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

[Jason Szumlanski]

I have installed many hundreds of Enphase CTs on live service conductors.
As long as the secondary is connected first, no problem. Same with
disconnecting them.

Jason


On Fri, Mar 8, 2024, 11:30 AM Sam Haraldson via RE-wrenches <
re-wrenches at lists.re-wrenches.org> 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
>
> [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
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