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Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

(OP)
We are working with some small (US) utilities developing interconnection requirements for non-residential photovoltaic systems larger than 25 kW.

I'm curious about a typical breakpoint for three-phase systems versus single-phase and if any utilities have specific requirements for maximum allowable phase imbalance or a size limit for single-phase inverters.

Thanks,

Dave  

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

RE: Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

(OP)
Thanks, David - I do have that and have scanned through it.

Still trying to figure what this means:  

"For other service types, the net metering facility must not impact the customer-generator's service conductors by more than 30 amperes."

But under the Level 2 requirements, I'm not seeing anything requiring three-phase systems, or not that I can find anyway.  

I was hoping for something fairly cut-and-dried that would spell out when three-phase inverters are required for a typical three-phase 480 V service.   Reading all these statutes and rules makes my eyes glaze over...

Cheers,

Dave

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

RE: Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

Dave,

The 30A is the limit without installing a disconnect. The committee thought this was the upper limit that could safely be interrupted by pulling the meter.

RE: Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

That 30 ampere requirement is part of the determination as to whether or not a disconnect is required (at least there is a 30A requirement there, don't know if that is the only place with out rereading it).  I've seen everyone of our net metering applications under those rules and people seem to get the phase choice correct by default; I've never seen a big (no, I won't define that) single phase inverter proposed where a 3-phase inverter could be used.  It may be that 3-phase inverters are cheaper than single-phase inverters for a given capacity.

RE: Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

(OP)
I was thinking about putting something in related to maximum phase current imbalance allowable.  But I guess it's not too much different than a customer on a three-phase service with a big phase imbalance in their load due to a large single-phase load.


 

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

RE: Larger Photovoltaic systems & Net Metering - 1-phase vs 3-phase

Yep, just think of the inverter as negative load.

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