Transmission Line Structure Research Articles

Microwave Characterization of Gamma Ray Irradiated Thin Film Embedded and Non-embedded Nb Resonators

Gamma radiation effects on superconducting microwave transmission line structures, which may find use in future radiation challenging environments, such as satellites or accelerators have been investigated. Two versions of weakly coupled through-type Nb microstrip transmission line resonator material stack-ups were explored. In one version, the Nb signal trace was encapsulated with 20 µm of HD-4110 and in the other version the top Nb was not encapsulated. Exposure of the resonators to gamma radiation was performed for 28 days at room temperature in a sealed vacuum chamber using Co-60 as the gamma radiation source. The quality factors of the resonators were extracted at various cryogenic temperatures below the critical temperature of Nb and resonant frequencies up to 20 GHz. A large dose of gamma radiation used in this work showed a small change in the Nb superconducting properties.

Measurement Characterization of Band‐Pass NGD Time Domain of a 101O‐Topology Passive Circuit

AbstractThe negative group delay (NGD) is one of less familiar electronic functions. So far, the time domain (TD) experimentation of NGD circuits remains a challenging task. This paper investigates an innovative TD measurement of a band‐pass (BP) NGD passive circuit. The topology of the considered BP NGD distributed circuit constituted by transmission line structure having a 101O‐geometrical shape is introduced. After the design description of the 101O‐structure, the NGD response illustrates from simulation and measurement based on S‐parameters. The NGD center frequency, bandwidth, and value are approximately 3.6 GHz, 33 MHz, and −4.9 ns, respectively. The TD measurement experimentation is based on the sine carrier‐modulated microwave signal generation with 50‐ns duration. The 101O‐NGD circuit input and output signals are plotted with innovative synchronization. It was shown from the TD‐simulated and measured results that the BP NGD effect induces an output envelope about 4.2 ns advanced of the test signal input.

Devising a method for reducing active power corona losses based on changing the structural parameters of a power transmission line

This paper reports a study into the influence of the main design parameters of power transmission lines on energy losses associated with the corona discharge; a method has been devised to reduce them. The structure of the split-phase wire, the distance to the ground, and between the centers of the phases of the line are determined at the design stage. Based on these structural parameters, the value of specific energy losses associated with the corona discharge is calculated. Studying the impact exerted on the amount of losses by each structural parameter makes it possible at the design stage to determine the structure of a power transmission line (PTL) with low energy losses. Reducing energy loss when transporting it along the line is one of the most important issues in the strategy for the development of the energy industry at the stage of the "green transition". It has been established that most structural parameters have a weak effect on the values of corona losses, and, if there is a significant impact, the implementation of such solutions leads to a large increase in the cost of constructing an overhead transmission line. Based on the analysis of the results of calculations of corona losses in power transmission lines, it was determined that the corona losses in the middle phase of the transmission line are much greater than in the extreme phases. That has made it possible to devise a method for reducing power corona losses associated with the alignment of the capacities of all phases of PTL. This effect is achieved by calculating, based on the developed method, the splitting step of the middle phase of PTL. The calculation of the splitting step is based on the preliminary determination of the capacity of the extreme phases and the substitution of calculated values in the resulting expression for the splitting step. The possibility of such a reduction in corona losses should significantly increase the energy efficiency of AC power transmission lines, especially in areas with large periods of different weather that provoke the occurrence of a corona discharge on the wires of their phases. This circumstance causes an increase in this type of power loss.

Techno-Economic Comparisons of HVAC and Simultaneous AC-DC Transmission

Electric power consumption has been increasing rapidly across the globe; this increase specially accelerated in the last decade. Consequently, existing transmission lines are becoming overloaded beyond their power transfer capability. The inadequacy of the transmission lines has contributed to power interruptions and instability of the power system. Construction of new transmission lines can be a solution to mitigate these problems. However, to build the whole structure of a new transmission line, a huge investment is required. Besides this, environmental concerns would create further barriers that delay the accomplishment of the project. Therefore, the effective and quickest solution to tackle this problem is enhancing the power transfer capability and stability margin of existing transmission lines. This paper studied the techno-economic feasibility of converting an existing HVAC line into a simultaneous AC-DC power transmission system to enhance power transfer capability as well as to improve power system stability. Using the proposed method, the loadability of Tana Beles to Addis Ababa 400 kV, 476.2 km AC line has increased to more than double which is from 1091.66 MW to 2196.85 MW. The active power loss and corona loss evaluation of the two systems ensured that simultaneous AC-DC system is more efficient than HVAC system. It is also shown that the instability can be effectively improved by simultaneous AC-DC power transmission with fast DC power modulation. From the economic point of view, rather than constructing new HVAC line, converting existing HVAC line into simultaneous AC-DC transmission system has a price reduction of about 107,984,968.56 USD or 32.46% of the new HVAC line cost. Considering a 35-year project life cost analysis, it is observed that the life cycle cost of the simultaneous AC-DC transmission system is about 29.2% lower than the life cycle cost of a new 400 kV HVAC line. Thus, the designed simultaneous AC-DC power transmission system has better technical performance and also is less costly than constructing a new HVAC line.

Load and Resistance Factor Design for Serviceability Limit State of Laterally Loaded Drilled Shafts for Transmission Line Structures in Sands

AbstractLoad and resistance factor design (LRFD) for serviceability limit state (SLS) of laterally loaded drilled shafts was explored for transmission line structures in sand, and the SLS resistanc...

Built-in Ring Transmission Line Structure for Signal Integrity Optimization of PAM4 Signaling in PCBs

In this article, we propose a built-in ring differential transmission line for four-level pulse amplitude modulation (PAM4) signal integrity optimization. An optimized ring structure, which comes from the simplistic idea to leverage the voltage produced by near-end crosstalk inside the ring, is attached at the end of the transmission line to improve the eye diagram. Additionally, we introduce the comprehensive design guideline with analytically derived formulas that is beneficial to designers to obtain an accurate design without significant effort. The proposed structure is implemented on a 100 mm transmission line, six-layer printed circuit board. The proposed structure can achieve an improvement of up to 32.9% eye height with a 4 Gsps PAM4 signal.

Miniaturized spoof SPPs filter based on multiple resonators or 5G applications

This paper presents a novel and compact band-pass filter based on spoof surface plasmon polaritons (SSPPs) concept for 5G applications. In the first place, an SSPPs unit cell including L-shaped grooves and its equivalent circuit model are introduced. The obtained results from dispersion analysis shows that cut-off frequency of the cell can be considerably decreased thanks to its geometrical configuration. In the second place, a miniaturized SSPP transmission line (TL) consisting of the proposed unit cell with cut-off frequency of 29.5 GHz is designed. Two mode convertors have been employed for efficient connection between coplanar waveguides and SSPP TL. Moreover, a new method based on loading one unit cell of SSPP TL by stub resonators is proposed in order to block a specific frequency band. An equivalent circuit model for the cell with the resonators is proposed to predict rejected frequency range. Thereafter, as an example of our method, a SSPPs filter operating at 26.5–29.5 GHZ is designed by means of connecting stub resonators with different lengths to provide close resonance frequencies. The circuit model, full wave simulation, and measurement results are in a good agreement. The results of proposed groundless SSPP TL and filter structures are promising to make groundless 5G applications possible.

Power swing detecting method using principal components analysis

During power swing, the distance protection is easily affected by the oscillations of voltage and current which may lead to the mal-operation of the protection. Therefore, a power swing detecting unit is needed to cooperate with distance protection. In this paper, a power swing detecting method based on the difference between the structure of transmission line under fault situations and that under power swing situations is proposed. Principal component analysis is deployed to process the voltage and current data to extract the structure feature of the transmission line under power swing and fault situations. To test the effectiveness of the proposed method, a simulation system is built in PSCAD/EMTDC and different disturbance scenarios are done. The test results indicate that the proposed method can reliably distinguish between power swing and fault situations. Besides, a comparison between the proposed method and methods mentioned in other works is been done. The comparison results show that the proposed method has an advantage in operating speed and is less affected by measuring noise.

Calculation of Geomagnetic Induced Current Effect in Hybrid Energy Transmission Line With Hydrogen and Superconducting Cable

To build the hybrid energy transmission line with the HTS cables and liquid hydrogen pipelines is one of the solutions to the carbon emission problem. However, geomagnetic storms caused by solar wind can generate Geomagnetic Induced Current (GIC) and Pipe-Soil Potentials (PSP) offset in hydrogen-electricity hybrid transmission line, which will threaten the safe operation of the hybrid energy system. In order to evaluate GIC and PSP effects of hydrogen-electricity hybrid transmission line accurately, the mechanism of GIC generation in hydrogen-electricity hybrid transmission line is researched in this paper based on the structure of hydrogen-electricity hybrid transmission line and the occurrence process of geomagnetic storm. Then, the GIC calculation model of buried transmission line is established according to the Distributed Source Transmission Line (DSTL) theory. Finally, an example analysis is carried out, the calculation results are verified using the monitoring data, the influence of GIC on the hydrogen-electricity hybrid transmission line is recognized, and two prevention methods of GIC effect are obtained.

Crosstalk reduction using novel cross-shaped resonators with via fence in high-frequency transmission lines

PurposeThe purpose of this paper is to design a suitable guard trace to reduce the electromagentic interference between two closely spaced high frequency transmission lines. A novel cross-shaped resonator combined via fence is passed down to alleviate far-end and near-end crosstalk (NEXT) in tightly coupled high-speed transmission lines. The distance between the adjacent transmission lines is increased stepwise as a function of trace width.Design/methodology/approachA rectangular-shaped resonator via fence is connected by a guard trace has been proposed to overcome the coupling between the traces that is separated by 2 W. Similarly, by creating a cross-shaped resonator via fence connected by guard trace that reduces the spacing further by 1.5 W.FindingsA tightly coupled transmission line structure that needs separation by a designed unit cell structure. Further research needs to be conducted to improve the NEXT, far-end crosstalk (FEXT) and spacing between the transmission lines.Originality/valueThis study portrays a novel method that combines the resonators via fence with a minimum spacing between the tightly coupled transmission lines which reduce the NEXT and FEXT; thereby reducing the size of the routing area. The resultant test structures are characterized at high frequencies using time domain and frequency domain analysis. The following scattering parameters such as insertion loss, NEXT and FEXT of the proposed method are measured as 1.504 dB, >30 dB and >20 dB, respectively.

Tunable microwave plasma coaxial resonator

We report the design, performance, and characterization of a tunable microwave plasma resonator based on a coaxial transmission line structure operated at atmospheric pressure. The adjustable tuners of the compact device enable over 20 dB enhancement of reflection coefficient by counterbalancing the impedance mismatch. The in situ tuning capability can also neutralize the sudden change in impedance upon plasma discharge, elongating the microwave driven plasma plume. It is observed that the fine adjustment of two small bolts can maintain a high device efficiency up to 96% with plasma load impedance, and a wide operation range can be covered by a single device.

Corrosion analysis of angle steel used in 500kV transmission tower

Transmission tower is the load-bearing structure of high-voltage transmission line, and its stability is very important for the reliable operation of grid equipment. In recent years, the corrosion of transmission towers has become increasingly prominent due to long-term service in the harsh field, which seriously affects its service life. In this paper, the corroded angle steel of high-voltage power tower was studied by different physical and chemical testing methods such as macro inspection, metallographic analysis, mechanical property test, chemical composition analysis, energy spectrum analysisand scanning electron micrograph analysis. The result reveled that the galvanized protective layer of the angle steel was well preserved without corrosion damage, and the corrosion spot on surface of the tower materail was caused by the corrosion of other metal parts nearby and then the rusting outcome flowed with rain water to its surface.

Risk Assessment of Wind Swing Flashover of Transmission Lines Based on Matter-Element Extension Model

In extreme weather, the line trip-out events caused by the wind swing of the transmission line occur frequently, severely affecting the normal operation of the power system. Since the structure of the operating transmission line is difficult to be improved, wind swing flashover risk assessment is of great significance for the operating transmission lines. In this paper, a transmission line wind swing flashover risk assessment model based on the matter-element extension model is proposed. The analytic hierarchy process (AHP) and entropy weight method are applied to comprehensively calculate the weight value of the selected assessment index. This model can assess the early warning level of a certain tower unit in the transmission line. Finally, the feasibility and effectiveness of the proposed assessment model are verified by practical examples.

High-efficiency compact SRR–CSRR–SIW antenna based on CRLH-TL

A high-efficiency compact split-ring resonator (SRR)–complimentary split-ring resonator (CSRR)–substrate integrated waveguide (SIW) rectangular resonator antenna based on a composite right/left-handed transmission line is presented in this paper. A four-element rectangular CSRR structure is etched on the front of the antenna, and a four-element rectangular SRR structure is loaded on the back of the metal to correspond with each other, thus forming a composite right/left-handed transmission line structure. By meandering technique, a rectangular CSRR is etched on the front of the metal surface to reduce the frequency and realize the miniaturization of the antenna. Combined with SIW rectangular resonator, the high-efficiency compact antenna is finally realized. Simulation and experimental results show that the −10 dB impedance bandwidth of the SRR–CSRR–SIW rectangular resonator antenna is 5.26∼5.29 GHz (1.14%) and 9.07∼9.15 GHz (0.88%). The resonance frequency is 5.26 and 9.11 GHz. The gains are 5.33 and 5.25 dBi. The antenna can be widely used in WLAN and WiMAX.

Frequency dependent parametric radiation through a nonlinear fundamentally slow travelling wave structure

AbstractThis article presents a nonlinear leaky wave antenna (LWA) with frequency dependent parametric radiation based on a fundamentally slow‐wave transmission line (TL) structure. Unlike a conventional LWA that radiates at the excitation frequency, the radiation for the proposed travelling wave structure relies on the parametric frequencies based on the injected pump signals. The proposed nonlinear fundamentally slow wave structure utilizes a periodic sharply bend TL loaded by varactor diodes as nonlinear elements. By utilizing the n = −1 spatial harmonic, the fundamentally slow wave structure can enter the leaky wave region at higher frequencies, where the parametric radiation results from the bifurcation of the injected pump signals. Such TL‐based nonlinear LWA reduces the design complexity and fabrication difficulty. The resulting parametric frequency radiation can be used for beam steering, which provides additional degree of design freedom.

Experimental study on stability behavior of equal-leg angle steel columns

This paper presents a comprehensive experimental investigation on the behavior of single equal-leg angle steel columns under compression. A total of 648 specimens adequately cover the most frequently used angles in transmission towers were tested using elaborately designed apparatus of three typical end constraints. The experimentally obtained bearing capacities were then compared with the predictions of four commonly used design codes to determine the quantitative discrepancy and assess the applicability of the codes. All four predictions for the concentrically loaded specimens were found to be universally conservative, but the predictions varied considerably for mixed and eccentric conditions. The design of latticed steel transmission structures (ASCE) provides more precise predictions for concentric and mixed conditions, while the technical code for the design of tower and pole structures of overhead transmission line (DL/T (type a curve)) provides more accurate predictions for eccentric conditions. The predictions of DL/T (type b curve) are excessively conservative. Based on the comparative assessment and the experiment data, in accordance with the basic form of ASCE expressions, this paper proposes modified calculation formulae for stability factors and effective length coefficients for eccentrically loaded angles using least-square fitting. The accuracy and applicability of these formulae were verified through comparison.

A Compact, High-Efficiency, Reflectionless Leaky-Wave Antenna

A compact, high-efficiency leaky-wave antenna (LWA) is presented in this letter. Comprised by a novel periodic transmission line structure, the developed LWA could radiate its input power by a peak radiation efficiency of 93% with a compact size of 3.63λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> × 0.24λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> . Besides, the LWA exhibits good reflectionless performance characteristics from dc to 19 GHz. The equivalent circuit representations are utilized to reveal its operation mechanism. It is verified that the LWA operates as a slotted half-mode substrate integrated waveguide with high-efficiency leaky-wave radiation in the upper leaky band. Meanwhile, it could serve as a low-loss slow-wave transmission (SW-TL) line with spoof surface plasmon polariton structure in the lower band. For verification, an LWA prototype was fabricated and measured, which has experimentally confirmed its simulated radiation performances.

Resistance Factors for LRFD of Laterally Loaded Drilled Shafts in Sands Characterized for Transmission Line Structures

In this study, the resistance factors (RF) in the load and resistance factor design (LRFD) for the drilled-shaft foundation of transmission line structures subjected to lateral loads were investigated. Various load test results were collected to establish a database and used in the reliability analysis. The first-order reliability method (FORM) was implemented to calibrate RF for the Broms, Brinch-Hansen, and Prasad and Chari methods. Loads for transmission line structures were categorized and characterized statistically for calibrating RF. Uncertainties of the transverse tension load (TTL), wind-on-structure load (WLs), and wind-on-ice-coated conductor load (WLc), all dominant in transmission line structures, were evaluated. RF varied largely with nominal load ratios of WLs/TTL and WLc/TTL, which should be considered for the selection of RF in the design to maintain a consistent safety margin. Increases in nominal WLs and WLc induced higher RF while increasing nominal TTL yielded lower RF. The higher RF values obtained in this study were due to the low bias factors of wind-induced loads and the large load factors of the tension and wind loads. The equivalent factor of safety (FSeq) was evaluated and analyzed for the proposed RFs.

Radiation Effects on Thin Flexible Superconducting Cables

We have studied the effects of gamma radiation on flexible superconducting microstrip transmission line structures, to explore their suitability for use in harsh environments where they may be subjected to radiation. In this work, we used two conductor variants: one with only Nb and another with a conductor stack of Al/Nb/Al. Spin-on polyimide HD-4110 was used as the dielectric substrate and both the variants were encapsulated with a layer of HD-4110 to increase the robustness of the structure by protecting the superconducting trace from potential mechanical damage. The resonators were irradiated at room temperature in a vacuum sealed chamber at a pressure of 1E-6 Torr using cobalt-60 as a source of gamma radiation. Samples were exposed to doses up to 60.8 Mrad (608 kGy). Quality factors of the resonators were extracted in the frequency range from 2 to 20 GHz, at various cryogenic temperatures between 1.2 K and 4.2 K, using a closed-cycle cryostat. We observed a small increase in microwave loss for higher temperature ranges, which points to a small change in the superconducting properties of the conductors. The results of this work show that low mass, flexible superconducting cables may be suitable alternatives to bulky coaxial cables for signal transmission at cryogenic temperatures in extreme (radiation) environments.

The Expected Values of Self- and Mutual Impedances of Overhead Lines and Impacts of on Sags and Phase Conductor Imbalances: Part 2

This paper presents a method that finds the expected values of self- and mutual impedances of overhead lines with the uncertainties such as the ground resistivity, conductor characteristics, and transmission line structures. For this purpose, this study designs a stochastic random sampling method that removes the uncertainties. A finite element analysis method that includes a single logarithmic closed-form solution to Carson’s improper integral is adopted. The impact of an increase in sags and an imbalance in phase conductors on self- and mutual impedances is examined. As a result, the expected values of the self- and mutual impedances of an overhead line are evaluated. It is also shown that as the sag ratio increases, the self- and mutual impedances decrease.