When the electrical potential between two clouds or between a cloud and earth reaches a sufficiently high value the air becomes ionized along a narrow path and a lightning flash results which can extend upto multiple kilometers.
buildings are protected from lightning by metallic lightning arrestors or surge arrestors extending to the ground from a point above the highest part of the roof. The arrestor has pointed edges on one side and the other side is connected to a long thick copper stripwire (down conductor) which runs down the building and connects to the earthing system.
in the event of lightning falling on the building, the lightning arrestor directs the charge through down conductor and into the earth through the earthing system, safely.

When the electrical potential between two clouds or between a cloud and earth reaches a sufficiently high value the air becomes ionized along a narrow path and a lightning flash results which can extend upto multiple kilometers.
buildings are protected from lightning by metallic lightning arrestors or surge arrestors extending to the ground from a point above the highest part of the roof. The arrestor has pointed edges on one side and the other side is connected to a long thick copper stripwire (down conductor) which runs down the building and connects to the earthing system.
in the event of lightning falling on the building, the lightning arrestor directs the charge through down conductor and into the earth through the earthing system, safely.