Supplying electric 400 metres away

[Guest123]

Smells like at least a 120mm SWA to me, possible 150mm.

 

[Jimmy Boy]

Lol@Lenny
J

 

[johnboy6083]

ive just ran it through a cable calc program i have, and its come up with 120mm as lenny said, but this is based on a few assumptions.

 

[malcolmsanford]

That is why it is crucial to have specs for something like this Lenny, I can't for the life of me see an office building having a total load of 58amps, unless it was a 3 story office block.

I don't think I would suggest a single phase supply with a 60amp load over 400mts, it is just not economical it would have to go to 3 phases

 

[snowhead]

The alternative is a journey of up to 30 minutes to get between the two headlands.

Toll Booths??

With electric gates, and flashing neon signs??
And of course 2, 3kw fan heaters for the operatives.

 

[Guest123]

but this is based on a few assumptions.

Until the OP opens up a bit, we can do no more buddy.:icon6:

 

[i=p/u]

just when i was getting in too reading this , the original poster is away too install 120mm

 

[johnboy6083]

ok, so ive made some more assumptions:

a) all of the loads will be small single phase loads, none more than 20A
b) they will be general building services: ie, lighting, power and heating
c) that there will be one circuit going to the first building, and then looping off to the second.
d) ive assumed a power factor of 0.8
e) ground temp of 20 degrees c at the highest (if the temp risesabove tis in the summer, then the heating will be off, and you wouldnt need air con so close to the sea anyway ;-)

its come up with a 3ph 32A supply at 35mm2. You would have to balance the loads and buy a 3ph board, but the savings would be enourmous on cable alone.

 

[i=p/u]

well might look blanced but isit ever

 

[Octopus]

The buildings are sort of offices used for monitoring purposes.

The load has been calculates at 58A which is why we are looking at 63A supply. Thanks for your idea of the extra core for the earth but would the earth potential voltage be a lot different between the meter buildings and the proposed new buildings? There is just under 400m of made up land using rocks to gain the height. Probably 300m is a sea wall.

It is an unusual project - almost unique - as I do not think that using concrete which would be on a rock formation would be suitable. The rock under the concrete would dry out in dry weather thus reducing the efficiency of the earthing.

Any constructive suggestions welcome.

Also, as this is for a charity, is anyone interested in it?

Maybe a challenge for a college..............

Are you wanting to play poker with us where we show our hand and you keep yours hidden?

The load has been calculated at 58A - by whom and based on what?

 

[snowhead]

It was someone just trying to find out the cable size and now they've gone of to spend £6k on Swa.

They should have hung around and found out they could have managed with 16mm t&E.

 

[Guest123]

That is why it is crucial to have specs for something like this Lenny, I can't for the life of me see an office building having a total load of 58amps, unless it was a 3 story office block.

I don't think I would suggest a single phase supply with a 60amp load over 400mts, it is just not economical it would have to go to 3 phases

I've given up trying to 2nd guess posters that dont divulge enough info from the start, I feel, if this was genuine, the services of a competant spark/consultant would already have been engaged.

 

[Engineer54]

For a cable run of 400 metres, no way would i run a single SWA, it needs to be a parallel supply, which will reduce the overall size of the SWA cable considerably, etc.... So if a 120mm was called for, then replace with 2 X 3 core 50mm or 70mm depending on actual requirements and restrictions at the load end. As for the earthing arrangement i would be inclined to extend the supply earthing, and if possible explore the possibilities of adding TT earthing, be it Ufer, copper tape, rods etc, that can be connected to the MET of the two buildings.

Until we know more, these are just base line assumptions, to give the OP a little more thought, in to how to tackle such an installation....

 

[hazelm]

We all wish the sea defence wall contained steel - that would make life a lot easier. The wall was built about 200 years ago from quarrying in the area and it carries a footpath and road across it.

The company operating across it is the oldest operating company in the world in its sphere and I am in the supporting charity company.

I will obtain the calculations and post them here as soon as I can. It is two single story offices, one of which is for battery supplies should the mains fail, but these offices are close to the sea and obviously need excellent insulation for low amounts of heating in the winter.

 

[Octopus]

I wouldn't be basing a design, nor be doing a budget for a build/change on the basis of input from a number of "unknown" people on the web if I were you.

Suggest you post the location and get at least 3 people to come and have a look and provide written outline plans.