- Problem 2 A 1000 Mva 20 Kv 60 Hzthree Phase Generator Is Connected Through A 1000 Mva 20 Kv4 345 Kvy Tr 1 (93.54 KiB) Viewed 22 times
Problem 2 - A 1000 – MVA, 20 – kV, 60 - Hzthree-phase generator is connected through a 1000 - MVA, 20 – kV4/345 – kVY transformer to a 345 – kV circuit breaker and a 345 – kV transmission line. The generator reactances are xa = 0.15, X6 = 0.3,Xa = 1.4(pu) and its time constants are Tä = 0.05, Tá = 1.0, TA = 0.1(s). The transformer series reactance is 0.06pu; transformer losses and exciting currents are neglected. A three-phase bolted fault (solid 3-phase phase short circuit) occurs on the line side of the circuit breaker when the generator is operated at rated terminal voltage and at no-load. The breaker interrupts the fault 3 cycles after fault inception (neglect the effect of the transformer on generator time constants.) Determine the following (a) The subtransient current (p.u.) through the breaker (b) The sub-transient current (kA) through the breaker (c) The RMS ac (symmetric) fault current (p.u.) after 3 cycles (d) The RMS ac (symmetric) fault current (KA) after 3 cycles (e) The RMS asymmetrical fault current the breaker interrupts (p.u.), assuming maximum dc offset (f) The RMS asymmetrical fault current the breaker interrupts (KA) assuming maximum dc offset