A lightning stroke which reaches a peak current of 30kA

A  lightning  stroke  which  reaches  a  peak  current  of  30kA  in  1μS  strikes  a  25  m
tower on a 275kV transmission line. The line has a ground wire joining the tops of the towers; its
surge  impedance is 500  Ω  . The tower surge impedance  is 120  Ω      and the ground footing
resistance is  60  Ω      . Determine whether the line  insulators will flashover as a consequence of
the surge,  assuming that their impulse flashover strength is 1050 kV.  A coupling factor 0.3 with
the phase conductor can be assumed; the impedance of the stroke channel can be ignored; a wave
velocity on the tower of 2.98 x 10^8 m/s can be assumed. Show the surge progressions in the
form of Bewley lattice diagram.