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PTP 250 User Guide Grounding and lightning protection
phn-2182_002v000
May 2011 2-13
Basic requirements
The following basic protection requirements must be implemented:
x
The ODU must be in ‘Zone B’ (see Lightning protection zones on page 2-11 ).
x
A lightning protection unit (LPU) must be installed within 600 mm (24 in) of the
point at which the drop cable enters the building or equipment room.
x
The drop cable must be bonded to the supporting structure in order to prevent
lightning creating a potential between the structure and cable, which could
cause arcing, resulting in fire risk and damage to equipment.
x
The drop cable must be grounded at the building entry point.
x
The drop cable must not be laid alongside a lightning air terminal.
x
All grounding cables must be a minimum size of 10 mm
2
csa (8AWG), preferably
16 mm
2
csa (6AWG), or 25 mm
2
csa (4AWG).
Grounding cable requirements
When routing, fastening and connecting grounding cables, the following requirements
must be implemented:
x
Grounding conductors must be run as short, straight, and smoothly as possible,
with the fewest possible number of bends and curves.
x
Grounding cables must not be installed with drip loops.
x
All bends must have a minimum radius of 203 mm (8 in) and a minimum angle of
90° ( Figure 2-2 ). A diagonal run is preferable to a bend, even though it does not
follow the contour or run parallel to the supporting structure.
x
All bends, curves and connections must be routed towards the grounding
electrode system, ground rod, or ground bar.
x
Grounding conductors must be securely fastened.
x
Braided grounding conductors must not be used.
x
Approved bonding techniques must be used for the connection of dissimilar
metals.