A
lightning arrester is a device used on
electrical power systems and
telecommunications systems to protect the
insulation and conductors of the system from the damaging effects of
lightning. The typical lightning arrester has a
high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.