Question

A 50 Hz, 250 MVA synchronous generator having inertia constant H=5 MJ/MVA is connected to an infinite bus through transformer and transmission line as shown below. The transformer reactance is based on 500 MVA, while the other impedances are based on the generator MVA Infinite bus 1 2 3 XL 0.1 pu - oto G1 V= 1.0 pu X 0.1 pu Xd = 0.3 pu at 500 MVA The generator is delivering 0.8 of full load current at a power factor of 0.8 lagging. If three-phase bolted fault occurs at bus 2, calculate the critical clearing time before which the fault must be cleared to avoid the generator pulling out of synchronism Sketch the equal-area criterion assuming that the fault is cleared at the critical clearing time and the system is intact when the fault is cleared.

Answer 1

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P(inpu) 1.0 A2 .64 Ai O Ag.21 P.8 haracteritie the genevator at steady-stale Sin do So39.792 O.6946 rad F CA L A threephane bolted fanlt at geverator makes tue output to be 2ero. bus 2 Ser= Cnitical deatrng aurfle Enan = Ch-S0) =-0-6945) 2.4471 rad. 1 areas A=Co.C4-0) Accelemtig A-0.64 (8er -0). Decelerating dmap Stn8-Di64) d8 area, Aze0 A2- -0.64 (Sman-8 Cos Sur-Cos Suan-0.64 (Sua d qual- Ap A2 cntericn Furr area 0.64 &r-0.64=Cas SCosdar -0.64 Seat O.64 er Cas Smogs .G4(S + Corsnar mars

+ Cors Enay Cas Sr 0.64 0.64(2.4471- a6945) Cos (2 4471) s Sur Cos 0.3533 Eer= Gs' (0.3533) - 1.2097Tad Ser-f209 69.312 tine To find the cntical chain'g Adngquotin Gle need t sowe tue the fuk uning PhM dt er CY 2X5X(1.2097-0.6945) AX50x0164 0.2264 see Critical claaning time