Protection of Substations
In most Lightning Protection applications
the protection levels are selected by the
owner of the property. The protection levels
in LP of substations are dictated by the
Basic Insulation Level (BIL) of the equipment
being protected. Standard IEEE
998
includes
a table that correlates the protection levels
with BIL. Obtain the information on BIL from
the utility company, prior to designing the
system. In LP protection of substations, all
terminal placement methods mentioned
in IEEE
998
are applicable including the
Collection Volume method. nVent ERICO
System
3000
can be mounted directly on
the structure, or on freestanding mast that
would be supplied
by the customer.
Long Lengths of Ericore
Downconductor
Most installations can be conducted with a
single Ericore cable as described earlier in
this manual. However, where the installation
involves a long single length of Ericore
cable, additional measures may be needed
to ensure that the voltage build up will not
exceed the voltage withstand rating of the
cable during a lightning strike.
Where the length of the Ericore cable
between the terminal and the grounding
system exceeds
70
m (
230
ft.) follow the
chart in Figure
33
of the manual.
However, if the result indicates that
additional measures are required, then
a single uninterrupted length of Ericore cable
cannot be run.
Protection of Tall Structures
The statistical probability of a lightning
strike to the side of the structure is
1
%
or
2
%, depending on the height of the
structure. This should be discussed with
the architect or the owner, since there
is a balance between the risk factor and
aesthetic appearance. Most skyscrapers
are built in highly developed areas, which
decreases the probability of a lightning
strike to the side of the structure. Only the
portion of the structure that extends above
the surrounding structures would be subject
of concern. In most instances, additional air
termination is not implemented.
