NUMERICAL MODELING FOR LEMP EFFECT EVALUATION INSIDE A TELECOMMUNICATION EXCHANGE

This paper presents a numerical modeling method developed for evaluati ng electromagnetic (EM) interference on the equipment inside a telecom munication exchange caused by a direct lightning stroke to a telecommu nication tower close (i.e., a few meters) to the exchange building, Co nsidering two different bonding configurations, EM interference is eva luated by calculating the electrical parameters: the EM fields, voltag es, 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 distributio n inside the building, The voltages and currents induced on shielded c ables were evaluated by means of a mixed technique, where the MOM proc edure is combined with a SPICE analysis, Numerical modeling was used f or two different situations: to simulate some experimental tests carri ed out in the field, where a 1.6 kA lightning current of a pulse gener ator was injected on the top of the 25 m high telecommunication tower close to a small exchange building; and to calculate the same paramete rs when a real lightning current strikes the telecommunication tower.