Discuss Supplying electric 400 metres away in the Commercial Electrical Advice area at ElectriciansForums.net

H

hazelm

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Does anyone have experience of providing a 63A supply from the meters to two separate buildings some 400 metres away.

Armoured cable will be used in underground ducting to two buildings about 50 metres apart from each other. These buildings will be on reclaimed ground from the sea with the sea just a couple of metres away. The building should never get flooded. Earthing solutions are sought as the gound is piled rock therefore earth rods need to be driven into the sea bed.

Would anyone like the challenge of plans?
 
That would be a nice challenge. What are these buildings retail outlets residential, catering or something else. Only ask as there maybe other standards to consider.

Also depending on the use and loading, I know you said 63 amp supply, then that distance with type of laod will determine your cable size.

Section 709 would also be a good guide for you, though specifically for marinas also relates to similar locations and these sort of environments

I see your thinking of using SWA, well in a marine type environment this is one of the few times I would advocate using an extra core inside the SWA for a CPC, I just think that the environment can be to harsh for a SWA CPC

Finally for the earthing I would be looking at something similar to Ufer earthing, utilizing the foundations if they are concrete for your earth arrangements.
 
H

hazelm

  • Thread Starter Thread Starter
  • #5
The reclaimed land was built 200 years ago and it is a carriageway, a listed building, going between two headlands close to the sea. The alternative is a journey of up to 30 minutes to get between the two headlands. Because of my company's business, we do not need planning permission for the buildings.
 

Jimmy Boy

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Arms
It would be interesting to see the results of a search of the post code of the building here.

here
 
H

hazelm

  • Thread Starter Thread Starter
  • #7
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..............
 
H

hazelm

  • Thread Starter Thread Starter
  • #9
It is a one mile causeway with a road running alongside between two headlands, the causeway having been built some 200 years ago and I am not aware of the causeway having been breached by the sea.

The land protected by the causeway would have been under the sea had this not been built.
 
H

hazelm

  • Thread Starter Thread Starter
  • #11
I should have said:

Maybe a challenge for a college in their electrical technical department!!!!!

My company will be buying the necessary cables and fittings!!!!!!!!!!
 
It is virtually impossible to design a concept on a forum by word of mouth but I'm assuming that the 400mtr supply run to this building is in SWA ................ This I would most likely if it was single phase use a 2 core and the SWA as "earthed". This would ensure that when you get to the outlying building the original earth at supply will be isolated from your TT supply as you are planning.

Though saying this, is there a reason you are not thinking about exporting the equipotential zone? It is only the metal work of boats that can not be connected to a PME, permanent buildings can be. So do these meters have a TN earthing system?

I work in a desert here and if there is any place that is drier I like to know, so Ufer earthing would not be a problem
 
im intrigued! id be happy conferring with a few of us on here to see if we could come up with a workable solution. Forst of all, could you prove that this is a charity, who are you in this organisation, and photos, existing load calcs ect please?
 
does tghe sea wall contain steel? this could be used as an earth electrode, provided it satisfies certain conditions, which it probably will.
 

Jimmy Boy

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Arms
Another drip feed of a question, can we just have the full details ?, what project, what charity, for whom,when,WHERE ?, supply characteristics of the feeding supply TT, TNCS or TNS ? what's going in the building ( Services ? ) can we export the earth ?
Give us details
 
G

Guest123

  • Thread Starter Thread Starter
  • #16
Smells like at least a 120mm SWA to me, possible 150mm.
 
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.
 
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
 
G

Guest123

  • Thread Starter Thread Starter
  • #21
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

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Arms
just when i was getting in too reading this , the original poster is away too install 120mm
 
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.
 
Last edited:

i=p/u

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Arms
well might look blanced but isit ever
 
O

Octopus

  • Thread Starter Thread Starter
  • #25
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

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Mentor
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.
 
G

Guest123

  • Thread Starter Thread Starter
  • #27
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.
 
E

Engineer54

  • Thread Starter Thread Starter
  • #28
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....
 
H

hazelm

  • Thread Starter Thread Starter
  • #29
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.
 
O

Octopus

  • Thread Starter Thread Starter
  • #30
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.
 

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