3 Phase Question (not DIY)

[chrisbyrd]

Hi All

Could somebody give me a little bit of advice

I've been asked to contact EDF for pricing for installing a new power connection, but I'm not going to be able to speak to the electrical guy for the next 48 hours or so

I've been told to arrange a '400 amp (per phase) 3 phase supply'

They have come back this morning to say they cant proceed with pricing any further until I can give them a KVA value for what we need. Apparently the maximum from the 400A service is 277KVA

We will only be running 'single phase' equipment, balanced fairly evenly accross the phases. The total 'single phase' usage is approx 650 amps - this is just about 'flat' - no daytime peaks etc

My question is, what sort of KVA value should I go back to EDF with to get things moving along? This is just budgetary pricing they're providing at this stage do dont worry - I'm not ordering this (fairly substantial) service without confirmation from our electrical guy - I just need to go back to EDF to get things moving along at this early stage

Thanks in advance

 

[Adam_151]

that 277 figure sounds about right for a 400A/phase service

Also note that the industrial tarriffs are more complicated than domestic, there is the physical supply size, i'm told and then you pay an availably charge for the size you are likely to use (I belive this gets figured in calculations to say the local tx is big enough, etc), if you go above this then you pay a much higher rate as you should have agreeed it in advance (bit like banks) if there is scope for 'load creep' it makes sense to get a bigger physical supply then you actually need and set the agreed availabily lower (with the reasoning that increasing this later is going to be much cheaper than digging the cable up to replace it)

 

[chrisbyrd]

Thanks adam

What does 277KVA translate to in terms of 'amps per (single) phase'?

 

[Adam_151]

Just think of it as three single phase supplies next to each other all supplying 277/3=92kva each, which is 92k/230 = 400A

 

[chrisbyrd]

perfect, thanks

 

[toasty]

Hold on though.

If you are currently using 650A on a single phase and the load won't be changing, then you are currently using approx 150KVA.

So I would suggest you ask for say 180KVA (i.e current load plus 20%)

277KVA is fine, but they'll charge you more per month for the expected usage.

Cheers
-Dan

 

[chrisbyrd]

So I would suggest you ask for say 180KVA (i.e current load plus 20%)

precisely what i asked for

thanks guys

 

[chrisbyrd]

£75,000 for the install - seems a bit excessive to me :/

although we need to pay about £650 to get a proper quote from them

 

[Chri5]

You might be able to suggest that if the cable requirement is lengthy and mostly on your property that you arrange the civils for the duct and inspection pit provision.

For a 1m trench, 6" pipe and a straight A to B route look at £100-£150 per metre with reinstatement.

Here's a decent PDF file showing duct depths (700mm), explaining sand fill and various other bits of solid information. One thing that did confuse me, was the suggestion that each phase of a HV run should be seperated in to it OWN duct feed.

Read the PDF if maybe of help

http://www.sppowersystems.co.uk/net...- Handling & Installation of cables up to.pdf

 

[chrisbyrd]

there's an existing 200a 3phase supply for the rest of the office units in the building

according to the meter, the current\max usage on that is 25\54 KW

is it likely to be possible to get this ugpraded to include what we need for our requirement (and hopefully save quite a bit of money) without any (too) major works by EDF?

is there a standard max capacity cable that they use for connections of this type?

 

[chrisbyrd]

does anyone know what they're likely to be able to upgrade the supply to on the existing cable, if there's a 200 3phase supply there currently?

 

[Spark123]

I think only EDF will be able to tell you this.

 

[chrisbyrd]

I think only EDF will be able to tell you this.

thats what i feared

they seem to be particuarly useless