Equipment Surge Protection-lightning-Protection-Institute
FREQUENTLY ASKED QUESTIONS
Does providing electrical protection for your equipment, warrant
placed and selected electrical protection equipment requires a
one-time known expense, whereas lightning
can be reoccurring, is totally unpredictable, and often results
in repair and replacement costs which are three times the one-time
cost for the electrical protection of a typical cell site.
Such damage can play havoc with communication budgets in
economically difficult times.
Does providing a capacitively coupled grounding system for the
maximum dissipation of lightning strike energy into the earth,
warrant the additional grounding effort and expense?
Yes. Most damage to
equipment and copper cable from a lightning strike is from the
resulting Ground Potential Rise (GPR) rather than from a direct
lightning surge. Special
grounding system design can reduce the possible GPR to a typical
grounding system to less than 300 Volts 8 out of 10 times.
Reducing the lightning induced GPR to a grounding system from
6000 Volts-Peak to approximately 300 Volts-Peak can prevent damage to
equipment at a typical cell site.
Is providing a capacitively coupled grounding system design cost
Yes. A single lightning strike to a typical cell tower
will average approximately $25,000 in equipment damages.
Sites experiencing lightning damage may be subjected to several
strikes in a year, pushing repair costs to $50K or more.
However, the addition of a capacitively coupled grounding
system design using radials, sacrificial anodes, and single-point
grounding techniques will usually add only about $8000 to the total grounding
a recommended 5-ohm ground to remote earth with a typical
grounding system using a single ground ring with ground rods,
provide the same lightning energy dissipation as a 5-ohm ground to
remote earth with a capacitively coupled grounding system?
A. Absolutely not.
Lightning surge current is made up of frequencies between DC and
2MHZ. Thus, when both grounding systems are measured resistively at 5 ohms, the
capacitively coupled grounding system for lightning provides a
much lower surge impedance to remote earth, and thus is a much
better grounding system. It
is difficult to determine exactly how much better, but I estimate that equipment protected by a 5-ohm ground to remote
earth using a single ground ring with ground rods will experience
a voltage rise five to ten times greater than equipment protected
by a 5-ohm ground to remote earth with a capacitively coupled
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