-2

I have a large piece of property and want to run a 2000' powerline from the power company meter to the house. Ideally, I would like 120/240 service with at 200 amps.

I think the power company can give me 480v service at the meter. I'm considering using 600V step up/step down transformers and 1-1-1 alum wire to keep the budget within reason.

The power company is not willing to extend their primary line any closer but I do have the equipment to install my own underground service between the meter an the house.

Does this project seem possible? Thanks for any suggestions!

10
  • 1
    If you'll take the tour, you'll note that this is a Question & Answer board, not a general discussion forum. This is a statement of a couple of facts. What, exactly, is your question? Please edit your question to clarify.
    – FreeMan
    Commented Mar 8, 2022 at 11:57
  • 2
    Generally better to have (and pay for) the power company extend their line, and locate the transformer closer to your house, since their connection is already high voltage, and they are in the business of moving power long distances.
    – Ecnerwal
    Commented Mar 8, 2022 at 13:45
  • 1
    IIRC You get into a bunch of different rules above 1000V (used to be above 600V, but that's changed due to code revisions to allow for HV PV systems) and your wire shopping may still eliminate a lot of "readily available" to have wire insulation above 600V.
    – Ecnerwal
    Commented Mar 8, 2022 at 18:30
  • 2
    @AKHomestead please edit your question to include this info. As you can see, it's vital to help keep the answers focused and on track. The more info, details & background you can give up front, the less time people have to spend guessing and suggesting things that are already out of the picture.
    – FreeMan
    Commented Mar 8, 2022 at 18:43

2 Answers 2

3

480V is problematic because it's 3-phase

Generally speaking, 480V comes as "3-phase" and is a commercial service with potentially more costs and fees, and demands on how you load it. Especially if you are rural, the power company may have a problem with you heavily loading one of the three phases. You need to talk with them about that.

Converting 3-phase to single phase evenly is very complicated and requires an intermediate conversion to DC - probably something you don't want to get into unless you're heavily into battery systems for extended grid-down operations. (which frankly is an option: have a substantial solar system and half a Tesla Model S's used battery pack, 50 KWH for about $9000... and cut the cord! Part of that is conservation, i.e. factoring the house's systems for off-grid power, not being wasteful. Note the upside of "no outages and, no electric bill, ever".)

However, if the power company is simpatico with the way you'll load their 480V distribution, then I would say, crunch the numbers but consider forgetting the step-up to 600V. Carry it the distance at 480V. After all, 480V gear is cheap commodity - I see it going by all the time on Craigslist. 600V is more bespoke, and that means having to search harder and spend more for transformers. Particularly a 480/600V transformer (a bog-standard 240/480--120/240V transformer could probably be set up in "boost mode", but the overcurrent protection on that would be super custom as the whole shebang needs to trip together) will be a tough find. The upshot is, it's probably better to stay at 480V and "throw aluminum at it". Then you will have a system any commercial electrician will instantly recognize.

Pole line may be cheaper

That kind of distance really screams "pole line". Not least, you are freer to use higher voltages on a pole line. A 2000' underground conduit is a daunting affair, and also at risk of wire theft. Direct burial 2000' of wire is a huge exposure risk for a wire cut due to rock penetration and settling. Just because there's so much of it.

A neat feature of pole line is you can step the voltage up to thousands of volts. Now you are limited only by wire insulation, or not even that if using separate wires spaced correctly. Remember, you really want a lightning arrestor wire up top.

#1 aluminum is not realistic

I don't know what voltage drop calculator is telling you #1 wire is OK, but that is totally unworkable and verging on insane. I get the impression that somebody didn't even bother doing a voltage drop calculation, and just "upsized the wire 1 size" - as if this covers all situations LOL. No, you'd be in for 11-20% voltage drop if you did that.

If you aim to jumper the transformer "to compensate", it doesn't work that way. Voltage drop is not a constant figure; it varies based on the current in the cable at that instant. So if you "cleverly" up-jumper the transformer to compensate for voltage drop at peak currents, then at low currents your voltage will be much too high. I have a factory building full of burned out sodium lights because some genius did exactly that.

One should aim for sub-5%, 6% at the absolute outside at 100% load. Assuming you run 600V transmission, so 80A@600V, then 4/0 wire (much larger than #1) gives you 5.75% at 100% load and 4.6% at 80% load.

Assuming you run 480V, so 100A@480V, then 350 kcmil wire (3 sizes larger) gives you 5.99% at 100% load and 4.79% at 80% load.

That's as low as I'd go.

#1 is totally unrealistic. I don't know who came up with that idea. That would work for a service size of 50-60A tops, which was the classical service size for an all-gas home, but out of the question for a heavily electric home where the owner says "200A service".

By the way, you don't need three large conductors if you're doing transformers, only two. I think running a ground wire is silly on a doubly isolated "2 transformers back to back" setup, but you should put in whatever size ground your AHJ makes you install. For price reference:

  • 3 wires 2000' of #4 ACSR overhead line = about $1800
  • 2 wires 2000' of #1 = about $3000
  • 2 wires 2000' of #4/0 = about $6000
  • 2 wires 2000' of 350 kcmil = about $12,000

Remember, regular wires are only rated to 600V, so even if NEC has been revised to allow higher voltages, you can't use them unless the wires are rated for it.

2

We did this for a 3 phase connection.

We had two matched transformers made to increase the voltage to 1000V and then dropped it at the other end.

The transformers had multiple connections to go +/- some small percentages so we could deal with the voltage drop as this was for a wind turbine and the effects can be interesting. We were measuring and monitoring 3 phase power and phase angle and we also fitted a power factor correction unit but I don't think you will have to go that far.

Not the answer you're looking for? Browse other questions tagged or ask your own question.