User's Manual

PTP 250 User Guide Grounding and lightning protection
phn-2182_002v000
May 2011
2-11
Grounding and lightning 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.
Motorola recommends that PTP 250 installation is contracted to a professional
installer.
WARNING
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.
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’ (Figure 2-1) 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.