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The basic principle of HVI conductors is
that the lightning current carrying conductor
is covered with insulating material to main-
tain the required separation distance from
other conductive parts of the structure.
ELECTRICAL PROTECTION + SAFETY
• Prevention of creeping discharge
• Have sufficient current carrying capability via sufficient cross
sectional area of the inner conductor
Components of an HVI conductor.
The specifically designed HVI conductors allow for the prevention of
creeping discharge and the safe dissipation of the lightning current
into the ground.
HVI conductors via their semi-conductive sheath prevent creep-
ing discharge of the lightning current by specifically influencing the
electric field within the ‘sealing end’ range. Therefore the lightning
current is trapped into the special cable and is safely dissipated
while maintaining the required separation distance. It is of vital
importance that the electric field within the ‘sealing end’ range not
be interfered with.
Types of HVI conductor
Since 2003, three different types of HVI conductor have been de-
veloped to meet the growing requirements of different installation
environments:
• HVI light conductor [separation distance = 45 cm (air), 90 cm (solid
material) - suitable for LPL 3, 4]
• HVI long conductor [separation distance = 75 cm (air), 150 cm
(solid material) - suitable for LPL 2 ,3, 4]
• HVI power conductor [separation distance = 90 cm (air), 180 cm
(solid material) - suitable for LPL 1, 2, 3, 4]
The HVI power conductor was found to be suitable for the Project
Lumen installation.
Maximum HVI conductor length
Based upon the separation distance calculations SANS / IEC 62305
Part 3 [1], the maximum conductor length of the HVI conductors was
calculated as follows:
Where:
k
m
= Insulation material - air = 1
S
= Separation distance = 0,88 m
k
i
= Selected Lightning Protection Level (LPL 1) = 0,08
k
c
= Number of down conductors = 1
Therefore:
L
max
= 11 m
The maximumHVI conductor length of 11mwould not be sufficient to
meet the requirements on the site due to the fact that the length to the
zero potential point (concrete steel reinforcing) was 18 m. Therefore
a lightning protection system using two HVI down conductors from
the air terminals had to be designed!
Isolated air termination system
The air termination system was designed to intercept the lightning
strike and prevent penetration into the protected space (i.e. LED screens
and frames). The air termination system was designed in accordance
with SANS / IEC 62305 Part 3 [1] using two methods of protection:
Angle of protection
The angle of protection was calculated using a lightning protection
level 1 system at a height of 18 m. The calculated angle of protection
= 27 °, which gives a zone of protection of 9,17 m from the top of the
air terminal. This zone of protection covers the structural steelwork
of the LED frames.
Connection to
Air terminal
Injection of
lightning
Impulse current
Inner conductor
High-voltage Resistant insulation
Semiconductive
Sheath
Sealing end range
Connection
to the
Equipotential
bonding
System
Angle of protection
LPL1 @ 18m high
Route of
HVI power
Conductor
h= Height
of the air
termination
rod
Distance of
Protection Zone
Angle of
Protection
a
3m HVI
Mast &
Bracket
27°
L
max
=
k
m
· S
k
i
·
k
c
Electricity+Control
April ‘15
16