A query about KVA and cost

[the pict]

A customer has been quoted 11,000 quid to upgrade to 3 phase a whole load of cable and a pole mounted 11kva are required is 11kva a standard or are they punting us one so to future proof further requests for loads
P

 

[telectrix]

is it 11 kVA or a transformer off a 11kV distribution network?

 

[the pict]

I cant say as the documents only say what they are providing although I imagine its much higher at source

 

[Intoelectrics]

I've just been quoted £129,000 to have a 750Kva transformer installed 100 mtrs away from the supply network. This includes the supply, installation & connection of the HV cable, associated protection devices & switch gear and the supply, installation and connection of the transformer, protection devices & switch gear.

The HV supply is 11KV to the proposed transformer

 

[the pict]

Jeez And I though we were getting shafted

 

[the pict]

the guy from SSE has told me that there is already 46KVA at the property but it is on one phase via the L1 and L2 and 2 cutouts OK I get that, so why add the 11KVA tranny and replace about 200 mtrs OH LV, anyone have any idea whats going on here, is my usual way of conversion letting me down KVA 46 x 1000/230 = 200 Amps which means the 11 KVA =48 amps so why part with 11,000 quid for an extra 48 amps perhaps I am wrong, any thoughts

 

[Lucien Nunes]

Sounds like confusion here. Overhead supplies are often 11kV (kilovolts), either single-phase or 3-phase. I don't think 11kVA (kilovolt-amperes) is relevant. It sounds like they need to replace the single-phase 11kV overhead line with 3-phase, and replace the single-phase 46kVA transformer with a 3-phase one of suitable size. If the new service is to be 100A, the transformer needs to be at least 3 x 100 x 230 = 69kVA.

 

[JD6400]

As always , I am probably wrong but it sounds like you have a 480v splitphase supply at the moment , and 46KVA would give you 2 x 23KVA = 2 x 100a in incomers.
Alot of places out in the sticks used to have it , I have heard it referred to as poor mans 3ph !
They will need the swap out the transformer and add an extra wire in for it to run 3ph to you .

If anyone else wants to use the new infrastructure within a set period they will compensate your client part of the costs for allowing a 3rd party to use what he has paid for to upgrade the line.

 

[JD6400]

I may be wrong on the 2 x 23KVA giving you 2 x 100a !?
If it is true splitphase I think you need to factor more in to the equation?
If one of our more learned posters could shed some light , I would be very grateful.

 

[the pict]

Sounds like confusion here. Overhead supplies are often 11kV (kilovolts), either single-phase or 3-phase. I don't think 11kVA (kilovolt-amperes) is relevant. It sounds like they need to replace the single-phase 11kV overhead line with 3-phase, and replace the single-phase 46kVA transformer with a 3-phase one of suitable size. If the new service is to be 100A, the transformer needs to be at least 3 x 100 x 230 = 69kVA.

I get it now I have misread one of the documents I think so I'll re read it
Thank you

 

[StephenRowley]

What's you client trying to power?

 

[Lucien Nunes]

I may be wrong on the 2 x 23KVA giving you 2 x 100a !?
If it is true splitphase I think you need to factor more in to the equation?

Nope, nothing wrong with that. Consider a transformer with two 230V secondaries rated for 100A. Connecting them in parallel gives you a single-phase 230V supply good for 200A or 46kVA. Connecting them in series gives you a 460V supply good for 100A or 46kVA, but if you earth the centre-tap and call it neutral, you can deliver it as 2x 100A 230V supplies but now with 460V between the lines if desired for high power loads.

 

[the pict]

What's you client trying to power?

Its a hotel refurb kitchen is mostly gas , 6 rooms a little shop cafe, and restaurant, showers in electric showers in 3 rooms,

 

[the pict]

\So is 11KV not overkill for a single customer as looking at the drawing sent by SSe it only serves my client

 

[Intoelectrics]

\So is 11KV not overkill for a single customer as looking at the drawing sent by SSe it only serves my client

11 kv would most likely be the supply voltage to the transformer. Are you saying its a 11kva 3phase transformer?

 

[the pict]

That is my assumption as we requested 3 phase to the development if I can I will attach the drawing if it would help

 

[Lucien Nunes]

So is 11KV not overkill for a single customer

It's not a matter of overkill. It sounds like the nearest 3-phase of any sort is 11kV, some distance from the present transformer location. To bring 3-phase to the property, they either have to convert the existing single-phase 11kV line to 3-phase and change the transformer, or put the 3-phase transformer where the 3-phase presently ends, and run the service from there to the property at 230/400V. Depending on distance, that might either be impossible, or might involve massively more copper, so converting the 11kV to 3-phase is likely the most sensible.

11kV line is cheap, that's why it's everywhere. Your 3x 100A supply at 230/400V only takes about 4A from the 11kV line so it can be a very lightweight cable, and two of the three conductors are there already.

 

[Intoelectrics]

If you requested around 100 Amps per phase then off the top of my head the transformer will be at least 25 kva, if I remember correctly?

 

[the pict]

Have a look at the file attached
P

 

[Lucien Nunes]

This is more or less how I envisaged. The red line is the 3-phase 11kV going past the location but the branch to the transformer is only single-phase, so that needs upgrading. Then the transformer gets changed to a 100kVA 3-phase one, and the overhead 230/400V cable from that to your customer, which is also single phase at the moment, needs replacing with 3-phase as well.

Seeing as your premises could be taking over 2/3 of the transformer's rating (69kVA of the 100kVA) it's not as though they are over-speccing it at your cost. Looks fine to me.