Master Projects

  • Design and test of a magnetic field sensor for the measurement of lightning magnetic fields (Semester or Master Project)

Contact person Antonio Sunjerga, tel. int. 34814

Description The aim of this project is to design a passive magnetic field sensor for the measurement of lightning magnetic fields. The sensor will be installed near the Säntis tower, which has been instrumented for lightning current measurements.

 

  • Mitigating the radiated emissions from a wireless charger (Semester or Master project)

 

Contact person :  Farhad Rachidi

Description  –  Most laws of nature feature invariance under time reversal (TR), which enables a wide range of applications of TR in different fields of engineering. Despite dealing with various practical issues, a general TR procedure can be simply summarized in two steps, (i) a diverging signal originated by a source (and distorted in an inhomogeneous medium) is captured by one or several receivers, and (ii) the captured time-domain signals are time-reversed and synchronously back-injected through the same medium. As a result, the back-propagated signals are refocused to the initial source point. In this project, we will study theoretically and experimentally the performance of TR when the back-propagation medium is not strictly identical to the direct time medium.

Remark: This project could be continued with a three-weeks stay in Iran (July 2017) in the framework of a new inter-universities education program, all expenses paid.

  • Electromagnetic Time Reversal in Changing Media (Semester project)

    Contact person:  Farhad Rachidi

    Description  –  The use of surge arresters helps improve network protection and increases the reliability of the transmission system. Direct lightning strikes to the transmission line towers or to the shielding wire can generate severe overvoltages at the tower body resulting in energy bypass by surge arresters. 

    In commercially available software packages, the frequency-dependent behavior of tower-footing grounding system is disregarded and the system is treated in a simplified fashion. In doing so, the grounding system is modeled either as a lumped resistor or as an equivalent circuit of the lumped inductor resistor and capacitor whose values are often calculated based on the quasi-static assumptions. It follows that these models fail in providing accurate results at high frequencies when used for the calculation of lightning generated overvoltages. 

    In this work, we propose to incorporate a frequency-dependent grounding model into the EMTP-RV software package and evaluate  the energy absorption of surge arresters when subjected to lightning. 

    • Impact of Frequency-dependent Grounding on the Efficiency of Surge Arresters Against Lightning Surges (Semester project)

       

 

Remark: This project could be continued with a three-weeks stay in Iran (July 2017) in the framework of a new inter-universities education program, all expenses paid.

  • Etude de la propagation d’impulsions électromagnétiques au travers de structures en bois ou en fibre de verre (in cooperation with Montena) (Master Project)

Contact person  Bertrand Daout (Montena)

Description  –  La société montena technology développe, produit et installe des systèmes d’essai de compatibilité électromagnétique, essentiellement dans le domaine impulsionnel à très haute intensité. Un des systèmes proposés consiste en un générateur d’impulsion de haute tension connecté à une ligne de transmission sous laquelle les objets à tester sont disposés. La taille de ces systèmes d’essai a considérablement augmenté et il est dès lors nécessaire de soutenir les parties métalliques par des structures diélectriques que l’on désire le plus transparent possible aux ondes électromagnétiques. Les matériaux possibles sont le bois et la fibre de verre. 

Il a cependant été constaté par mesure et par simulation que de telles structures, selon leur volume, leur forme, ou leur position peut influencer les performances des lignes de transmission (réflexion ou transmission ralentie). Le but de ce travail est de comprendre les phénomènes en jeu et de déterminer dans quelle mesure des structures en bois peuvent être utilisées comme structure portante (portique de départ) mais aussi comme parois de bâtiments sans perturber la forme d’onde de l’impulsion double-exponentielle avec un temps de montée de l’ordre de grandeur de la nanoseconde.

Les buts du travail sont les suivants :

  • Etude des cas réels problématiques déjà rencontrés.
  • Modélisation des matériaux (bois et fibre de verre) dans le domaine de fréquence nécessaire.
  • Simulations électromagnétiques 3D de cas basiques avec un front d’onde plane en impulsionnel et en fréquentiel (variation de l’épaisseur, de la taille, de la géométrie, des paramètres électriques des matériaux, etc…)
  • Simulations de cas réels.
  • Elaboration de règles de design pour les futures installations.
  • Mesures de confirmation de quelques cas simples sur une ligne de transmission à l’échelle.

Further information – Two-page document.

 

  • Lightning Protection of Large Wind Turbines (Master Project)

Contact person  Alexander Smorgonskiy, tel. int. 34814

Description  – The increasing number of wind turbine installations in different countries makes their reliability of crucial importance. Due to the typical installation zones, lightning events represent one of the main causes of damages of these types of power plants.Consequently, the design of lightning protection of modern wind turbines will be a challenging problem that requires the modelling of the electromagnetic transient response of main turbine structural elements(tower and blades along the presence of composite materials) in order to study the transient processes induced into the electrical power system. In this project, we propose to use the finite-element method(FEM) to model a wind turbine in view of the design of its lightning protection system. To this end, use will be made of the electromagnetic time domain module of the COMSOL multiphysics code which solves transient wave equation governing the structure. The advantage of COMSOL is that it can be applied directly in time domain and it can also include thermal effects and mechanical stresses resulting from the energy dissipation in composite laminates due to the circulation of eddy currents.

 

  •  Regional study of the link between temperature and lightning activity in Switzerland (Master Project)

Contact person  Amirhossein Mostajabi, Phone: 3 4882

Description  – It has been an issue of great attention to investigate whether lightning is susceptible to variations in the surface air temperature. Previous studies suggest that the response of lightning activity to surface air temperature could be investigated using data on thunderstorm days, satellite-based lightning data, upper-tropospheric water vapor content, Schumann resonances, and the global electrical circuit from a global point of view. In this prject, we proose to study the response of local lightning to local temperature near the Säntis mountain (2502 m ASL) in the eastern Swiss Alps during the period 1880-2015. 

  •  Surface Discharge of Liquid-Dielectric Interface (in cooperation with Selfrag AG) (Master Project)

Contact person  Dr. Abbas Mosaddeghi (Selfrag AG), Dr. Reinhard Müller-Siebert (Selfrag AG), Prof. Farhad Rachidi (EPFL ; tel. int. 32620).

Further information – Attached description

 

  • Analysis of lightning currents measured at Säntis Station (Semester or Master Project)Analysis of lightning currents measured at Säntis Station

Contact person – Mohammad Azadifar, tel. int. 32667

Description  –  A new station for the measurement of lightning currents was set up at the Säntis tower. The current is measured at two locations along the tower, using, at each height, two different sensors. Maintenance, monitoring and control functions are carried out remotely over the Internet using National Instruments Compact-RIO modules linked via 100Base-FX fiber optics Ethernet to a control room that is connected to the Internet over a standard ADSL link on the Säntis. Since the installation of the measuring equipment on May 19, 2010 and subsequent testing, the system successfully recorded more than 180 lightning flashes. The objective of the project is to analyze the obtained urrent waveforms and extract statistical parameters. 

 

  • Correlation of the lightning data obtained at Säntis Measurement Station with meteorological data (Semester or Master project)

Contact person – Mohammad Azadifar, tel. int. 32709

Description  – Considering the importance of global warming and climate change, the problem of possible relationships between climate and lightning activity has recently attracted the attention of researchers. Positive correlations between global lightning activity and global temperature variations have been already confirmed in several studies where it has been shown that a 1-degree Celsius variation in the temperature would result in an increase of lightning activity, ranging from 10% to 100%. The objective of this project is to correlate direct lightning current measurements obtained at Säntis tower with meteorological data available from the Swiss Meteo.

  

  • Application of Electromagnetic Time Reversal to Locate Faults in Power Networks (Semester or Master Project)

Contact person  Zhaoyang Wang, tel. int. 30276

Description – The objective of the project is to develop a method and algorithm based on the Electromagnetic Time-Reversal (EMTR) for locating faults in power systems. The use of the EMTR technique appears to be particularly promising for locating faults in passive and active electrical distribution networks in view of their radial structure. The method will be tested and validated using numerical simulations and experimental testing.

 

  • Time Reversal Cavity in Transmission Line Networks (Semester or Master Project)

Contact person – Zhaoyang Wang, tel. int. 30276 

Description  The concept of time-reversal cavity was proposed for acoustic waves and later extended to electromagnetic waves, using the Lorentz reciprocity principle. It is accepted that a time-reversal cavity is a theoretical concept and cannot be realized experimentally. Although this is true in a 3-D situation, preliminary studies suggest that in the case of power networks in which waves propagate along the longitudinal direction of the lines (1-D situation), such a time-reversal cavity is realizable. We propose to design, simulate and experimentally validate such a cavity for the case of inhomogeneous power networks.