Numerical Computation Of Electromagnetic Fields Research Articles

Lightning Surge Analysis of a Microwave Relay Station Using the FDTD Method

Microwave relay stations are key components in controlling power grids and maintaining their stability, but lightning strikes to the stations may cause faults, malfunctions, or even physical damage to microwave radio equipment. To protect equipment from lightning, it is necessary to predict surge phenomena in a microwave relay station, and design effective lightning protection methodologies. Recently, numerical electromagnetic field computation methods to solve Maxwell's equations have entered widespread use for analyzing surge phenomena in 3-D structures such as buildings and towers and in grounding structures such as grounding grids. In this paper, we apply the finite-difference time-domain (FDTD) method to the surge analysis of a microwave relay station. First, to validate the applicability of the FDTD method, we set up a reduced-scale model of a microwave relay station. Using this model, we measured the distribution of the currents flowing through the station and compared the measured results with those simulated by the FDTD method. Second, through FDTD-based surge simulations, we analyzed the effects of the reinforcing bars of a building, the route of the ground wire of a waveguide, and the layout of a deep earth electrode on the lightning current distribution.

Analysis of FE

Purpose – The consideration of uncertainties in the numerical computation of electromagnetic fields has recently gained a lot of attention. Most publications focus on the creation of models for the uncertainty quantification, however, neglect the inaccuracy of the applied finite element model itself. Thus, the purpose of this paper is to analyze the influence of mesh quality on stochastic cogging torque calculations. Design/methodology/approach – The presented work consists of three steps. At first, a conventional analysis of the influence of mesh accuracy onto cogging torque is presented. Afterwards, the method is extended to stochastic calculations. Based on a comparison of the convergence behavior of both approaches, a method for more accurate cogging torque predictions with fewer necessary calculations is derived. Findings – An improved method to calculate probability predictions at minimum computational cost is presented and applied. Research limitations/implications – The presented approach requires the exact knowledge of the system’s stochastic variation boundaries. Originality/value – A fast method for more accurate stochastic cogging torque calculations is developed.

Surge characteristics of a twisted pair

AbstractWe used the method of moments (MoM), which is a numerical electromagnetic field computation method, to study the surge characteristics of twisted pair single‐phase electric power lines. The results show that wires stranded with less than several turns per meter have almost the same surge characteristics as parallel lines, but the surge impedance decreases in tens of % when the number of strands increases. To verify the simulation results, we measured the surge characteristics of a model line of twisted pair experimentally, and there is good accordance between them. It is possible to simulate the surge in twisted pair covered with polymer dielectric insulators by MoM.Moreover, we studied the surge characteristics of twisted pair which is inserted into a metal tube. According to the results, the effect of the strand is smaller than that in free space without the metal pipe. There are two propagation modes in common mode: fast surge and slow surge. Few influences of the number of strands on the surge velocity occur in the fast propagation surge, but the increase of the surge impedance and the slowdown of the propagation speed are caused by twining in the slow propagation mode. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 1–9, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20737

A Simulation Study of Lightning Surge Characteristics of a Distribution Line Using the FDTD Method

Recently, numerical electromagnetic field computation methods, which solve Maxwell's equations, have become a practical choice for the lightning surge analysis of power systems. Studies of lightning surge response of a transmission tower and lightning-induced voltages on a distribution line have already been carried out using the numerical electromagnetic field computation methods. However, a direct lightning stroke to a distribution line has not yet been studied.The authors have previously carried out pulse tests using a reduced-scale distribution line model which simulate the direct lightning stroke to a distribution line. In this paper, first, the pulse test results are simulated using the FDTD (Finite Difference Time Domain) method which is one of the numerical electromagnetic field computation methods, and comparisons are shown to validate the application of the FDTD method. Secondly, we present lightning surge characteristics of an actual-scale distribution line obtained by the FDTD method. The FDTD simulation takes into account the following items: (i) detailed structure of the distribution line; (ii) resistivity of the ground soil; (iii) propagation speed of the lightning return stroke.

Numerical Computation of Electromagnetic Fields by the Time-Domain Boundary Element Method and the Complex Variable Method

Numerical Computation of Electromagnetic Fields by the Time-Domain Boundary Element Method and the Complex Variable Method

Surge Characteristics of Twisted Pair

We used the Method of Moments (MoM), which is a numerical electromagnetic field computation method, to study the surge characteristics of twisted pair single phase electric power lines. The result shows that wires stranded less than with several turns/m have almost same surge characteristics as parallel lines, but the surge impedance decreases in tens of % when the number of the strands increases. To verify the simulation results, we measured the surge characteristics of a model line of twisted pair experimentally, and there is good accordance between them. It is possible to simulate the surge in twisted pair covered with polymer dielectric insulators by MoM.Moreover, we studied the surge characteristics of twisted pair which is inserted into a metallic tube. According to the result, the effect of the strand is smaller than that in free space without the metallic pipe. There are two propagation modes in common mode that are fast surge and slow one. Few influences of the number of the strands on the surge velocity occur in the fast propagation surge, but the increase of the surge impedance and the slow down of the propagation speed are caused by twining in the slow propagation mode.

Long-time numerical computation of electromagnetic fields in the vicinity of a relativistic source

We propose an implicit scheme for the calculation of electromagnetic fields in the vicinity of short electron bunches moving in a transversally bounded domain, as it has place in particle accelerators. The scheme is able to accurately model curved boundaries and does not suffer from dispersion in direction of motion. It is based on splitting the discrete curl operator in its transversal and longitudinal parts. Unlike previous conformal schemes the new method has a second order convergence without the need to reduce the maximal stable time step of the conventional staircase approach. This feature allows the usage of a moving mesh easily. Several numerical examples are presented and the algorithm is compared to other approaches.

Analysis of electromagnetic field transient on branch feeders by numerical electromagnetic field computation

AbstractThis paper presents the fundamental surge phenomenon when a step voltage is applied to a horizontal line above the ground which has branch feeders. We study line current and voltage at joint with the method of moments that calculates electromagnetic field in frequency domain. It is widely noted that the current reflection factor changes to a third at the junction of the same three lines in conventional transmission line theory based on TEM wave, and the stepwise current reflected appears overlapping to the incident current. On the other hand, the reflected current from the joint shows the inductive characteristic or the capacitive one depending on the angle between lines, which varies gradually and not stepwise in our numerical analysis considering TM wave. The time characteristic of the voltage at joint depends on the angles also, and the peak voltage slightly exceeds the voltage by the transmission line theory. These phenomena are caused by the electromagnetic coupling between the main line and branch lines. In addition to the computer simulations, we measured the currents in the reduced‐scale model lines and the results show the validity of our analysis regarding changes of the reflected current depending on the angles. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 1–8, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10176

Surge Simulation in Pulse Transformer Model by Numerical Electromagnetic Field Computation

In this paper we present transient analysis of transformer models by the moment method in frequency domain. The results show that the secondary voltage has the peak which is higher than the voltage calculated by the primary voltage and the winding ratio. The inductance of the winding and the capacitance between windings have an influence on a surge in the transformer winding. In addition to the transient analysis we calculate the inductance from time responses and the impedance in low frequency, and compare them with the analytical equation which is based on Nagaoka factor.

線路分岐部の過渡電磁界解析

This paper presents the fundamental surge phenomenon when a step voltage is applied to a horizontal line above the ground which has branch feeders. We study line current and voltage at joint with the moment method that calculates electromagnetic field in frequency domain. It is widely noted that the current reflection factor changes to a third at the junction of same three lines in conventional transmission line theory based on TEM wave, and the stepwise current reflected appears overlapping to the incident current. On the other hand, the reflected current from the joint shows the inductive characteristic or the capacitive one depending on the angle between lines, which varies gradually and not stepwise in our numerical analysis considering TM wave. The time characteristic of the voltage at joint depends on the angles also, and the peak voltage is slightly large compared with the voltage by the transmission line theory. These phenomena are caused by the electromagnetic coupling between the main line and branch lines. In addition to the computer simulations, we measured the currents in the miniaturized model lines and the results make the validity of our analysis clear about changes of the reflected current depending on the angles.

Formulations based on region-oriented charge simulation for electromagnetics

An integral method for numerical computation of electromagnetic fields based on discrete magnetic charges and electric currents has been presented. Three different region-oriented formulations have been evaluated for 2D-planar and axisymmetric magnetostatics. Also an eddy currents formulation has been considered. Results of error analysis for a canonical problem are included. All magnetostatic and eddy current formulations have been applied to a practical problem related to power transformer design.

Computation of Electromagnetic Fields in Axisymmetric Rf Structures With Boundary Integral Equations

This paper discuss the numerical computation of electromagnetic fields in axisymmetric structures with piecewise constant dielectric medium and variable boundary conditions. It is assumed that the fields are constant with respect to the angular variable. The implementation is based on the boundary integral equation method and a solution is found by the method of moments. In this work special attention has been paid to the accuracy of the ifeld computation near the boundaries. To this end, special integration techniques have been developed. In simple cases where comparisons are possible, the numerical solutions agree very well with the analytical ones.

Wavelet-Galerkin method for computations of electromagnetic fields

A general wavelet-Galerkin method for the numerical computation of electromagnetic fields of bounded regions involving multimedia and an efficient approach to handle arbitrary boundary conditions are presented in this paper. The numerical results indicate that the present method is a strong contender to the well established finite element method.

The versatility of a multiformulational approach in the solution of electromagnetic field problems

In this paper the usefulness of a multiformulational approach to the numerical computation of electromagnetic fields of technical interest, including coupled problems, is discussed. Several field computation problems arising from various application areas are presented to sample some of the many formulations required to face the existing computational needs. The problems are solved by means of a code designed for a multiformulational management of field computation, and the versatility of the approach and the obtained results are discussed.