Determine the required MVA rating of the circuit breaker CB for the system shown in given figure. Consider the grid as infinite bus. Choose 6 MVA as base. Transformer 3-phase, 33/11 kV, 6 MVA, 0.01+j0.08 p.u. impedance. Load 3-phase 11 kV, 5800 kVA, 0.8 lag, j0.2 p.u. impedance. Impedance of each feeder 9+j 18 $$\Omega $$.

Three sections of a feeder are provided with circuit breakers CB1, CB2, CB3, CB4, CB5 and CB6. For a fault F as indicated in figure.

A rectangular current pulse of duration T and magnitude 1 has the Laplace transform