PTP 450 Configuration and User Guide
Grounding and lightning protection
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pmp-0815 (August 2015)
Grounding and lightning protection
This section describes the grounding and lightning protection requirements of a PTP 450
installation.
Electro-magnetic discharge (lightning) damage is not covered under warranty.
The recommendations in this guide, when followed correctly, give the user the
best protection from the harmful effects of EMD. However 100% protection is
neither implied nor possible.
The need for power surge protection
Structures, equipment and people must be protected against power surges (typically
caused by lightning) by conducting the surge current to ground via a separate preferential
solid path. The actual degree of protection required depends on local conditions and
applicable local regulations. Cambium recommends that PTP 450 installation is contracted
to a professional installer.
Standards
Full details of lightning protection methods and requirements can be found in the
international standards IEC 61024-1 and IEC 61312-1, the U.S. National Electric Code
ANSI/NFPA No. 70-1984 or section 54 of the Canadian Electric Code.
Lightning protection zones
The ‘rolling sphere method’ (
) is used to determine where it is safe to mount
equipment. An imaginary sphere, typically 50 meters in radius, is rolled over the
structure. Where the sphere rests against the ground and a strike termination device (such
as a finial or ground bar), all the space under the sphere is considered to be in the zone of
protection (Zone B). Similarly, where the sphere rests on two finials, the space under the
sphere is considered to be in the zone of protection.
Figure 39
Rolling sphere method to determine the lightning protection zones
Assess locations on masts, towers and buildings to determine if the location is in Zone A or
Zone B:
Zone A: In this zone a direct lightning strike is possible. Do not mount equipment in
this zone.
