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<p><font face="Candara">Synco</font></p>
<p><font face="Candara">That is generally used for electrical cables
and is to ensure the cable capacitance isn't influencing the
measurement.</font></p>
<p><font face="Candara"><br>
</font></p>
<p><font face="Candara">For electrical cables there are other checks
as well.<br>
</font></p>
<p><font face="Candara"><a class="moz-txt-link-freetext" href="https://electrominst.com/test-technology/insulation-resistance/polarization-index-test-da-test/">https://electrominst.com/test-technology/insulation-resistance/polarization-index-test-da-test/</a></font></p>
<p><font face="Candara"><br>
</font></p>
<p><font face="Candara">I'm not sure that this group gets unvolved
in any of those tests</font></p>
<p><font face="Candara"><br>
</font></p>
<p><font face="Candara">Mark<br>
</font></p>
<p><font face="Candara"></font><br>
</p>
<br>
<div class="moz-cite-prefix">On 26/01/21 11:00, Synco Reynders
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAKNOA8LAbv7vOyRU3aZwrMP_8L4OWpB8b6puiLXwqbrMFW30uw@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">I'm no expert although I was told the import
aspect of insulation testing is the duration of the reading -
a reading should be at least 1minute, up to 10 minutes for
large equipment... and the resistance should always increase.
The Megger manual (<a
href="https://www.instrumart.com/assets/Megger-Guide-to-Insulation-Testing.pdf"
moz-do-not-send="true">https://www.instrumart.com/assets/Megger-Guide-to-Insulation-Testing.pdf</a>
page 15) suggests sampling at the 60 second and 30 second
marks and using the ratio.</div>
<div dir="ltr">/s<br>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, 25 Jan 2021 at
11:33, Mark Beckett <<a href="mailto:m.beckett@amuri.net"
moz-do-not-send="true">m.beckett@amuri.net</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 bgcolor="#FFFFFF">
<p><font face="Candara">A word of caution about testing
cables well beyond their rating.</font></p>
<p><font face="Candara">It punches holes which later
become a problem.</font></p>
<p><font face="Candara">We have a number of communication
cables that are 120v rated, and were tested using 500v
meggers. We're now seeing many fail.</font></p>
<p><font face="Candara"><br>
</font></p>
<p><font face="Candara">Mains cables and devices are
tested at twice their rated design (ie 500vDC) UNLESS
it has a specification to only test at 250VDC.</font></p>
<p><i><font face="Candara">We have a number of power
supplies that have protection devices rated at 250v.</font></i></p>
<p><font face="Candara"><br>
</font></p>
<p><font face="Candara">Tenma make a low cost fully rated
device that sometimes appears on special.</font></p>
<p><font face="Candara"><a
href="https://nz.element14.com/tenma/72-9400a/insulation-tester-1kv-5gohm/dp/249951801"
target="_blank" moz-do-not-send="true">https://nz.element14.com/tenma/72-9400a/insulation-tester-1kv-5gohm/dp/249951801</a></font></p>
<p><font face="Candara"><br>
</font></p>
<p><font face="Candara">Mark<br>
</font></p>
<br>
<div>On 25/01/21 00:49, Andy Gardner wrote:<br>
</div>
<blockquote type="cite"> <br>
On 24/01/21 10:41 pm, Mark Atherton wrote: <br>
<br>
<blockquote type="cite">The modern insulation used on
enamelled copper wire (even the thin stuff) seem to
tolerate 5kV OK. I have also tried the lowest voltage
cable I could find (CAT5) and strapped a twisted pair
across the unit at full smoke without incident. <br>
</blockquote>
<br>
Cat 5 has polyethylene insulation rather than the more
common PVC. <br>
<br>
<br>
<br>
<br>
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