Two synchronous machines are connected through three phase transformer to the transmission line as given in Fig. The ratings and reactance’s of the machines and transformers are: Machines 1 and 2: 100...

Two synchronous machines are connected through three phase transformer to the transmission line as given in Fig. The ratings and reactance’s of the machines and transformers are:

Machines 1 and 2: 100 MVA; 20 kV; Xd”=X₁=X₂=20%; X₀ = 4%; Xn= 5%

Transformers T₁ and T₂ : 100MVA; 20 / 345  kV ; X=8%

The line reactance’s are X₁=X₂= 15% and X₀=50%. The system is operating at nominal voltage without prefault currents when a  single line to ground fault occurs on the phase ‘a’ at bus 3 with fault impedance (Z_f) 0.8 p.u. Determine the subtransient current to ground at the fault and draw the sequence network.