Supplying electric 400 metres away

H

hazelm

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.
 
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.
 
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..............
 
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.
 
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?
 
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
 
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
 
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.
 
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hazelm said:
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..............
Click to expand...

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?
 
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.
 
malcolmsanford said:
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
Click to expand...


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.
 
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....
 
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.
 
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.
 
Since I fancy a guess, how about the Cob at Porthmadog, built in 1811? Not only a road and a footpath along it, but a very nice narrow gauge railway!

If this is for the Ffestiniog Railway Society, then any help is good, chaps.
 
HandySparks said:
Since I fancy a guess, how about the Cob at Porthmadog, built in 1811? Not only a road and a footpath along it, but a very nice narrow gauge railway!

If this is for the Ffestiniog Railway Society, then any help is good, chaps.
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Do I signal a yes here? Maybe I have given away too many points!! :wink_smile: lol

The loadings

Lighting 1kw
Heating 6kw
IT 1kw
Kitchen & drain 3kw

Each building is 10m by 4m approx

Any constructive thoughts are welcome.
 
For me with that kind of loading you would be looking at nearer 40 amp rather than the 63 amp your were looking for. IMO diversity would get that to around 30 amps for commercial property, but make it 40amps for good measure.

4amps of IT is perhaps a little excessive as well and so is the 4amps for lighting. Heating will obviously be your main problem but a well built well insulated building will off set some of that.

Are the above figures combined or for each building
 
Yes interesting thread, just info is so limited... if its a monitoring station you would need to know what is been monitored and if it uses power 24/7 (possible storage heating if daytime only), its possible the quoted demand is correct but need a breakdown, now this isnt my field so not sure on the regs here as it would be out of the scope of the 17th but is it possible to up the voltage then derate at offices... i would also be taking a minimum of 80amp supply with the suggested design load, you just know someone gonner stick an extra Heater or two on.
 
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darkwood said:
Yes interesting thread, just info is so limited... if its a monitoring station you would need to know what is been monitored and if it uses power 24/7 (possible storage heating if daytime only), its possible the quoted demand is correct but need a breakdown, now this isnt my field so not sure on the regs here as it would be out of the scope of the 17th but is it possible to up the voltage then derate at offices... i would also be taking a minimum of 80amp supply with the suggested design load, you just know someone gonner stick an extra Heater or two on.
Click to expand...


Off-peak storage heating would need an extra circuit so a separate armoured cable - that is out of the question, I am afraid.

I totally agree with future proofing which is what we have done for the installation at the works on one headland, but we are talking about the other end of the causeway. Monitoring? well, just traffic really, everything goes on outside and it is really a controlling monitor station operating battery powered lights. The second room being the battery room.


The loadings

Lighting 1kw
Heating 6kw
IT 1kw
Kitchen & drain 3kw

Each building is 10m by 4m approx

Any constructive thoughts are welcome.
 
I never said off peak in seperate supply you just set up timer and contactor array then the front end meter would then be duel tarriff, thus only requiring the one supply.
 
hazelm said:
Off-peak storage heating would need an extra circuit so a separate armoured cable - that is out of the question, I am afraid.

I totally agree with future proofing which is what we have done for the installation at the works on one headland, but we are talking about the other end of the causeway. Monitoring? well, just traffic really, everything goes on outside and it is really a controlling monitor station operating battery powered lights. The second room being the battery room.


The loadings

Lighting 1kw
Heating 6kw
IT 1kw
Kitchen & drain 3kw

Each building is 10m by 4m approx

Any constructive thoughts are welcome.
Click to expand...

You really need to get somebody to come and LOOK at the site. Are you representing the organisation of trying to design it and sell to them?
 
Murdoch said:
You really need to get somebody to come and LOOK at the site. Are you representing the organisation of trying to design it and sell to them?
Click to expand...



No - at this point in time, no outside contractors have been involved. I am part of the team in the charity for which my time is given free of charge.
 

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Supplying electric 400 metres away
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