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Wow glad I found this hopefully this helps.
Building a ground mount 50 kw (if allowed to) grid tied system. Have to go under a State Hwy. I would like to use UF as it's easier to install. pretty sure I will need to run 24'3" of conduit under the States ROW (using a mole). Can I run UF inside 3" conduit? THHNW (can I direct bury this)?
I may have to buy a Utility Transformer if their grid can't handle it. Any rough idea what that costs?
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Thanks for the enlightenment.
 

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50 KW is natively 208.33 amps, but since you'd run that continuously, you'll need to derate 125% so 260.5 amps. That will necessitate 400 kcmil wires, but more would be better for voltage drop reasons*.


I gather at some point you ran UF cable out to a shed... and that's kinda your experience with outdoor feeders, and you're trying to stay close to your comfort zone. Don't worry about it. It's big-boy stuff, but it's not rocket science. Running fat conductors in conduit isn't that different than what you've done, just it's individual wires and it's in pipe. The only trick is, you must assemble and anchor (i.e. bury) the entire conduit pipe before you pull the wires in. But that actually makes the project go easier, e.g. you don't have to trench the whole thing in one go. So just keep it a straight shot and simple.

On circuits this big and expensive, direct burial is pennywise and pound foolish. All-in, the wiring will be almost $4/foot! ** The ability to pull that stuff out of the pipe for maintenance is important, unless you have a wire theft problem, then you want direct burial to slow down the thieves**.

State highway RoW's are a LOT wider than 24'3", that would barely cover the distance between white lines! I would expect more like 60-100' RoW. The county tax office could tell you exactly. You'll want conduit all the way across their RoW, that so you can service/change the wire/add wires (e.g. fiber for datacomm) without any "imperial entanglements" as Obi-Wan Kenobi said.


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* That's a calculation: bigger wire costs more but it also means you're selling more power back to the PoCo. I did a quick number-crunch and got 16,000 hours to payback for a bump to 500 kcmil, assuming 12 cents/kwh and the panels averaging 50% power. Given 2600 hrs/yr of sunlight in PA, I get 8 year payback. That's because 500 kcmil is a "sweet spot" pricewise, due to popularity of that size. **

** That's aluminum of course; the payback on copper is LOL never. Nothing wrong with aluminum at these large feeder sizes. Aluminum is also the best way to stop copper thieves; the same ampacity aluminum wire only has about 1/16 the scrap price as copper, not least, same-ampacity wires are about half the weight! w1
 

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Wow glad I found this hopefully this helps.
Building a ground mount 50 kw (if allowed to) grid tied system. Have to go under a State Hwy. I would like to use UF as it's easier to install. pretty sure I will need to run 24'3" of conduit under the States ROW (using a mole). Can I run UF inside 3" conduit? THHNW (can I direct bury this)?
I may have to buy a Utility Transformer if their grid can't handle it. Any rough idea what that costs? View attachment 642243 View attachment 642243
Thanks for the enlightenment.
Start with getting permission for crossing the ROW from the State... This will take an act of GOD! 24 feet is just the pavement not the ROW for the highway, you may find the ROW to be more like 100-200 feet depending on drainage grading.

Check with your serving utility as they will purchase and install the correct transformer. No one else will have the answer.
Also some states have rules and regulations for solar systems this large. 50 kw certainly is not needed for a residence. You may find that your utility will not let you even connect this to their grid.
I recommend that you hire an engineering firm and them draw up the plans for open bid.
 
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