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| On Mar 13, 3:17 pm, bud-- <remove.budn...@isp.com> wrote:
> On transmission line behavior Martzloff writes:
> "From this first test, we can draw the conclusion (predictable, but too
> often not recognized in qualitative discussions of reflections in wiring
> systems) that it is not appropriate to apply classical transmission line
> concepts to wiring systems if the front of the wave is not shorter than
> the travel time of the impulse. For a 1.2/50 us impulse, this means that
> the line must be at least 200 m long before one can think in terms of
> classical transmission line behavior."
>
> Houses don't have 200 meter branch circuits.
Then we include the entire circuit. It's not just the branch
circuit. Wires down the street and maybe three miles of electrical
(plasma) connectors to the cloud. Maybe even four miles of conductor
through the earth. Surges are an electrical circuit from cloud
through house and earth. That circuit would be a more than 0.15
miles.
Transmission line is too short if discussing a trivial surge that a
plug-in protector might protect from. But we are not discussing
surges made irrelevant by protection inside all appliances. Discussed
are a type of surge that typically causes damage. That electrical
circuit might be seven miles long. And still, that current source
(surges are typically current sources) must find a path from cloud to
earthborne charges. Voltages will increase as necessary so that surge
current will flow. Either current creates trivial voltage if earthed
via a low impedance ground connection. Or current may create (for
example) 8000 volts destructively through an adjacent TV (Page 42
Figure 8).
That lossy 'transmission' line also induces surges on adjacent wires
if permitted inside a building. Other wires bundled with that surge
wire (wire going to a plug-in surge protector) may also suffer from
surge currents connected capacitively or inductively. Just another
reason for earthing surges; keeping surges outside a building. Better
protection means the seven mile circuit from cloud to earth does not
enter a building. Then the 'transmission line' from cloud, through
utility wires to earth does not include household wiring.
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