We have a large solar farm that is tied to a 3phase padmount all the inverters are single phase inverters ,with a loss of one phase primary how would this system shut down with the other 2 phases hot and the inverters that are one the good phase will continue to generate not to mention the feroresinance condition when this happens isn't there a code section 705.40 that doesn't allow this type of install.
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Solar Farm
- Thread starter newt
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- Placerville, CA, USA
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- Retired PV System Designer
We have a large solar farm that is tied to a 3phase padmount all the inverters are single phase inverters ,with a loss of one phase primary how would this system shut down with the other 2 phases hot and the inverters that are one the good phase will continue to generate not to mention the feroresinance condition when this happens isn't there a code section 705.40 that doesn't allow this type of install.
No. IMHO. UL will probably require a single three phase inverter to shut down on loss of one phase (or one phase conductor).
jaggedben
Senior Member
- Location
- Northern California
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- Solar and Energy Storage Installer
705.42 is more relevant to the discussion, but still open to interpretation IMO.
With that said, the code probably should require (although it doesn't) that a 3-phase feeder for multiple single-phase inverters be connected through a common-trip circuit breaker (and not a fusible disconnect), at least if connected through a transformer. There was thread here somewhat recently on unbalanced currents in that sort of situation when a fuse blows in only one phase conductor.
With that said, the code probably should require (although it doesn't) that a 3-phase feeder for multiple single-phase inverters be connected through a common-trip circuit breaker (and not a fusible disconnect), at least if connected through a transformer. There was thread here somewhat recently on unbalanced currents in that sort of situation when a fuse blows in only one phase conductor.
705.42 is more relevant to the discussion, but still open to interpretation IMO.
With that said, the code probably should require (although it doesn't) that a 3-phase feeder for multiple single-phase inverters be connected through a common-trip circuit breaker (and not a fusible disconnect), at least if connected through a transformer. There was thread here somewhat recently on unbalanced currents in that sort of situation when a fuse blows in only one phase conductor.
if you have a loss of 1 phase of a primary source I would want all inverters to trip offline other wise you are backfeeding primary voltage on a down conductor (feroresance}
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
if you have a loss of 1 phase of a primary source I would want all inverters to trip offline other wise you are backfeeding primary voltage on a down conductor (feroresance}
Yes, I believe that's correct. An a common trip circuit breaker would protect against the situation where the phase lose is due to an overcurrent trip on one phase. It may or may not help if the phase loss happens a different way.
I managed to find the thread from last year that touches on these issues.
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