The answer depends on the type of CT.If it has an internal resistor which converts the measuerment to a voltage, it is okay to clamp on live.If it is purely a CT that outputs a different current to be measured, then they can create an inductive kick ant shock and destroy.-GlennSent from my 'smart'phone, so please excuse typos and spelling errors.------ Original message------From: Sam Haraldson via RE-wrenchesDate: Fri, Mar 8, 2024 11:29 AMTo: RE-wrenches;Cc: Sam Haraldson;Subject:[RE-wrenches] Clamping CTs Around Live Conductors - White Paper References and/or Anecdotal Information RequestedDear 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 SAM HARALDSON Field Operations Director(406) 551-61351515 N. Rouse Ave Bozeman, MT 59715Locally owned and operated since 2012
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