Refer to Figure P12.13(a) and assume that The generator neutral is not grounded. Before the fault Va = V = 1 angle 0 degree. (a) Calculate I^f with the breaker open. (b) Calculate I^f with the breaker dosed. Use Figure P12.13(b) to model each phase of the transformer. Solution circuit breakeer is open i = V/ Z+ + Z- +Z BECOZ zero sequence current flow in the closed loop = 1/j2.5 = - j 0.4 if circuit breaker is closed i = V/ Z+ + Z- +Z +Zo = 1/j2.6 = -j0.38.