Upgrading from single-phase to two-phase?

[jon26]

How easy is it for the utility company to convert from a single-phase electricity supply to a 2-phase supply. What is involved?

Apparently this may be more cost effective than a new 3-phase supply. It is a large house that may require more than a single-phase supply can cope with.

However, until someone mentioned 2-phase to me recently I wasn't aware that 2-phase was an option, any views would be appreciated.

 

[Taylortwocities]

If the supply cable is 3 phase (or 3phase capable) then you're in luck.
Otherwise the DNO will need to run in a new cable. And that's not cheap!

Usually there will only be a single phase provided unless a multi-phase supply was installed at some time/

 

[jon26]

The house is in the sticks somewhat and currently fed via a single-phase supply apparently the nearest three-phase is available half a mile away. There is a dedicated pole mounted transformer on the end of the overhead supply, are they able to take the second-phase from that?

 

[JohnW2]

How easy is it for the utility company to convert from a single-phase electricity supply to a 2-phase supply. What is involved? Apparently this may be more cost effective than a new 3-phase supply. It is a large house that may require more than a single-phase supply can cope with. However, until someone mentioned 2-phase to me recently I wasn't aware that 2-phase was an option, any views would be appreciated.

When you talk of 'cost effective', do you mean in terms of installation or running costs? I have a 3-phase supply to my (also large) house, and the running costs (tariffs) available to me don't seem to be any different from those for single-phase supplies.

As for installation costs, I would have thought that it's likely that they would be more-or-less the same for 2-phase and 3-phase (since the supply cable is most likley to be either 1- or 3-phase, pretty unlikely to be 2-phase) - and, as has been said, the magnitude of that cost will depend upon the nature of the supply cable.

Kind Regards, John.

 

[JohnW2]

The house is in the sticks somewhat and currently fed via a single-phase supply apparently the nearest three-phase is available half a mile away. There is a dedicated pole mounted transformer on the end of the overhead supply, are they able to take the second-phase from that?

Are you saying that the transformer is half a mile away, or that it is local to the supply to your house?

Kind Regards, John.

 

[jon26]

The house is in the sticks somewhat and currently fed via a single-phase supply apparently the nearest three-phase is available half a mile away. There is a dedicated pole mounted transformer on the end of the overhead supply, are they able to take the second-phase from that?

Are you saying that the transformer is half a mile away, or that it is local to the supply to your house?

Kind Regards, John.

The pole is only 50 metres away but I think the supply to it runs about a mile over the hills (and this could only be a single phase supply). Not entirely sure how it works, can you take a 1, 2 or 3 phase supply from a transformer full stop or does it depend on what type of supply is supplying the transformer?

In terms of cost effectiveness, it is the capital cost to upgrade that I was meaning.
Kind regards,

 

[Stoday]

Two phase supplies of 240-0-240 are obsolete (unless they've been revived in the last 20 years).

The original idea was to use light construction single phase HV lines in rural areas. Cheaper than heavier 3 phase HV lines. These had 11kV to 240-0-240V transformers. They were known as split phase. They became redundant in the 1980's in Eastern England because O&M turned out to be higher on light construction HV.

So you see, it's only a cheap n nasty way of upgrading rural supplies. If the local network is three phase, you'll get either a single 230V supply or a 400V three phase supply. Not a 230-0-230V nor two phases from a three phase distributor.

 

[Paul_C]

There is a dedicated pole mounted transformer on the end of the overhead supply, are they able to take the second-phase from that?

Are there two or three high-voltage lines bringing power to the transformer on the pole? If they're telling you that the nearest three-phase supply is half a mile away, then it's probably only two. That means that only a single-phase supply can be derived from that HV supply line.

However a single-phase line can provide power in the form of a single-phase 3-wire supply which provides 240 & 480V. For residential use, you wouldn't have anything connected across 480, but the load would be split between the two poles of the supply. Such 1-phase 3-wire systems are quite common in rural areas.

However, if the existing transformer is just a 2-wire 240V type, and the supply to the house is only 2-wire, then even that conversion is likely to be expensive, as not only would a new supply need to run to the house, but also a new transformer would be needed. Even if the existing transformer is a type which can be reconnected for 240/480V 3-wire, then it might need replacing anyway if a much high load is contemplated.

 

[jon26]

Two phase supplies of 240-0-240 are obsolete (unless they've been revived in the last 20 years).

The original idea was to use light construction single phase HV lines in rural areas. Cheaper than heavier 3 phase HV lines. These had 11kV to 240-0-240V transformers. They were known as split phase. They became redundant in the 1980's in Eastern England because O&M turned out to be higher on light construction HV.

So you see, it's only a cheap n nasty way of upgrading rural supplies. If the local network is three phase, you'll get either a single 230V supply or a 400V three phase supply. Not a 230-0-230V nor two phases from a three phase distributor.

Thanks, yes I think the nearest 3-phase network is half a mile away and the cost to bring it over the hills to the transformer was ten's of thousands! So I guess what you are saying is that we're stuck with the 240V single-phase unless we want to spend big money?!

 

[Paul_C]

Not entirely sure how it works, can you take a 1, 2 or 3 phase supply from a transformer full stop or does it depend on what type of supply is supplying the transformer?

The latter. If there are only two high-voltage lines coming across the fields to the pole, then it's a single-phase supply. In order to have three-phase service available, it needs to be three HV lines arriving at the pole/transformer.

Two phase supplies of 240-0-240 are obsolete (unless they've been revived in the last 20 years).

{.....}

They became redundant in the 1980's in Eastern England because O&M turned out to be higher on light construction HV.

There are still quite a lot of in service in this part of Eastern England (the depths of rural northeast Norfolk).

 

[ericmark]

In a large house we were uncertain as to if a 100A would be enough so we fitted a three phase fused isolator which in turn fed three consumer units which in turn fed the different circuits within the house. We then took the 100A supply to all three fuses. This gave then a number of options should it prove that the 100A was not enough.
1) More than 100A single phase as our three fuses limited the supplies to the consumer units to their max of 100A.
2) A three phase supply
3) A split phase supply
However on returning to see how the owners had got on there was no overload problem and they found they could run on a 100A without a problem. I think it is rare for any house not to run with 100A and although making provisions may be a good idea I would expect you to find it's not required.

 

[Stoday]

There are still quite a lot of in service in this part of Eastern England (the depths of rural northeast Norfolk).

Of course.

Obsolete, like Windows Vista and older versions are obsolete. Still used, but not for new.