the simulation of transmission lines under open-circuit, energization, and fault conditions. However, because the proposed model does not derive from the method of characteristics, it can run with simulation times greater than the propagation delay of the transmission line. It is shown that the proposed approach outputs accurate results for time steps that are 10%, 100%, 200%, and 400% of the propagation delay of the transmission line. Thus, one major advantage of the proposed approach is that it can be used to reduce runtimes in the representation of short transmission lines in large complex networks by increasing time steps without compromising accuracy.

Analysis of waveguide polarizers using equivalent network and finite elements methods

Current research is dedicated to the development of new theoretical model for guide polarization converter with irises. New created model is derived based on the equivalent circuits and transmission line representations. Specific feature of the model consists in the possibility of account of irises thickness in the simulations by approximate single-mode method. Using equivalent lumped elements of the circuits we obtained general scattering matrices of the polarization transformer for fundamental modes of vertical and horizontal linear polarizations. Besides, numerical simulations and optimization of the device were carried out by finite elements method. Good agreement of obtained optimal sizes and polarization characteristics is observed. Provided by the polarizer phase difference between two orthogonal polarizations falls within range 90°±5° in the operating Ku-band. Calculated ellipticity coefficient is better than 1.5 dB. Developed model can be applied for designing of new waveguide polarization converters, filters and other waveguide components with irises.

Drude Dispersion in the Transmission Line Modeling of Bulk Absorbers at Sub-mm Wave Frequencies: A tool for absorber optimization

Semiconductor (SC)-based bulk absorbers operating in the (sub-) THz range are discussed. The conductivities of the bulk media are described by the Drude model for electron gas where the electron density is controlled. The Drude model predicts the existence of two frequencies of interest: one associated with the scattering time of the electrons and a second associated with the plasma frequency. The dimensions of the absorbers for a specific frequency range can be minimized by tuning the doping levels. Eventually, the maximum ohmic absorption from a bulk material is achieved when the real part of the characteristic impedance of the absorber is matched to the one of the surrounding medium and the imaginary part of the characteristic impedance is high so that the power entering the material is actually transformed in heat. Using a classic transmission line representation, a matching layer is introduced to further increase the absorption capabilities of an SC slab. Measurements using a time-domain spectroscopy (TDS) system show the increased accuracy of the Drude model

A Model-Based DC Fault Location Scheme for Multi-Terminal MMC-HVDC Systems Using a Simplified Transmission Line Representation

Accurately determining the location of DC pole-to-pole short-circuit faults in modular multilevel converter (MMC) based multi-terminal HVDC (MTDC) systems is key issue in ensuring fast power recovery. This paper proposes an effective DC fault location scheme for the MMC-MTDC that uses an estimated R-L representation of the transmission lines. By using the measured voltage and current data from both ends of the faulted DC line, the proposed fault location formulas can calculate the location of the fault with high accuracy. The simplified R-L representation greatly reduces the computation burden of the fault detection algorithm. Electromagnetic transient (EMT) simulations of a four-terminal MMC-MTDC system on PSCAD/EMTDC are used to confirm the effectiveness of the proposed approach. The results verify that the proposed scheme is robust and almost not affected by the transmitted power or the fault resistance.

Transmission Line Representation of the Capacitive Via-Plate Interaction Toward a Capacitor-Free Via Model

Conventional physics-based via circuit model takes into account the capacitive coupling between via barrel and power/ground plane by a via-plate capacitor, whose calculation relies on a complex expression involving an infinite summation of Hankel functions. In this paper, a capacitor-free via model is proposed and realized by way of a novel transmission line representation of the via-plate capacitance. In particular, the via-plate capacitor is replaced by an open-circuited transmission line (OC-TL) with equal input admittance. The resultant capacitor-free model obviates the need of calculating the sum of infinite series. Instead, it only requires identifying the length of the OC-TL by simple closed-form expressions. Hence, the proposed efficient capacitor-free via model is able to facilitate the modeling of realistic multilayer printed circuit boards (PCBs) and packages. Both numerical and measurement results validate the proposed OC-TL-based via model.

Lightning Strike to a Tall Grounded Object: Part 1. Circuit Modeling With Direction Dependence

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.

Study of Passband and Stopband Properties of Sheet-Beam Folded Waveguide Structures

In this paper, the passband and stopband characteristics of a sheet-beam folded waveguide structure (FWS) were studied using the equivalent circuit analysis, which is based on the transmission line representation of a rectangular waveguide (WR) and its derived structures. The dispersion and characteristic impedance results obtained for the FWS show the space harmonic nature of the periodic structure. The standard expression of interaction impedance was modified by replacing the characteristic impedance of the waveguide with that of the FWS to better understand the performance of the device near the band edges. The dispersion and the characteristic impedance which were obtained from the transfer matrix of a single period of FWS were analyzed and compared with that of the simple WR. The dependence of the bandgap (stopband) on the size of the beam tunnel was also studied in this analysis. An FWS with a sheet-beam tunnel was fabricated using the micromachining techniques with optimized cutting parameters and well-sharpened cutting tools under minimum quantity lubrication (MQL) conditions. The dimensional and electrical parameters of the structure were measured. The dispersion measurements were carried out. The deviations of the measured dispersion from the values obtained by equivalent circuit analysis are between +0.4%/−0.47% in the entire cold passband and +0.4%/−0.26% in the operating passband 210–250 GHz and are within permissible limits. The simulated measurements of interaction impedance match with the values obtained by the equivalent circuit analysis to be within 10% in the operating passband.

Transmission-Line Model for Materials with Spin-Momentum Locking

We provide a transmission line representation for channels exhibiting spin-momentum locking (SML) which can be used for both time-dependent and steady-state transport analysis on a wide variety of materials with spin-orbit coupling such as topological insulators, heavy metals, oxide interfaces, and narrow bandgap semiconductors. This model is based on a time-dependent four-component diffusion equation obtained from the Boltzmann transport equation assuming linear response and elastic scattering in the channel. We classify all electronic states in the channel into four groups ($U^+$, $D^+$, $U^-$, and $D^-$) depending on the spin index (up ($U$), down ($D$)) and the sign of the $x$-component of the group velocity ($+,-$) and assign an average electrochemical potential to each of the four groups to obtain the four-component diffusion equation. For normal metal channels, the model decouples into the well-known transmission line model for charge and a time-dependent version of Valet-Fert equation for spin. We first show that in the steady-state limit our model leads to simple expressions for charge-spin interconversion in SML channels in good agreement with existing experimental data on diverse materials. We then use the full time-dependent model to study spin-charge separation in the presence of SML, a subject that has been controversial in the past. Our model shows that the charge and spin signals travel with two distinct velocities resulting in well-known spin-charge separation which is expected to persist even in the presence of SML. However, our model predicts that the lower velocity signal is purely spin while the higher velocity signal is largely charge with an additional spin component which has not been noted before. Finally, we note that our model can be used within standard circuit simulators like SPICE to obtain numerical results for complex geometries.

Characterization of Transmission Lines on PCB from S-Parameters by Determining the Dielectric and Conductor Losses at the Crossover Frequency

Full characterization of transmission lines fabricated on printed circuit boards is presented in this paper. For this purpose, the frequency at which the attenuation curves associated with the conductor and dielectric losses cross over is first determined to exactly separate the corresponding contribution to the total attenuation. Afterward, permittivity, loss tangent, effective geometry, and rms roughness are obtained from the propagation constant and characteristic impedance data for allowing the transmission line representation up to 20 GHz. Using the extracted parameters, the excellent model-experiment correlation for the S-parameters of the lines is observed. In fact, the curves of complex-impedance versus frequency are also corrected from undesired resonances typically occurring in experimental data. Finally, it is demonstrated that the extracted parameters allow performing causal time-domain simulations.

Design, Analysis and Characterisation of Spoof Surface Plasmon Polaritons based Wideband Bandpass Filter at Microwave Frequency

&lt;p&gt;This paper presents the wideband bandpass filter (BPF) in the microwave frequency domain. The realisation approach is based on spoof surface plasmon polaritons (SSPPs) phenomenon using plasmonic metamaterial. A novel unit cell is designed for filter design using an LC resonator concept. Then SSPPs BPF is realised using an optimised mode converter and five unit cells. This paper includes a brief design detail of the proposed novel unit cell. The passband of BPF is achieved at approximately 1.20 - 5.80 GHz, 3dB bandwidth is tentatively 4.60 GHz and the insertion loss is less than 2 dB approximately over the passband. The overall dimension of fabricated filter is (90 x 45) mm. A basic schematic of transmission line representation is also proposed to evaluate the BPF structure.&lt;/p&gt;

A Study of an FDTD‐Based Frequency‐Dependent Line Model for Electromagnetic Transient Simulations

SUMMARYElectromagnetic transient (EMT) simulations of power systems require accurate representation of models in a wide range of frequencies. This of course applies to the representation of transmission lines, and the phase‐domain frequency‐dependent line model is often used to this end. The phase‐domain line model does not require modal transformation in EMT simulations but requires modal decomposition at its model identification stage, and there are cases where it fails to fix switchovers of propagation modes with respect to frequency. Thus, a frequency‐dependent line model which essentially avoids modal decomposition is desired. This paper studies the possibility of a frequency‐dependent line model based on the FDTD (Finite Difference Time Domain) method as a candidate which satisfies the above‐mentioned requirements. First, improvements regarding computational efficiency and numerical stability are made to Kordi's FDTD‐based frequency‐dependent line model. Then, the following points are clarified using the developed model: (i) Waveform deformations due to propagation modes with different velocities can be reproduced completely without modal decomposition; (ii) As the time step size becomes larger, waveforms obtained by the developed model become less accurate due to the embedded filter for numerical stability. These points assure, if the error due to the embedded filter is reduced, that the developed model can become a useful frequency‐dependent line model without model identification problems.

Wind adaptive modeling of transmission lines using minimum description length

The transmission lines are moving objects, which positions are dynamically affected by wind-induced conductor motion while they are acquired by airborne laser scanners. This wind effect results in a noisy distribution of laser points, which often hinders accurate representation of transmission lines and thus, leads to various types of modeling errors. This paper presents a new method for complete 3D transmission line model reconstruction in the framework of inner and across span analysis. The highlighted fact is that the proposed method is capable of indirectly estimating noise scales, which corrupts the quality of laser observations affected by different wind speeds through a linear regression analysis. In the inner span analysis, individual transmission line models of each span are evaluated based on the Minimum Description Length theory and erroneous transmission line segments are subsequently replaced by precise transmission line models with wind-adaptive noise scale estimated. In the subsequent step of across span analysis, detecting the precise start and end positions of the transmission line models, known as the Point of Attachment, is the key issue for correcting partial modeling errors, as well as refining transmission line models. Finally, the geometric and topological completion of transmission line models are achieved over the entire network. A performance evaluation was conducted over 138.5km long corridor data. In a modest wind condition, the results demonstrates that the proposed method can improve the accuracy of non-wind-adaptive initial models on an average of 48% success rate to produce complete transmission line models in the range between 85% and 99.5% with the positional accuracy of 9.55cm transmission line models and 28cm Point of Attachment in the root-mean-square error.

Mitigation of erroneous oscillations in electromagnetic transient simulations using analogue filter theory

An efficient and simplified procedure is proposed for the reduction of high-frequency oscillations and erroneous magnitude peaks in electromagnetic transient simulations in power transmission systems modelled by the lumped electric parameters approach. This procedure consists of the inclusion of analogue filters in the equivalent representation of multiconductor transmission lines without modifying its electromagnetic propagation characteristics. The analogue filter modelling is conducted as a function of the line length and line parameters. The proposed simulation methodology is applied directly in the line modelling, which means that the filtering/correction process represents a real-time process during simulations, without post-processing filtering techniques using digital filters or variations in the solution methods. The results obtained directly in the time domain by the proposed modelling/simulation methodology are compared with simulations obtained from well-established line models using the numerical Laplace transform and the Bergeron method.

Frequency domain model for transient analysis of lightning protection systems of buildings.

A frequency domain modeling approach for lightning protection systems (LPS) of buildings is described and validated in this paper. The model is based on a 2-port transmission line representation of each conductor, and the further assembling of a network representing the complete structure. Horizontal and vertical conductors are modeled using formulas based on the complex images method, in order to take into account frequency dependence. Variation of electrical parameters with height is also considered for vertical conductors. This is accomplished by means of a non-uniform modeling approach based on conductor subdivision and cascaded connection of chain matrices computed for each segment. The results from the model are validated by means of comparisons with measurements reported elsewhere, as well as simulations using PSCAD/EMTDC.

Eliminating Measurement Cable Effects From Transformer Admittance Measurements

Admittance frequency-sweep measurements is an accepted procedure for characterizing transformer terminal behavior for the purpose of frequency-dependent black-box modeling. The errors introduced by the measurement cables is with one existing practice mitigated by removal of the associated shunt capacitance effect. In this paper, it is shown that the accuracy can be greatly improved by using transmission-line representation of the measurement cables with parameters obtained from standard cable data or from S-parameter measurements. The procedure is demonstrated for the modeling of a 45 MVA generator step-up transformer requiring cable lengths of six meters and an upper frequency limit of 10 MHz.

Coupled line based unequal dual band power divider

ABSTRACTThis article presents theoretical design of dual band unequal power divider based on coupled line structure. The structure consists of two coupled line segments along with five transmission line segments used to satisfy unequal matching characteristic. The isolation is achieved using a circuit, which is a combination of inductor, capacitor, and resistor. Design equations of proposed power divider and the circuit providing isolation are based on circuit representation of ideal transmission lines. Simulation and measured results are given to verify the theoretical design equations. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:953–956, 2016

FDTD法に基づく瞬時値解析用周波数依存線路モデルの検討

Electromagnetic transient (EMT) simulations of power systems require accurate representation of models in a wide range of frequencies. This of course applies to the representation of transmission lines, and the phase-domain frequency-dependent line model is often used to this end. The phase-domain line model does not require modal transformation in EMT simulations but requires modal decomposition at its model identification stage, and there are cases where it fails to fix switchovers of propagation modes with respect to frequency. Thus, a frequency-dependent line model which essentially avoids modal decomposition is desired. This paper studies the possibility of a frequency-dependent line model based on the FDTD (Finite Difference Time Domain) method as a candidate which satisfies the above-mentioned requirements. First, improvements regarding computational efficiency and numerical stability are made to Kordi's FDTD-based frequency-dependent line model. Then, the following points are clarified using the developed model: (i) Waveform deformations due to propagation modes with different velocities can be reproduced completely without modal decomposition; (ii) As the time step size becomes larger, waveforms obtained by the developed model become less accurate due to the embedded filter for numerical stability. These points assure, if the error due to the embedded filter is reduced, that the developed model can become a useful frequency-dependent line model without model identification problems.