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<p>What I should have said is that an actual earth ground (bonding)
will not protect the Ethernet circuit from lightning protection.
But it is of course necessary for 60 Hz-style safety.</p>
<p>The key is to put the clamping circuit's reference point as close
as possible to the actual circuit being protected. The farther
away you put that "ground strap" the more likely your Ethernet
card will go up in smoke. Because all that energy from the
lightning gets put onto that long ethernet cable. <br>
</p>
<p><br>
</p>
<p>Bob</p>
<p><br>
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<p><br>
</p>
<div class="moz-cite-prefix">On 11/5/19 2:59 PM, Bill Whitlock
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1662820729.1044659.1572983949716@mail.yahoo.com">
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<div style="color:black;font: 10pt arial;">Jim,
<div><br>
</div>
<div>I'm sure it was Neil who coined the phrase "sump theory of
grounding" to mean that currents, especially noisy ones, flow
into soil and simply disappear forever.</div>
<div><br>
</div>
<div>Regarding earth grounding of lightning protection, I don't
fully understand Code in this regard. Yes, lightning strikes
themselves need a path to earth - since the strike is a
discharge of huge capacitance between clouds and earth soil.
But the most common equipment damage comes from voltages
magnetically induced into terrestrial conductors of all
kinds. Direct strikes to premises wiring would be
catastrophic. Of course, there is also a sudden drop in
electric field in the vicinity and this is a problem for
"floating" (un-grounded) objects. Perhaps this is the Code's
concern. As mentioned earlier in this thread, it sure would be
great if they could explain their reasoning!</div>
<div><br>
</div>
<div>I think of the strike itself as the (temporary) primary of
a one-turn transformer. All those metal objects on the ground
(or in the air, for that matter) are secondaries. Thousands of
volts can be induced into a 20-foot-long conductor, depending
on whether or not it's parallel to the bolt. I've read that
there are about as many cloud-to-cloud discharges as
cloud-to-earth, so any orientation is vulnerable.</div>
<div><br>
</div>
<div>Bill Whitlock<br>
<br>
<br>
<div
style="font-family:arial,helvetica;font-size:10pt;color:black">-----Original
Message-----<br>
From: Jim Brown <a class="moz-txt-link-rfc2396E" href="mailto:jim@audiosystemsgroup.com"><jim@audiosystemsgroup.com></a><br>
To: proaudio <a class="moz-txt-link-rfc2396E" href="mailto:proaudio@bach.pgm.com"><proaudio@bach.pgm.com></a><br>
Sent: Tue, Nov 5, 2019 11:32 am<br>
Subject: Re: [ProAudio] AES on the west coast, was Re:
Ampex/ProAudio List Dinner<br>
<br>
<div dir="ltr">On 11/5/2019 10:07 AM, Bob Katz wrote:<br
clear="none">
> An actual earth ground is unnecessary and frankly,
useless.<br clear="none">
<br clear="none">
Not true, Bob. Indeed, it is a critical component of
lightning <br clear="none">
protection, which is why it is required by electrical
codes. <br>
</div>
</div>
</div>
</div>
</blockquote>
<div class="moz-signature">-- <br>
<pre><font class="3D""" face="3D"Courier"">
If you want good sound on your album, come to
Bob Katz 407-831-0233 DIGITAL DOMAIN MASTERING STUDIO
Author: <b>Mastering Audio</b>
<a href="https://www.digido.com/">Digital Domain Website</a>
No trees were killed in the sending of this message. However a large number
of electrons were terribly inconvenienced.</font>
</pre>
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