Cable Size

[surineman]

Hi Everyone,

I have a 2000 kVA transformer 27.6 kV/ 600 V
The transformer and electrical service cabinet both are going to be outside and located very close by each other.
The code asks for breaker and conductor (secondary) not more than 125% of rated current.
1)What would be the most economical secondary cable.(2500 amps considering the 125%)
2)Is there any specific rule regarding not having splitter box for that level of amps? (as oppose to have a real nice distribution panel)

Thanks in advance

 

[mpparent]

My opinion:

Use 500kcmil conductors (380A). Anything over that and a contractor will want to strangle you. I'm not sure what you mean by a "splitter box".

Mike

 

[surineman]

By splitter box I mean:

The outgoing cable after main breaker would go to a set of terminals which all of feeders to branch breakers are tied to those terminals.

As oppose to have a real bus bar and feed the branch circuit breaker from bus bar.

For 500kcmil I should use 7 conductor per phase (wow)

 

[Dobber1978]

Please correct me if I am wrong as I am still fairly new to this myself.

I am using the Ontario Electrical Code (OEC) as a reference here so you may have to look into the requirements in your area.

In the OEC it states that if you use single copper conductor in free air you can push 660 A down a 500MCM cable, so with this being said if you can get the required spacing between cables you should be able to use less then 7 per phase.

 

[mpparent]

Well..

In NEC land, I don't believe there is any Code section restricting you from doing what you're explaining (assuming I'm understanding you correctly). However, I don't know that what you're proposing is a good idea. I hope you reconsider your position, and use a service entrance rated switchboard.

Mike

 

[resqcapt19]

I would look at bus duct. With that type of load and a very short run, the lenght differences in the parallel runs can become a problem.
Don