Simulation Of Transmission Lines Research Articles

Numerical investigation of soliton dynamics, injection into the transition region of a soliton diode

We investigate soliton–antisoliton interactions by numerical simulation of a nonlinear transmission line. Long Josephson junction acts as a nonlinear transmission line in which soliton solutions are obtained form Sine–Gordon equation. By proper initial and boundary conditions solitons and antisolitons are obtained inside the same junction, simulating the so called soliton diode. The role of loss in the annihilation of solitons and antisolitons injected to the transition region of the soliton diode is investigated by numerical simulation of their dynamics and phase revolution along the junction. It is shown that such loss can greatly reduce the speed of solitons and antisolitons, lowering the frequency response of the device. A so called “locally-lossy” soliton diode is proposed and it is shown that this configuration maintains annihilation process without much degradation of the device speed.

Experimental Research on Lightning Influence of 500kV Transmission Lines in Complex Terrains

This paper presents the lightning influence of complex mountainous terrains in 500kV transmission lines and the corresponding methods to improve lightning withstanding level for the safety and stability of power system. According to the general situations and space distributions of lightning activities in East China, that is, mountainous areas are more serious than plains. Four groups of discharging experiment are conducted by the construction of solid models that simulate transmission line routes in mountains. Meanwhile, some commonly used effective methods are studied in detail to reach a conclusion that the lateral rod can reduce shielding rate most efficiently. Then the operation principles and effect factors of lateral rods are analyzed theoretically through the establishment of Electro-geometric Model (EGM), and a large number of repetitive discharging tests are also executed to count and calculate the experimental shielding rates. Experimental results indicate that different terrains have a significant influence mostly on the lightning shielding rate of lines. The lateral rod can largely reduce the shielding rate and the protection effects are influenced by the rod length and angle. The conclusion obtained corroborates the theoretical analysis, which can be widely used as reference in practical applications and lightning protection transformation assessments

Teaching Distance Relay using Matlab/Simulink Graphical user Interface

This paper describes the modeling of distance relay using Matlab/Simulink package. SimPowerSystem toolbox was used for detailed modeling of distance relay, transmission line and fault simulation. Inside the modeling, single line to ground (SLG) fault was choose to be the fault type and Mho type distance characteristic was choose to be as the protection scheme. A graphical user interface (GUI) was created using GUI package inside Matlab for the developed model. With the interactive environment of graphical user interface, the difficulties in teaching of distance relay for undergraduate students can be eliminated.

Comparison of Nonuniform Transmission Lines With Gaussian and Exponential Impedance Profiles for $Z$-Pinch

The circuit simulation of nonuniform transmission lines that were under consideration for the next generation of petawatt-class <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$Z$</tex></formula> -pinch drivers was performed. It was confirmed that the power-transport efficiency of the designed radial transformer with an exponential impedance profile is higher than that with Gaussian profiles. Based on Fourier's theorem and the principle of superposition, it was found that there are considerable low-frequency components for the input voltage of a half-sine wave with an angular frequency of 14 Mrad/s. Compared with the exponential transformer, the Gaussian transformers amplify the low-frequency components to a lower extent, which makes the difference in power efficiency between the two types of transformers. The radial transformer also serves as a passive high-pass filter, and the Gaussian transformer may give better performance than the exponential transformer does if the signal transport rather than the power transport is concerned.

Influence of Turbulence Intensities onto Transmission Line Conductor Wind Loads

The rationality of transmission line responses, tower responses, etc., are determined by the computed wind loads, which are directly correlated with the free-stream turbulences that generated at different ground roughness conditions, different terrains, etc.. Accounting for this problem, the flow fields around transmission line conductor LGJ630/45 are computed by solving Navier-Stokes equations to study the influence of Tis (turbulence intensities) onto wind load characteristics. The results show that, the peak-values of power spectrum density (PSD) results of both lift and drag are obviously influenced by TIs, while their corresponding frequencies are kept the same at different TIs; with the increase of Tis, the time-averaged value of conductor drag decreases nonlinearly and monotonically. Thus, given the influence of TIs onto wind loads, field observed free-stream values should be used as inputs for numerical simulations, and then the obtained wind loads can be adopted to accurately simulate transmission line gallopings and windage yaws.

Using Subgridding FDTD Method to Incorporate Air Gap Breakdown in the Analysis of Lightning Induced Voltage

A subgridding formulation of Agrawal coupling equations of transmission line with branch and distributed electromagnetic excitation is proposed. This algorithm enables us to solve the transmission line system using different temporal and spatial step on different branches. The method is used to calculate the lightning induced over-voltage on the transmission line installed with air gap component branch. The air gap is modeled by disruptive effect method with small time step, while the transmission line is simulated using large time step. With the help of this method, the simulation of transmission line with air gap component can avoid long time computation. As an example, the protection effectiveness of surge arrester with series air gap is studied using the proposed method.

Investigation of errors in simulation of devices with distributed parameters

This study deals with the application of the method of transformation functions for investigating the systematic errors in simulation of devices with distributed LC and RC parameters. The specified errors occur while using the traditional techniques. This study also examines the impact of frequency deviation on the values of model transformation functions. In addition, analytical expressions eliminating the systematic errors of simulation of long-distance transmission lines are proposed.

Alternating Direction Explicit-Latency Insertion Method (ADE-LIM) for the Fast Transient Simulation of Transmission Lines

This paper describes the alternating direction explicit-latency insertion method (ADE-LIM) for the fast simulations of transmission lines. LIM is one of the fast transient analysis techniques for large networks. However, because this method is based on an explicit finite-difference method, it has a limitation of the time step size for the numerical stability condition similar to the finite-difference time-domain technique. On the other hand, the ADE method is one of the finite-difference methods and has advantages of less computational complexity and numerical stability. In this paper, we propose ADE-LIM as an improved method of LIM. This method can circumvent the above time step limitation problem because the method is based on the ADE algorithm. Numerical results show that ADE-LIM is about 3-3.5 times faster than LIM in the transmission line analyses with appropriate accuracy.

An Inverse Scattering Approach to Soft Fault Diagnosis in Lossy Electric Transmission Lines

In this paper, the diagnosis of soft faults in lossy electric transmission lines is studied through the inverse scattering approach, extending a recently reported study on lossless transmission lines. The considered soft faults are modeled as continuous spatial variations of distributed characteristic parameters of transmission lines. The diagnosis of such faults from reflection and transmission coefficients measured at the ends of a line can be formulated as an inverse problem. The relationship between this inverse problem and the inverse scattering theory has been studied by Jaulent in 1982 through transformations from the telegrapher's equations of transmission lines to Zakharov-Shabat equations. The present paper clarifies and completes the computation of the theoretic scattering data required by the inverse scattering transform from the practically measured engineering scattering data. The inverse scattering method is then applied to numerically simulated lossy transmission lines to confirm the feasibility of the studied approach to soft fault diagnosis.

Two methods for transmission line simulation model creation based on time domain measurements

Abstract. The emission from transmission lines plays an important role in the electromagnetic compatibility of automotive electronic systems. In a frequency range below 200 MHz radiation from cables is often the dominant emission factor. In higher frequency ranges radiation from PCBs and their housing becomes more relevant. Main sources for this emission are the conducting traces. The established field measurement methods according CISPR 25 for evaluation of emissions suffer from the need to use large anechoic chambers. Furthermore measurement data can not be used for simulation model creation in order to compute the overall fields radiated from a car. In this paper a method to determine the far-fields and a simulation model of radiating transmission lines, esp. cable bundles and conducting traces on planar structures, is proposed. The method measures the electromagnetic near-field above the test object. Measurements are done in time domain in order to get phase information and to reduce measurement time. On the basis of near-field data equivalent source identification can be done. Considering correlations between sources along each conductive structure in model creation process, the model accuracy increases and computational costs can be reduced.

Higher-order soliton-effect pulse compression in a nonlinear left-handed transmission line

This work introduces a method of pulse compression based on a higher-order soliton effect in a left-handed nonlinear (LH-NL) transmission line with series nonlinear capacitances. A circuit simulation of the LH-NL transmission line which is based on a finite-difference method shows that if a higher-order soliton is replaced by a fundamental soliton launched into the line, the self-phase modulation (SPM) will dominate the group velocity dispersion (GVD). As a result, the pulse compression is realized in a specific length dependent on the soliton order.

Passive Intermodulation Due to Self-Heating in Printed Transmission Lines

This paper proposes a mechanism by which third-order intermodulation distortion, due to self-heating, is generated in transmission lines. This work shows how transmission lines made of several materials, whose properties are independent of the electric and magnetic fields, can generate important levels of intermodulation distortion. A circuit model supported by finite-element simulations is presented to account for the temperature generation and also for its impact on the nonlinear performance. Closed-form expressions are used to calculate the generated intermodulation products and are derived from the circuit model and compared with simulations. Finally, measurements and simulations of different transmission lines are presented, showing very good agreement.

Inverse Scattering for Soft Fault Diagnosis in Electric Transmission Lines

Today's advanced reflectometry methods provide an efficient solution for the diagnosis of electric transmission line hard faults (open and short circuits), but they are much less efficient for soft faults, in particular, for faults resulting in spatially smooth variations of characteristic impedance. This paper attempts to fill an important gap for the application of the inverse scattering transform to reflectometry-based soft fault diagnosis: it clarifies the relationship between the reflection coefficient measured with reflectometry instruments and the mathematical object of the same name defined in the inverse scattering theory, by reconciling finite length transmission lines with the inverse scattering transform defined on the infinite interval. The feasibility of this approach is then demonstrated by numerical simulation of lossless transmission lines affected by soft faults, and by the solution of the inverse scattering problem effectively retrieving smoothly varying characteristic impedance profiles from reflection coefficients.

Robust Passivity Enforcement Scheme for Time-Domain Simulation of Multi-Conductor Transmission Lines and Cables

This paper proposes an algorithm to enforce passivity on the time-domain simulation model for a multi-conductor cable or transmission line. The model is first reformulated in a form which reduces the severity of passivity violations. The frequency sweep method is then used to identify any remaining passivity violating regions of the model's frequency response. These small passivity violations are then removed using a linear constrained least squares algorithm to perturb the diagonal elements of propagation matrix. The passivity enforcement algorithm is applied to the Universal Line Model (ULM), a widely used robust phase domain formulation implemented in many commercial electromagnetic transients simulation programs. Two examples of multi-conductor underground cable systems, one for ac and the other for HVDC transmission are presented to demonstrate the proposed approach.

An FFT-Accelerated Time-Domain Multiconductor Transmission Line Simulator

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A fast time-domain multiconductor transmission line (MTL) simulator for analyzing general MTL networks is presented. The simulator models the networks as homogeneous MTLs that are excited by external fields and driven/terminated/connected by potentially nonlinear lumped circuitry. It hybridizes an MTL solver derived from time-domain integral equations (TDIEs) in unknown wave coefficients for each MTL with a circuit solver rooted in modified nodal analysis equations in unknown node voltages and voltage-source currents for each circuit. These two solvers are rigorously interfaced at MTL and circuit terminals, and the resulting coupled system of equations is solved simultaneously for all MTL and circuit unknowns at each time step. The proposed simulator is amenable to hybridization, is fast Fourier transform (FFT)-accelerated, and is highly accurate: 1) It can easily be hybridized with TDIE-based field solvers (in a fully rigorous mathematical framework) for performing electromagnetic interference and compatibility analysis on electrically large and complex structures loaded with MTL networks. 2) It is accelerated by an FFT algorithm that calculates temporal convolutions of time-domain MTL Green functions in only <formula formulatype="inline"><tex Notation="TeX">$O({N_{\rm t} \log ^2 N_{\rm t} })$</tex></formula> rather than <formula formulatype="inline"><tex Notation="TeX">$O(N_{\rm t}^2)$</tex></formula> operations, where <formula formulatype="inline"> <tex Notation="TeX">$N_{\rm t} $</tex></formula> is the number of time steps of simulation. Moreover, the algorithm, which operates on temporal samples of MTL Green functions, is indifferent to the method used to obtain them. 3) It approximates MTL voltages, currents, and wave coefficients, using high-order temporal basis functions. Various numerical examples, including the crosstalk analysis of a (twisted) unshielded twisted-pair (UTP)-CAT5 cable and the analysis of field coupling into UTP-CAT5 and RG-58 cables located on an airplane, are presented to demonstrate the accuracy, efficiency, and versatility of the proposed simulator. </para>

Microwave modulation of terahertz quantum cascade lasers: a transmission-line approach

We report on microwave impedance measurements of metal-metal ridge-waveguide terahertz quantum cascade lasers. Experimental data, recorded at 4 K in the 100 MHz–55 GHz range, are well reproduced by distributed-parameter transmission-line simulations, showing that the modulation cutoff is limited by the propagation losses that increase for higher microwave frequencies, yielding a 3 dB modulation bandwidth of ∼70 GHz for a 1 mm-long ridge. By using a shunt-stub matching we demonstrate amplitude modulation of a 2.3 THz QCL up to 24 GHz.

Spice Simulation and Experimental Study of Transmission Lines with TVSs Excited by EMP

This paper presents the experimental study and SPICE simulation of transmission lines without or with transient voltage suppressors (TVSs) radiated by a fast rise-time electromagnetic pulse. TVSs are usually attached to transmission lines to protect terminal loads from surge interferences. The currents of the terminal loads and TVSs are obtained experimentally and numerically by using the SPICE circuits of transmission lines and TVSs. The results show that the induced energy dissipated through one termination will become larger when a TVS is attached to the other termination of the transmission line. And experimental results reveal that TVSs can provide protection for the loads, but the protection effectiveness may be not enough against fast rise-time surges.

Time-Domain Green's Function-Based Sensitivity Analysis of Multiconductor Transmission Lines With Nonlinear Terminations

Time-domain sensitivity analysis of multiconductor transmission lines is derived from the dyadic Green's function of the 1-D wave propagation problem. The rational nature of the Green's function permits the generation of a time-domain macromodel for the computation of transient voltage sensitivities with respect to both electrical and physical parameters, completely avoiding similarity transformation. Through simulations of multiconductor transmission lines with linear and nonlinear terminations, comparisons are made with the perturbative approach and standard frequency-domain techniques for multiconductor transmission lines.

Backflashover simulation of HV transmission lines with enhanced counterpoise groundings

This paper deals with the backflashover phenomenon in HV overhead transmission lines (TLs) with towers grounded by means of long counterpoises, typically used in high resistivity soils. Although long counterpoises are effective in reducing the grounding impedance at power frequency, their impulse response may affect negatively the TL backflashover rate. The study is focused on the enhancement of TL lightning performance obtainable by adding a small number of vertical grounding rods to horizontal counterpoises. An extensive ATP-EMTP parametric analysis, based on a detailed 161 kV TL model including the leader progression model (LPM) of line insulations and the non-linear transient behaviour of grounding systems, has been carried out taking into account several different values of soil resistivity as well as varying numbers, locations and lengths of additional vertical rods. Critical lightning current ranges causing backflashover have been then predicted for several lightning waveforms, of different severity. The paper shows that the addition of a few vertical grounding rods significantly improves TL lightning performance by increasing critical lightning current values, even if their influence is negligible at power frequency. The authors have ascertained an increment of average critical backflashover current up to ∼55% for some typical TL grounding system configurations and lightning waveshapes.

High-Power Pulsed RF Extraction From Nonlinear Lumped Element Transmission Lines

Electrical soliton bursts are generated on a range of simulated and experimental nonlinear lumped element transmission lines (NLETLs). The design parameters necessary to achieve high frequency waveforms with peak voltage amplification are investigated, and the control over output frequency is demonstrated. An explanation of the fundamental problem of extracting extended bursts of solitons to linear load resistances is offered, along with the results from successful novel NLETL-based soliton burst generators tested at low voltages.