Lightning Protection Systems
Lightning is actually a visible discharge of static
electricity within a cloud and also between clouds. The light
protection system offered by us provides a means by which this
discharge might leave or enter the Earth without actually
passing through the damaging non-conducting parts of a
structure, like those made of wood, brick, tile of- concrete.
Such a lightning protection system does not prevent lightning
from striking but provides a means for controlling it and
preventing damage by providing a low resistance path for the
discharge of lightning energy.
The Lightning Protection System has undergone many changes and
today's lightning protection system exhibit the best in terms
of design, materials and installation, thus valuable life and
property can be well protected from nature's hazardous and
exciting phenomenons like, lightning. Lightning is a unique
form of energy and an expert can only install proper
protection systems against it.
The BS6651:1992 norms states that
the provision of conventional lighting protection system should be
There are certain principle design
considerations of a conventional lighting system as per the BS
6651 norms, these are- •Air Termination Network
•Earth Termination Network
Air Termination Network
This phenomenon is applicable on
high risk structures like, explosives factories, nuclear power
plants wherein no part of the roof should be more than 2.5m from
from an air termination conductor. This can be done by applying a
5m x 10m mesh to the roof. 10m x 20m Mesh 60 m.
Generally for most structures a
mesh measuring 10m x 20m is actually sufficient. The range of air
termination protection is considered to be 45 for heights up to
20m. Above this height the production zone is determined by the
"rolling sphere method" i.e., 140m.
The location of the down conductor
is majorly influenced by the architectural design. This is like,
there has to be one down conductor after every 20m. These are
evenly spaced at not more than a distance of 20m. These must be
rooted as directly as is possible from the air termination to
earth termination networks and the loop should not exceed eight
times the width of it's open side.
Earth Termination Network
Every Down conductor should be
provided with a separate Earth Termination. For testing purpose
the provision should be made in each down conductor.
The Bs6651norms mentions that the resistance to earth for complete
lightning protection at any point should not exceed beyond 10
ohms. This norm also mentions that the combined length of the
earth rod system should be no less then 9m, while each individual
earth rod should be not less than 1.5m in length.
As soon as lightning protection
system is struck, its electrical protection with respect to earth
is considerably raised and if resistance provided by the down
conductor is more than the other metal work on the structure, the
discharge looks for alternative path to Earth by way of side
Thus, it is important that all the exposed metal work is bonded
into the lightning protection installation.