Transmission Line Geometry Research Articles

Assessment of the accuracy of the modal-domain line models with real and frequency-independent transformation matrix for electromagnetic transient simulation in lines with underbuilt cables

This paper investigates the potential inaccuracies associated with using a modal-domain model featuring a real and frequency-independent transformation matrix in simulating electromagnetic transients on power overhead lines equipped with underbuilt wires. Three transmission line configurations are examined: one without underbuilt wires, one with a single underbuilt wire, and another with two underbuilt wires. Comparisons between the simulated voltages computed using the modal-domain approach and a more accurate phase-domain model as a reference reveal that the modal-domain approach leads to inaccuracies in the simulated voltages. These inaccuracies intensify with an increase in the number of underbuilt wires and the soil resistivity. Differences of up to approximately 24 % in the peak values of the simulated voltages were observed, considering the transmission line geometry analyzed in this study. Based on these findings, it is recommended that for simulating transients in overhead lines with installed underbuilt wires, phase-domain models, such as the Universal Line Model, should be employed.

Modeling Magnetic Fields around Stranded Electrical Transmission Lines via Finite Element Analysis (FEA)

This paper aims to design the fundamental basis for an Unmanned Aerial System (UAS)-driven, remote, and non-invasive current sensing application. Using the COMSOL software, the methodology presented here consists of the Computer Aided Design (CAD) for stranded Transmission Line (TL) geometries composed of 7 to 91 sub-filaments and discretized via tetrahedral-element-based meshes. The radiated Magnetic Field (MF) around each TL is then solved by means of Finite Element Analysis (FEA) after selecting the proper materials for TLs under the coil geometry analysis study. For each TL, all resultant MFs’ norms are presented as tabulated data, with respect to the inducing currents. Eventually, the complex mathematical model needed to evaluate these MFs, radiated around stranded TLs, is surpassed by the scalable models designed through this study. The min/max MFs radiated around each TL resulting from the min/max injected current values are hence obtained. This would serve in the accurate choosing/positioning of magnetic-based sensors in UAS applications, reliably. Additionally, related future works are concretely presented.

A Test System for Transmission Expansion Planning Studies

This paper introduces a 17-bus 500 kV test system intended for transmission expansion planning (TEP) studies. The overhead lines used in the system are based on an actual 500 kV transmission line geometry. Although several test systems have been developed for various forms of power system analysis, few are specifically tailored for TEP studies at the transmission voltage level, as opposed to the distribution voltage level. Current test systems for TEP studies are limited to single loading conditions only for normal operating conditions, and the majority of these systems are intertwined with issues related to the energy market or devised specifically for integrating new generations and loads into the existing power systems. However, ensuring a test system satisfies both voltage drop and line loading criteria during both normal and all single contingency operations is crucial in TEP studies, and addressing these issues under contingency conditions poses notable challenges. Moreover, practical TEP scenarios involve varied loadings, including peak load and dominant loading (60% of peak load) scenarios, while the existing test systems are configured solely for single loading conditions. To address these technical gaps, this paper introduces the 17-bus test system operating at a transmission voltage level of 500 kV, meeting technical requirements under normal and all single contingency operations for both peak load and dominant load scenarios. Detailed specifications of the proposed test system and load flow analysis at both normal and contingency conditions for different loading conditions are presented. This test system serves as an invaluable resource for TEP studies.

High impedance Josephson junction resonators in the transmission line geometry

In this article, we present an experimental study of microwave resonators made out of Josephson junctions. The junctions are embedded in a transmission line geometry so that they increase the inductance per length for the line. By comparing two devices with different input/output coupling strengths, we show that the coupling capacitors, however, add a significant amount to the total capacitance of the resonator. This makes the resonators with high coupling capacitance to act rather as lumped element resonators with inductance from the junctions and capacitance from the end sections. Based on a circuit analysis, we show that the input and output couplings of the resonator are limited to a maximum value of ωrZ0/4Zr, where ωr is the resonance frequency and Z0 and Zr are the characteristic impedances of the input/output lines and the resonator, respectively.

High efficiency radio frequency pulse generation in a nonlinear corrugated coaxial transmission line with ferrite saturated by permanent magnets.

The work on the development of a generator of high-power, high-frequency pulses based on a nonlinear transmission line with saturated ferrite is presented. A feature of the generator is that the ferrite rings are saturated in the field of permanent magnets, unlike traditional generators with a solenoid wrapped around the transmission line. Due to the changed structure of the inner conductor, which is a corrugated conductor, the line has spatial dispersion. The paper demonstrates the generation of high-frequency pulses with a duration of up to 6ns and a center frequency of 2.7GHz. This pulse duration with a frequency above 2GHz was not previously observed in traditional nonlinear transmission line geometry. The maximal peak power achieved was 70MW for an incident voltage pulse of 90kV. The energy efficiency of video pulse energy conversion into radio pulse was 6% [G. Kataev, Electromagnetic Shock Waves (Sov. Radio, Moscow, 1963)]. The paper discusses the performance of RF and microwave NiZn ferrites for the purposes of radio pulse generation.

RF Pulse Generation in a Gyromagnetic Nonlinear Transmission Line With Periodically Placed Ferrites and Permanent Magnets

This article presents a work on development of a high-power radio pulse generator, which is a gyromagnetic nonlinear transmission line (GNLTL) in which periodically placed NiZn ferrites are saturated by an axial magnetic field produced by permanent magnets periodically placed inside the transmission line. Structurally, the line is a corrugated coaxial waveguide with permanent NdFeB magnets placed inside the inner conductor of the line. The transmission line geometry was optimized using numerical simulation by finite-difference time domain (FDTD) method. The excitation of high-frequency oscillations in the developed transmission line at central frequency of 1 GHz and above is shown experimentally using ferrite rings with 45 and 28 mm outer and inner diameters. The maximum peak power of microwave oscillations obtained in the experiments is 110 MW at the central frequency 1.3 GHz. The obtained RF power is comparable to that of more common GNLTL with continuous filling by ferrite rings having the same transverse size.

Numerical Analysis on the RF Characteristics of the Gyromagnetic Nonlinear Transmission Lines

The gyromagnetic nonlinear transmission line (GNLTL) is a special transmission line loaded with ferrite cores, which can be used as a kind of wideband high-power microwave (HPM) source due to the pulse modulation mechanism. This article carried out a series of simulations and analyses focused on the RF characteristics of GNLTL. Based on the classic transmission line model (TLM) method, a numerical model linking the transmission line equations and the microscopic magnetization dynamics equations was established. The simulations systematically studied the effects of key parameters on the output characteristics especially the RF characteristics, including the effects of transmission line geometry, excitation pulse, magnetic material, and the biasing magnetic field. The simulation results and analyses revealed that almost each parameter has effects on the output, and the effects of different parameters are different. The research introduced in this article preliminarily reveals how the output microwave varies with the parameters and provides a method to find the appropriate parameter values of a GNLTL.

Mitigation of the Electric and Magnetic Fields of 500-kV Overhead Transmission Lines

The electric and magnetic fields of overhead high voltage transmission lines are still a critical problem for new construction because of their biological effects on the human body. This issue has been a subject of scientific interest and public concern for the risk of the electric and magnetic fields on living organisms. Accordingly, the overhead transmission lines are considered a source of such this risk due to their high electric and magnetic fields in the populated areas. Because of the recent concerns that electric besides magnetic fields, generated by overhead transmission lines, electric power researchers have been trying to find effective methods for the mitigation of the electrical and magnetic fields to be in the range of acceptable limits. Researchers have been trying to find transmission line geometries that will reduce these electric and magnetic fields. Therefore, in this article two novel methods of reducing the electric and magnetic fields are discussed, one is to change the position of the center phase to optimize the delta configuration and the other is to use more than two shielding wires with calculating the currents in these wires. The obtained results of the two proposed methods are compared with the electric as well as magnetic fields, and the right-of-way values of the present conventional configuration. Additionally, this article presents a case study carried out on an Egyptian 500 kV high voltage overhead transmission line for the mitigation of magnetic and electric field intensities.

50 Ω transmission lines with extreme wavelength compression based on superconducting nanowires on high-permittivity substrates

We demonstrate impedance-matched low-loss transmission lines with a signal wavelength more than 150 times smaller than the free space wavelength using superconducting nanowires on high permittivity substrates. A niobium nitride thin film is patterned in a coplanar waveguide (CPW) transmission line geometry on a bilayer substrate consisting of 100 nm of epitaxial strontium titanate on high-resistivity silicon. The use of strontium titanate on silicon enables wafer-scale fabrication and maximizes process compatibility. It also makes it possible to realize a 50 Ω characteristic impedance across a wide range of CPW widths from the nanoscale to the macroscale. We fabricated and characterized an approximately 50 Ω CPW device with two half-wave stub resonators. Comparing the measured transmission coefficient to numerical simulations, we determine that the strontium titanate film has a dielectric constant of 1.1×103 and a loss tangent of not more than 0.009. To facilitate the design of distributed microwave devices based on this type of material system, we describe an analytical model of the CPW properties that gives good agreement with both measurements and simulations.

Metallization of ZnSb and contact resistance

We present results on electrical resistance of metal contacts to ZnSb. We synthesized the thermoelectric semiconductor ZnSb with specific doping concentrations by adding Cu as an acceptor to the melt, followed by solidification, crushing, ball-milling, hot-pressing, sawing, and polishing yielding wafers suitable for substrates for further processing. Many batches were made yielding different doping concentrations. We defined transmission line geometries in deposited metal films for specific contact resistance measurements. We prepared sets of Cu, Ti, and Ni films, respectively. We measured the contact resistance vs annealing temperatures. For Cu/ZnSb samples, we observed a specific contact resistance from 5 × 10−7 to 4 × 10−5 Ω cm2. We also measured the carrier concentration of ZnSb. The measurement data of the specific contact resistance had systematic dependence on doping concentration and annealing temperature and were analyzed by a model incorporating different transport mechanisms across the energy barrier at the metal–semiconductor interface. The data were discussed in terms of systematic variation in barrier height and density of states effective mass. We proposed these arising as a consequence of interactions at the interface and a nonparabolic valence band. We have also monitored the interface of the ZnSb substrate and metal films with transmission electron microscopy.

A Review of Nonlinear Transmission Line System Design

Nonlinear transmission lines (NLTLs) have been increasingly studied to produce high power microwaves (HPM) at higher repetition rates than conventional HPM devices without requiring the same auxiliary systems. The ability to array NLTLs to produce higher power and achieve beam steering provides an additional capability. This review summarizes the various NLTL topologies designed to achieve these design objectives. Specifically, we summarize modeling and experimental studies for three primary topologies: the lumped element NLTL, the split ring resonator, and the traditional transmission line geometry using nonlinear materials. The lumped element NLTL and the traditional transmission line constructed with nonlinear materials lend themselves to higher power applications, while the split ring resonator is better suited for applications involving antennas. We provide a detailed summary of past studies for these topologies and conclude by exploring ongoing work and future opportunities for technological development.

Modeling deformed transmission lines for continuous strain sensing applications

Transmission lines are essential components in various signal and power distribution systems. In addition to their main use as connecting elements, transmission lines can also be employed as continuous sensors for the measurement and detection of external influences such as mechanical strains and deformations. The measuring principle is based on deformation-induced changes of the characteristic impedance. Reflections of an injected test signal at resulting impedance mismatches can be used to infer applied deformations. To determine the effect of deformations on the characteristic impedance, we develop a numerical framework that allows us to solve Maxwell’s equations for any desired transmission-line geometry over a wide frequency range. The proposed framework utilizes a staggered finite-difference Yee method on non-uniform grids to efficiently solve a set of decoupled partial differential equations that we derive from the frequency domain Maxwell equations. To test our framework, we compare simulation results with analytical predictions and corresponding experimental data. Our results suggest that the proposed numerical framework is able to capture experimentally observed deformation effects and may therefore be used in transmission-line-based deformation and strain sensing applications. Furthermore, our framework can also be utilized to simulate and study the electromagnetic properties of complex arrangements of conductor, insulator, and shielding materials.

Microwave devices based on template-assisted NiFe nanowires: fabrication and characterization

Ferromagnetic nanowires have attracted extensive interest in the development of monolithic microwave integrated circuits for future microwave reciprocal and non-reciprocal devices. The aim of the present investigation is to explore the magnetization dynamics in NiFe nanowires using a field sweep ferromagnetic resonance (FMR) technique. We also fabricated microwave devices, such as phase shifters and notch filters, on these ferromagnetic nanowired (FMNW) substrates in microstrip transmission line geometry. 1D NiFe nanowires have been synthesized by a dc electrodeposition technique in anodic alumina oxide membranes. Detailed microstructural and magnetic properties of deposited nanowires were investigated. The FMR technique was used to study the dynamic properties in the frequency range from 15 to 25 GHz. The angular variation of resonance field yields the intrinsic parameters such as gyromagnetic ratio and effective field. The resonance field increases up to 7 kOe for changing the nanowire’s axis from parallel to perpendicular direction. The stop-band frequency can be modulated up to 30 GHz and phase shifter showed a differential phase shift of 80 deg cm−1 at higher frequency band with an external magnetic field of 5.3 kOe. It is observed that the superlative frequency which corresponds to the highest differential phase shift for NiFe nanowires improved considerably above 33 GHz.

Loss and saturation in superconducting travelling-wave parametric amplifiers

We have developed a coupled-mode analysis framework for superconducting travelling-wave parametric amplifiers using the full Telegrapher’s equations to incorporate loss-related behaviour. Our model provides an explanation of previous experimental observations regarding loss in amplifiers, advantages of concatenating amplifiers to achieve high gains, and signal gain saturation. This work can be used to guide the design of amplifiers in terms of the choice of material systems, transmission line geometry, operating conditions, and pump strength.

SYNTHES OF ROBUST ACTIVE SHIELDING SYSTEMS OF MAGNETIC FIELD GENERATED BY GROUP OF HIGH-VOLTAGE POWER LINES

Aim. The synthesis of robust active shielding system of magnetic field, generated by group of high voltage power lines for reducing the induction of the initial magnetic field to the sanitary standards level and reducing the sensitivity of the system to variations in the plant parameters is given. Methodology. The synthesis is based on the solution of a multi-criteria stochastic game, in which the gain vector is calculated on the basis of the Maxwell equations solutions in the quasi-stationary approximation. The equilibrium state of the game is based on the stochastic multiagent optimization algorithms of the multiswarm particles. The initial parameters for the synthesis of active shielding system are the location of the high voltage power lines with respect to the protected from transmission line space, geometry and number of cables, operating currents, as well as the size of the protected space and normative value magnetic field induction, which should be achieved as a result of screening. The objective of the synthesis of the active shielding system is to determine their number, configuration, spatial arrangement, wiring diagrams and compensation cables currents, setting algorithm of the control systems as well as the resulting value of the induction magnetic field at the points of the protected space. Results. Robust active shielding system synthesis results for reduction of a magnetic field generated by group of high voltage power lines is given. The possibility of a significant reduction in the level of induction of the magnetic field source within and reducing the sensitivity of the system to variations in the plant parameters is given. Originality. For the first time carried out the synthesis of the robust active shielding systems of magnetic field generated by group of high voltage power lines within a given region of space. Practicalvalue. Practical recommendations on reasonable choice of the number and spatial arrangement of compensating cables of robust active shielding systems of the magnetic field generated by the group of high voltage power lines is given.

SINGLE-CIRCUIT ACTIVE SCREENING OF MAGNETIC FIELD GENERATED BY SEVERAL OVERHEAD TRANSMISSION LINES IN RESIDENTIAL AREA

Purpose . The synthesis of active screening system of magnetic field, generated by several high voltage overhead transmission lines, with the help of single compensation cables is presented. Methodology. The initial parameters for the synthesis of active screening system parameters are the location of the high voltage overhead transmission lines with respect to the protected transmission line space, geometry and number of cables, operating currents, as well as the size of the protected space and normative value of magnetic flux density, which should be achieved as a result of screening. The objective of the synthesis of the active screening system is to determine their number, configuration, spatial arrangement, wiring diagrams and compensation cables currents, setting algorithm of the control systems as well as the resulting value of the induction magnetic field at the points of the protected space. Synthesis of active screening system is reduced to the problem of multi objective nonlinear programming with constraints in which calculation of the objective functions and constraints are carried out on the basis of the Maxwell equations solutions in the quasi-stationary approximation. The problem is solved by a stochastic multi swarm multi agent particles optimization, which can significantly reduce the time to solve it. Results. Active screening system synthesis results for reduction of a magnetic field generated by several high voltage overhead transmission lines are presented. The possibility of a significant reduction in the level of source magnetic flux density within a given. Originality. For the first time the synthesis of the active screening systems of magnetic field generated by the several high voltage overhead transmission lines within a given region of space is carried out. Practical value. Practical recommendations on reasonable choice of the number and spatial arrangement of compensating cables of active screening systems of the magnetic field generated by the several high voltage overhead transmission lines is given.

Ultra-broadband Polarization-Independent Wide-Angle THz Absorber Based on Plasmonic Resonances in Semiconductor Square Nut-Shaped Metamaterials

Metamaterials are considered to be a promising candidate of making THz absorber for function devices to replace natural materials. Based on geometry evolution, the electromagnetic characteristics of metamaterials can be tailed to enhance the weak THz response of natural materials. Appropriate constituent selection and inhomogeneous geometry constructions are proved to be effective to extend the narrow frequency band of traditional metal resonator-based metamaterial absorbers. In this work, doped silicon was used as the only constituent, and the inhomogeneous geometry was designed in a very simple way (so-called square nut structure) with the assistant of transmission line theory and geometry evolution methodology. Ultra-broadband absorption from 1.6 to 5 THz was verified numerically with an efficiency over 90 %. Various plasmonic resonance modes including surface plasmon polaritons (SPP) together with local surface plasmonic resonance (LSPR) tuned by the inhomogeneous structures and cavities contributed to this broadband absorption. Further working with this geometrical variation concept, our “wheel hub-like” structure achieved ultra-broadband absorption from 0.98 to 5 THz. Our investigations could provide an alternative design methodology for the design of metamaterial THz absorbers.

Helicopter Live-Line Work on 1000-kVUHV Transmission Lines

Live-line work methods using helicopters in the vicinity of 1000-kV transmission lines were simulated with finite-element modeling of the electric-field distributions. The effect of the approach path of the helicopter live-line work platform toward the energized conductor was computed. Predicted electric fields on the line worker head, body, arms, and legs were compared with measured results from a single-phase ultra-high-voltage (UHV) mock-up, and with calculation results from the simulation of an extra-high-voltage (EHV) 500-kV transmission-line geometry. The UHV conductor-to-work platform discharge occurred at a distance of about 2 m, in line with standard flashover models. Additional shielding efficiency of about 4 dB is recommended for the electrically conductive clothing when working on the UHV lines in China, compared to EHV lines.

Investigation of a stripline transmission line structure for gyromagnetic nonlinear transmission line high power microwave sources.

A stripline gyromagnetic nonlinear transmission line (NLTL) was constructed out of yttrium iron garnet ferrite and tested at charge voltages of 35 kV-55 kV with bias fields ranging from 10 kA/m to 20 kA/m. Typically, high power gyromagnetic NLTLs are constructed in a coaxial geometry. While this approach has many advantages, including a uniform transverse electromagnetic (TEM) mode, simple interconnection between components, and the ability to use oil or pressurized gas as an insulator, the coaxial implementation suffers from complexity of construction, especially when using a solid insulator. By moving to a simpler transmission line geometry, NLTLs can be constructed more easily and arrayed on a single substrate. This work represents a first step in exploring the suitability of various transmission line structures, such as microstrips and coplanar waveguides. The resulting high power microwave (HPM) source operates in ultra high frequency (UHF) band with an average bandwidth of 40.1% and peak rf power from 2 MW to 12.7 MW.

Low-disorder microwave cavity lattices for quantum simulation with photons

We assess experimentally the suitability of coupled transmission line resonators for studies of quantum phase transitions of light. We have measured devices with low photon hopping rates t/2pi = 0.8MHz to quantify disorder in individual cavity frequencies. The observed disorder is consistent with small imperfections in fabrication. We studied the dependence of the disorder on transmission line geometry and used our results to fabricate devices with disorder less than two parts in 10^4. The normal mode spectrum of devices with a high photon hopping rate t/2pi = 31MHz shows little effect of disorder, rendering resonator arrays a good backbone for the study of condensed matter physics with photons.