What is Better?

from what I've heard "copper is cheap and abundant", just don't let the Meth-heads know where ya buried the cable.

Sounds to me like you need to have a proper load calculation done on both properties before you go any further with designing these conductor runs. A 100 KW of three phase power is a lot of power for a "small farm house". Even at 220 V single phase... 100 KW sure sounds like a ridiculous amount of power for a "small farm house".

This sure sounds like a school project to me, as such, doing a couple of proper load calculations and coming to realistic demand values would be a good learning opportunity and is the basic data you need before continuing with this design..

thanks all for your replays, it is not a school project and i am doing it for my own benefit; and for the load I only estimated it real quick because I am Planing to have like 10 air conditioners (window types ) lighting fixtures (internal & external ), 3 water pumps, etc.

Also, the copper will cost triple the amount if i used the Aluminum, but i am asking what should I also consider beside the price since it is going to be for lifetime step.

as soon as you mention 3PH most people here think of commercial or industrial operations, typically residences aren't supplied with 3 PH. its true that aluminum can carry this amount but its not the best idea. aluminum has high expansion and contraction rates so its connections are critical. overheating and fires are very possible. many places in the US have banned its use for these reasons.

Actually aluminum is the primary material used for primary feedlines from the utility connection point to the main distribution box.

Very few places use copper in residential or light commercial primary feeders now.

"typically residences aren't supplied with 3 PH"

this is true for the US only.

Use a search engine and find a cable sizing site. Don't ask strangers.

You should re-calculate your load and this time estimate it real slow.

That's enough power for many small farm houses...unless they are farm "grow houses".

Estimating power "real quick" usually leads to "real expensive" construction costs.

On a 100 KW feeder based on a 220 VAC single phase power source for a 400 meter run you would be needing either 4 4/0 (12 mm dia) aluminum conductors in parallel for each leg or 2 MCM 500 (18 mm dia) or 1 MCM 1000 (26 mm dia) sized conductor for each leg.

On a 380 VAC three phase feed you would be right at the limits with a single 4/0 (12 mm dia) size aluminum feeder for each phase and the common return.

No matter how you cut it its going to be expensive.

In Dubai, United Arab Emirates, that distance would be too far a distance, so you would need MDP (mini distribution pillar) installed between your house and the nearest substation. I don't remember but the max. distance for underground cable run from utility supply must be 300 meters. Once that achieved, then I could help you with design. the MDP has two to three outgoings that one could bring your house supplied with? :)

It sounds as though British Standard 7671 would be very useful bedtime reading.

80 - 100 KW seems very high even for air conditioning loads and especially so for a small farm house.

What dimensions of house are we talking here and what ate ambient outdoor VS indoor temperatures you will be dealing with?

I was recently over in Turkey and they typically see 120+F summertime temps with high humidity and blazing sun. Even with that I did not see a single house that had more than 6 10K - 15K BTU room air conditioner units installed of which not one of them uses much more than a KW at best.

This is an extremely long run for a residence....normally you would have a step down transformer within shouting distance....Bearing in mind that higher voltage requires a smaller wire size, I would get a step up transformer at the beginning of this run, and step up to 600v 3Ø and use aluminum wire(4/0), and then step down the voltage next to the house...

My first response would be use transformers at each end to increase the transmission line voltage, and thus reduce the current carrying requirements and have less losses as well. Most EE's will suggest saving money by investing in a step - up - step - down configuration. Of course, now you would have 2 - 100kw PT's. So there might be a trade off in cost/ distance, I'm betting the smaller guage cables will offset the Xfmr costs.

After I'd stopped laughing I came up with a 185mm² 4c SWA for 380V. Even that is pushing things with 4% VD @ 100KW.

PS that was for copper, I couldn't be bothered to look out the BS7671 tables for Al.

Half a kilometer distance from the distribution line is a far enough of a distance that I would consider a distribution transformer and get your power feed at a higher voltage from your utility.

Putting things in perspective and comparisons:

100KW is 1/10 of a megawatt, that's a lot of electricity.

If all this is for a small farm house, what are you doing in it? Sounds like you may be operating a moonshine still and heating the mash with electric heating. That's a lot of moonshine, do you have a market for it?

Unless you have your own hydroelectric power plant a guy who lives in "a small farm house" won't be able to afford the electricity at 100KW.

Suggest you re-evaluate the predicted loads and start from the beginning. Also get yourself an EE specializing in power distribution to assist you. The mistakes you make could be very costly or dangerous without him

Good Luck, Old Salt

Hydroponic pot farm? Grow lights and a deep well?

You got yer lights, pumps, ventilation, climate control.....adds up

Maybe both! Moonshine marinated pot! I love the idea. Marketing slogan-->"A high with a buzz!"

Good Luck, Old Salt

That's a long way to run LV at that sort of loading _{(as others have said that is a lot for what you have described)} especially underground.

Recheck your loading calcs/estimates and then perform a conductor sizing exercise.

If you want to know whether Al is as good as copper......yes it is iff it is correctly sized, correctly installed and properly terminated with unobstructed access to the terminations for inspection and maintenance, and there is enough cable slack to reterminate a few times during the life of the installation if required. It's most definitely less costly than Cu.

al, I agree it is a long run for L.V. I have said it above in #4 or so as I cut and paste:

In Dubai, United Arab Emirates, that distance would be too far a distance, so you would need MDP (mini distribution pillar) installed between your house and the nearest substation. I don't remember but the max. distance for underground cable run from utility supply must be 300 meters. Once that achieved, then I could help you with design. the MDP has two to three outgoings that one could bring your house supplied with? :)

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Now I am also saying this. If he is in Dubai or not but we all agree on this that his L.V run is too long of a run. As far as I have known, the utility would accept a max. run of 300m or so. 1) He is saying an underground cable run. So first he must get either confirm or get approval from the power company whether or not his long run would be acceptable according to the local regulations. If not, then they could give him some info as to how far they either having the MDBP already installed in the area or would be installing one for his premise? If they already have one already there then he could get the distance as to how far? It must be in the 30 0m length. If not already (as it must be the case look like:) then he must ask whether they could provide one near his home. If they say they could then at what distance it would be from his premise. If there is a near substation and they could install an MDP between his premise and the substation, what distance the MDP would be of his premise then? Once that distance is known then we could calculate the rest distance from M.D.P to his premise. Then we could find the cable size, the voltage drop, etc. Say the distance of the substation to his house is 400 m. In the view of the 300 m requirement, they must have an M.D.P installed from the substation at a distance of 120 m, per say. Then 400 m - 120 m = 280 m which one has size the cable for. That would the distance be between the utility supply (M.D.P) and his premise, the house or so. That would save money on cable etc.2) If there isn't any other way and he has some overhead transmission and distribution in the area, then he could run an overhead line with Dist. transformer and H-Pole right next to his premise. That is not my line of work though. He could have a PT with that KVA? 3) These people don't put enough info to begin with. They just like the forum's brainstorming? They don't bother visiting the utility offices because the Arabs setting in those offices are like dogs, barking at people. They think the rest of the people are just their SLAVES. I think they need proper education that a small band of people called Jews in Israel has beaten their ass not once but multiple times. Only dog is best barking in his or her yard, nothing else...My apology in advance!

....don't hold back now.

Yes, dealing with authorities is not a joy ride any where in the world.

Old Salt is right, get an EE to recalculated your load and design. My house typically uses 1 kw, and I can see how a big house with lots of HVAC could use 10 kw, but 100 KW can power over 10 houses, even big houses in the UAE.

use al cables of suitable size after calculating for drops etc. armoured cable will be better