Lem said:
See this posting to a second thread started with the same posting
as this one.
It says the following.
The article below is misleading. They talk of earthing "all incoming
utilities" but fail to recognize that any incoming 'utility' is not simply
a single wire, as evidenced by their stating "even the CATV wire drops down
to earth ground." It's a coax cable folks, not a 'wire', and the wire in
the middle is not 'earthed' or else there's be no signal. It IS however,
'protected', to some degree, by the shield, which is what's earthed.
Power lines are more problematic. True, the incoming power line 'earth'
should be 'earthed', as they describe, but the others are not, or else your
incoming power would be a direct short to each other through this common
'earth' point.
The 'protection' for power and signal lines is an arc gap suppressor to
that common earth ground which, hopefully, arcs a lightning strike to earth
at that point rather than having it find earth through the devices, or you,
in the home so lucky you end up with only a few hundreds, or thousands, of
volts transients dancing around on the home wiring and your home equipment
with the brunt going through the arc gap suppressors.
Now you, as a human being, are probably safe from those remaining
transients, unless you have your finger stuck in a socket, but electronic
devices are not as they ARE plugged into the socket. And it is those
transients that an in-house transient/surge suppressor is meant to deal
with, not 'lightning strikes' per see.
It is true that small in-house 'protectors' are essentially useless if the
home utilities AREN'T properly protected (earthed) but the implication
derived from the small snippet that if the home has 'proper' incoming surge
suppression that it's then 'safe' for electronic devices (I.E. they're
sufficiently 'protected') is simply hogwash.
It should also be obvious that if the surge protector has no path to earth
then it's function is lost, which means the outlet(s) it's plugged into
must have the proper earth, or it's own wired earth. I.E. Using a '3 wire
to 2 wire adapter' on a surge suppressor disables the majority of it's
protection.
'Protection' is a multistage process. You have the 'protection' on the
utilities themselves, meaning the power company equipment/line outside the
home, which absorb the brunt of most faults. Then there is the protection
going into the home, which depends on the incoming line impedance to limit
the surge. And then you have protection (or lack thereof) from the
'remnants' left on the interior wiring.
