2. LIST OF CONTENTS
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LEAP INFRAASYS PVT LTD
1- What is lightning & lightning protection
system?
Anatomy of a Lightning Stroke,
2- Why need lightning protection?
Need for lightning protection,
Calculation of need for protection as per
standard,
3- Main concept of the protection.
4- Component parts:-
a) Air Terminations;
b) Down Conductors;
c) Earth Terminations;
d) Earth Electrodes.
3. What is lightning & lightning protection system?
Lightning- Electrical discharge of
atmospheric origin between cloud and
earth comprising one or more impulse of
many kilo amps.
Lightning protection system- The whole
system of the conductors used to protect a
structure from the effects of lightning.
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4. Anatomy of a Lightning Stroke
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As a thunderstorm grows, electrical
charges build up within the cloud.
Oppositely charged particles gather at
the ground below. The attraction
between positive and negative charges
quickly grows strong enough to
overcome the air's resistance to
electrical flow. Racing toward each
other, they connect and complete the
electrical circuit. Charge from the ground
then surges upward at nearly one-third
the speed of light and we see a bright
5. Electrons begin
zigzagging
downward. This
is the “stepped
leader.” As the stepped leader
nears the ground, it
draws a streamer of
positive charge upward.
As the leader and
streamer come together,
a powerful electrical
current begins flowing.
Current begins
the return stroke,
an intense wave
of positive
charge traveling
upward about
60,000 miles per
second.
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6. Why need lightning protection?
More impulse of Kilo amps, is injurious for
the peoples and animals, either directly or
indirectly by causing fire and explosions
and it can also disturb the Electrical /
Mechanical system.
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7. need for lightning protection
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Where large numbers of people congregate.
Where essential public services are concerned.
Where the area is one in which lightning
strokes are prevalent.
Where there are very tall or isolated structures.
8. Calculation of need for protection as per standard
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• The probability of a structure or building
being struck by lightning in any one
area is the product of the ‘lightning flash
density, Ng’ and ‘effective collection area’
of the structure.
• The lightning flash density is the number
of (flashes to ground) per km² per year.
• The effective collection area of a
structure is the
area on the plan of the structure extended
9. Example to check the necessity of lightning protection
Checking of protection requirement for hospital building
I/P O/P
Length (L) m 70 Collection area (Ac) m²
width (W) m 12
(LXW)+2X(LXH)+2X(WX
H)+∏H² 2794
Height (H) m
10
The probable number
of strikes (risk) to the
structure
per year is:
P =Ac X Ng X 10¯6,
Where Ac=collection
area Ng=Flash
density 0.0019558
Thunder storm days /
year
From IS 2309, location
wise 30
Flash density (Ng)
Lightning flashes per
km² per year 0.7
Weighting factor
A (Use of structures) 1.7
Overall multiplying
factor
1.4
B (Type of
construction)
0.8
C (Contents or
consequential effects)
1.7
D (Degree of isolation) 2
E (Type of country) 0.3
Overall risk factor 0.0027130862.7 x 10¯³
As per IS 2309, clause no. 8.16 if result is greater than 10¯5, then protection is necessary
10. Main concept of the protection
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Air termination installed above the
structure intercept lightning discharges
and sends the current to the ground
electrode through the down conductor
(Fig-1).
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18. Component parts
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The principal components of a lightning
protection system are as follows:
a) Air Terminations;
b) Down Conductors;
c) Earth Terminations;
d) Earth Electrodes.
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19. Air terminations
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Air termination networks may consist
of vertical or horizontal conductors or
combined of both.
Minimum Dimensions Component
Parts
Reference- Clause no.12.1.1 (IS-2309)
Component(Air termination) Dimensions
(mm)
Area
( mm2)
Aluminium, copper and galvanized
steel strip
20 X 3 60.00
Aluminium, aluminium alloy or
phosphor bronze and galvanized
steel rods
10.0 dia 78.54
20. Down Conductors
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Conductor that connects an air termination with
an earth termination. The function of down
conductor is to provide a low impedance path
from the air termination to the earth electrode so
that the lightning current can be safely
conducted to earth.
The following table defines the
minimum dimensions for down
conductors according to
IEC 1024-1
Down
Conductor
Material Down Conductor (mm2)
Cu 16
Al 25
21. Earth Termination
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The part of the lightning protective system
which is
intended to discharge lightning current in to
the
general mass of earth.
22. Earth Electrode
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• The part of the earth termination
making direct
electrical contact with earth.
• The function of the earth electrode is to
dissipate
the lightning strike safely in to the
ground.
