Length Of Transmission Line Research Articles

Time-Frequency Transformation Technique with Various Mother Wavelets for DC Fault Analysis in HVDC Transmission Systems

HVDC transmission has become a cost-effective option for transferring high voltage over greater distances. Protecting an HVDC transmission line is more challenging than protecting an AC transmission line due to its low impedance and absence of zero crossing DC current. Power electronic devices have finite overload capability, and standard relays are ineffective for HVDC line protection. Heavy current is generated by DC faults in HVDC (T/L), hence it is necessary to treat DC line faults in short, medium, and long HVDC (T/L) systems with different fault resistance. It is crucial to research fault detection methods based on time-frequency analysis by choosing appropriate algorithms using various (MW) methodologies for short, medium, and long HVDC transmissions at various fault resistances in order to protect the HVDC system. In this work, we examine how the length of an HVDC transmission line and fault resistance at both sides (inverter and rectifier) affects the selection of suitable mother wavelets for DC fault, using mean parameter and time-frequency transformation. SimPower System of Matlab is used to evaluate the impact of HVDC transmission line length and fault resistance on the selection of suitable mother wavelets. Simulation results show that Coif3 is an ideal wavelet for fault detection in medium transmission lines at different fault resistances. On the other hand, Rbio3.1 is more suitable for fault detection in long transmission lines at various fault resistances. For short and medium HVDC transmission lines, different mother wavelets were found to be suitable at different fault resistances. Therefore, it is essential to carefully consider the specific characteristics of the transmission line and the fault scenario when selecting a mother wavelet for accurate fault location.

Dynamic Interactions between Parallel Grid-Forming Inverters in a Microgrid

The potential instability issues caused by the dynamic interactions between parallel grid-forming inverters are examined. The approach adopted for analysis is s-domain admittance-based eigenvalue and mode shape analysis. This admittance is based on a five-node circuit diagram after the conversion of each electric circuit element and inverter control unit into impedance models. Eigenvalue analysis results show that unstable resonance modes may exist due to the interactions of two parallel inverters. Impacts of transmission line length, the converter control’s virtual impedance unit, and the voltage feed-forward unit are examined via the eigenvalue and mode shape analysis. The results show that the virtual impedance control has a negligible influence on the resonance while the voltage feed-forward unit stabilizes the resonance. Finally, the stability analysis is validated using electromagnetic transient (EMT) simulations.

Balanced single/dual band trisection filters

ABSTRACT This work presents balanced microstrip filters with asymmetrical frequency response based on a balanced trisection topology. The proposed balanced trisection topology has the feature of being used in single and multiband microwave filters. In this work, in order to test the topology flexibility, we address two applications, one for a single-band filter and the other for a dual-band filter. This topology introduces TZs on either side of the passband edges, improving the selectivity on one side of the passband. The non-adjacent resonators of the single-band trisection balanced filter are based on a Pi-network balanced resonator which is composed by six transmission lines (TLs) and two inductors (Ls). The differential-mode (DM) and common-mode (CM) resonances can be chosen independently with a proper selection of the impedances and the electrical lengths of TLs in order to have high DM stopband and intrinsic high common mode rejection (CMR). The Pi-network was modified and analyzed under the even and odd mode technique to have a dual-band behavior. Good agreement between simulation and measurement was achieved.

Influence of off-grid/grid-connected operation on stability of large-scale photovoltaic system

Off-grid or grid-connected operation of large-scale photovoltaic system may cause stability problems. When the system performs off-grid operation, energy storage, as balance node, regulates power and frequency, then also influences stability. Under grid-connected operation, the external power system balances power and frequency regulation, and energy storage only equilibrium wave power. Although a detailed model for a single photovoltaic generation system has been established, the connection of numerous photovoltaic units is difficult to model and simulate, and it can easily cause dimension disaster. In order to analyze stability effectively of off-grid/grid-connected operation of large-scale photovoltaic system, we first establish the equivalent model of a photovoltaic farm through the method of dynamic aggregation of wind turbines, and then obtain indicators affecting the stability considering the reactance matrix of the transmission line. When the real part of the oscillation mode sensitivity index is greater than zero, oscillation mode approaches the imaginary axis, indicating that the PV system stability deteriorates. Conversely, the PV system is regionally stable. Finally, the effects of the number of photovoltaic units and transmission line length on stability are theoretically analyzed, and the theoretical derivation is validated through simulations. More PV units and a longer transmission line increase the likelihood of instability through the sensitivity of the oscillation mode.

A dynamically tunable discrete-element transmission line pulse generator

The Frozen Wave Generator (FWG) is a megawatt-class radio frequency pulse forming network that converts DC input up to ones-of-GHz center frequency (fc) by superposing an ensemble of alternately charged reactive storage elements. In this work, we demonstrate an all-solid-state, dynamically tunable, and chirp-capable FWG using the lumped-element transmission line (LETL) topology. A 12-segment LETL-FWG switched using a MOSFET is demonstrated and directly compared with a literature standard coaxial-based system. Comparison metrics for pulse width (tpulse) are studied as a function of the transmission line length and respective LC parameters. The chirp- and dynamic-tuning-capability as well as the high volumetric power density of the system are demonstrated by comparing the predicted and measured bandwidth, rise-time, pulse width, and delay-time from a 7.5 × 30 × 3 cm3 printed circuit board. The experiment resulted in dynamically tunable pulse trains with 15–24 ns pulse widths (40–80 MHz) and >35% conversion efficiency and an ∼80% reduction in volume compared to vacuum-relativistic pulsers in the same peak power class.

Impact of large-scale photovoltaic-energy storage power generation system access on differential protection of main transformer under symmetrical faults

The low voltage ride-through (LVRT) requirements demand large-scale photovoltaic (PV) power generation system remain connected to the grid during faults. It results in considerable impact on the characteristics of fault current. This paper combines charge-discharge characteristics of the energy storage (ES) with PV generation system to enhance the LVRT capability. Based on the inverter control strategy and specific LVRT requirements, fault current characteristics of the PV-ES power generation system is discussed in this paper. In order to analyze the fault characteristic, the fault current expression as three-phase short-circuit faults occurs on both sides of the main transformer is calculated. Furthermore, taking the winding connection of the transformer into account, the ratio of differential current to braking current is further derived to find out the factors influencing the performance of the transformer differential protection. It is found that factors influencing the transformer differential protection include the rated capacity of the PV-ES generation system, fault severity, the length of transmission line and so on. And as the rated capacity of the PV-ES power generation system increase, the transformer differential protection would experience reduced sensitivity or even do not trip. The findings of this paper can lay a foundation for further improvement of the transformer differential protection. The elaborate performance evaluation of transformer differential protection, including the operation condition of the second harmonic braking element, is presented and verified by simulation using MATLAB/Simulink.

ADAPTIVE AUTOMATIC VOLTAGE REGULATION IN THE ELECTRICAL GRID USING SINGLE-PHASE LINEAR VOLTAGE REGULATORS

Ensuring the required voltage level in rural electric grids is a necessary condition for the efficient operation of agricultural enterprises and comfort in rural life. The overstated length of rural power transmission lines leads to excessive voltage deviations at consumer inputs. The existing methods and technical means of voltage regulation do not in all cases allow to provide the necessary level of voltage in the grid. (Research purpose) The research purpose is developing a method and device for phase-by-phase automatic voltage regulation in the electrical grid using linear voltage regulators, to illustrate the possibilities of its application. (Materials and methods) Used general scientific research methods, methods: literary review, theory of automatic control, electrical engineering. We analyzed the literary sources. We have studied the methods and technical means of voltage regulation in electrical grid. (Results and discussion) A new method and device for adaptive automatic voltage regulation in the rural electrical grid with the use of a separate phase-by-phase installation of linear voltage regulators have been proposed. We considered an example of the implementation of the method in a rural electrical grid with an uneven load in phases. (Conclusions) It was revealed during the review of voltage regulation methods that adaptive automatic control methods are promising, involving control of voltage deviation at consumer inputs and determination of the regulation coefficient based on this. It was determined that the use of the proposed method and device provides a normalized voltage value at consumer inputs by means of adaptive automatic phase-by-phase voltage regulation in the electrical grid with separately phase-by-phase linear regulators controlled by an adaptive automatic voltage regulation system that generates control commands based on data processing from voltage sensors installed at control points of the grid, including at consumer inputs.

Research on online monitoring system of fusion transmission line based on multi-source data

With the rapid development of China’s national economy, the length of transmission lines is increasing steadily, and the operating status of high-voltage transmission lines is directly related to the operational safety and efficiency of the entire power grid, but the sensors of transmission lines can only monitor one type of fault, and the fault analysis has limitations, which makes it impossible to comprehensively judge the operating status of transmission lines. This paper designs a transmission line online monitoring system based on multi-source data fusion, which adopts the improved Kalman filter algorithm. The data collected by the front-end system is fused, analyzed and shared in real time through the edge computing fusion terminal, so as to achieve a comprehensive judgment on the operation of transmission lines and improve the safe and stable operation level of transmission lines.

Deep neural learning based optimization for automated high performance antenna designs

The present paper introduces an optimization-oriented method here practiced for designing high performance single antennas in a fully automated environment. The proposed method comprises two sequential major steps. The first one devotes configuring the shape of antenna and determining the feeding point by employing the bottom-up optimization (BUO) method. In this algorithm, the number of microstrip transmission lines (TLs) used to model the radiator is increased consecutively and the shape of the antenna is revised up to finding the initial satisfying results. Secondly, for determining the best design parameters of the configured antenna shape in the first step (i.e., width and length of TLs), deep neural network (DNN) that is based on Thompson sampling efficient multi-objective optimization (TSEMO) is applied. The recommended optimization method is successfully attracted as a problem solver for designers to tackle the subject for antenna design such as the complexity and large dimensions of structures. Hence, the main advantage of the implemented optimization method in this article is to noticeably decrease the required designer’s involvement automatically generating valid layouts. For validating the suggested method, two wideband antennas are designed, prototyped and subjected to experiment. The first optimized antenna covers the frequency band 8.8–10.1 GHz (13.75 % bandwidth) characterized by a maximum gain of 7.13 dB while the second one covers the frequency band 11.3–13.16 GHz (15.2 %) which exhibits a maximum gain of 7.8 dB.

Ultra‐miniaturised C ‐band power divider using capacitive loading and defect grounded structures

This article reports a compact Power Divider design employing a combination of a capacitive load and Defect Grounded Structures (DGS) on GaAs substrate for MMIC technology in the C band. The integration of these two techniques offers a compact power divider with a decrease in quarter-wave transmission line length from λ/4 to λ/16 and harmonic suppression up to 50 GHz. Capacitive loading reduces the size, and DGS improves harmonic suppression and further decreases the size of the structure. The designed power divider is simulated in Ansys HFSS 19.2 and provides a return loss of 25.66 dB, with an insertion loss of 3.01 dB at 5.4 GHz and isolation of 13.37 dB. Isolation is further improved to 30.89 dB using a parallel combination of resistor and capacitor in the isolation network. The prototype of the proposed circuit has been fabricated using RT/duroid® 5880 as substrate. Measurement results show insertion loss and return loss of 3.02 and 23.46 dB. Isolation of 22.43 dB was achieved. The proposed design provides a size reduction of 73.7% with harmonic suppression up to 10th harmonics by 10 dB, making it suitable for high-performance monolithic microwave integrated circuits (MMIC).

100-MW-Level Experiments of a Gyromagnetic Nonlinear Transmission Line System

The wideband high-power microwave systems have the advantages of wide energy spectrum, electron beam independence, compactness, and low cost. The gyromagnetic nonlinear transmission line (GNLTL) has drawn much attention for its potential as a novel solid-state, frequency-agile, and compact wideband source. The working mechanism of GNLTL is different from that of the traditional electric vacuum tubes, and the strong dispersion and nonlinear characteristics make it difficult to be accurately theoretically calculated and simulated. In this article, a 100-MW-level GNLTL system based on a Tesla-type driver was designed and constructed. A series of test experiments were then carried out to investigate the effects of different configurations, including delay line length, ferrite cores’ assembly orientation, transmission line length, bias magnetic field magnitude, and excitation voltage. The changing laws of the key parameters of the output microwaves including the peak power, modulation depth, center frequency, and percentage band are summarized and the underlying physical mechanisms are analyzed. The results may be instructive for the predesign of GNLTLs, especially for the devices operating at high power. In addition, a multiple center frequency points’ phenomenon was discovered in the output signal, which may bring new application possibilities for GNLTL.

Design and Performance of a Ferrite Transmission Line Sharpener for Trigger Generator Used in FLTD

Tens of thousands of gas switches in fast linear transformer driver (FLTD) need to be switched ON synchronously, which requires gas switch triggers with fast rise time and low jitter. At present, the pulse rise time of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 100$ </tex-math></inline-formula> -kV gas switch trigger is often sharpened by a gas switch. Although the gas switch sharpener can reduce pulse rise time, it is difficult to control the pulse jitter because of the dispersion of gas discharge. Using a ferrite nonlinear transmission line to steepen pulse rise time has been widely used in high-power microwave fields. In this article, a ferrite transmission line is proposed to replace the gas switch sharpener. By establishing the simulation model of the ferrite transmission line, the effects of pulse amplitude, transmission line length, and structural parameters on the sharpening rise time are analyzed. An experimental platform was established to test the sharpening performance of two different structural ferrite transmission lines. The test results show that the ferrite transmission lines can reduce the trigger pulse rise time from 124 ns to less than 16 ns, and the jitter of the whole trigger device is less than 2.5 ns, which can be used to replace the gas switch sharpener.

Communication—Novel Verification of an Impedance Model Considering Electrode Porosity and Li-Ion Diffusion in Lithium-Ion Batteries

A model composed of a transmission-line structure with a Randles-type circuit is regarded as a useful model for lithium-ion battery electrodes. However, when used for the impedance fitting analyses, the parameters needed to be given for calculations, the parameters to be practically obtained, and the accuracy of the obtained values have not been clarified yet. Herein, we reveal that parameters in this model can practically be obtained simultaneously from the impedance fitting calculations when the values of transmission-line length and diffusion length are provided. Then, their accuracy is investigated by examining the correlations between the parameters in the fitting calculations.

Transmission Lines Impedance Fitting Using Analytical Impedance Equation and Frequency Response Analysis

Rational function approximation is commonly used to fit the transmission line impedance over a wide frequency range. Nevertheless, it is computationally costly and challenging to implement in practical applications due to the high number of approximations required to fit the impedance curve for the high-frequency range. Therefore, a novel fitting method of multiconductor transmission line (MTL) based on the analytical impedance equation of a transmission line using the impedance frequency response measurement is presented in this paper. The proposed fitting method is a function of the transmission line length since it is based on the analytical impedance equation of a finite transmission line. Furthermore, the proposed model uses a constant set of equations and calculated parameters to fit the impedance frequency response for a wide range of frequencies. Moreover, the proposed model parameters are calculated using derived resonance equations and the impedance frequency response measurement. In addition, an algorithm is developed to further fit the proposed model to the impedance frequency response measurement of the transmission line. MTL impedance frequency response is measured using a real-time digital simulator (RTDS). To ensure the accuracy of the proposed model, a comparison between the proposed model and vector fitting (VF) is presented.

Ge p-i-n Photodiode as 60-Gbit/s Optical NRZ-OOK Data Receiver

By the pulsed, heterodyned, and modulated laser illuminations, the impulse and noise responses of O-band germanium (Ge) p-i-n waveguide photodetector (WPD) with different transmission-line designs are characterized for receiving the NRZ-OOK data beyond 60 Gbit/s. The Ge lateral p-i-n WPD reveals an optical responsivity of 0.63-0.74 A/W at 1327.5 nm under −1.8 V bias.The noise equivalent power (NEP) is increased from 0.11 to 0.2 pW/√Hz by shrinking the transmission-line contact electrode length from 280 to 80 μm. After optimizing the transmission-line designs with shorter length and less right corner number (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⊥</sub> #) between PD and bonding pad, the Ge lateral p-i-n WPD improves its RLC response to suppress its switching time with broadened receiving bandwidth. Shrinking the connecting transmission-line length from 280 μm to 80 μm extends the flattened S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> spectral response from 51 to 57 GHz by up-shifting the inductor inductor-induced frequency notch from 58 to 61 GHz, as confirmed by the shrank spiral curve in the Smith chart with the decreased inductance by shortening the transmission-line electrode. The dual-wavelength optical heterodyne analysis demonstrates that the Ge p-i-n WPD significantly improves its analog receiving bandwidth from 29.5 to 44.3 GHz measured at 6-dB decay. The sub-ps laser pulse illumination observes that the Ge p-i-n WPD response shortens its impulse response from 23.14 to 19.92 ps by reducing the contact inductor length (by 200 μm) and right corner number (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⊥</sub> #) from 4 to 2) of its electrode. When receiving the optical NRZ-OOK data stream, the long-electrode (L = 280 μm, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⊥</sub> # = 4) device reveals only 53-Gbit/s receiving performance. The short-electrode (L = 80 μm, C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⊥</sub> # = 2) Ge lateral p-i-n WPD with significantly reduced inductance successfully receives the NRZ-OOK data beyond 56 Gbit/s and 60 Gbit/s under error-free communication criterion of BER<10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−12</sup> and BER<10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> , respectively.

Concise or comprehensive? Predictors of impact assessment choices for electric transmission line projects.

Environmental impact assessment (EIA) procedures required in the United States and many other countries are often highlighted as a major hindrance to timely and efficient deployment of critical infrastructure projects. Under the U.S. National Environmental Policy Act, a more extensive environmental impact statement (EIS) review can take several more years and cost much more than a succinct environmental assessment (EA). This not only affects the project in question, but also likely informs how-or whether-additional projects are pursued. Thus, understanding key predictors of the EA versus EIS choice sheds light on supply-side considerations affecting infrastructure deficits. Using the case of NEPA reviews conducted for 244 transmission line projects between 2005 and 2018 by two U.S. federal agencies in the western United States, the Bureau of Land Management (BLM) and Department of Energy (DOE), this addresses the following question: What project features most predict whether EA or an EIS is used to assess a transmission line project? Drawing upon NEPA assessment guidance and agency NEPA records, we use a regression classification tree to analyze how protocols and project attributes relate to assessment choice. The result is essentially a null finding: transmission line length is by far the most important predictor of whether a project receives an extensive EIS or a shorter EA, with little predictive value provided by other attributes. While absolute project size undoubtedly influences impacts, the lack of further differentiation in what predicts use of EISs versus EAs suggests assessment does not simply respond to project details but also shapes proposal and design choices beforehand.

Measurement of the ICRH antenna phasing using antenna strap probe based diagnostic system in EAST tokamak

To operate the ion cyclotron resonance heating (ICRH) antennas in a better heating state and produce relatively low impurities, it is necessary to control the antenna spectrum by changing the antenna phasing. As the electrical length of the antenna feeding transmission lines is changing as a matter of the standing wave pattern at the ceramic supports, 90° elbows, T-connectors and antenna loops, we chose to measure the current at the grounding points of the antenna loops by antenna strap probe. The voltage drops along a small, several millimeter-long paths at the end of the antenna loops give a signal that is proportional to the current in the antenna loop. Through the simulation of the antenna strap probe and the actual measurement of the antenna phasing under vacuum conditions, the reliability of the antenna strap probe based diagnostic system have been successfully proved. Moreover, this system was successfully applied to the ICRH daily experiments in the spring of 2021. In the near future, the active real-time feedback control of the antenna phasing system will be developed based on this diagnostic system in the EAST tokamak.

Dynamic Response of Transmission Lines Crossing High-Speed Railway

Transmission lines crossinghigh-speed railways are prone to cable rupture accidents, due to the frequent effects of train-induced wind. In this work, we propose a numerical simulation method for the dynamic response of transmission line caused by high-speed train, and validate it by field testing. We investigate the action mechanism of train-induced wind on transmission lines and the time domain responses of cables. Meanwhile the influences of different parameters are discussed, including train speed, train length, span length, and height of transmission lines. It shows that the response caused by the passing of high-speed trains lasts for tens of seconds, and the cumulative damage caused by train induced wind should not be ignored. Increasing the height of transmission line, changing the span length, or installing damping devices can effectively overcome the line vibration or mitigate its impact. The proposed method can help to improve the structure design of transmission lines crossing high-speed railway and can also be used for the design and optimization of damping devices.

Generalized fault diagnosis method of transmission lines using transfer learning technique

Recent artificial intelligence-based methods have shown great promise in the use of neural networks for real-time detection of transmission line faults and estimation of their locations. The expansion of power systems including transmission lines with various lengths have made the fault detection, classification, and location estimation process more challenging. Transmission line datasets are stream data which are continuously collected by various sensors and hence, require generalized and fast fault diagnosis approaches. Newly collected datasets including voltages and currents for faulty and non-faulty situations might not have adequate and accurate labels that are useful to train neural networks. In this paper, a novel transfer learning framework based on a pre-trained LeNet-5 convolutional neural network is proposed. This method is able to diagnose faults for different transmission line lengths and impedances by transferring the knowledge from a source convolutional neural network to predict a dissimilar target dataset. By transferring this knowledge, faults from various transmission lines, even without sufficient data samples with labels, can be diagnosed faster and more efficiently than the existing methods. To prove the feasibility and effectiveness of this methodology, seven different datasets that include various lengths of transmission lines are used. The robustness of the proposed methodology against the generator voltage fluctuations, variations in fault locations, fault inception angle, fault resistance, and phase difference between the two generators are well studied to prove the reliability of this technique for fault diagnosis of transmission lines.

A new differential protection algorithm for transmission lines connected to large-scale wind farms

The fluctuated output power of the large-scale wind farms (WF) and their fault transient characteristics have an adverse effect on the current differential protection systems of the transmission lines. With increased transmission line length and in the case of weak output power from the WF, the differential current between both line ends increases in normal conditions since the capacitive current is comparable to the load current. This paper proposes a new differential protection algorithm for transmission lines connected to large-scale wind farms. The proposed current differential protection algorithm is developed based on the signs of the phase current samples at both line ends, instead of utilizing directly the current magnitudes. The similarity between the signs of the phase current samples at both line ends is evaluated utilizing the signed correlation criterion, and the fault detection index is calculated to discriminate the internal faults from other events. In addition, a new online technique is introduced to adjust the protection settings considering the different output power levels of the WF. The conducted PSCAD/EMTDC simulation studies confirm the acceptable performance of the proposed protection algorithm for numerous normal and fault scenarios, including different fault resistances and inception angles as well as all fault types. The effect of line length, type of wind turbine generator, and different values of WF output power are also considered.