What sized cable to use?

Is this in France?

In the UK, isn't the wiring up to the meter the leccy company's problem anyway, ie DIY that part isn't an option?

My friend is in the UK. The plan is to have the meter about 350m away from the house. EON will connect to the newly constructed meter enclosure, which will be close to their new transformer, and he will connect from there to his house, thus assuming all responsibility for the cable, the way-leave and the voltage-drop.

LGF

Not on new connections; the work is divided into what the leccy company must do and what can be done competitively to leccy company standards

Is the meter enclosure on EON's or the friend's land, or on someone else's land? There may be security risks from tampering with supply or theft of electricity on the load side of the meter.

I don't think you'll be able to export a PME earth 350 metres from the meter to the house, so it would be better if the cable to the house can be supplier's work and the supplier provide a PME at the house.

Owain

I was wondering about the earthing arrangements, and couldn't quite understand why the electrician wasn't going to TT the whole thing. RCBOs have been specified for most circuits as far as I can work out. The meter enclosure will be in a hedge, at the foot of the pole with the transformer on it. Tampering could be an issue - wouldn't it be hilarious to turn it off!!!

I think EON quoted about =A330K for the new transformer and connection to the house - seems good value to me!

LGF

How long is a piece of string? You need more detail than that to assess the likely (and future) loading

SNIP

It will probably pull out a lot easier when attached to the back of a cable thieves lorry!

The voltage drop is less relevant in mains wiring than the power loss

- heating effect.

nevertheless I would install 100A cable simply because its so little more you might as well.

And gives you enough to run a heat pump as well...

No reason not to run it yourself either, and simply leave the hookup to the power company.

I installed mine. A lot cheaper than the leccy co doing it. They gave me the cable and a safety tape.

Odd way to do it, but it works for me..

As far as I'm aware you are permitted a small percentage voltage drop from the origin of an installation (i.e. 350m away). So, for a lighting circuit, this is supposed to be 3.5% max. I'm not sure how easily that will be achieved given that the lighting circuit is going to add ~50m.

What's 100A cable?

Not an answer to your actual question, but a point regarding the pulling of large cables.

At our work, where they had to pull at 240mm2 they pulled it in as 2 sets of 120mm2 singles, paralleled up.

They said the tended to use singles rather than a fat cable due to manual handling and cable flexibility / termination considerations.

On 19/07/2011 13:42, legrandfromage wrote: ...

and for replacing it when someone nicks the lot.

Colin Bignell

Ferret onna string, send ferret down pipe, attach progressivly thicker string until strong enough to pull lube'd cables through.

JGH

That I think is worth noting. I'd not want 350m of cable between the meter and house. It'll have to be quite chuncky and therefore enimently knickable. Not to mention the power loss, assume a 10v drop that's 1/2 a unit for every 50A of load or 1/2 a unit for a 5A load over 10 hours, the base load of a normal house with people in it is around 5A.

Pretty sure the power companies are happy for others to dig trenches, lay cables themselves and they just check that it's all been done properly and connect up. As has been said they may even supply the cable as it will be their responsibilty once connected.

I think it is a crazy idea to be running 350m at LV after the service head. You will be responsible for the voltage drop and it will be almost impossible to meet the regulations (3% lighting 5% power) throughout the property without using oversize cables. If you want to run the cable, fine, but let the DNO take it over and have the service head and meter at the house end. As someone else has said otherwise you will end up footing the bill for heating the ground around the cable. If you ever install solar panels then you are meant to keep the voltage drop(rise) to 1% which will be more difficult if the service head is

Circuit protection for conductors in parallel is not simple.

Or possibly even 100A per phase to make it worthwhile...

Probably easier to come at this from the other way and work out the maximum voltage drop per metre (Vdm) that we can tolerate. Lets argue that the cable run is a distribution circuit (seems fair) and hence is subject to a 5% drop limitation, so in this case 20V as this is a 400V circuit. Lets assume 100A/phase.

Vd = Vdm * 350 * 100 = 20

so 20 / ( 100 * 350 ) = 0.6mV/m

To get under 0.6mV/A/m you would need 70mm^2 4 core SWA which gives a drop of 0.55 mV/A/m (I am assuming 70 deg C limit cable here - Table

However this is complicated by a few things. Firstly the voltage drop specced for the cable is based on the assumption its running at max temperature. 70mm^2 is good for 150A (Table 4D2A), so this is actually going to be an unrealistic pessimistic figure to use.

Its further complicated because for cables with conductor sizes over

Its yet more complicated by the fact that this will not be a balanced three phase load, and hence there will be a neutral current which will also account for some voltage drop.

So all in all you need more detail of the actual loads to do a decent calculation. (however gut feel suggests the 50mm^2 SWA may well be adequate for a 60A/phase install)

(Don't that the above as gospel without checking - its late, and I may have missed something!)

Why?

You can't guaranty the current flows equally down each conductor. Its actually easy to fully protect them, just put a fuse in each conductor. It just doesn't allow full use of the available copper.