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Sam,<br>
<br>
As long as the CT leads are properly terminated, opening or closing
the clamp-on CT core is nothing different that what a clamp-on
ammeter is doing. Make a mistake and pull the leads out of the
multimeter and you may have a high voltage arc. There are other
problems with using a multimeter in this manner: 1) that the current
ranges are usually fused and the fuse may not clear a high voltage
arc, and 2) switching current ranges may temporarily open the
circuit.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar
<p><br>
</p>
<div class="moz-cite-prefix">On 3/8/2024 8:29 AM, Sam Haraldson via
RE-wrenches wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAGKtuy=Vhq4FtYjM0vTr_MejD-bVMeoOzPumU-0LhZk7XqAvVw@mail.gmail.com">
<div dir="ltr">Dear Wrenches,
<div><br>
</div>
<div>I'm trying to determine whether or not it is acceptable to
clamp monitoring CTs around hot conductors. For this question
please assume the CT wires are landed in their proper
terminals and that proper PPE/safety protocol is employed.
The monitored currents in question are residential services of
600A or less. Is there harm to the CT by clamping them around
a hot conductor? </div>
<br>
The physics of a CT from my brief research states that,<i>
"...the secondary of a current transformer should not be
disconnected from its burden while current is in the primary,
as the secondary will attempt to continue driving current into
an effective infinite impedance potentially generating high
voltages and thus compromising operator safety." </i>This begs
the question how I can use my DMM clamp meter w/o causing damage
or is the italicized text related to very high current
applications from the world of medium and high voltage equipment
and not as pertinent to the residential and light commercial
world I work in?
<div><br>
</div>
<div>
<div>I suspect this is a no-brainer answer for the
seasoned professionals on the list and I'll be most
appreciative for any proof (no matter how brief) you wish to
share. Ultimately we wish to minimize the need to perform
power shut downs and interrupt client service when
installing load monitoring CTs to a home but only wish to do
so if it is part of a safe and non equipment-harming
process.<br>
</div>
<div><br>
</div>
<div>Sincerely,</div>
<div>Sam Haraldson </div>
<div><br>
</div>
<div>
<div>
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