II. ELECTRICAL EQUIVALENT MODE
The cylindrical metal structure can be considered as a
grid of conductors electrically connected to each other
forming a cage as shown in Fig. l(a). The cage has
been simulated by means of an electric equivalent
network. The equivalent model takes into account that
the lightning current flowing into the conductors, as
an effect of a direct lightning stroke, presents
significant harmonic components not exceeding 10
MHz. This upper limit does not allow the
representation of conductor elements using simple
lumped parameters. The condition