480 wye solar to 208 wye transformer connections 225kva

[GoldDigger]

I'm looking at electromonkpv's post about connecting a 208 wye inverter to a 2phase system. Probably it should be the start of a new thread, but it looks to me like you overlooked his description.

Yes, I did.

I am also very curious about where electromonkpv is connecting to a two phase utility system!
A Scott-T does not do any good with a single phase system, and even a Leyton 3-2 will do no good for connecting a three phase inverter to single phase service.

 

[electricmonkpv]

2-phase, 5wire grid x 3-phase, 4wire inverters in Philly

2-phase, 5wire grid x 3-phase, 4wire inverters in Philly

Yes, I did.

I am also very curious about where electromonkpv is connecting to a two phase utility system!
A Scott-T does not do any good with a single phase system, and even a Leyton 3-2 will do no good for connecting a three phase inverter to single phase service.

We opted to feed into the 2-phase grid-derived system via (2) 14.4 kW and (1) 9 kW 3-phase inverters, out of concern that individual 1-phase inverters could result in imbalance on the 2 utility phases, if one or more drops out or is shut off for maintenance. Our ~40 kW rooftop system won't likely cause PECO (POCO) any problem, even if it was 100% imbalanced on one phase (?), but I assumed that if we asked them, "Can we connect a system capable of 10 kW unbalanced current for days or months?", they'd probably say 'No.'

New Question:
What kind of power consumption might be typical in a 50 kW transformer with no load/input (circuits open) on the 3-phase (solar PV) side? I'm curious whether we should be considering a timer- or photo-controlled relay-switch to shut it down at night.

 

[jaggedben]

We opted to feed into the 2-phase grid-derived system via (2) 14.4 kW and (1) 9 kW 3-phase inverters, out of concern that individual 1-phase inverters could result in imbalance on the 2 utility phases, if one or more drops out or is shut off for maintenance. Our ~40 kW rooftop system won't likely cause PECO (POCO) any problem, even if it was 100% imbalanced on one phase (?), but I assumed that if we asked them, "Can we connect a system capable of 10 kW unbalanced current for days or months?", they'd probably say 'No.'

To each his own, but I probably would have asked them. They can't surprise you with a 'Yes' if you don't ask. (It's the opposite situation that presents a conundrum for me: when I really think it should be 'yes' but I'm wary of giving them a chance to say 'No'.)

Interesting that 705.100 refers to three-phase and not multi-phase, so by the NEC you arguably don't have to worry about that.

New Question:
What kind of power consumption might be typical in a 50 kW transformer with no load/input (circuits open) on the 3-phase (solar PV) side? I'm curious whether we should be considering a timer- or photo-controlled relay-switch to shut it down at night.

There's been some discussion of that here (tried for a minute to find it, but couldn't). I believe most of the feedback has been that it is not cost effective. That is, the relay and accoutrements cost the same or more than the energy saved.

 

[PWDickerson]

I costed out a night-time disconnect system for a 150 kW PV array, and it didn't make financial sense. When I posted about it here, several others agreed that this is generally not a cost effective solution.