EQUIPMENT DAMAGE FROM LIGHTNING INDUCED GROUND
POTENTIAL RISE (GPR) RESULTS FROM THE LACK OF PROPER SINGLE
POINT GROUNDING (SPG) AND ISOLATION OF POWER AND DATA CIRCUITS
FROM REMOTE GROUND
EXECUTIVE SUMMARY:
Equipment damage from lightning induced GPR is
totally preventable with engineering design of the grounding
system, correct bonding of the equipment to ground bars, and
isolation of equipment from other ground planes.
Too often, communication companies fail to
take steps to protect their assets from lightning and ground
potential rise damage assuming that their infrastructure
insurance will cover their losses. However, it often takes
months for insurance providers to respond to claims and there is
almost always unforeseen residual damage to electrical equipment
which will not reveal itself for six months or more following an
event.
It is very important to understand that
equipment damage is actually the lesser part of your troubles
and cost to your company. The greatest cost component to a
lighting strike or GPR event is ‘downtime’ followed by increased
maintenance cost as a close second. As a rule of ‘thumb’ you can
triple your equipment damage cost from a lightning strike to
estimate total financial damages. In some cases, client anger
from their own business downtime that results from your downtime
may much more than triple your eventual damages. Many a
communication tower has been abandoned following a single
lightning strike.
RECOMMENDED SOLUTION:
Nearly all electrical equipment damage from
lightning may be placed into two categories; improper site
grounding from lightning induced GPR, and the failure to isolate
equipment circuit connections to a remote ground plane.
There are no codes available in print today
that recommend protection of equipment from lightning strike
energy. However, IEEE Standard 1692-2011 is available and
expertly details methods for the protection of equipment from a
lightning strike.
Current available recommendations from other
sources are very sketchy, provide little or no support, and
rarely is GPR mentioned. When GPR is sometimes alluded to,
shunting devices such as gas tubes, MOV's, and SCR's are
recommended as possible solutions. Sources not providing
necessary information to design against lightning induced GPR
include NEC, NESC, and NFPA 780, and Motorola’s Standards and
Guidelines for Communication Sites (R56 Issue B).
Shunting devices will not protect electronic
equipment from a GPR, whether induced from lightning or from a
power line earth return fault. Shunting devices merely offer an
additional path off the site to remote ground and guarantee a
connection to the communication path in the reverse direction
from which they were intended to operate. This of course also
guarantees the destruction of your equipment.
Since the elimination of the remote ground
path (copper communications wires) may not be a reasonable
solution, why not the next best thing? Isolate the wire-line
conducting path. Remember that this only one part of a two-part
solution. Proper bonding and grounding of equipment is the other
part of your solution.
The single most important solution of
equipment damage from lightning induced GPR, is the utilization
of a Single Point Ground (SPG) and a capacitively coupled radial
grounding system. If the SPG is not considered or placed
correctly, you can expect equipment damage to plague you
forever, even with a perfectly designed radial grounding system.
LPGI & Affiliates has 42 years of professional
experience in all types of grounding and electrical protection
from lightning. We are your answer to the very expensive
downtime that may occur with your next lightning strike.
Cellular tower sites, TV Antenna sites, radar sites, wind farms,
substations and power plants are our specialty.
Our consulting fee with AutoCAD Drawings and a
step by step procedure on the resolution of your lightning
issues will be a fraction of your total cost to your next
lightning strike.
LPGI & Affiliates
962 Coronado Drive
Sedalia, CO 80135-8303
303-688-5800
Fax: 303-688-5551
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