Frequency Dependence Of Electrical Parameters Research Articles

Evaluation of synthesized new cellulose derivatives to make diodes and investigation of electrical and photoelectrical characteristics of these diodes

Firstly, two new cellulose derivatives (CelB33′44′TD and Cel44′OA) were synthesized, which were confirmed by FTIR and 13C CP-MAS NMR spectra. These derivatives were then used in the construction of new diodes (Au/CelB33′44′TD/p-Si and Au/Cel44′OA/p-Si). Later, the atomic force microscope (AFM) images of the interface layers were taken, and the current–voltage (I–V) graphs of the diodes were determined both in the dark and under different illumination intensities (DIIs). Using the Bethe's thermionic emission (TE) theory the ideality factors and barrier heights of the diodes, using the Cheung & Cheung functions the ideality factors, series resistances and barrier heights of the diodes, and using the Norde function the barrier heights and series resistances of the diodes were calculated. Finally, the capacitance–voltage (C–V) and conductance–voltage (G–V) graphs of the diodes at different frequencies (DFs) were examined and some frequency-dependent electrical parameters of the diodes were calculated using the 1/C2–V plots.

Comparison of Rational Krylov and Vector Fitting in Transient Simulation of Transmission Lines and Cables

This paper presents stringent comparisons between Vector Fitting (VFIT), Relaxed Vector Fitting (R-VFIT) and Rational Krylov Fitting (RKFIT) techniques in the fitting of transmission line and cable functions to rational forms while accounting for the frequency dependence of electrical parameters. The fitting procedures encapsulate new solution strategies to improve fitting performance. Various case studies are presented to assess the performance of RKFIT in terms of model order reduction, passivity violation and computing times. In addition, the use of RKFIT in obtaining the frequency dependent cable model (FDCM) is demonstrated for the first time together with a resolved case study that showed unstable behavior with the universal line model (ULM) methodology.

Transient analysis of power transmission towers above lossy ground with frequency dependent electrical parameters considering the water content of soil

Adequate soil modeling is fundamental to assessing the grounding impedance of the grounding system and the transient responses in power systems. This paper aims to investigate three soil models with electrical parameters varying with frequency and water content, namely Smith-Longmire, Scott, and Messier models, and their impact on the ground potential rise (GPR) waveforms of vertical grounding rods. Besides that, the transient induced voltages across the string of insulators induced are also investigated for lightning currents representative first, and subsequent return strokes are employed. The harmonic grounding impedance (HGI) is calculated for rods of 3, 15, and 30 m buried in frequency-dependent (FD) soil model using commercial electromagnetic software (FEKO) with the Method of Moments (MoM) for a range of 100 Hz to 10 MHz. Simulation results show a significant modification of the calculated HGI beyond a particular frequency. The induced transient GPR waveforms show a notable reduction in their voltage peaks when the FD soil model is compared with those computed using the frequency-independent (FI) soil model. Finally, a backflashover analysis is carried out that demonstrates its dependence on the rod length, water content, and the specific soil model employed.

Studies of structural, dielectric and impedance spectroscopy of electroceramics: (Ba0.05Bi0.95)(Fe0.95Zr0.05)O3

The polycrystalline sample (Ba0.05Bi0.95)(Fe0.95Zr0.05)O3 was prepared by solid state reaction method at 850 °C. The crystal structure and surface morphology of the sample were obtained by using X-ray diffractometer and a scanning electron microscope respectively. The frequency dependence of electrical parameters using impedance spectroscopy provides the dielectric behavior and grain and grain boundary effect toward resistance and capacitance of the sample. The conduction mechanism of the sample was studied from frequency dependent ac conductivity. The ferroelectricity of the sample was studied by p-E loop at room temperature. The slope from J–E characteristics was found to be nearly equal to 1.

Transient Analysis of Grounding Electrodes in Multilayer Soils Using Method of Moments

Grounding electrodes are expected to provide a low-impedance path for faults and lightning transient currents and protect the safety of electrical equipment and nearby people against dangerous induced potentials. In this context, a precise model of the grounding electrodes is needed to represent a certain electrode arrangement buried in stratified soil. This paper computes the grounding impedances of different grounding systems buried in three different soil configurations (homogeneous, 2-layer and 3-layer soil) modeled by its frequency-dependent electrical parameters. A simulation model using a commercial full-wave electromagnetic software FEKO to compute the grounding impedances is presented. Method of Moments(MoM), a frequency-domain numerical method, is employed to compute the grounding impedance in a frequency range of100 Hz to 5 MHz. Next, the developed ground potential rise(GPR) generated by two types of lightning currents (first and subsequent return strokes) injected into these grounding systems is computed. Time-domain GPR of each grounding system is also determined using the Vector Fitting (VF) technique combined with the ATP-software. Results show that GPR waveform is reduced when frequency-dependent soils are employed. This reduction is more pronounced in homogeneous and in 2-layersoils of high and moderated resistivity whereas the 3-layer soil has a minor impact due to the lower soil resistivity

Assessment of the Influence of Ground Admittance Correction and Frequency Dependence of Electrical Parameters of Ground of Simulation of Electromagnetic Transients in Overhead Lines

Assessment of the Influence of Ground Admittance Correction and Frequency Dependence of Electrical Parameters of Ground of Simulation of Electromagnetic Transients in Overhead Lines

An alternative model for aerial multiconductor transmission lines excited by external electromagnetic fields based on the method of characteristics

In this paper, a model of aerial multiconductor transmission lines with frequency-dependent electrical parameters for the simulation of time-domain electromagnetic transients due to incident electromagnetic fields is presented. The frequency dependency of the electrical parameters is taken into account using the penetration impedance; this allows applying the method of characteristics without having to resort to modal transformations. With this alternative approach, transforming the transmission line partial differential equations to ordinary differential equations is performed in the phase domain, which simplifies the mathematical development of the method and also the numerical solution. The validity of the proposed model is shown with five study cases involving different transmission systems and excitations.

Lightning Response of Multi-Port Grids Buried in Dispersive Soils: An Approximation versus Full-wave Methods and Experiment

In this paper, application of multi-conductor transmission line model (MTL) in transient analysis of grounding grids buried in soils with frequency-dependent electrical parameters (dispersive soil) is investigated. In this modeling approach, each set of parallel conductors in the grounding grid is considered as a multi-conductor transmission line (MTL). Then, a two-port network for each set of parallel conductors in the grid is then defined. Finally, the two-port networks are interconnected depending upon the pattern of connections in the grid and its representative equations are then reduced. Via solving these simplified equations, the transient analyses of grounding grids is efficiently carried out. With the aim of validity, a number of examples previously published in literature are selected. The comparison of simulation results based on the MTL shows good agreement with numerical and experimental results. Moreover, in despite of numerical methods computational efficiency is considerably increased.

Estimation of Energy Stress of Surge Arresters Considering the High-Frequency Behavior of Grounding Systems

This paper presents a probabilistic evaluation of energy absorption capability of transmission line surge arresters (SAs), based on Monte-Carlo method. In the presented approach, a wideband model of tower-footing grounding system is adopted taking to account both constant and frequency-dependent soil electrical parameters. Furthermore, the effect of multistroke lightning flashes on the energy stress experienced by SAs is taken into account. To this aim, simulation is performed for a typical 400-kV transmission line which is modeled in EMTP-RV. From the simulation results, it is found that the absorbed energy is significantly affected by the modeling type of grounding system, i.e., static or wideband model. This effect seems to be more pronounced for the soil characterized by frequency-dependence electrical parameters. The presented results show that wideband modeling of grounding system can affect the estimated lifetime and the energy absorption capability of SAs. Hence, the wideband model of grounding system is suggested to be taken into account for the proper selection and sizing of SAs.

Improved Method for Predicting the Performance of the Physical Links in Telecommunications Access Networks

A novel approach is presented which is able to predict the available maximal data transfer rate of SHDSL connections from measured frequency dependent electrical parameters of wire pairs. Predictions are made by a fuzzy inference system. The basis of the operable and tested method will be introduced, then an improved version is shown, in which the problems derived from sampling of continuous functions of electrical parameters are eliminated by wavelet transformation. Also possibilities for simplification of the problem and a way of reducing the dimensions of the applied rule bases are presented. As the set of the measured data leads to sparse rule bases, handling of sparseness is unavoidable. Two different ways—fuzzy interpolation and various membership functions—will be introduced. The presented methods were tested by measurements in real telecommunications access networks.

Measurement-based electrical parameters of power transformers for Frequency Response Analysis interpretation-Part II: Winding Part II: Winding analysis

For a practical Frequency Response Analysis (FRA) interpretation applicable to power transformers, frequency dependent electrical parameters of the core and windings in broad frequency range should be identified through non-destructive measurements. Since the core parameters are determined in Part I, electrical parameters of windings (resistances, capacitances) and leakage paths surrounding windings (leakage/zero-sequence impedances) of a distribution transformer will be discussed in this paper. Due to the fact that most parameters associated with the windings currently can only be measured at or around power frequency through diagnostic testing methods, the practical parameter-based FRA interpretation is not possible. To deal with this problem, the paper proposes a new approach based on the combination of different measured driving-point impedances and relevant analysis of the duality-based equivalent circuit in determining frequency dependent parameters associated with transformer windings. Results show that the physical FRA interpretation can be reasonable obtained for the test transformer in low and medium frequency range.

Time-Domain Analysis of Frequency-Dependent Electrical Parameters of Soil

The analysis of the impact of the frequency dependence of electrical parameters of soil on the lightning response of electrical systems has often been based on frequency-domain approaches. In this paper, a causal time-domain field formulation including the frequency dependence of soil parameters is proposed. The consistency of the developed formulation is proved considering a canonical electromagnetic problem and also comparisons with experimental results. The proposed formulation is useful for application of techniques such as the finite-difference time-domain method in problems involving dispersive soils.

Transformer model with saturation effects for frequency‐domain transients simulation

In this study, a model of one-phase transformers with saturation effects, suitable for low- and mid-frequency electromagnetic transient simulations using the numerical Laplace transform is presented. Substitution and superposition theorems are invoked to convert the saturation non-linear condition of the transformer into a series of time-sequential switching manoeuvres. Model advantage is that frequency dependence of electrical parameters is naturally taken into account and, together with the capability of including non-linear phenomena, leads to a valuable tool to validate time-domain models based on convolutions.

Study of multiferroic properties of Bi2Fe2WO9 ceramic for device application

The Bi2Fe2WO9 ceramic was prepared using a standard solid-state reaction technique. Preliminary analysis of X-ray diffraction pattern revealed the formation of single-phase compound with orthorhombic crystal symmetry. The surface morphology of the material captured using scanning electron microscope (SEM) exhibits formation of a densely packed microstructure. Comprehensive study of dielectric properties showed two anomalies at 200[Formula: see text]C and 450[Formula: see text]C: first one may be related to magnetic whereas second one may be related to ferroelectric phase transition. The field dependent magnetic study of the material shows the existence of small remnant magnetization ([Formula: see text]) of 0.052[Formula: see text]em[Formula: see text]/g at room temperature. The existence of magneto-electric (ME) coupling coefficient along with above properties confirms multi-ferroic characteristics of the compound. Selected range temperature and frequency dependent electrical parameters (impedance, modulus, conductivity) of the compound shows that electric properties are correlated to its microstructure. Detailed studies of frequency dependence of ac conductivity suggest that the material obeys Jonscher’s universal power law.

A Reduced Graphene Oxide Based Radio Frequency Glucose Sensing Device Using Multi-Dimensional Parameters.

A reduced graphene oxide (RGO) based glucose sensor using a radio frequency (RF) signal is demonstrated. An RGO with outstanding electrical property was employed as the interconnector material between signal electrodes in an RF electric circuit, and it was functionalized with phenylbutyric acid (PBA) as a linker molecule to bind glucoses. By adding glucose solution, the fabricated sensor with RGO and PBA showed detecting characteristics in RF signal transmission and reflection. Frequency dependent electrical parameters such as resistance, inductance, shunt conductance and shunt capacitance were extracted from the RF results under the equivalent circuit model. These parameters also provided sensing characteristics of glucose with different concentrations. Using these multi-dimensional parameters, the RF sensor device detected glucose levels in the range of 1–4 mM, which ordinarily covers the testing range for diabetes or medical examination. The RGO based RF sensor, which fits well to a linear curve with fine stability, holds considerable promise for biomaterials detection, including glucose.

Capacitively Coupled Resistivity measurements to determine frequency-dependent electrical parameters in periglacial environment—theoretical considerations and first field tests

Capacitively Coupled Resistivity measurements to determine frequency-dependent electrical parameters in periglacial environment—theoretical considerations and first field tests

Aerial line model for power system electromagnetic transients simulation

In this study, a new model for aerial multiconductor transmission lines with frequency dependent electrical parameters is presented. The new model is called here A-line model and is a two-port model based on the method of characteristics and finite differences that does not require segmenting the transmission line. The frequency dependence of electrical parameters due to field penetration in conductors and Earth is taken into account by means of the penetration impedance or skin impedance. Moreover, in the proposed model there is no need of splitting in propagation modes; therefore, the numerical implementation is very simple. With the purpose of validation, results from the numerical Laplace transform and universal line model are employed. From the results, it is found that the A-line model is accurate and robust with an execution speed that makes it a strong candidate for real-time simulations.

Wide-Band Modeling of Tower-Footing Grounding Systems for the Evaluation of Lightning Performance of Transmission Lines

This paper presents the evaluation of lightning performance of transmission lines considering the wide-band modeling of their associated tower-footing grounding systems. To this aim, first, the grounding system admittance matrix over the frequency range of interest is obtained by making use of the method of moments solution to Maxwell's equations. In the next stage, the matrix pencil method is used to infer the pole-residue identification of the obtained admittance matrix. Finally, the obtained pole-residue model is incorporated into the EMTP-RV in the form of a state-space block. The back-flashover analysis is done for a typical 132-kV transmission line, while the tower-footing grounding system is modeled in three different ways namely: 1) static-model, 2) wide-band model assuming constant electrical parameters for the soil, and 3) wide-band model assuming frequency-dependent electrical parameters for the soil. From the simulations, it is found that the inclusion of the wide-band model of the tower-footing grounding system can markedly affect the total probability of back-flashover in transmission lines. This effect is more pronounced when the frequency dependence of soil electrical parameters is taken into account. It is shown that considering the wide-band modeling of tower-footing grounding system can affect (either decrease or increase) the total back-flashover probability of transmission lines.

An Investigation on the Frequency Dependence of Soil Electrical Parameters

This paper presents the results of an investigation into the frequency-dependent electrical parameters for different types of soil as a function of moisture content. The frequency dependence of soil electrical parameters is very important in the design of grounding systems. In fact, the performance of grounding systems is greatly dependent upon various factors such as soil type, particle size, water content, temperature, frequency, and the like. The resistivity and relative permittivity for four different soils were measured and analyzed in the frequency range of 1kHz ? 1MHz. Soil resistivity declined as moisture content and frequency increased. In particular, the frequency dependence of soil resistivity was significant as the moisture content was low. In contrast, the relative permittivity of soil dramatically declined at the frequency of 10kHz or below as the moisture content increased, showing the opposite pattern in terms of variation patterns, compared to resistivity.

Modeling the Frequency Dependence of Electrical Parameters of Soil

An original semitheoretical causal model was developed to describe the frequency dependence of electrical parameters of soil in the representative frequency range of lightning currents. The expressions of such model, based simply on the measured low-frequency soil resistivity, can be promptly applied to general soils in practical problems. The model allows the user to adopt different levels of conservativeness to take the dispersion of the frequency dependence of soil and eventual uncertainties into account. The comparison of experimental results and those provided by this model denoted its consistency.