—
Technical reference
IEC/BS 62305-3 Physical damage
to structures life hazard
The rolling sphere method
The rolling sphere method simple means of
identifying areas structure that need protection,
taking into account the possibility side strikes to
the structure. The basic concept applying the
rolling sphere structure illustrated above. values mesh size corresponding the
Class LPS
Class LPS Mesh size (m)
I 5
II 10
III 15
IV 20
110 FURSE® EARTHING LIGHTNING PROTECTION
QUALIT SOLUTIONS FOR SAFEGUARDING PEOPLE, STRUCTURES AND SERVICES
. The protective
angle afforded air rod determined from
Table IEC/BS 62305-3.
Varying the protection angle change the
simple 45° zone protection afforded most
cases 6651.
—
01 Application the
rolling sphere method
—
02 The protective
angle method for
a single air rod
—
01
—
02
Tip air termination
Reference
plane
Protective
angle
Radius of
protected area
Height air
termination rod
above the reference
plane the area
to protected
h
A
C
Rolling
sphere
radius
Air termination
required
—
Table Max.
The protective angle method
The protective angle method mathematical
simplification the rolling sphere method. The
protective angle (α) the angle created between the
tip (A) the vertical rod and line projected down
to the surface which the rod sits (see above).
The protective angle afforded air rod is
clearly three dimensional concept whereby the
rod assigned cone protection sweeping
the line the angle protection full 360°
around the air rod. Furthermore the new standard
uses the height the air termination system
above the reference plane, whether that be
ground roof level.
The protective angle method better suited for
simple shaped buildings.
The rolling sphere method was used 6651,
the only difference being that IEC/BS 62305
there are different radii the rolling sphere that
correspond the relevant class LPS (see Table
4). values rolling sphere radius corresponding
to the Class LPS
Class LPS Rolling sphere radius (m)
I 20
II 30
III 45
IV 60
—
Table Max.
The protective angle differs with varying height
of the air rod and class LPS. However this method is
only valid height equal the rolling
sphere radius the appropriate LPL.This method suitable for defining zones of
protection for all types structures, particularly
those complex geometry
