<div dir="ltr">Hi Sam,<div><br></div><div>The "secondary" of the CT is the side connected to the meter. The primary is the side that gets wrapped around the conductor or busbar on which you are measuring current. So yes, make sure that the secondary is connected to its "burden" (the meter, or a shorting block) before inducing any current in the primary. With a split-core CT, or a handheld clamp meter (as you noted), you can install the CT around a conductor while the conductor is in service. Just make sure the secondary is already connected. (I'm sure there is some exception for certain types of sensitive meters, but I've never had a problem. And yes, as you say, this is assuming that you are using proper PPE, etc for working around live circuits.)</div><div><br></div><div>Blake</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Mar 8, 2024 at 8:31 AM Sam Haraldson via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><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><div dir="ltr" class="gmail_signature"><div dir="ltr"><div dir="ltr"><table cellpadding="0" cellspacing="0" style="font-family:Montserrat,Tahoma,sans-serif"><tbody><tr><td style="padding:0px 10px 0px 0px;vertical-align:top"><a href="https://www.google.com/url?q=https://onsiteenergyinc.com/&source=gmail-html&ust=1677085494759000&usg=AOvVaw2NN36GoM1sjnS4RdC8Svt-" rel="noreferrer" style="border:none" target="_blank"><img src="https://i.postimg.cc/4xVVZ5jT/email-logo.png" alt="OnSite Energy" align="top" width="85" height="85" style="display: block;"></a></td><td style="padding:0px;vertical-align:top"><table cellpadding="0" cellspacing="0"><tbody><tr><td colspan="2" style="padding:0px;vertical-align:bottom"><div color="#514ca0" style="padding:0px;color:rgb(81,76,160);font-size:11pt;font-weight:600;text-transform:uppercase">SAM HARALDSON <span style="font-size:8pt"> </span></div></td></tr><tr><td style="padding:0px 5px 0px 0px;vertical-align:bottom"><div color="#f9a145" style="padding:0px;color:rgb(249,161,69);font-size:9pt">Field Operations Director</div><div color="#514ca0" style="padding:0px;color:rgb(81,76,160);font-size:7pt;line-height:8pt">(406) 551-6135<br></div><div color="#514ca0" style="padding:0px;color:rgb(81,76,160);font-size:7pt;line-height:8pt">1515 N. Rouse Ave Bozeman, MT 59715</div><div color="#f9a145" style="padding:0px;color:rgb(249,161,69);font-size:7pt;line-height:9pt">Locally owned and operated since 2012</div></td><td style="padding:0px;vertical-align:bottom"><a href="https://www.google.com/url?q=https://onsiteenergyinc.com/bcorp&source=gmail-html&ust=1677085494759000&usg=AOvVaw0EluC1lXtz2KlRFag-htKe" rel="noreferrer" style="border:none" target="_blank"><img src="https://i.postimg.cc/2y1LtFnM/email-bcorp.png" alt="B Corporation" width="22" height="33" align="bottom" hspace="2" vspace="2" style="display: block;"></a></td></tr></tbody></table></td></tr></tbody></table></div></div></div></div></div></div><div></div></div>
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</blockquote></div><br clear="all"><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><span style="color:rgb(136,136,136)"><br></span></div><div><div dir="ltr" style="color:rgb(136,136,136)"><div dir="ltr"></div></div><span><p dir="ltr" style="line-height:1.38;margin-top:12pt;margin-bottom:12pt"><span style="font-size:12pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:700;vertical-align:baseline;white-space:pre-wrap">Blake Gleason, PE | Employee Owner</span><span style="font-size:12pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:700;vertical-align:baseline;white-space:pre-wrap"><br></span><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">Director of Innovation and Technical Excellence<br></span><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">O: 510-845-2997 x128</span><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"><br></span><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap">C: 510-867-5878</span></p><p dir="ltr" style="line-height:1.38;margin-top:12pt;margin-bottom:12pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;vertical-align:baseline;white-space:pre-wrap"><span style="border:none;display:inline-block;overflow:hidden;width:200px;height:105px"><img src="https://lh4.googleusercontent.com/9HZ43SgRr_bF_Yd-CLwdZP7MjUXXSYm84_EQ6NxrpYEfn8zrwHdL7zSPGVhtOGMB9NCLVH480W0EJe-8kQSN-ZAoE8gM1mTT9vEUz26kGgN7I-UfWWpqeYea0LVHI9M9wpgYI_0H" width="200" height="105" style="margin-left: 0px; 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