Numerical modeling for LEMP effect evaluation inside a telecommunication exchange

This paper presents a numerical modeling method developed for evaluating electromagnetic (EM) interference on the equipment inside a telecommunication exchange caused by a direct lightning stroke to a telecommunication tower close (i.e., a few meters) to the exchange building. Considering two different bonding configurations, EM interference is evaluated by calculating the electrical parameters: the EM fields, voltages, and currents. A special method of moment (MOM) wire-grid procedure using "dipole" and "loop" type basis and test functions was used as a numerical tool. A simple model was also developed for simulating the equipment mechanical structures which modify the field distribution inside the building. The voltages and currents induced on shielded cables were evaluated by means of a mixed technique, where the MOM procedure is combined with a SPICE analysis. Numerical modeling was used for two different situations: to simulate some experimental tests carried out in the field, where a 1.6 kA lightning current of a pulse generator was injected on the top of the 25 m high telecommunication tower close to a small exchange building; and to calculate the same parameters when a real lightning current strikes the telecommunication tower.