MAX ALLOW POI FOR 1.5 MW SOLAR

[inforaj]

This is for a commercial project, and The owner had 2-POI (one-1600A and the other is 1000A).
option-1, In this option, we used the two transformers (one step-up and step-down transformer) and run a low-ampacity cable.
option-2, we use the 12 nos of inverter and 4 combiner panels (each panel has 3 inverters) and run the high ampacity cable.

Please suggest to me which option is cost-effective and has more reliable and low losses.

I really appreciate it, and Thanks in advance.

 

[ggunn]

There is no simple answer to your question. With just conductors your losses are due to voltage drop, and how much loss there is depends on the size and number of conductors you use and how much you are willing to spend on them. With the transformers the losses will vary depending on the transformers themselves (and how much they cost) as well as the voltage drop in your MV conductors. 6500' is a long way, though, so your losses will be significant no matter which way you go.

We used transformers once to do this for a 1000' run, but when we ran the numbers considering the cost of the transformers and conductors we used and what the losses were in them, and compared them with what it would have cost to run conductors at the inverter native voltage with comparable losses, it was pretty much a wash. One thing: our higher voltage was only 2kV. Anyway, it's possible that for your much longer run the transformer solution would be more viable, but you'll have to pick some options and run the numbers.

 

[inforaj]

There is no simple answer to your question. With just conductors your losses are due to voltage drop, and how much loss there is depends on the size and number of conductors you use and how much you are willing to spend on them. With the transformers the losses will vary depending on the transformers themselves (and how much they cost) as well as the voltage drop in your MV conductors. 6500' is a long way, though, so your losses will be significant no matter which way you go.

We used transformers once to do this for a 1000' run, but when we ran the numbers considering the cost of the transformers and conductors we used and what the losses were in them, and compared them with what it would have cost to run conductors at the inverter native voltage with comparable losses, it was pretty much a wash. One thing: our higher voltage was only 2kV. Anyway, it's possible that for your much longer run the transformer solution would be more viable, but you'll have to pick some options and run the numbers.

Yeah, that's right. POI is very far from the module locations; that's why we are getting lots of losses. is this possible to backfeed the 1600A existing main breaker to 1600A solar system-derated?

 

[electrofelon]

ITs not going to feasible to stick with array voltage. Even if you could get that up to the 1200VDC range, you are talking 1500 amps which would be roughly 20 sets per pole of 500 AL PV wire, so even say you get a mega bulk price deal at $2 per foot (which is cheaper than regular 500 XHHW AL) that is at least half a million dollars (although probably quite a bit less as you would likely find the sweet spot of losses vs wire cost to be a much higher VD figure than you might think, could well be 1/3 or less of that). All you would need at 13.8Kv is 3 #2 CN cables (about $1.90/foot pre covid, $2.50 last summer, not sure now, you would probably use 1/0 with 1/3 neutral but whatever). So that is in the neighborhood of 50k for that wire, plus transformers of course. Poles would almost certainly be cheaper.

 

[wwhitney]

Seems like 1707A of inverter output interconnected at a 1600A POI would be an issue.

Is paying the utility to extend their primary closer to your solar farm a viable possibility? And/or taking service at a primary voltage to avoid the step down transformer?

Cheers, Wayne

 

[inforaj]

Seems like 1707A of inverter output interconnected at a 1600A POI would be an issue.

Is paying the utility to extend their primary closer to your solar farm a viable possibility? And/or taking service at a primary voltage to avoid the step down transformer?

Cheers, Wayne

That's the conceptual and assumptions only, and the details will be done later.

 

[petersonra]

It sounds to me like someone has not thought this through all the way. Is it normal to build a solar farm more than a mile away from where it connects to the grid?

 

[pv_n00b]

Generally, a site is evaluated for ease of interconnection first since adding utility infrastructure is expensive and the utility expects the developer to pay for it.