Fred wrote:

...
If your house if FIRMLY attached to the pole transformer, "surges" are
virtually impossible UNLESS you get hit by lightning.

"You" don't have to get hit. Strikes to power lines can cause damaging
surges into a building. So can close strikes. Surges can also enter on
cable and phone wires. And there are other sources of damaging surges.

NO surge
protector, no matter how expensive, says anything about LIGHTNING
PROTECTOR, ever. That would be a lie.

The surge guru at the NIST looked at essentially a worst case event - a
100,000A lightning strike to the high voltage wire on a utility pole
(with transformer) behind a house with typical urban overhead
distribution. There are multiple paths to earth. The surge to the house
was 10,000A max for each service wire to the house. Service panel
suppressors are readily available with higher ratings. The probability
of a worse strike is close to zero.

You can protect from very close lightning strikes.

Lightning strikes to a building, of course, require lightning rods.

The 23KV primary phase of
America's 3 phase Tesla multiphase AC power system is quite stable. The
natural magnetic hysteresis of the 60 hz core in your distribution
transformer prevents any pulses from being sent to your house until the
lightning protector in its primary fuse holder explodes in defeat.

Doesn't need the transformer. In the example above, a utility lightning
arrestor (installed on all the distribution transformers around here)
dumps the strike to earth via the grounding electrode on the pole. Since
the resistance to earth of that electrode is a few ohms at best, the
"ground potential" at the pole rises thousands of volts above "absolute
earth potential", and more particularly, above the earth potential at
the house. Since the secondary neutrals are connected to the "ground" at
the pole, this causes a large surge on the neutral to the house. A
significant portion of that surge is transferred to the hot wires by
inductive and capacitive coupling.

Usually the next worst to lightning for surges are normal and abnormal
utility operations. Potentially one of the worst of these is switching
of power factor correction capacitors. Utility produced surges can also
get into a building and cause damage to equipment.


"Surge Protector" is a great sales gimmick.

It is a "gimmick" use by the IEEE in an excellent guide on surges and
surge protection at:
http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf

And by the US-NIST in a surge guide at.
http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
This one is less technical and aimed at the unwashed masses.

Both say surges from lightning and other sources are a problem and you
can protect against them.
===============

In something that hasn't come up in this thread - the NIST guide, using
US insurance information as one source, suggests that high voltage
between power and cable/telephone/.... wires causes much of the damage,
not just a surge reaching equipment through the power wires. The IEEE
surge guide has an example of such damage starting pdf page 40.

To protect from high voltage between power and phone/cable wires, the
ground wire from the entrance protector for both phone and cable has to
be short and connect to the power earthing system near the power
service. If wires are too long, surges coming in on phone or cable
wiring can produce high voltage between those wires and power wires.
That is what is shown in the IEEE guide example starting pdf page 40.
With a large surge, the building ground can rise thousands of volts
above "absolute earth potential". Much of the protection is that power
and phone and cable wires rise together.

Particularly for expensive equipment with power and phone/cable
connection a plug-in suppressor may be useful. All interconnected
equipment needs to be connected to the same suppressor, and all external
wires - phone/cable/... - need to go through the suppressor. The voltage
on all wires is clamped to the ground at the suppressor. (This is also
in the example in the IEEE guide starting pdf page 40.)

--
bud--