Main Breaker and Ground Fault Protection

[Shaneyj]

Hi all, couple questions mainly concerning ground fault protection - this is my first design implementing GFP on a system wide level.
Here is the scenario:
A transformer in a supervised location with a primary over 1000V and secondary below 1000V feeding a switch gear with 3 feeder breakers. The primary will be protected by fuses.
Using 450.3a the primary side fuses can be up to 250% of the transformer current rating, and no overcurrent protection required on the secondary.
Is there merit to a secondary side main breaker in the switch gear?
Do I need it to provide GFP?
Can GFP be adequately achieved using only the feeder breakers?

Thanks for your input.

 

[jim dungar]

Ground faults are most likely to occur on the feeders, so they should have GFP regardless if you have a single secondary main device with GFP.

 

[petersonra]

You could put gf relays on the feeders and use them to trip the main breaker. But then you get a single downstream gf and all your feeders are off.

 

[Shaneyj]

Thanks for the replies... Does the G in an LSIG breaker cover this without the need of relays/sensors?

 

[jim dungar]

Thanks for the replies... Does the G in an LSIG breaker cover this without the need of relays/sensors?

Yes.