CEM compatibilité électromagnétique et réseaux d'énergie,perturbations,effets et solutions
Latreche, Med Elhadi
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In recent decades, electromagnetic disturbances become increasingly troublesome for electrical and / or electronic systems. These can also be a source of disturbance to neighboring systems or other users of the same system. This gives rise to a named discipline: EectroMagnetic Compatibility EMC ie the art of operating sensitive electrical systems in a disturbed electromagnetic environment but also reduces the disturbances caused by the electrical systems in their design. Multiple standards are therefore yet appeared and appear in order to regulate the levels of electromagnetic radiation that systems must withstand without altering their normal operation as well as maximum levels of electromagnetic interference that they produce during their operation. The fields liable to disturb the correct operation of an electricity network are derived primarily from the: ÿ Transient phenomena due to circuit breakers and disconnectors operations. ÿ Transient phenomena due to dielectric perforation. ÿ Overvoltage and overcurrent due to short circuit in systems of grounding. ÿ Transient phenomena due to the direct or indirect effects of lightning. ÿ Non-specific electromagnetic source for energy networks, such as transient high frequency of low voltage, electrostatic discharge, and radio broadcasts. ÿ Particular phenomena, such as nuclear electromagnetic pulse and geomagnetic interference. The objective of this thesis is the development of models and computational tools that allow the estimation of voltages and currents induced by external electromagnetic fields; particularly those produced by lightning in the air mesh networks and shielded cables. This thesis deals with the problem into breaking it down into three problems: ÿ Identification of the disturbance: presenting an overview of models describing the electromagnetic radiation associated with the return stroke lightning, as well as methods for calculating the electromagnetic fields produced by lightning, in the air and within the soil. ÿ Calculation of currents and voltages induced on overhead lines: by solving the coupling equations based on the theory of transmission lines by using the finite difference time domain method ""FDTD"".