Simulation of lightning electromagnetic fields and their interaction with low voltage power installations : By Arturo Galván Diego

Sammanfattning: An increasing number of damages of electric nature are being observed on modem electronic sensitiveequipment connected to low voltage power installation (LVPI) networks when they are exposed tolightning electromagnetic fields (LEMPs), or indeed, any other electromagnetic pulse (EMP). The wayin which these fields affect the electronic equipment depends on the properties of the interferencesource, the electromagnetic interaction and the hardness of the device. The aim of this study was tomodel some of the process of the lightning flash that generate the adverse electromagneticenvironment and to investigate the transient response of simple and complex LVPI networks whenexposed to natural lightning Sashes.Two models, based on experimental observations in long sparks, were developed to describe thestepped leader and the return stroke processes of cloud-to-ground flashes. The models, which are ableto reproduce the main features of measured LEMPs, can easily be used or adapted for engineeringpurposes in order to evaluate, by analytical simulations, overvoltages upon aerial and undergroundcables.Two analytical techniques, one for simple and other for complex installations, were developed andvalidated by experimental data gathered when several LVPI networks were exposed to LEMPs. Thepredictions of the lightning induced voltages upon the networks are done in time domain, avoidingcomplex Fourier transformations otherwise required in other proposed models.By using the two techniques, the transient response of different LVPI networks to lightningelectromagnetic fields generated by natural lightning flashes was investigated. It was found that theamplitude and wave shape of the lightning induced voltage upon the networks depends on thefollowing factors: source of interference, value and position of the loads connected to the LVPI,measuring point, angle of incidence, height of the installation, soil conductivity, number of outlets andthe effect produced by the natural shielding of the building housing the aerial conductors.