How often does your 120 VAC exceed 330 volts? 330 volts is
a number even printed on plug-in protector boxes. If AC line
imperfections were occurring that high with any frequency,
then you were replacing every dimmer switch, clock radio, AC
powered smoke detector, and major household appliances
frequently. Those 330 volt transients typically don't exist
from the utility. Therefore the protector remains inert -
does nothing - sees no such imperfections.

AC line imperfections are less voltage. Expensive
electronic equipment contains internal protection that makes
'imperfections' even up to 600 volts irrelevant. Appliances
already contain internal protection. Protection that assumes
the major and destructive transients will be earthed before
entering a building.

The transient that does exist typically once every eight
years is a common mode transient on AC electric that 1)
occurs quickly (in microseconds), 2) requires a complete
circuit to earth ground in order to do appliance damage (which
is why phone appliances are so often damaged), and 3) that a
plug-in protector does not even claim to protect from.

Protectors are effective when they make the 'less than 10
foot' connection to earth ground. Called 'whole house' type
protectors. That is what a utility installed protector does
IF your building has been wired to post 1990 code requirements
for earthing. A utility typically does not even check that
your earthing exists. Household earthing being the
homeowner's responsibility; not utilities. No earth ground
means no effective protection even from that utility provided
protector that typically costs a very expensive $5 per month.

Of course utilities can charge so much because so many
homeowners spend much more money on ineffective plug-in
protectors. That utility provided protector costs many times
less per protected appliance and does more (assuming the post
1990 earthing exists). But the best protection for the money
is a homeowner installed 'whole house' protector installed in
breaker box and with the necessary earthing connections. Home
Depot even sells the Intermatic IG1240RC. Many others are
available.

Unplugging is unreliable. The human is typically available
and awake less than 1/3rd of each day. But effective 'whole
house' protection means no need to unplug; needs no unreliable
human to provide protection. 'Whole house' protector is
always there; doing what existing internal appliance
protection requires to not be overwhelmed.

Bottom line: a protector is only as effective as its earth
ground. Something that plug-in protectors fear you might
learn and avoid mentioning.

Ricky Eck wrote:
Actually those are not as uncommon as some people think. Line
"Surge Protectors" from the electric company can be purchased. It
is supposed to work better then ones in your home. This is
according to the electric company. However, as I stated before,
I would be skeptical on it. I have not researched it too much,
and I don't know if they come with a guarantee of your equipment
if something did fail. I would think that there is someone out
there that works for the power company, that can give us some
info on these protectors. I too would be curious if they are
damaged after a surge of lightning. I would also like to find
out if they protect against the imperfections in the electrical
grids. Meaning when the power changes in voltages.

I still stick to my methods of unplugging said devices when
storms approach. Remember that what we have here are man made
devices, and said man made devices, is why we have this message
group. Mainly because they easily break. And said man made
devices is what keeps many of those on this board, in business.
So, if you want to support your fellow repairman, keep 'em
plugged in.. I am sure there will be a lot of happy
repairman out there. Just remember, if you do need to take it
to a repairman, take it to a small business man, not a major
chain. The major shop's money just ends up in some rich man's
hands. Money spent at your local business man's shop, will
help feed his family.

Oh, to answer your "?"... I don't know. Maybe there is an
electrician with the power company that can answer this "?".