Cambium Networks PTP 250, User Manual

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PTP 250 User Guide Grounding and lightning protection
phn-2510_002v000 (Mar 2012) 2-17
General protection requirements
To adequately protect a PTP 250 installation, both ground bonding and transient voltage
surge suppression are required.
Basic requirements
The following basic protection requirements must be implemented:
x
The ODU must be in ‘Zone B’ (see Lightning protection zones on page 2-16 ).
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
cross-sectional area (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 13 ). 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.