Resistance Matrices Research Articles

A new approach towards more accurate modeling of mechanical defects in power transformer windings

In many cases, power transformers can continue their normal operation despite mechanical defects in their windings. However, estimating the lifespan and assessing the risk of using a transformer with mechanical defects depend on detailed studies of insulation aging and the distribution of transient voltages along the winding, and consequently, the likelihood of partial discharge. Risk assessment studies can only be effectively conducted through accurate modeling of transformers across a wide frequency range. In this study, an attempt has been made to investigate the impact of winding mechanical defects on the transformer equivalent circuits parameters using finite element method precisely modeling of transformer windings, without applying approximation or common simplifications. To compare the effect of each mechanical defect on the resistance, inductance, and capacitance matrices arrays, an index called fault classification accuracy has been used. The investigations have shown that the capacitance matrix arrays undergo the most significant changes for all types of modeled defects in this research. To examine the impact of defects on the transformer frequency response, a π coupled model that directly uses output matrices of finite element modeling has been employed. The sensitivity of various components of frequency response has also been investigated for the used model.

유한요소법을 이용한 Resistance, Inductance 및 Capacitance 행렬 추출

유한요소법을 이용한 Resistance, Inductance 및 Capacitance 행렬 추출

Calculation of the Inductance and Resistance Matrices of Medium-Frequency Transformers

Calculation of the Inductance and Resistance Matrices of Medium-Frequency Transformers

A special property of resistance matrices

A special property of resistance matrices

A method to control distributed energy resources in distribution networks using smart meter data

Voltage regulation has been one of the major challenges for distribution network operators (DNOs) due to the integration of distributed energy resources in the recent years. Control approaches mitigating over-voltage (OV) generally require full network model, which for low-voltage distribution networks (LVDNs), can be inaccessible to DNOs. This paper presents a novel data-driven model-free control framework for improving voltage regulation in 4-wire 3-phase LVDNs. In the proposed approach, first, using smart meter data, the aggregated resistance and reactance matrices of the network are estimated. Then, these matrices serve as an input for the proposed optimal power flow (OPF) method to control the DERs’ active and reactive power outputs. This method also lets the DNO adjust the fairness in prosumers’ generation curtailment. The performance of the proposed approach is evaluated in various case studies conducted on a real-world low-voltage test feeder. The simulation results exhibit significant effectiveness in solving the OV problem associated with DERs. For example, in the studied network, the proposed approach limits the maximum voltage of the network to 1.1 pu, while without having control over the DERs output power, it can even overpass 1.17 pu during the peak generation period. In addition, utilizing DERs’ reactive control capability reduces the amount of active power curtailment, and prosumers are able to collectively inject 5.66% more active power.

Comparison of properties of carbon reinforced plastic obtained on the basis of semicrystalline polyimideR‐BAPBand other high‐temperature‐resistant thermoplastic matrices

AbstractHeat resistant thermoplastic matrices offer potential advantages over thermoset polymers and represent a promising alternative in advanced composite applications. In the present work, the properties of carbon fiber reinforced plastics (CFRPs) based on the developed semicrystalline polyimide R‐BAPB were studied and compared with those of highly heat‐resistant thermoplastic polymers such as amorphous polyetherimide Ultem‐1000 and semicrystalline polyetherketone PEEK. To obtain CFRP, an approach was used basing on the uniform distribution of polymer powders on continuous carbon fibers by electrostatic spraying followed by their impregnation in heated calenders and hot pressing. The thermal and thermomechanical properties of CFRPs based on mentioned above polymers were studied. The effect of temperature on the mechanical behavior of CFRPs, including flexural properties and interlaminar fracture toughnessG1C, was investigated as well. CFRPs based on PEEK and R‐BAPB are found to have the highest thermal stability and heat resistance. The maximum flexural strength, which practically does not change in a wide temperature range from −50 to 180°C, is observed for CFRP based on R‐BAPB polyimide. Among the investigated CFRPs, the highest value of interlaminar fracture toughness is shown by CFRPs based on semicrystalline R‐BAPB.

Feasibility of incorporating SO42--ions in zeolite-like matrices based on alkaline aluminosilicate binders

Factors determining minimization of the influence of sulfate environments on concrete and risk of corrosion of embedded steel reinforcement have been analyzed. Coatings based on alkaline aluminosilicate binders were proposed to prevent transport of the sulfate ions into concrete. The formation of water resistant zeolite-like matrices on the alkaline aluminosilicate binder of the Na2O-K2O-Al2O3-SiO2-H2O system at 20 ± 2 °C can be provided by the use of calcium-containing modifying additives. Optimized molar ratios between oxides of binder constituent were SiO2/Al2O3 = 4–5 and K2O/(Na2O + K2O) = 0.15–0.30. The results of the study show that the speed of incorporating sulfate ions in cement matrix of binder from the sulfate environment is dependent upon a cation and ranks as follows: (NH4)2SO4 > MgSO4 > Na2SO4 > CaSO4. Complete protection of concrete against the penetration of sulfates can be reached when the developed coating is applied in a thickness of 3 mm.

Validation of an HPLC-HR/MS method for the determination and quantification of six drugs (morphine, codeine, methadone, alprazolam, clonazepam and quetiapine) in nails.

Keratinized matrices, including nails, are among the most resistant matrices that can be analyzed in cases where remains are deeply decomposed and relatively non -invasive for living people. In order to exploit these new matrices in the search for exogenous substances, it is necessary to develop analytical technologies capable of achieving high levels of sensitivity. In this technical note, an easy method is presented for the simultaneous extraction and quantification of three narcotic substances (morphine, codeine, methadone), two benzodiazepines (BDZ) (clonazepam and alprazolam) and an antipsychotic (quetiapine) from nail matrix by analysis in Ultra High-Performance Liquid Chromatography at High Resolution Mass Spectrometry (HPLC/HR-MS). The method has been validated following the Standard Practices for Method Validation in Forensic Toxicology of the Scientific Working Group for Forensic Toxicology. Nail specimens from eight authentic postmortem cases and thirteen living donor samples were extracted and analyzed. Of the eight postmortem samples, five resulted positive for at least one of the three substances searched. Ten of the thirteen living donor specimens were positive for at least one of the targeted benzodiazepines or quetiapine.

Electronic Modeling for Resistive Textile Matrices

Textile pressure sensing has been proved to be useful for activity recognition in both wearable and ambient intelligence domains. The sensors are organized in a matrix format and their resistances are linked to the pressure asserted onto them. While there have been many works exploring its applications, the relationship between the resistance distribution and the numeric data output, has not been thoroughly studied. In this paper, we first demonstrate that there is not a simple, point-by-point mapping between the resistance distribution and the output voltage distribution, then build a generalized model to describe this relation, viz. to provide the answers to the forward and backward questions. The model’s correctness is verified using the data measured from a rheostats prototype board. We then demonstrate the model’s applications in helping 1) obtain the resistance distribution from the measured voltage matrix, 2) decide the proper analog settings to match the textile matrix, and 3) understand the effects of damages from the long-term usage. The methods and conclusions in this paper are also general for the other resistive textile matrices and could serve as a useful tool in both the design and application phases.

On resistance matrices of weighted balanced digraphs

Let G be a connected graph with . Then the resistance distance between any two vertices i and j is given by , where is the th entry of the Moore-Penrose inverse of the Laplacian matrix of G. For the resistance matrix , there is an elegant formula to compute the inverse of R. This says that where A far reaching generalization of this result that gives an inverse formula for a generalized resistance matrix of a strongly connected and matrix weighted balanced directed graph is obtained in this paper. When the weights are scalars, it is shown that the generalized resistance is a non-negative real number. We also obtain a perturbation result involving resistance matrices of connected graphs and Laplacians of digraphs.

Forest fragments prioritization based on their connectivity contribution for multiple Atlantic Forest mammals

Natural environments worldwide are increasingly restricted to smaller and isolated patches, resulting in major threats to biodiversity. To prioritize conservation efforts, it is important to assess the relative contribution of the habitat remnants to landscape connectivity. We prioritized remnants of Atlantic Forest in Argentina based on their contribution to the connectivity requirements of mammals that are sensitive to landscape transformation by analyzing habitat connectivity and availability for five species with varying habitat requirements and dispersal abilities. We combined graph-based analysis with occupancy models to calculate the resistance matrices and the node attributes, incorporating anthropogenic pressures. Results of connectivity indices were combined for all species so that those that were more sensitive to the loss of connectivity and/or availability had a greater influence on the final prioritization. Five patches had maximum priority for conservation and were vital to maintaining both landscape connectivity and habitat availability. These patches were particularly important for smaller species with low dispersal abilities, for which they constitute suitable habitats. Four percent of the patches were identified as irreplaceable stepping-stones that connected habitat patches for species with intermediate dispersal distances. Patch connectivity was not equally important for all species as they had different dispersal abilities and sensitivity to anthropogenic pressures, which means that the process of territorial planning based on landscape connectivity must include very careful selection of the species involved. With this multi-species model, we generated a spatially explicit tool that proved useful to prioritize forest patches to conserving Atlantic Forest mammals and other fragmented Neotropical forests.

Evaluation of Methodology for Lightning Impulse Voltage Distribution over High-Voltage Windings of Inductive Voltage Transformers

Knowledge of lightning impulse (LI) voltage distribution over transformer windings during the design stage of the transformer is very important. Specific design differences in inductive voltage transformers make the transient analysis approach different to the approach to the power transformers. In this paper, a methodology for acquiring lightning impulse voltage distribution over high-voltage (HV) winding of inductive voltage transformers is presented and evaluated. Resistance, inductance, and capacitance matrices are calculated using the integral and boundary element methods (BEM) approach. Additionally, in order to improve the capacitance matrix solver, adaptive cross approximation (ACA) is applied. These parameters are then used to solve the equivalent circuit model in time domain. In order to evaluate the methodology, an experimental and numerical investigation of the layer discretisation, iron core influence, and accuracy of the proposed methodology is performed. The comparison of numerical results with measurements confirms the validity of the methodology.

Accelerated numerical modeling of RF circuits using network characteristic mode analysis

AbstractA fast numerical modeling approach based on network characteristic mode analysis (CMA) is presented and investigated for analyzing electrical layouts in miniature RF filters, such as surface acoustic wave filters. In this approach, a generalized eigenvalue decomposition is performed on the Z‐parameters of an electrical layout at one or two sampling frequencies that can be computed and extracted with any numerical full‐wave method. The obtained eigenvalues are used to extract modal resistance, inductance, and capacitance matrices for each eigenmode. The frequency dependence of the modal resistance matrix can be assumed a priori or determined automatically, and the modal inductance and capacitance matrices are assumed frequency independent. These modal matrices are then used to approximate the Z‐parameters at any other frequencies to provide the response of the electrical layout, which can then be combined with the frequency responses of other components, such as resonators, to yield the electrical response of an entire RF filter. Compared with the previously developed analytic extension of eigenvalues, this fast CMA‐based method is less affected by the frequency variation of eigenmodes since the frequency dependences of the eigenmodes are implicitly canceled out in its formulation. The accuracy of this approach is evaluated by comparing with results from full‐wave analyses. For RF circuits whose electrical sizes are small and whose frequency range of interest is relatively small, the proposed CMA‐based fast frequency sweep approach is found to be sufficiently accurate and highly practical for engineering applications.

Thermal Resistance Matrix Extraction from Finite-Element Analysis for High-Frequency Magnetic Components

The thermal management of magnetic components for power electronics is crucial to ensure their reliability. However, conventional thermal models for magnetic components are known to have either poor accuracy or excessive complexity. Contrary to these models, the use of Thermal Resistance Matrices is proposed in this paper instead, which combine both accuracy and simplicity. They are usually used to characterize semiconductor devices, but not for magnetic components. The guidelines to apply Thermal Resistance Matrices for magnetic components are discussed in detail. The accuracy of this model is validated by 3D FEA simulations and experimental results, showing an absolute error lower than 5 ∘C and a relative error between −6.4% and 3.9%, which is outstanding compared to the carried-out literature review.

Математическая модель измерительного комплекса для определения внешних параметров вибраторных активных фазированных антенных решеток в ближней зоне.

When measuring characteristics of the modern multi-element active phased antenna arrays amplifications method may have problems processing the results of measurements, due to the complexity of the exact adjustment of the overall active phased array, the fluctuations of the parameters of microwave amplifiers, the failure of individual elements, the inadmissibility of the full radiation of aperture antennas in an anechoic chamber. Electrodynamic modeling of active phased array antennas in specialized programs usually requires very large computational costs and it is very difficult to take into account fluctuations in parameters and failures of active phased array elements. In this regard, a mathematical model of the measuring complex is proposed for estimating the field distribution in the near zone of vibratory antenna arrays and generating radiation patterns. The estimation methodology is based on direct measurements of the amplitude-phase distribution of the field of the antenna system on the selected surface in the immediate vicinity of its aperture using a sounding antenna. The main relations for the model are the well-known expressions for calculating the field distribution in the near zone of a vertical symmetrical vibrator, the method of induced electromotive force, and matrix relations for converting the field into various coordinate systems. The model of the measuring complex is used to evaluate the characteristics of the active phased array in the near and far zones. However, it can be used to check real experimental data, taking into account fluctuations in the parameters of the amplitude-phase distribution in the aperture, and failures of antenna elements. The conducted research has shown a good agreement between the calculated characteristics of the active phased array using the proposed model and the aperture method. The time for calculating the antenna directivity characteristics in the proposed model is 30 minutes. The main time is associated with the addition of resistance matrices with elements related to each new position of the probe antenna. However, this time is not comparable to the time required to implement the measurement model in specialized electrodynamic modeling packages.

Electrode and Electrolyte Materials From Atomistic Simulations: Properties of LixFEPO4 Electrode and Zircon-Based Ionic Conductors

LixFePO4 orthophosphates and fluorite- and pyrochlore-type zirconate materials are widely considered as functional compounds in energy storage devices, either as electrode or solid state electrolyte. These ceramic materials show enhanced cation exchange and anion conductivity properties that makes them attractive for various energy applications. In this contribution we discuss thermodynamic properties of LixFePO4 and yttria-stabilized zirconia compounds, including formation enthalpies, stability, and solubility limits. We found that at ambient conditions LixFePO4 has a large miscibility gap, which is consistent with existing experimental evidence. We show that cubic zirconia becomes stabilized with Y content of ~8%, which is in line with experimental observations. The computed activation energy of 0.92eV and ionic conductivity for oxygen diffusion in yttria-stabilized zirconia are also in line with the measured data, which shows that atomistic modeling can be applied for accurate prediction of key materials properties. We discuss these results with the existing simulation-based data on these materials produced by our group over the last decade. Last, but not least, we discuss similarities of the considered compounds in considering them as materials for energy storage and radiation damage resistant matrices for immobilization of radionuclides.

Sedimentation of Snow Particles in Still Air in Stokes Regime

AbstractWe compute the resistance matrices of realistic 3‐D snow particle shapes obtained from microcomputed tomography data of snowpack samples and a phase field model. Using these resistance matrices, we calculate the sedimentation of the particles in still air in Stokes regime. We find that particles attain preferred orientations and the mode of motion is either drifting or spiraling. Simple laws, relating average drag and rotation torque coefficients to the particles' sphericity, are established which lead to a new formulation of a snow particle's average terminal velocity. The presented models are valid in Stokes regime in still air, corresponding to particle sizes up to ∼100 μm but can reasonably be extended to moderately higher Reynolds numbers (∼1 mm) and used for estimating mean settling velocity in turbulent conditions. Though not all relevant atmospheric conditions are covered, our study provides the basis for addressing more complex conditions in the future.

Basic relationships for Hall half-plane structures with multiple extended contacts on the boundary: Applications to the extraction of physical parameters and optimization of graphene and vertical Hall devices

The basic relationships for a Hall plate with N non-symmetric contacts placed in an arbitrary magnetic field are a set of N-1 relationships that are necessary and sufficient for the existence of a complex electrostatic potential function. By the application of the boundary conditions, they turn into a linear system of N-1 compatibility conditions involving the terminal voltages and currents. The construction of the basic relationships requires the positions of the contact extremities on the real axis of the canonical domain (the upper half-plane) as well as the electric and magnetic parameters of the Hall device. The conduction and resistance matrices can be obtained easily from the basic relationships. They give an effective method for predicting the performance of both horizontal and vertical Hall effect devices and provide a useful method for designing these types of planar devices.

Calibration of an AC Zero Potential Circuit for Two-Dimensional Impedimetric Sensor Matrices

The alternating current zero potential circuit (AC-ZPC) has been recently proposed for two-dimensional resistive sensor matrices, where each matrix row is driven by an AC signal at an individual frequency and every column is read separately. The AC-ZPC method enables the simultaneous measurement of all sensors in the matrix and is insensitive to DC offset voltages of amplifiers. This work aims to investigate the feasibility of the AC-ZPC method for matrices of impedimetric sensors and to propose a calibration approach for suppressing the measurement deviations caused by row interface impedances. The feasibility of the AC-ZPC measurement method for the impedimetric sensor matrices and the proposed calibration approach have been proved by both simulation and implementation results. Based on the commercial impedance measurement circuit AD5933, a prototype has been realized. It achieves a measurement deviation below 1% in the range from 1.9 $\text{k}\Omega \vert \vert 361.7$ pF to 15.9 k $\Omega \vert \vert 102.0$ pF.

Resistance matrices of balanced directed graphs

ABSTRACT Let G be a strongly connected and balanced directed graph. We define the resistance between any two vertices i and j of G by using the Moore–Penrose inverse of the Laplacian matrix of G and define the resistance matrix by . This generalizes the resistance in the undirected case. In this paper, we show that R is a non-negative matrix and obtain an expression to compute the inverse, determinant and cofactor sums of R.