Lightning damage occurs by two primary means, direct contact and inductive
coupling.
Direct Contact - Lightning makes direct
contact with conductors including: power lines, grounding systems, telephone
and cable TV lines, and any metal objects which are part of the grounding
system. The lightning injects energy into the system causing a fast
rise in voltage and current, and also changing the normal sine wave pattern
of the alternating current (AC) system.
Inductive Coupling - When lightning strikes
the ground, buildings, trees, or surface waters, high current flow into the
earth creates large magnetic fields (magnetic fields are always created when
electrons move in a conductor). Once the lightning strike ends, the
magnetic fields do not disappear, but rather, the magnetic fields collapse
inward and produce high voltage transients on any conductors in the area.