Patrice Labie

Calculating the impedance of a grounding system

Following up previous research concerning low frequency electromagnetic emission from a grounding system [Nekhoul et al., 1995], the authors suggest a methodology which allows a complete electromagnetic study by finite element method (FEM) of a grounding system in the significant frequential spectrum of a stroke of lightning or a short circuit (f/spl les/1 MHz). In this study as well as calculating the electromagnetic field at any point in space (ground and air), we pay particular attention to variation with frequency of the impedance of a grounding system. Suggested modelling takes into account eddy currents in buried conductors and ground and non-linear phenomena (ionization of the ground) around the buried conductors when high currents flow via the earth. It also deals with displacement currents when their effect becomes noticeable in the earth for high frequency. The interest of this work lies in data needed to implement an optimal grounding system in non-homogeneous media. All the results of calculations are compared with measurements made by the French Electricity Board (E.D.F., France).

A shell element for computing 3D eddy currents-application to transformers

A skin depth-independent shell element to model thin conducting sheets is described in a finite element context. This element takes into account the field variation through depth due to skin effect. The finite element formulation is first described, then boundary conditions at the edge of conducting shells and the possibility of describing non conducting line gaps and holes are discussed. Finally, a computation of an earthing transformer model with an aluminium shield modelled with shell elements is presented. >

A finite element method for calculating the electromagnetic fields generated by substation grounding systems

This paper develops a basic idea which allows low frequency electromagnetic fields generated by cylindrical conductors, with very small radii compared with their length, to be calculated. The proposed method can be applied to both power overhead conductors and those buried in a conducting environment. The paper presents a direct application for this concept which consists in calculating the electromagnetic fields created by a substation grounding system following an accidental short circuit or a lightning stroke. The finite element method (FEM) with several formulations is used. Currents in the cylindrical conductors which make up the earth network grid are taken into account without volume meshing; simple line discretization of these is carried out. Electromagnetic fields generated by leakage currents and currents induced underground are taken into account. Furthermore, open boundaries of both air and earth environments are processed by introducing a spatial transformation. This application for an earth network enables to show the advantages of FEM processing compared with the method traditionally used in antenna theory for this kind of problem. >

Coupled problem computation of 3-D multiply connected magnetic circuits and electrical circuits

This paper presents the theory and the validation of a new finite-element formulation to realize the coupling between electrical circuits and multiply connected magnetic circuits, using a magnetic scalar potential as state variable. For this purpose, we used formulations in reduced magnetic scalar potential versus T/sub 0/ taking into account electrical circuits and a total magnetic scalar potential taking into account cuts.

Homogenization for Periodical Electromagnetic Structure: Which Formulation?

This paper proposes a general finite element approach for the frequency-domain homogenization of electromagnetic periodical structures. Based on local finite element resolutions on a cell, the method allows taking into account the local effects at the macroscopic level through the determination of equivalent macroscopic permeability and conductivity laws. Examples of the modeling of eddy current losses in windings are presented.

Eddy-current effects in circuit breakers during arc displacement phase

This paper deals with the modeling of eddy currents generated by arc motion during opening phases of low voltage circuit breakers. Two kinds of modeling are tested. While the first one consists in determining eddy currents in splitter plates, the second one is devoted to the calculation of eddy currents in electrodes. All simulations are carried out with a T-/spl Phi/ finite-element method formulation and no new mesh at each time step is required.

Comparison of FEM-PEEC Coupled Method and Finite-Element Method

This paper analyzes the efficiencies of the new coupling between finite-element methods (FEMs) and the partial element equivalent circuit method (PEEC), which are computation time and memory space. To show its performance, a common mode filter is modeled by the coupling and the results are then compared with those of a FEM analysis. The comparison shows that the coupling is very efficient to model electromagnetic systems comprising magnetic materials and systems of complex thin conductors.

Coupling PEEC-Finite Element Method for Solving Electromagnetic Problems

A coupling of the partial element equivalent circuit method with the finite element method for solving magneto-harmonic electromagnetic problems is proposed. The new formulation, which combines the main advantages of the previous methods, is particularly well suited for modeling electromagnetic complex devices including a large number of conductors.

Computations of Source for Non-Meshed Coils With A–

In this paper, different ways to compute electromagnetic source fields for non-meshed coils will be described for magnetic vector potential A and electric scalar potential V formulation (A - V formulation). The originality of this paper is demonstrated by the source computations for A- V formulation with non-meshed coils. Usually, coils for A- V formulation are meshed, and non-meshed coils are studied with reduced magnetic vector potential Ar and electric scalar potential V formulation (Ar - V formulation). Different source computations for A - V formulation will be applied on an induction machine with non-meshed coils.

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Purpose – This paper seeks to model magneto‐harmonic solid conductors in the presence of ferromagnetic materials.Design/methodology/approach – The approach takes the form of a coupling between the FEM and the PEEC method.Findings – The paper shows one how to use the FEM‐PEEC coupled method to model a problem comprising solid conductors and ferromagnetic materials and compare its results with the FEM.Research limitations/implications – The formulation allows one to treat linear material in the magneto‐harmonic assumption.Originality/value – The two methods FE and PEEC are well‐known. The innovation here is coupling these methods in order to profit by the main advantages.