transformer sizing

[karthik]

Hello all... What is the load factor,spare capacity and type of transformer to be considered while sizing the transformer for residential,commercial & industrial projects as per NEC.What are the protections to be considered with respect to the capacity and type of projects as per NEC.

Regards
Karthik

 

[iwire]

Re: transformer sizing

The NEC is not concerned with spare capacity only that what you install today will operate safely.

90.1 Purpose.
(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

(B) Adequacy. This Code contains provisions that are considered necessary for safety. Compliance therewith and proper maintenance will result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

(C) Intention. This Code is not intended as a design specification or an instruction manual for untrained persons.

As for specific NEC transformer protection and installation rules look to Article 450.

 

[karthik]

Re: transformer sizing

many thanx for ur quick reply.Does NEC code talks about the following.

1. Upto & beyond which capacity the busducts has to be used instead of cables.
2. Upto & beyond which capacity the transformer protection like differenrial,restricted earth fault to be provided.
3. Where i can get the standard transformer impedence with respect to capacity & voltage levels.

Need help..........

 

[charlie b]

Re: transformer sizing

The NEC does not tell us any of those things.

It sounds like you are in over your head here. You are asking us to essentially teach you how to design something. You want us to tell you everything you need to know about selecting and protecting a transformer. That is too much to ask from a Forum of this type. We are here to help each other resolve issues and answer questions. But we are not a design school or an apprenticeship program. Since you are a "senior design engineer," you should be asking these types of questions from your supervisor or from the licensed PE who is in responsible charge of your projects.

 

[karthik]

Re: transformer sizing

I think u misunderstood the question what i have asked...As per British & Indian standards transformer rating above 750KVA needs to be provided with busducts in the secondary side as per the codes.Same way they have mentioned certain transformer protections like differentail & restristed earth fault to be provided above 2000KVA as per the standards.

I hope now i made it clear what iam trying to ask you...