On 07/18/04 21:28, Larry Fine said...
there will still be plenty of induced
currents in any metal around.
That is something I never thought of! And it is so true!
Often, the nails in a house produce charring in
the wood surrounding them, and they're not even
part of a circuit. Imagine the induced currents
in your house wiring, where one end of every circuit
is grounded (the neutral).
This means that, even if the breaker were open, you could end up with spikes of thousands of volts applied to the equipment!
the best TVSS setups use main-service voltage
clamping cascaded with point-of-use secondary
clamping combined with current-limiting for sensitive
electronics. A certain portion of surges are
generated within the building by other equipment.
Again, didn't we all think the voltages had to do with the way the lightning's energy spread out? The fact of induction is VERY important in this process.
Remember, current requires a difference
of potential (a.k.a., voltage), and bonding reduces
potential differences. Unfortunately, that can
lead to ground loops, but them's the breaks.
Yes, but there is an interesting phenomenon that I noticed as electronic components evolved from audio only to audio plus video. You will have no hum when there are NO ground loops, as in "star" grounding of an audio-only component. You will have hum when there are a few ground loops, as in grounded cable plus a grounded plasma chassis. BUT if you have lots and lots of grounds, eventually the tendency to hum will go away because no single ground path will have enough current (and therefore voltage due to IR drop) to create hum. I have seen this in homes where the system hummed when half-wired, but was totally clean when finished, with no attention paid to ground loops until we were done...and then none was needed.
Finally, while it's said that "electricity follows
the path of least resistance", the truth is that
electricity can have many parallel paths. Do
your lights go out when you turn on the stove
or A/C? Of course not! Same for lightning.
Electricity follows ALL paths that have less than infinite resistance, and the amount on any one path is strictly proportional to the resistance of that path. The above statement is only the most obvious one, but people have been killed by ignoring the reality of other paths.
