Sam,
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.
Kent Osterberg
Blue Mountain Solar
On 3/8/2024 8:29 AM, Sam Haraldson via RE-wrenches wrote:
Dear Wrenches,
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?
The physics of a CT from my brief research states that,/"...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." /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?
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.
Sincerely,
Sam Haraldson
OnSite Energy
<https://www.google.com/url?q=https://onsiteenergyinc.com/&source=gmail-html&ust=1677085494759000&usg=AOvVaw2NN36GoM1sjnS4RdC8Svt->
SAM HARALDSON
Field Operations Director
(406) 551-6135
1515 N. Rouse Ave Bozeman, MT 59715
Locally owned and operated since 2012
B Corporation
<https://www.google.com/url?q=https://onsiteenergyinc.com/bcorp&source=gmail-html&ust=1677085494759000&usg=AOvVaw0EluC1lXtz2KlRFag-htKe>
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