[RE-wrenches] Clamping CTs Around Live Conductors - White Paper References and/or Anecdotal Information Requested

[Sam Haraldson]

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

[image: 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
[image: B Corporation]
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