I have been working on Etap Software to understand the basic protection scheme using Current Transformer, circuit breaker and Relays. But i am having trouble in the coordination of the tripping in the circuit breaker and i am not able to rectify it. I would like to know what ratings and what i have to change to have a coordinated tripping in circuit breaker?
You need to look at the circuit breaker curves and consider current vs. time to trip. You may also need to look at clearing time. I believe clearing time may be a function of prospective fault current. I don't know if breakers at the level indicated have both thermal and magnetic trip mechanisms, but you need to know that and consider both curves in any breakers that are dual action.