"w_tom" wrote in message
...
Ok sir. Explain to us how a plug-in UPS provides common mode
protection. Also cite the manufactuer's spec that claims that
common mode protection (and good luck).

No problem. He
http://sturgeon.apcc.com/techref.nsf/partnum/990-7015/$FILE/7015-1.pdf
Section 9.4

Do you understand what common mode means with respect to the above spec and
do you understand how that differs/same as the general concept of common
mode and how that relates to these issues?

In order to protect a device from an undesirable voltage arriving over the
power cable one simply shunts that unwanted voltage such that it appears
equally on all the wires on that power cable i.e. AC-hot, AC-neutral and
the ground wire which connects to the chassis of the device. That shunt is
done with capacitors and surge diodes or MOV devices etc. or in the old days
on your phone line with a spark gap. That's basically what a surge
suppressor does. The device's input components therefore see no intolerable
VOLTAGES and it survives. It makes no difference to the device if the whole
device(chassis and all) jumps to a million volts during the episode. Ever
heard of a Faraday Cage?

Also please explain how those 130 ohms impedance in 50' of
12 AWG wire is not significant when earthing even a trivial
100 amp surge?

Not relevant. What happens on an airplane? The protection issue isn't
grounding a surge current; the issue is maintaining important components at
a stable/safe voltage with respect to one another such that nothing gets
damaged. Ever heard of a Faraday Cage?

In the meantime, please explain how earth ground at a hydro
electric plant is at all related to single point earth ground
for a building,

In large buildings as in hydroelectric plants there is NO SINGLE POINT
ground but multiple connections to a common ground cage/plane. On an
airplane there isn't even one point to ground except an ionized air column t
hat chooses its own path for a few microseconds at a time on occasion.
Ever heard of the concept of a ground plane? Every heard on the concept of
capacitive coupling and AC impedance? How does a Faraday Cage relate to a
ground plane?

for a PA or stereo system, for the PC board
layout of A/D converters, or any other simple electronic
system where ground loops can be a problem. You do understand
the concept of ground loop?

You're walkin into my backyard now. Now what's the difference in design of
that DA for 8 bit 800MHz conversion and 24 bit 200KHz conversion? DAs are
more fun that ADs.

Good. Please then show us how
the ground at a power station has any relevance?

Now for the completely irrelevant topic of ground in an
airplane:

It's entirely relevant to demonstrating that you have no understanding of
the issues in question.

The answer is that the principles of how to do system input protection on an
airplane are IDENTICAL to how to do them at home or in a high rise.

The NUMBER ONE FAILURE of an incompetent designer in this arena is to
mistake that a ground connection has much to do with the issue; it does
NOT. The ground connection has much more to do with other issues like the
safety of the guy who is using the box and the UL and the national
electrical code. Why do you suppose that US home wiring didn't even include
a 3rd wire(ground) until the 50's? Do you think some new physical law was
suddenly discovered?

One can protect a gadget from surges WITHOUT a ground wire or any ground at
all; that's the WHOLE point. Shunt the surge voltage such that it's common
moded and to the chassis at the input and outputs and the device is
protected.

Ron Reaugh wrote:
"w_tom" wrote in message
...
There is nothing cost effective adjacent to the computer. No
UPS nor power strip protector that will protect computer
hardware.

That's simply wrong/false. A good UPS or good surge
protector WILL protect a PC. Do you understand the concept
of common mode?

Computer internal protection assumes the building
has implemented a 'whole house' protector on AC mains
connected less than 10 feet to central earth ground.

That's simply wrong/false. There is nothing magic about 10
feet except that an electrical pulse travels about that far
in 10 nanoseconds. What do you suppose the risetime of a
lightening bolt is and how does that relate to that 10
feet? Define "central earth ground" and what it's
important characteristics are. Where is the "central earth
ground" on an airplane, car, ISS or on the Antartic pole
US base(over a mile thick cold pure ice)? Are all PCs and
electronics gadgets there doomed? Ever heard on the concept
of a Farady cage?

Protection as it was even done and well proven before WWII.

Yes, for those who actually understand it. What does the
"central earth ground" look like at a major power station,
substation or hydroelectric dam? Where's it located?