1. A 100 MVA, 11 kV generator with X"= 0.20 p.u. is connected through a transformer to a bus bar that supplies three ide

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1 A 100 Mva 11 Kv Generator With X 0 20 P U Is Connected Through A Transformer To A Bus Bar That Supplies Three Ide 1 (79.34 KiB) Viewed 35 times

1. A 100 MVA, 11 kV generator with X"= 0.20 p.u. is connected through a transformer to a bus bar that supplies three identical motors as shown in the figure and each motor has X"= 0.20 p.u and X' = 0.25 p.u. on a base of 20 MVA, 33 kV. The bus voltage at the motors is 33 kV when a three- phase balanced fault occurs at the point F. Calculate: (a) the subtransient current in the fault. (b) the subtransient current in the circuit breaker B. (c) the momentary current in the circuit breaker B. (d) the current to be interrupted by circuit breaker B in (i) 2 cycles,(ii) 3 cycles, (iii) 5 cycles and (iv) 8 cycles. Also, compare the results. G M₁ ST 100 MVA 11 kV X"=0.2 100 MVA 11/6.6 kV 10% 20 MVA 33 kV X" = 0.2 p.u. X'= 0.25 p.u. B Figure 1: Symmetrical Fault M₂ M₁