New supply

[Peter44444]

Hi all

I am wanting to put in a new supply. It would be commercial. For my boatyard business. I have a domestic supply at the moment to my home on the same site. This comes from a HV line 300m away at the end of my track. It comes from a transformer on the side of the HV post. The transformer supplys only me. The HV lines are single phase I believe as there are three wires. It goes underground 30m to a steel box with my meter then 300m under my track to the site. Obviously the voltage drop is considerable! 

I would like a 100-200A supply.

as I see it I have three options.

1. Get another cable put in from the transformer 30m to a secondary steel box with meter then run under the track 300m to the site. No way leave needed. Overhead lines aren't an option. Cable would need to be huge. How big would you think?

2. In another direction there is a nearer HV pole with no transformer.  Run a cable from here above or below ground 60m across a farmers field to the edge of my land then put a meter box in and run above or below ground 140m to the site. Way leave required from farmer.

3. Explore the idea of running a HV line across the farmers field to the site and cut out the problem of long LV cables and voltage drop.

There are no three phase cables nearby so I am not exploring this route.

as I am doing this on a budget I want to get as much information as possible. I have been warned that if you get a quote from uk power networks and decide not to go ahead then then punish you for it on the second Enquiry by putting the price up. I could really do with a site visit pre quote but they don't seem to work like this. 

Does anybody on on here have experience of putting in new supplies and the costs involved in doing so? I have machinery to do the cable laying so I would do as much as possible myself.

I'd gratefully appreciate any advice.

many thanks,

Peter

 

[Andy™]

MV / HV is TP, so if there are 3 lines then its likely to the TP.

 

[Peter44444]

Ok that's very interesting. I'd been told tthree phase power lines could be spotted because they have 4 wires, 3 positive and 1 negative. But you are confident that Its likely a three phase? that would be very useful to have three phase on site if it were possible.

 

[ProDave]

This is probably beyond what this forum can help with. We are electricians, not the supply company.

There is a procedure for applying for a new supply, you have to specify what you want and they will quote for it.

Some items on the quote sill be non contestable items, like the actual connection to the network.  Some items will be contestable, like digging trenches and putting in ducts to take the cable. If it's your land, you can do that bit yourself.

To give my own example for a domestic supply to a new build house, I as quoted about £2k for all works. but by arranging for the trenches to be dug and a road crossing to be made, I got that down to £1K whch I thought was still plenty for two men to turn up, opull a cable through a duct and connect it.
 

 

[Andy™]

you were told wrong... there is no neutral. there is also no positive or negative on DC AC either

 

[ProDave]

Ok that's very interesting. I'd been told tthree phase power lines could be spotted because they have 4 wires, 3 positive and 1 negative. But you are confident that Its likely a three phase? that would be very useful to have three phase on site if it were possible.

A 3 phase HV (probably 11KV) line will have 3 wires. A single phase one will have just two wires.  If 3 phase is available at the pole then a 3 phase supply may suit your needs better.
 

 

[Andy™]

also, if there are only 2 lines then its also possible to get a split phase supply

 

[Peter44444]

Am I right in thinking a split phase supply is where you split three phase into three single phase circuits? A sparky I know thought it would be good for me to have three phase if poss as he could split the phases to send them in three directions around the yard in single phase and where I have a couple of workshops he could recombine the phases to give me three phase supply. Does this sound acceptable? He also thought Over the 300m the TP cable would be cheaper than a SP one allowing for the voltage drop.

i fear you may be right prodave but this is still great information. Maybe somebody will pipe up who has worked in the supply industry.

 

[Lurch]

there is also no positive or negative on DC eitehr

ITYM AC.

 

[Andy™]

split phase is 2 phases 180 degrees apart, not 120. so you get 460v phase - phase. but you also need either 2separate boards or a single board designed for 460v. a normal TP board is not rated high enough to split phase

you cant really split the TP supply to different places then combine it either. its either TP from origin or its not

ITYM AC.

oops

 

[ProDave]

Another thought.

you already have a supply to your kiosk 30 metres from the pole. THAT is where the DNO's responsibility ends.  At only 30 metres from the transformer, I would expect the supply to be quite robust there.

I suspect your volt drop issues are the 300 metres of cable from the kiosk to your house / business.

That is YOUR cable. You (or your electrician) can replace that with a much thicker cable without involving the DNO so it is just the cost of the cable, digging a trench for it, and the electricians time to connect it.  you might well find just upgrading that cable solves all your problems at considerably less cost than getting a new supply.

At a VERY rough estimate, you are probably looking at a 50mm2 2 core steel wire armoured cable (certainly nothing smaller)

 

 

[Peter44444]

Ok I'm afraid I'm getting a bit left behind with the three phase talk, sorry! I've never had any working experience with it.

In laymans terms what are the options I could consider with three phase? Bearing in mind what I need is 100A-200A worth of single phase outlets around the yard and a couple of three phase outlets for workshops and running a winch.

why is splitting phases beneficial?

 

[Peter44444]

Prodave you are bang on I could beef up my line and improve things. I currently have the line restricted to 80A after the meter but before the 300m run. We've gotten by for 30 years with the voltage drop.... Occasional flickering lights! When I talk to my electrician mate and we discuss diversity we came to the conclusion my house uses up the available 80A already. And there isn't enough left to supply the yard as well. I have an electric shower which must soak up 40A or so on its own. The options where either a new supply or limit the domestic to 60A and outside to 20A which isn't really ideal. Improving it to 100A would give me 20A more but  I don't think it's enough unfortunately.

@Peter44444 Can you post a photo ?

Sorry a  photo of what?

 

[Lurch]

In laymans terms what are the options I could consider with three phase?

You can have 3 phase, or you can't. What exactly do you mean, with what options? You need to start from the end of the circuit, work out what you are powering and then choose a suitable supply type, and by you I mean the electrician installing this lot.

why is splitting phases beneficial?

It isn't necessarily, I think you lead some people down the wrong track with the 3 overhead wires on HV thing.

 

[ProDave]

If you have been getting by for 30 years, then there can't be anything that big in use in the yard then can there? and if it's your business you won't be showering and working at the same time (and can tell your familly when not to shower if you need to run something big in the yard)

Do you know what size cable is there between the kiosk and the house?

A 3 phase supply will in effect give you 3 times more capacity, but you were saying that's too expensive shich is why I threw in the option of upgrading the existing cable. It will still only give you a total of 80A but with much less volt drop.
 

 

[Peter44444]

Lurch the talk of splitting the phases confused me. It sounded like there were different types of three phase supply. Again three phase is something I have no experience of. 

At at the end of the road I look up and there is a telegraph post which supports three electricity lines. On the side of the post is a grey transformer and coming out the transformer is one armoured cable which is my supply. That's as clear as I can make it. 

 

[Peter44444]

@Peter44444 A photo of the HV posts & lines you have at present 

I'll go and take one tomorrow

prodave I believe it's 35mm cable and yes I get by at the minute as like you say I might ask the family not to use the shower while I use the welder. But with more customers the demand is going up. And the sparky who would be doing it says he won't put more outlets in for me without increasing the supply. As he says its on its limit already

you say a three phase supply is 3x capacity? So could 100A TP give me 300A single phase?

 

[Lurch]

a three phase supply is 3x capacity? So could 100A TP give me 300A single phase?

Yes. A 3 phase supply is in effect 3 single phase supplies, and a 100A 3 phase supply is 3 100A single phase supplies.

 

[Peter44444]

Ok great so on a very rough estimate what cable size might I need for a 300m run of three phase? At 100A. Would it be 4core swa? Is the armouring used as an earth? I guess there may be completely different earthing arrangements for three phase... all I'm wondering is if there's an option to use a core as an earth. in which case would you need a 5 core swa? I was taught to steer clear of relying solely on armouring as an earth.

 

[NozSpark]

I've just done a quick calculation on the Doncaster site.... comes out at 120mm for 100A 3ph