Transmission Line Model Research Articles

Advanced Fault Detection in Power Systems Using Wavelet Transform: SIMULINK-Based Implementation and Analysis

Traditional methods struggle to find faults in power transmission lines. This paper presents an approach for short transmission lines, leveraging the power of wavelet transforms. Traditional methods analyze time-domain signals, limiting their ability to differentiate fault transients. Wavelet transforms, offering a combined time-frequency analysis, provide a deeper understanding of these transients. A detailed short transmission line model is built in SIMULINK. Diverse fault scenarios are meticulously simulated, and current signals undergo wavelet transform analysis. Key features extracted from the wavelet coefficients act as fingerprints of potential faults. These features are then utilized to develop a robust fault detection algorithm specifically designed for short transmission lines. The proposed method promises enhanced fault detection capabilities compared to existing techniques in this domain. The results, presented in subsequent sections, will shed light on the effectiveness of wavelet transforms in empowering smarter and more reliable transmission line operations.

Two-port quantum model of finite-length transmission lines coupled to lumped circuits

Two-port quantum model of finite-length transmission lines coupled to lumped circuits

An impedance matching section based on composite right/left‐handed transmission line model in viewpoint of phase shift and noise figure

AbstractIn this paper, a genetic‐based synthesis approach for an impedance matching section based on a composite right‐/left‐handed (CRLH) transmission line model called CRLH transmission line impedance matching section (CRLHTLIMS) in viewpoint of transmission phase shift and noise figure is newly presented. To find the unknown values of right‐/left‐handed inductances and capacitances of a CRLHTLIMS, a type of global optimization algorithm called continuous parameter genetic algorithm is used. The length, transmission phase shift, and noise figure of the CRLHTLIMS are computed by using simple equations. Different examples for a uniform CRLHTLIMS are given. According to the results, this approach is an easy and effective way for the synthesis of transmission line impedance matching sections in viewpoint of transmission phase shift and noise figure.

Method for lightning flashover types identification on transmission lines utilizing OPGW optical polarization state signal characteristics

The Optical Fiber Composite Overhead Ground Wire (OPGW) has undergone rapid development and has been extensively applied in the realm of intelligent power system status monitoring. This article conducts research on lightning signal waveform in optical fibers within the context of lightning fault location using the OPGW optical polarization state method. A transmission line model is simulated employing ATP-EMTP to capture electrical characteristics when lightning strikes the OPGW. Subsequently, by employing the Faraday magneto-optical effect principle, electrical signals are transformed into optical polarization states within the internal fibers of OPGW. Using such data, the optical signal propagation characteristics when lightning strikes OPGW are deduced. Finally, a method for discerning between induced lightning and direct lightning strikes through the analysis of time-frequency domain characteristics in OPGW. This method addresses the limitation of traditional OPGW lightning monitoring, which is unable to deduce electrical signals, thus achieving precise identification of lightning-induced transient faults in transmission lines.

Effects of low-frequency voltage on nonlinear standing wave excitation, plasma uniformity, and ion dynamics in dual-frequency asymmetric capacitive discharges

It is known that in very-high-frequency (VHF) capacitively coupled plasmas, the higher harmonics generated by nonlinear sheath motion can enhance the standing wave effect (SWE), which can lead to center-peaked plasma density profiles. In this work, an improved nonlinear electromagnetic model incorporating a transmission line model, an electron momentum balance model, a bulk plasma model, a collisionless nonlinear numerical sheath model, and an ion Monte-Carlo collision (MCC) model is developed to study the effects of low-frequency (LF) voltage VL on the nonlinear standing wave excitation, plasma uniformity, and ion energy and angular distribution functions (IEDFs and IADFs) in dual-frequency (DF) asymmetric capacitive argon discharges at relatively low pressure of 3 Pa. The plasma diffusion in the radial direction and ion dynamics within the LF oscillating sheath are self-consistently considered. The LF voltage VL at 2 MHz varies from 0 to 700 V while the HF voltage VH at 60 MHz is fixed at 100 V. Simulation results indicate that without the addition of an LF source (i.e. VL= 0 V), there are a considerable number of high-order harmonics with short wavelengths, leading to significant SWE and central peak in the radial plasma density profile. Nevertheless, the high-order harmonic excitations tend to be weakened and merely occur around the phase of the full LF sheath collapse due to a shorter characteristic damping time of the surface waves as VL increases. This, combined with increased surface wavelengths of both the driving frequency and the higher harmonics at a higher VL , leads to suppressed standing waves and improved plasma uniformity. Meanwhile, the simulations show that both the low and the high energy peaks of IEDF move towards higher energies, and the energy peak separation width ΔE becomes wider with the increase of VL . The IEDF at the radial center of the powered electrode exhibits a broader ΔE than that at the edge. For the IADF, an increased VL results in more ions incident on the electrode with a smaller deflection angle. Because of a thinner sheath and a higher sheath voltage at the electrode center, the peak value of IADF at the electrode center is greater than that at the edge.

Revitalizing Oxygen Reduction Reactivity of Composite Oxide Electrodes via Electrochemically Deposited PrOx Nanocatalysts.

Solid oxide fuel cells that operate at intermediate temperatures require efficient catalysts to enhance the inherently poor electrochemical activity of the composite electrodes. Here, a simple and practical electrochemical deposition method is presented for fabricating a PrOx overlayer on lanthanum strontium manganite-yttria-stabilized zirconia (LSM-YSZ) composite electrodes. The method requires less than four minutes for completion and can be carried out under at ambient temperature and pressure. Crucially, the treatment significantly improves the electrode's performance without requiring heat treatment or other supplementary processes. The PrOx-coated LSM-YSZ electrode exhibits an 89% decrease in polarization resistance at 650°C (compared to an untreated electrode), maintaining a tenfold reduction after ≈400h. Transmission line model analysis using impedance spectra confirms how PrOx coating improved the oxygen reduction reaction activity. Further, tests with anode-supported single cells reveal an outstanding peak power density compared to those of other LSM-YSZ-based cathodes (e.g., 418mWcm-2 at 650°C). Furthermore, it is demonstrated that multicomponent coating, such as (Pr,Ce)Ox, can also be obtained with this method. Overall, the observations offer a promising route for the development of high-performance solid oxide fuel cells.

Model and experimental analysis of influence of selected parameters of hydraulic line on displacement pump pressure pulsations damping

Among practitioners, the prevailing view is that the use of a discharge line made of an elastic hose allows users not only to isolate the pump unit from the rest of the system for transferred vibrations, but also to obtain the passive damping of pressure pulsation generated by the pump flow rate pulsation. The objective of the model and experimental research described in this article was to confirm or disprove the common opinion that a discharge line with an elastic hose is a sufficient element to damp the pressure pulsation caused by the displacement pump. The article presents experimental studies of the influence of various hydraulic lines on pressure pulsation damping. The research was carried out in the time and frequency domains. A mathematical model of a hydraulic long transmission line is also presented and an analysis of the parameters of hydraulic lines affecting the amplification or damping of pump pressure pulsations was carried out.

Research on Digital Twin Dynamic Modeling Method for Transmission Line Deicing System

A digital twin is recognized as a pivotal technology in a new type of power system monitoring as it provides an effective method for monitoring the vibration caused by ice shedding in overhead transmission lines. The digital twin model differs from traditional models in that it has the characteristics of precise mapping and real-time simulation. These emerging characteristics lead to urgent updating of the existing modeling approaches. Therefore, the current study proposes a dynamic digital twin modeling method for transmission line ice-shedding systems. In this approach, an analytical solution for conductor deicing oscillation is proposed to describe the span and tension unchanged in any time period and then segmented and iteratively corrected with measured time-varying parameters to implement real-time simulation functionality. A dynamic geometric model for transmission lines is proposed based on the Unity3D platform. In addition, a human-computer interaction visualization platform is proposed to display twin data, with the objective of realizing precise mapping of real transmission lines. Finally, an application of this systematic approach to continuous three-span wire demonstrates the feasibility and effectiveness of the proposed approach.

Fault Identification of UHVDC Transmission Based on DF-AD and Ensemble Learning

High-resistance ground faults are difficult to detect with existing ultrahigh voltage direct current (UHVDC) transmission fault detection systems because of their low sensitivity. To address this challenge, a straightforward mathematical method has been proposed for fault detection in UHVDC system based on the downsampling factor (DF) and approximation derivatives (AD). The signals at multiple sampling frequencies were analysed using the DF, and the AD approach was used to generate various levels of detail and approximation coefficients. Initially, the signals were processed with different DF values. The first, second, and third order derivatives of the generated signals were calculated by the AD method. Next, the entropy features of these signals were computed, and the Random Forest-Recursive feature elimination with cross-validation (RF-RFECV) algorithm was used to select a high-quality feature subset. Finally, an ensemble classifier consisting of Light Gradient Boosting Machine (LightGBM), K Nearest Neighbor (KNN), and Naive Bayes (NB) classifiers was utilized to identify UHVDC faults. The MATLAB/Simulink simulation software was used to develop a ±800 kV UHVDC transmission line model and perform simulation experiments with various fault locations and types. Based on the experiments, it has been established that the suggested approach is highly precise in detecting several faults on UHVDC transmission lines. The method is capable of accurately identifying low or high resistance faults, irrespective of their incidence, and is remarkably resistant to transitional resistance. Furthermore, it exhibits excellent performance in identifying faults using a small sample size and is highly reliable.

Electrochemical impedance spectroscopy analysis of dye-sensitized solar cells composed of electrospun composite photoanodes: A comparative study of natural and synthetic sensitizers

In this study, a transmission line model is applied to the electrochemical impedance spectroscopy (EIS) data of the fabricated dye-sensitized solar cells (DSSCs) to evaluate the charge transfer mechanism through the cells. Natural dye from black plum (Syzygium cumini) fruit was used as a cell sensitizer (SC-DSSC) and compared its photovoltaic and electron transport capabilities to those of a cell using a synthetic sensitizer (N719-DSSC). TiO2/ZnO electrospun composite nanofibers were used as the semiconductor layer of the photoanode to enhance electron transfer. The EIS analysis revealed the role of electron resistances through shant, interfaces, and electrolyte solution by measuring the electron transfer kinetic parameters of each element. Based on the results, the SC-DSSC and N719-DSSC are appropriate photovoltaic cells because their ratios of effective electron diffusion length to photoanode thickness are 12.5 and 2.8, respectively. The EIS analysis showed that the electrospun composite nanofiber coated on the photoanode reduces the semiconductor layer's electrical resistance to the cell's total resistance. The extracted natural dye also boosted electron lifetime to 3.68 ms and diffusion coefficient to 54.3×10−6 m2/s while minimizing back-electron recombination at the semiconductor-electrolyte interface. Moreover, the semiconductor-electrolyte interface resistance is over 85% of the overall resistance for both DSSCs and controls electron transport through the cells, which is due to the dye-semiconductor binding intensity. Based on the photovoltaic data, the SC-DSSC cell efficiency was lower than N719-DSSC which is attributed to its higher electron transfer rate-controlling element. Thus, enhancing dye-semiconductor interactions will decrease the rate-controlling impedance and enhance cell performance.

A pilot protection based on low frequency component model for HVDC transmission lines

AbstractReliable and fast identification of high‐voltage direct current (HVDC) transmission line faults is important to the safety of power system. In traditional DC transmission line protection, differential protection is invulnerable to high fault resistance, but it needs long time delay for the influence of distributed capacitance current. In order to solve this problem, a novel pilot protection is proposed. The characteristics of the voltage and current processed by low‐pass filter under different fault conditions are analysed, and based on it the protection criteria is proposed. When external fault occurs, it reflects the line capacitance where the first forward fault traveling wave passes, which is increasing until equal to the whole line capacitance, then remains constant. However, when internal fault occurs, its value is negative in the initial stage, and after that its value is very different from the whole line capacitance. The analysis proves that this pilot protection method has fast operation speed, and can be applied for a relatively long period of time. What is more, the applicable time of superposition principle is considered in the analysis, which is not considered in many literatures. An UHVDC system is modelled for simulation in PSCAD/EMTDC, and the correctness and effectiveness of the proposed scheme is verified.

Detection of a Cobalt-Containing Interphase at the Li6PS5Cl-NMC111 Interface by In Situ μXANES and EIS

Sulfide electrolyte all-solid-state lithium batteries (ASLBs) with uncoated Li-NixMnyCo1−x−yO2 (NMC) cathodes suffer from a large capacity loss during initial cycling and an increase in cell impedance. Decomposition reactions are known to occur at the Li6PS5Cl-NMC111 interface due to incompatibility between the two materials. If a stabilizing coating is applied to the NMC, it delivers full capacity during initial charge. However, the loss in capacity during discharge still occurs. The interface was studied by μXANES and through EIS analysis. A chemically-formed interphase was detected by μXANES, evident from reduction of Co at an uncoated NMC particle surface. This interphase was produced by decomposition at rest. To study the effect of the interphase on electrochemically active surface area, piecewise in situ EIS was performed and the data was modeled using a transmission line model (TLM). The charge transfer resistance RCT was used to estimate the volume specific active surface area (aact). The median value for aact was 296 cm−1, a factor of 7.5 lower than the theoretical value of 2216 cm−1. This provided evidence of a lower electrochemically active surface area in the ASLB.

A light Darwin implementation of Maxwell’s equations to quantify resistive, inductive, and capacitive couplings in windings

High operating frequency is an enabler of high key performance indicators, such as increased power density, in electrical machines. The latter enhances the cross-coupling of resistive–inductive–capacitive phenomena in windings, which may lead to significant loss in performance and reliability. The full-wave Maxwell’s equations can be employed to characterize this coupling. To address the frequency instability that arises as a result, a simplification known as the Darwin formulation can be employed, where the wave propagation effects are neglected. Still, this modification is prone to ill-conditioned systems that necessitate intricate pre-conditioning and gauging steps. To overcome these limitations, a fast 2D formulation is derived, which preserves the current continuity conservation along the model depth. This implementation is validated experimentally on a laboratory-scale medium-frequency transformer. The computed impedances for the open- and short-circuit modes of the transformer are validated using measurements and compared with the multi-conductor transmission line model that is widely adopted for the analysis mentioned above. The developed formulation demonstrates a high accuracy and outstanding frequency stability in a wide frequency range, becoming an efficient and computationally light method to investigate the interconnected resistive, inductive, and capacitive effects in windings.

Thermal annealing induced graphite/diamond structure processed by high-voltage hydroxide ion treatments

Ohmic contacts with low specific contact resistance are necessary for fabrication of diamond electronic devices. This work reports that graphite/diamond ohmic contacts can be obtained by thermal annealing of diamond, patterned by hydroxide ion treatment. Surface graphitization of diamond is achieved through rapid thermal annealing at 1050 °C in vacuum. The thickness of graphite layer is found to be dependent on the duration of annealing with an approximate rate of 3.3 ∼ 3.6 nm/minute. The alteration in surface structure is analyzed using Raman spectra, showing a continuously enhanced G peak with increasing annealing time. Early stages of graphitization are discovered by X-ray photoelectron spectroscopy, after annealing diamond samples for merely 0.5 ∼ 2 min. Additionally, a distinct atomic interface between graphite and diamond is observed via cross-sectional transmission electron microscopy. Further, the surface graphite is selectively etched by hydroxide ion treatments, protected by gold patterns. In the end, the specific contact resistance of the graphite/diamond contact is determined to be 2.53 × 10-4 Ω cm2 employing the transmission line model.

Dielectric Terahertz Characterization of Microwave Substrates and Dry Resist

Microwave fabrication and design techniques are commonly employed in the terahertz (THz) domain. However, a characterization of commercially available microwave dielectric materials is usually lacking at sub-THz and THz frequencies. In this work, we characterized four substrates by Rogers and an Ordyl dry resist between 0.2 and 2 THz, in terms of relative permittivity and loss tangent. The reflectance spectra of the investigated materials were retrieved by means of THz time-domain spectroscopy in reflection mode and post-processed according to a transmission-line model in which the materials’ parameters are fit by means of the Havriliak–Negami variation of the Debye model. The relative permittivity of the investigated materials showed negligible frequency dispersion in the sub-THz and in the THz range. In terms of the loss tangent, the Rogers substrates revealed a more pronounced frequency-dispersive behavior among different materials, as dictated by the Havriliak–Negami model. The Ordyl resist was dispersive in the 0.2–1.2 THz range and presented a nearly constant loss tangent value between 1.2 and 2 THz. These results may represent a reference for the development of innovative components for THz and sub-THz emerging applications.

TiO2 nanocone photoanodes by Ar ion-beam etching and physics-based electrochemical impedance spectroscopy

TiO2 nanocone (NC) arrays were produced by argon ion beam etching of nanotube (NT) arrays prepared by Ti anodizing. The anti-reflection performance of NC arrays was enhanced by anodizing a 1 μm-thick Ti film deposited on a p-type silicon substrate. The NC morphology was maintained upon heat treatment up to 400 °C, where the anatase phase was formed. Higher temperature treatments resulted in agglomeration and the formation of the rutile phase. The photoelectrochemical performances of the NC and NT arrays on Ti/Si substrates and the NTs on the Ti disk, both annealed at 400 °C, were compared. The photocurrent curves of the samples on Ti/Si were qualitatively different from NT on Ti. Impedance spectroscopy revealed that the response is dominantly from the p-Si substrates, which can be almost ideally described by the diffusion-recombination governed by the minority electronic carriers. NT on Ti can be characterized by the transmission line model for nanoporous electrodes where the transverse and interfacial capacitances are described by Havriliak-Negami capacitance functions with fixed exponents of either 1 and ½ at high- and low-frequency limits. The model then powerfully deconvolutes TiO2 response from the limited information at the low frequencies for NT and NC on Ti/Si, which can be related to the photoelectrochemical performance. Mott-Schottky analysis of well-defined capacitance parameters from the Havriliak-Negami function allows the physics-based description of the spatially and energetically distributed dopant defects in nanostructured materials.

A Design Method and Application of Meta-Surface-Based Arbitrary Passband Filter for Terahertz Communication.

A meta-surface-based arbitrary bandwidth filter realization method for terahertz (THz) future communications is presented. The approach involves integrating a meta-surface-based bandstop filter into an ultra-wideband (UWB) bandpass filter and adjusting the operating frequency range of the meta-surface bandstop filter to realize the design of arbitrary bandwidth filters. It effectively addresses the complexity of designing traditional arbitrary bandwidth filters and the challenges in achieving impedance matching. To underscore its practicality, the paper employs silicon substrate integrated gap waveguide (SSIGW) and this method to craft a THz filter. To begin, design equations for electromagnetic band gap (EBG) structures were developed in accordance with the requirements of through-silicon via (TSV) and applied to the design of the SSIGW. Subsequently, this article employs equivalent transmission line models and equivalent circuits to conduct theoretical analyses for both the UWB passband and the meta-surface stopband portions. The proposed THz filter boasts a center frequency of 0.151 THz, a relative bandwidth of 6.9%, insertion loss below 0.68 dB, and stopbands exceeding 20 GHz in both upper and lower ranges. The in-band group delay is 0.119 ± 0.048 ns. Compared to reported THz filters, the SSIGW filter boasts advantages such as low loss and minimal delay, making it even more suitable for future wireless communication.

Design of a Dual-Band Printed Antenna for Modern Wireless Communications and Internet of Things Applications

Wireless technology is increasingly influenced by the advanced technological development of antennas. With the rapid expansion of Internet of Things ( IoT) application in the contemporary communication networks, the demand for small printed antennas is increasing, due to their small size and ease of design and manufacture to suit their various application. In this paper, the antenna is designed which is operating at two different frequency bands 2.40GHz and 5.78GHz. The design parameters of the antenna have been calculated using the transmission line model, and an antenna design program has been used for the simulation process is HFSS ( High frequency simulator structure ) tool, which is based on Finite Element Method (FEM). In this work, the proposed slot dual band patch antenna is implemented using FR4 substrate material with a thickness 1.6mm and relative permittivity 4.4. The size of the proposed antenna is just (28 × 27.7mm). The proposed antenna has Omni-directional radiation patterns on most of the operating band. The dual band antenna is designed by adding a slot to the top of the radiated patch. Therefore, the proposed dual- band antenna shows good performance, which is suitable for modern wireless communications and Internet of Things (IoT) applications. The measurements are found to be in good accordance with the simulated results.

Ensemble learning based transmission line fault classification using phasor measurement unit (PMU) data with explainable AI (XAI).

A large volume of data is being captured through the Phasor Measurement Unit (PMU), which opens new opportunities and challenges to the study of transmission line faults. To be specific, the Phasor Measurement Unit (PMU) data represents many different states of the power networks. The states of the PMU device help to identify different types of transmission line faults. For a precise understanding of transmission line faults, only the parameters that contain voltage and current magnitude estimations are not sufficient. This requirement has been addressed by generating data with more parameters such as frequencies and phase angles utilizing the Phasor Measurement Unit (PMU) for data acquisition. The data has been generated through the simulation of a transmission line model on ePMU DSA tools and Matlab Simulink. Different machine learning models have been trained with the generated synthetic data to classify transmission line fault cases. The individual models including Decision Tree (DT), Random Forest (RF), and K-Nearest Neighbor (K-NN) have outperformed other models in fault classification which have acquired a cross-validation accuracy of 99.84%, 99.83%, and 99.76% respectively across 10 folds. Soft voting has been used to combine the performance of these best-performing models. Accordingly, the constructed ensemble model has acquired a cross-validation accuracy of 99.88% across 10 folds. The performance of the combined models in the ensemble learning process has been analyzed through explainable AI (XAI) which increases the interpretability of the input parameters in terms of making predictions. Consequently, the developed model has been evaluated with several performance matrices, such as precision, recall, and f1 score, and also tested on the IEEE 14 bus system. To sum up, this article has demonstrated the classification of six scenarios including no fault and fault cases from transmission lines with a significant number of training parameters and also interpreted the effect of each parameter to make predictions of different fault cases with great success.

Boosting the performance of low‐cost eco‐friendly pyramidal absorbers with a Salisbury screen

AbstractInstead of using expensive highly performing conventional pyramidal absorbers, in some cases, the use of absorbers based on very cheap eco‐friendly materials is an attractive alternative. The authors introduce a novel technique to improve the absorption bandwidth of these intrinsically low‐quality absorbers by adding a Salisbury screen at the base of the pyramidal absorber, which adds two extra design parameters. The first is the resistive sheet surface impedance, and the second is the resonance frequency of the Salisbury screen. By tuning these two parameters, better impedance matching can be obtained. This is verified with the help of a transmission line model, full‐wave simulations, and measurements. The method is applied to two different lower‐quality absorbers found in the literature. In the first absorber, the operating bandwidth is increased at the lower frequency side by 40%, and in the second one, this is about 90%. Finally, a prototype of an eco‐friendly combined absorber is designed and fabricated. The measurement validates the expected behaviour.