On 5/19/2016 2:24 AM, Roscoe wrote:


Anything you do to minimize voltage spikes on your power line is a good
thing...just keep in mind that the typical surge suppression device
needs a good path to ground to function properly.

Plug-in protectors do not work primarily by earthing a surge.

The IEEE surge guide (link in trader's post) explains (starting page 30)
plug in protectors work by limiting the voltage from each wire (power
and signal) to the ground at the protector. The voltage between the
wires going to the protected equipment is safe for the protected equipment.

Since protection is by limiting the voltage between wires, all
interconnected equipment needs to be connected to the same protector and
all external connections, like coax, must go through the protector.


FWIW, most homes don't have a good ground system. You'll typically find
the outdoor connection from the #6 ground wire to the ground rod is
loose and/or corroded.

Suppose you have a house earthed with a ground rod having near
miraculous 10 ohms resistance to earth (and ignoring the impedance of te
connecting wire), and a 1,000A surge is earthed. The building "ground"
system will rise 10,000A above 'absolute' earth potential. In general
70% of the voltage drop away from a ground rod is in the first 3 feet.
The earth over 3 feet away will be at least 7,000V from the building
'ground' system.

Much of the protection is that all wiring - power, phone, cable, ... -
rises together. That requires a short ground wire from phone and other
entry protectors to a common connection point on the power earthing
system. (An example of a ground wire that is too long is in the IEEE
surge guide starting page 30.)

A surge expert at the NIST has written "the impedance of the grounding
system to `true earth' is far less important than the integrity of the
bonding of the various parts of the grounding system."