Protection In Un Grounded System

What are you talking about? A three wire delta three phase system?

I was talking about 3-wire delta system where in process plant if one phase goes off the other two phases cater the load.

Now what type of protection should be considered here ?

1. As it is unearthed system earth fault protection reqd. or not ? or how?

2. What are the other ways by which I can protect the system?

3. I want to use the protection in switch gear.

The answer to all those questions can be found in your local electrical code.

Don't get hung up on imbalance. Imbalance between phases is normal. However, imbalance across three phases and neutral TOGETHER is what can be used to infer an earth fault.

I need exact protection with ansi codes for unearthed system & how it will be taken care? What are the equipment required for this?

Kindly suggest.

So why didn't you ask in the first place, instead of wasting time? Your best bet is to talk to a local Electrical Engineer. If you haven't already got one, there's plenty of consultancy resource to be found in your local phone book.

Back to the drawing board with you! Find a good engineer with skill set needed, and have him solve the problem first hand. Bad advise can be had here, but it won't solve your problem. Good advise also, still not solving your problem.

See[for instance]:

http://www.laevercoproducts.com/media/f4db850abfbbb335ffff8080ffffd523.pdf