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 NCC-1701 08-06-2009 06:05 PM

Power transmission (Ranch / Farm)

Here's a general question I'm throwing out for discussion. I'm a year or 2 away from starting on the house.

I own a section of land in W. TX., 1/2 mile wide X 2 miles long. A pic. is worth a 1,000 words (see below). The problem is I want to build a house on a hill on the far side of the road about 1 mile from the power line.

------------x----------------}---------------------------------------
|.............. x.......................}......................... .............................|
|...............x.......................}......... .............................................|
|...............x.......................}......... .............................................|
|.............. x-----P...............}................... H................................|
|.............. x.......................}......................... .............................|
|...............x.......................}......... .............................................|
|...............x.......................}......... .............................................|
------------x----------------}---------------------------------------

x = transmission line
H = New House
P = Pole w/200A service
P --> H ~ 1 mile

The local Coop tells me to run the line is ~\$52,000 a mile. Ouch!

I figured I could get some surplus poles and insulators and set them myself. What I'm wondering is, could I step up the 200a, run the lines on the poles up to the road and then in a pipe under the road and back to more poles up to the house with a step down transformer? Getting the transformers (surplus?), doing the math to get to the wire size, pushing the pipe under the road, etc. shouldn't be too hard. I'm guessing/hoping that the loss at the transformers and the line loss would be negligible.

I see ranches all over with what look like owner installed lines (probably from a long time ago).

Any reason I couldn't this? I know I could do it for a lot less that \$52K.

Thanks,
Kevin

 micromind 08-06-2009 08:28 PM

To get 100 amps at the house, you'd need two 25 KVA transformers. Any transformer this size can be used in either direction of power. One side of each transformer will need to be 240 volts. One of them must be 120/240, the other one can be just 240.

Usually, we shoot for about 3% voltage drop for feeders. This will keep the lights from dimming when the well pump kicks on, etc.

If the transformers are 600 volt, you'll need 4/0 copper or 400 MCM aluminum to stay close to 3%. Copper simply won't work for overhead, and if you're using aluminum designed for overhead it'll be 397 MCM and have a galvanized steel wire in the center for strength.

Smaller wire will cause the voltage at the house to be less stable, lights will flicker, electronic things won't last as long, ect.

If it were me doing this at my house, I'd use 2400 or 4160 volt transformers. The overhead wire would be #6 or #8 aluminum. I've spent considerable time doing linework professionally though. Working with these voltages is really not DIY. Remember, 2400 volts is what they use in an electric chair!

How to do this depends on what the load is as well as your ability to work with large or high voltage wire.

Rob

 Yoyizit 08-06-2009 08:42 PM

Capt. Kirk, I presume. . .?

Higher voltage = less copper cost = higher risk.

With Micro's options you can pretty well compute the costs vs. voltages vs. risk.

These higher voltages are almost certainly fatal and voltages above 600 v puncture the skin so you lose the benefit of skin resistance.
Maybe some of the 52 kilobucks goes into liability insurance.

You might also consider a generator; the price per kwh can be the same as commercial elec.. 1 gal of gasoline = 38 kwh of energy and an eng/gen may be 20% efficient.

Average house usage is about 4A at 240v.
For the peak demand you might want to go with some type of energy storage. Then your cost will be in deep-cycle batteries or a flywheel.
With the insolation in your area, solar can probably provide water heating.
Running water powering a small turbine might give you another 500w.

 kbsparky 08-06-2009 09:25 PM

You don't really want to get into the high-voltage transmission business.

Very dangerous stuff to work with. :huh:

Things like lightning can wreck your system in seconds, especially if you don't have the proper safety cutouts, fuses, etc. :eek:

You'd be surprised at how much all the proper equipment costs to purchase, install and maintain. :whistling2:

 spark plug 08-06-2009 09:27 PM

Stringing High Voltage wire not a DIY project!

As Poster# 2 (Yoyizit) pointed out. Working with High Voltage Power lines and Transformers is not a DIY project. Besides, I wouldn't want to be tickled by a 4160 Volt transformer, either. (Never mind the higher voltages.) Not to mention complying with State regulations and overcoming other technical and logistical obstacles, you will not bring in this project even at \$52,000.! On a practical level, it would be worthwhile negotiating with the Power Utility about bringing down or sharing the cost. (Now (after the unfortunate accident on the Taconic State Parkway) More than ever):drink:Don't Drink and Drive!!!

 InPhase277 08-06-2009 11:43 PM

I'd just set a 40 HP pump at one end, and a 25 kW generator with hydraulic turbine at the other, and pipe them together with some sturdy hose...

But seriously, I'm no lineman, but at \$52k, I'd give it a shot! But I have years of experience with electrical systems and transformers in general, so my learning curve would be a little different than the average DIY'r. As with any project, I'm sure with some time and care and personalized instruction it could be done. Sure 2400 V will kill you, but they key is to get the lines strung before they are energized:laughing:

Maybe a contractor would work with you. Maybe you could set the poles, and have the wire on site, and they could string the conductors and terminate them for a discount. I dunno...

 vsheetz 08-07-2009 12:51 AM

I'd investigate spending the \$52k on solor, wind, energy effeciancies, and other methodologies - and stay off the grid and reduce your ongoing electric costs.

 NCC-1701 08-07-2009 04:54 PM

I'm investigating the 'alternative' option at a house very close to this property. Out here, solar hot water is a no brainer. In fact during the summer a 'cold' shower is 100F+.

I've always looked at it like 240V would do me in so 2400 or 4160 wouldn't make me more dead. Granted the margin or error is even smaller and should be given it's due weight. I hadn't thought of the lightening so I realize I have a lot more investigating to do.

Thanks again.
K.

 Yoyizit 08-07-2009 05:15 PM

Quote:
 Originally Posted by NCC-1701 (Post 311654) so 2400 or 4160 wouldn't make me more dead.
It might make you less presentable at your funeral.:eek:
240v with wet skin and small contact area might prevent you from releasing your grip; over time I guess you'd die from fibrillation if your yelling didn't bring help.

Speaking of pumps, there are several ways to transmit 1 kw to 24 kw of power but calculating the losses over 1 mile might be tricky. Low flow rate = low losses = a large pipe.
24 kw = 32 hp. HP = GPMxHD/40xEFF, with pump efficiency being 15% to 90% and HD in feet, with 14.7 psi = ~ 34'.
Here's stuff on pipe loss.
http://www.engineeringtoolbox.com/pe...oss-d_619.html
http://www.engineeringtoolbox.com/da...ion-d_646.html
http://www.engineeringtoolbox.com/pr...pes-d_404.html

Here's a link on the xmission of power.
http://en.wikipedia.org/wiki/Power_transmission

Pneumatic sounds like fun and not very lossy, and if your high pressure pipe breaks the ground will erupt (if you bury it) and you and your method will be on the evening news. Plus, it will scare the armadillos, rattlesnakes and scorpions.

A one mile long buried, flexible, permanently-lubed driveshaft doesn't sound practical but get some bids. It'd be about the diameter of car driveshaft.

Michael Lindeburg's has a very concise summary of what you need to know to take the Mechanical Engineers' PE exam and using his formulas you will quickly find out what is non-electric, practical and relatively safe as far as shock danger.
It's on the Web somewhere (The New York Public Library's website?) but a hard copy might be available to you for free at your local library or through interlibrary loan.

 philS 08-07-2009 06:41 PM

1701 -- How about an estimate of your power needs? You say a 100 A service but how much A do you figure you really need? And how much in daytime vs nighttime? The \$52k is probably not unreasonable which means that all sorts of alternatives may be cost effective. This means that a careful analysis of your power needs could save you big bucks.

As you say, solar hot water is a no-brainer. But in that case you may be able to do solar house heating as well. For cooking it's probably going to be cheaper for you to buy or rent a big propane tank, which gives you also an alternative for home heating (and winter clothes drying?).

Get rid of all those loads and solar panels with batteries (plus a genset) may be quite cost effective. Yes, installing that stuff yourself involves a learning curve but there are endless books and websites where you can get help. As opposed to building your own power transmission system, which as people have pointed out is not a typical DIY gig.

Just my 2c worth, though it's based on some experience.

 CDH 08-07-2009 09:32 PM

If it is a transmission line they are not going to let you tap off of it anyway, unless it has an underbuild ie distribution voltage, if they the co-op run a line in to you it is probably going to be #4 or #2 acsr single phase primary and neutral,usually they add a little to your bill each month for years until you have paid for the cost of the line to be built. 52,000.00 seems high you could probably get a local lineman or line contractor to build you a single phase line a lot cheaper than that,I know I would if I was closer to you, big thing is see how far it is to the closest distribution line and you will know how long your line needs to be.

 Yoyizit 08-07-2009 10:13 PM

With El Paso's avg. insolation, 36 sq. meters of solar panel at 10% efficiency will give you 24 kw.

 kbsparky 08-08-2009 12:02 PM

\$10 a foot amounts to \$52800.00 for a mile.

Sounds reasonable from that point of view.

If you add up the costs of conduit, heavy-gauge copper wire, transformers, trenchers, etc., you could easily exceed that cost.

Having the power company do the install means they will accept the responsibility for installation, maintenance, upkeep, repairs, storm damage, etc.

Depending on your total loading requirements, and the amount of time you are planning to spend living there, now may be a good time to research the possibility of building an off-the-grid house using the savings from your development costs as a baseline for your power system at the house.

Solar array panels, wind turbines, and an on-site LP or diesel powered generator set could be bought for \$50K .... :wink:

 Scuba_Dave 08-08-2009 12:18 PM

Yeah, I think I'd go solar & wind power plus gen
Propane for stove/heat if needed
Even if you could do it for less one lightning storm might just offset all the savings
And of course if there is any problem at any point its your issue to hire someone to fix, repair or troubleshoot

 AllanJ 08-08-2009 08:29 PM

Somehow I wanted to say that if you can figure on getting the surplus transformers and figure on setting the poles and stringing the wire yourself, then you save a lot on paid labor. Doing this project in 4160 volts is hardly more complex (only more repetitive and tedious) compared with running 110 volts overhead for 100 yards or so with one hot, one ground, smaller insulators, and just a coupl'a poles.

While you could take power from the electric company at a higher voltage, you'll still be paying for a second transformer, one that the company will be putting on its pole just for you since everyone else on the street takes 120/240 volts.

Turning the power off while you work is just the same as turning off the main breaker (240 volts) in an ordinary panel.

You'll need the permit and inspections from the town of course.

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