A New Approach to the Modeling of Anisotropic Media with the Transmission Line Matrix Method

A reformulation of the Transmission Line Matrix (TLM) method is presented to model non-dispersive anisotropic media. Two TLM-based solutions to solve this problem can already be found in the literature, each one with an interesting feature. One can be considered a more conceptual approach, close to the TLM fundamentals, which identifies each TLM in Maxwell’s equations with a specific line. But this simplicity is achieved at the expense of an increase in the memory storage requirements of a general situation. The second existing solution is a more powerful and general formulation that avoids this increase in memory storage. However, it is based on signal processing techniques and considerably deviates from the original TLM method, which may complicate its dissemination in the scientific community. The reformulation presented in this work exploits the benefits of both methods. On the one hand, it maintains the direct and conceptual approach of the original TLM, which may help to better understand it, allowing for its future use and improvement by other authors. On the other hand, the proposal includes an optimized treatment of the signals stored at the stub lines in order to limit the requirement of memory storage to only one accumulative term per field component, as in the original TLM versions used for isotropic media. The good behavior of the proposed algorithm when applied to anisotropic media is shown by its application to different situations involving diagonal and off-diagonal tensor properties.

Towards Modeling Partial Discharge Phenomena and Propagation in Power Networks Using the Transmission-Line Matrix Method

Partial discharge (PD), where high field strengths on power cables cause charge build up and discharge within a dielectric at sites of imperfections or inhomogeneities, can lead to noise issues and potential failure of the dielectric. This paper presents the first stage of a research activity that aims to develop a transmission-line matrix (TLM)-based simulation “workbench” useful to investigate PD events in a transmission line. The proposed approach allows the predicting of the electromagnetic disturbances generated by the PD event, and the analysis of external field coupling, such as from intentional electromagnetic interference or lightning, which can add to the field stresses. The paper is focused on defining the right modeling method to simulate PD phenomena in a transmission line context. The best approach to integrate the PD model with the model of the transmission line, useful to describe the propagation of the conducted and radiated emissions produced by PD, is analyzed. A first workbench is proposed, and the first simulation results are described. The paper concludes with the topics of further research.

An ADE-TLM Algorithm for Modeling Wave Propagation in Biological Tissues with Debye Dispersion

In this paper we present a Transmission Line Matrix (TLM) algorithm for the simulation of electromagnetic wave interaction with a Debye dispersive medium. This new formulation is based on the use of the polarization currents in the medium. The auxiliary differential equation (ADE) method is considered to deal with dispersion after the classical discretization. The accuracy and efficiency of this approach were tested on 1D Debye medium by calculating the reflection coefficient on an air-dielectric interface. The potential of the developed algorithm to model the existence of tumors in a human breast is also demonstrated. The obtained results compared with the analytic model show a good agreement. The number of operations needed for each iteration has been reduced, hence the computational time in comparison with time convolution techniques, while maintaining a comparable numerical accuracy.

Simulation and Protection of Lightning Electromagnetic Pulse in Non-Metallic Nacelle of Wind Turbine

When the nacelle of a wind turbine is struck by lightning, lightning electromagnetic pulse (LEMP) is generated inside the nacelle and consequently impacts inside electronic devices or even seriously destroys them. In order to study the LEMP inside the nacelle, this paper firstly built a full-scale model of a non-metallic nacelle. The lightning electromagnetic environment in the nacelle was simulated and analyzed by the transmission-line matrix method. Then the protective measures of applying metallic shielding mesh on the nacelle were studied, including the mesh size and material of the shielding mesh on the protective effect. The results show that LEMP in the nacelle can be effectively attenuated by metallic shielding meshes. The shielding effect is highly dependent on the conductivity of the shielding mesh material and the mesh size.