Short Circuit Current for Sychrinized DG Set.

NO! The Circuit Breaker HAS to have a capacity of more than 126kA for SURE. You should be looking at 150kA CBs. These will be current-limiting breakers and will act much before any relay can act, however rapid the relays are. This is known as 'reflex trip'....quite similar to what happens in the human body.

Please study the catalogs of top switchgear companies to learn more about rapid-trip circuit breakers.

This might help...

http://www.scribd.com/doc/6413900/practicalpowersysprotection

Go for solution given by KVS! Alternately, you can go for current limiting reactors to limit the fault current to less than that of the CB breaking capacity. But, then be careful about voltage drop in the reactors.

Ampilfying my post a little, here is an oscillogram collection from LS Industrial Systems, whose Susol MCCBs (based on the rotary double-break design pioneered by Schneider Electric) are one of the fastest CBs in the world....1.3 milliseconds of clearing time on a prosepctive 150kA !!! (Please note the peak current let through)