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Interesting app note. Interesting problem. <br>
<br>
How far from this metal roof (grounded I presume) is the bottom of
the modules ?<br>
<br>
This app note is mainly talking about the area of the module from
the mounting bracket which should<br>
be quite a bit less than the modules area from a distance above a
grounded metal plate like this roof.<br>
<br>
How far above the metal roof are the modules ? If they are real
close, raising them slightly might<br>
be enough to lower that capacitance enough to stop the TL from
tripping.<br>
<br>
Another thing you could do, but would of course cost money would
be to split the array up for<br>
more inverters.<br>
<br>
This app says that 1400 nano-Farads is an approximate point for
problems. That's for 50 Hz.<br>
It will be around 6/5 worse at 60 Hz.<br>
<br>
If you have a capacitance meter (impedance bridge or meter), you
could measure the capacitance<br>
of the array. Disconnect the + and - from the inverter first of
course. Then, tie the plus and<br>
minus of the combined array together and connect that to one
terminal of the capacitance meter.<br>
Connect the other lead of the capacitance meter to the roof and/or
ground and it ~should~ show<br>
the capacitance you are interested in.<br>
<br>
This is one of those newer compromises associated with the higher
efficiency TL inverters (anybody's,<br>
not just SMA's of course), and also the newer code requiring TL
(non-isolated) inverters above 300 volts<br>
and everything else new we have to all learn about. <br>
<br>
<br>
Welcome to the future ! ( from Firesign Theater's "I
think we're all [solar] bozos on this bus" )<br>
<br>
<br>
boB<br>
<br>
<br>
<br>
<br>
On 3/13/2014 7:31 PM, Marco Mangelsdorf wrote:<br>
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<p class="MsoNormal">Friends,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We have run across an odd technical problem
at our
commercial install at a laundromat on our island. Attached
is the
description of the issue from SMA. We don’t know much except
that we are
switch out the TL inverters to the old style US inverters
because SMA has no
fix for the phantom ground tripping. The issue is beyond our
feeble understanding.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any observations to share?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">marco<o:p></o:p></p>
<br>
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