Lightning Protection System (LPS)
IEC/BS 62305-1 has defined four Lightning
Protection Levels (LPLs) based probable
minimum and maximum lightning currents.
Air termination system
The role air termination system capture
the lightning discharge current and dissipate it
harmlessly earth via the down conductor and
earth termination system. highlights that the air termination
components should installed corners,
exposed points and edges the structure.
External LPS design considerations
The lightning protection designer must initially
consider the thermal and explosive effects caused at
the point lightning strike and the consequences
to the structure under consideration. Depending
upon the consequences the designer may choose
either the following types external LPS:
• Isolated
• Non-isolated
External LPS design considerations
An Isolated LPS typically chosen when the structure
is constructed combustible materials presents a
risk explosion.
IEC/BS 62305-3 advocates the following, any
combination, for the design the air termination:
• Air rods (or finials) whether they are free-standing
masts linked with conductors form mesh
on the roof
• Catenary (or suspended) conductors, whether
they are supported free-standing masts or
linked with conductors form mesh the roof
• Meshed conductor network that may lie direct
contact with the roof suspended above
it (in the event that paramount
importance that the roof not exposed a
direct lightning discharge)
The standard makes quite clear that all types of
air termination systems that are used shall meet the
positioning requirements laid down the body of
the standard. This will ensure that the event a
lightning current discharge the structure,
the correct design and choice components
will minimise any potential damage.
An external LPS consists of:
• Air termination system
• Down conductor system
• Earth termination system
These individual elements LPS should be
connected together using appropriate lightning
protection components (LPC) complying (in the
case 62305) with IEC/BS 62561
series.
These LPLs equate directly classes Lightning
Protection System (LPS).—
Technical reference
IEC/BS 62305-3 Physical damage
to structures life hazard
IEC/BS 62305-3. Therefore important
to use correctly designed air termination system.
The main body this part the standard gives
guidance the design external Lightning
Protection System (LPS), internal LPS and
maintenance and inspection programmes.
LPL Class LPS
I I
II II
III III
IV IV
—
Table Relation between Lightning Protection Level
(LPL) and Class LPS (IEC/BS 62305-3 Table 1)
109
TECHNIC REFERENCE IEC/BS 62305 PHYSIC DAMAGE STRUCTURES LIFE HAZARD
.
The correlation between the four levels LPL and
LPS identified Table essence, the greater
the LPL, the higher class LPS required. Conversely non-isolated system
may fitted where such danger exists.
The three basic methods recommended for
determining the position the air termination
systems are:
• The rolling sphere method
• The protective angle method
• The mesh method
These methods are detailed over the following pages. This part the suite standards deals
with protection measures and around structure
