Nobody described how much more earthing is installed in switching
centers (COs), electric substations, etc just to obtain a little
better earthing. A ten foot earth ground rod can be a massive
earthing improvement for surge protection. And then high reliability
facilities may spend $thousands more just to make that earthing but a
little better. Why so much extra conductors and labor for just a
little better ground? Because every little better earthing means that
much more surge protection. What makes a protector even more
effective? Better earthing.

So yes, where surge damage is not acceptable, then facilities will
do that much more work just to get a little better earthing. Earthing
is critical for direct lightning strikes without failure. Does that
mean a homeowner without a massive earthing mat should do nothing? Of
course not. Locating 3 meter ground rods (per post 1990 NEC
requirements) less than 10 feet from breaker box and telco provided
surge protector means significantly better protection. Anyone
building a new home should plan their surge protection where footings
are poured - see nobody's reference to cadwelding. Footings with
appropriately installed conductors (rebar) provide a home with
significant improvement (Ufer grounds). Protection should be planned
when the footings are poured. Better earthing (surge protection) for
so little money.

Nobody also discusses single point earth ground that is essential
for surge protection. Why? Again, a protector is only as effective
as its earth ground. Single point earth ground is essential to an
effective protector.

Some homeowners don't have that single point option due to failures
by the builder. One utility describes how to fix that defective
earthing:
http://www.cinergy.com/surge/ttip08.htm

Why do serious facilities do so much for their earthing system?
Earthing provides surge protection - where surge energy must be
harmlessly dissipated. And then, as Nobody notes, sometimes that
earthing system gets compromised by geology we did not know about.

What happens if damage occurs? We return to locate an earthing
defect. Even a nearby pipeline may adversely affect that earthing
system. If damage results, then discover a defect in the earthing
system. As Nobody demonstrates, so much labor to make earthing even
better because a surge protector is only as effective as that earth
ground.

BTW, battery racks do not absorb surge energy. Another concept even
taught in basic circuit theory - superposition. To surges, that
battery rack is equivalent to a short circuit. Batteries do not
absorb energy (if ignoring a battery's internal resistance). Those
batteries essentially connect surge currents to wires on both sides of
those batteries. To a surge, batteries are electrically equivalent to
a wire. Batteries are typically well earthed - meaning those
batteries will act just like a shunt mode surge protector - connecting
surge energy into earth. Batteries don't work as surge absorbers.
Batteries connect (shunt, divert, clamp) surge energy into earth.

On May 5, 6:31 pm, "nobody " wrote:
I've been a TV repairman. I'm now a "communications electrician" which
means I deal with telephone lines/switches, land-mobile radio, microwave
radio systems, security systems, and the like; in high-voltage
switchyards and substations. We deal with huge surges from switching
transients and direct lightning hits on the transmission lines. I know
first-hand what happens when surges hit. When I said "transmission
lines", I'm talking both from the 60hz side as well as the RF side as
the lengths are sufficient to act that way.

Define "ground" or "earth", Mr w_tom. Have you ever run an ANSI spec
ohms test on one? I think not. I've done grounding for military tactical
radio systems and complete commo systems. What you think is "ground" may
not be ground at all due to soil composition. I've seen ground rod
"farms" made up of 20+ vertical 8' rods on a 10 foot grid come up in the
500 kilohms range when the same rods in the same location would test
lower than 1000 ohms if those same stakes were buried sideways 18" below
surface.

Substations/switchyards have "ground mats" of heavy copper wire in a
grid spacing of 1-2 feet and about 6 feet under everything that's
covered with gravel. It's also cad-welded at all intersections to
prevent corrosion. This ground mat system is also used at well-designed
radio sites. Even with this elaborate grounding system, a major
malfunction at 230KV can create such a voltage differential to induce
fatal "step voltage" between your legs.
.http://ballengearry.com.au/papers/St...e_update_for_2...

For 120Vac grounding on our equipment, we try our best to bring all
equipment grounds (racks and cable trays as well) to a single point that
*then* connects to the building's ground as close as possible. We do
have the advantage of most equipment running off DC at 24, 48, or 130
Vdc on huge battery racks that can absorb a lot of surge energy...